Description: <p><font size="3" style>National Measured Alkalinity Data derived from data stored in the U.S. EPA Water Quality Portal.</font><br /></p><p><font size="3" style><b>Description:</b> National Measured Alkalinity Data derived from data stored in the U.S. EPA Water Quality Portal.<br /></font></p><p><font size="3" style><b>Forms Retained:</b> Total alkalinity as calcium carbonate(mg/L, mg/l CaCO3)<br /></font></p><p><font size="3"><b>Data Date Range:</b> 01/2000 – 12/2023</font></p><p><font size="3"><b>Acquisition Date:</b> 1/16/2024</font></p><p><font size="3"></font></p><p><font size="3"><b>Query Links:</b> https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Alkalinity&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&sorted=no&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET</font></p><p><font size="3"><b>Min. Value:</b> -497</font></p><p><font size="3"><b>Max. Value:</b> 99100</font></p><p><font size="3"></font></p><p><font size="3"><b>Units in Source/Original Dataset:</b> <Null>, mg/L, ueq/L, mg/l CaCO3, ppm</font></p><div><div><b><font size="3">Background</font></b></div><div><font size="3">Alkalinity is a measure of the ability of the water body to neutralize acids and bases and thus buffer changes in pH level (Stumm1981). Higher alkalinity indicates a greater capacity to neutralize acids. Alkalinity is important for maintaining a stable environment for aquatic life species that are sensitive to pH changes and is important for drinking water, agriculture, and industry. Natural sources of alkalinity include the dissolution of limestone, dolomite, and other carbonate minerals. Human activities, such as agriculture and industrial processes, can also influence alkalinity levels in freshwater systems.</font></div><div><font size="3"><br /></font></div><div><font size="3">Alkalinity is related to positive acid neutralizing capacity (ANC) and acidity is often used to mean negative ANC. Samples analyzed for ANC are unfiltered and alkalinity are filtered. ANC value would be equivalent to alkalinity for samples without titratable particulate matter. However, for the purposes of this dataset, only samples reported as alkalinity are included.</font></div><div><font size="3"><br /></font></div><div><font size="3">Total alkalinity is measured by titrating a sample with sulfuric acid and identifying the equivalence or inflection points where buffering is weaker and there is an abrupt change in pH with small amounts of acid (USGS 2024). With the addition of a strong acid around pH 8.3, all the carbonate ions [CO2−] have been completely converted to bicarbonate ions [HCO−3], and around pH 4.5, bicarbonate is fully converted to carbonic acid [H2CO3] which is dissociated into CO2 plus water. Some other ions that can affect inflection points include borate, hydroxide, phosphate, silicate, dissolved ammonia, and the conjugate bases of organic acids.</font></div></div><div><font size="3"><br /></font></div><div><font size="3"><b>Dataset</b></font></div><div><font size="3">This dataset focuses primarily on samples reported as alkalinity and no conversions were performed e.g., ANC reported milli equivalents per liter were not converted to mg/L as CaCO3.<br /></font></div><div><font size="3"><br /></font></div><div><font size="3">This dataset is a collection of surface water alkalinity samples collected across the United States from 2000-2023 from the Water Quality Portal (WQP), which integrates publicly available water quality data from the USGS National Water Information System (NWIS) and the EPA Water Quality Exchange (WQX) Data Warehouse. These water quality data records are provided by many federal, state, and tribal organizations and other partners. Because these data are from secondary sources, the U.S. EPA cannot ensure that the information is accurate, current, or complete. Therefore, users should verify the data from the original sources before drawing site specific conclusions.<br /></font></div><div><font size="3"><br /></font></div><div><font size="3"><b>Quality Assurance/Quality Control (QA/QC) and identified issues</b><br /></font></div><div><font size="3">An automated Quality Assurance/Quality Control (QA/QC) protocol was developed using a mix of Python and R-scripts to remove or identify potentially erroneous values and outliers from the WQP data download. The quality of the WQP measured data was evaluated as follows.</font></div><div><font size="3"><div><ul><li>Generally – do not delete data. Add a screening column to keep track of decision-making to remove records/observations.</li><li>Review the geographic/temporal scope and data types of the acquired data to the project objectives—it might not be necessary to process all data from a given data set. Map stations in a GIS to further refine and select data based on analysis selection criteria: geographic area, watersheds, bounding box, waterbody type, etc. This also provides the opportunity to conduct quality assurance checks based on spatial location (e.g., are the “estuarine” sites located near the coast).</li><li>Remove values reported with units of measurements different than mg/L.</li><li>Flag values < -16 and greater than 3750 mg/L as CaCO3. These range classes are based on the maximum and minimum of all values observed in surface water samples collected during the National Rivers and Streams Assessment (NRSA) (USEPA, 2022).</li><li>Convert to same units for all relevant alkalinity values to mg/L (Table 1). These outliers are shown as gray symbols on the map.</li><li>Review and flag samples identified in the WQP with sample processing issues (e.g., suspected contamination, exceeding sampling hold time) that don’t meet the requirements or thresholds of end use. For the Freshwater Explorer, values were colored gray.</li><li><br /></li></ul></div></font></div><div style="text-align:center;"><img alt src="https://lh3.googleusercontent.com/pw/AP1GczOjAQ-pCdskH5Wwl7ZMlSbHTLma6TfrOcwpI-Y9_D4oUVF9s0xOLIdkB1E0IOZR18LHZMsZy4J4qZ6bneSHsI-HCprjF9bFMEyu3T9pvE6phMi078Vkwg9stTvGKE2W1UMIQSY-aB3DpDHg3QWZxAzXtg=w624-h189-s-no-gm?authuser=0" /><br /></div><p style="text-align:center;"><strong>Table 1</strong><span style="font-size:small;">. Unit conversion to mg/L for measured alkalinity samples.</span><br /></p><p>Examples of errors found in the source dataset include negative alkalinity values, units of measurements not consistent with alkalinity measurements (e.g., <Null>, CaCO3) and entries suspected to be µg/L but reported as mg/L based on the natural and anthropogenic ranges of alkalinity. Users should verify the data from the original sources before drawing site specific conclusions. Generally source specific issues within the dataset will become apparent as QC steps are performed. Individual contributing organizations can be found in the final and original datasets if the end user would like to filter for specific sampling partners.<br /></p><p>The resulting dataset is presented as a summarized collection of information for each unique sampling location and the original data flagging process helps to exclude unreliable and errant values from the final statistics. The R code developed to perform the QA/QC steps are available from cormier.susan@epa.gov<br /></p><p><b><br /></b></p><p><b>Terms of Use</b></p><p><b>Freshwater Explorer Data Disclaimer</b></p><p>This data is intended for exploratory and discussion purposes. Although statutory provisions and U.S. Environmental Protection Agency (EPA) regulations contain legally binding requirements, these data and related information are not regulatory nor do they change or substitute for any provisions or regulations. The information does not substitute for the Clean Water Act, a National Pollutant Discharge Elimination System permit, or EPA or state regulations applicable to permits; nor is this material a permit or regulation itself. Thus, it does not impose legally binding requirements on EPA, states, tribes, or the regulatory community. This information does not confer legal rights or impose legal obligations on any member of the public. Mention of any trade names, products, or services is not and should not be interpreted as conveying official EPA approval, endorsement, or recommendation.</p><p>While EPA has used its best efforts to include complete and accurate information in this system, EPA cannot be held responsible for errors or omissions and is not liable for any direct, indirect, or consequential damages resulting from using this secondary information. Some potential sources of error have been assessed by the U.S. EPA resulting in the removal of some samples from the original data sets. However, all sources of potential error cannot be eliminated from the measured data reported in the Freshwater Explorer or the data used to develop predictive models. Therefore, the U.S. EPA cannot fully ensure either the original data or the values calculated from them. Conclusions and assessments drawn from the use of the Freshwater Explorer are the responsibility of the user.</p><p>Please check sources, scale, accuracy, dates, and other available information. Please confirm that you are using the most recent copy of both data and metadata. Reliance on the information contained in this system by any party cannot be used as a defense in any administrative or judicial proceeding.</p><p>This dataset may be revised periodically. EPA can revise this dataset without public notice to reflect changes in EPA policy, guidance, and advancements in the field of biological assessments. EPA welcomes public input on this document at any time. Send comments to FreshwaterExplorer@epa.gov, Center for Environmental Measurement and Modeling, Office of Research and Development, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr, Cincinnati, OH 45268.</p><p><br /></p><p><b>Preferred citation:</b> Wharton, C., and Cormier. S. 2024. U.S. EPA Freshwater Explorer v2 national measured alkalinity metadata and dataset. USEPA. https://arcg.is/0OuDn80</p><p><br /></p><p><b>References</b></p><p>Hunt, D.T.E. and A.L. Wilson. 1986. The Chemical Analysis of Water: General Principles and Techniques. 2nd ed. Royal Society of Chemistry, London, England.</p><p>Hillman, D.C., J.F. Potter, and S.J. Simon. 1986. National Surface Water Survey, Eastern Lake Survey-Phase I, Analytical Methods Manual. EPA/600/4-86/009. U.S. Environmental Protection Agency, Las, Vegas, NV.</p><p>Oblinger Childress, C. J., W. T. Foreman, B. F. Connor, and T. J. Maloney. 1999. New reporting procedures based on long-term method detection levels and some considerations for interpretations of water-quality data provided by the U.S. Geological Survey National Water Quality Laboratory. Open-File Report 99-193, US Geological Survey, Reston, Virginia.</p><p>Stumm, Werner (1981). Aquatic chemistry: an introduction emphasizing chemical equilibria in natural waters. New York: Wiley. ISBN 0-471-04831-3. OCLC 6889980.</p><p>U.S. EPA, 1987. Handbook of Methods for Acid Deposition Studies: Laboratory Analyses for Surface Water Chemistry. EPA/600/4-87/026. U.S. Environmental Protection Agency, Office of Research and Development, Washington D.C.</p><p>USEPA. 2022. National Rivers and Streams Assessment 2023 - 2024: Laboratory Operations Manual. EPA841-B-22-008. U.S. Environmental Protection Agency, Office of Water, Washington, DC.</p><p>USGS. 2024. Alkalinity Calculation Methods. https://or.water.usgs.gov/alk/methods.html</p><p>Youden, W.J. 1969. Ranking laboratories by round-robin tests. In Precision Measurement and Calibration. H.H. Ku, ed. NBS Special Publication 300, Vol. 1. U.S. GPO Washington, D.C.</p>
Copyright Text: Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021. https://doi.org/10.5066/P9QRKUVJ.
National Water Quality Monitoring Council, 2024 Water Quality Portal, accessed 01, 16, 2024, https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Alkalinity&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&sorted=no&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET, https://doi.org/10.5066/P9QRKUVJ.
Description: <div><b>Description:</b> National Measured Ammonia Data derived from data stored in the U.S. EPA Water Quality Portal.</div><div><b><br /></b></div><div><b>Data Date Range:</b> 01/2000 – 12/2023</div><div><b><br /></b></div><div><b>Acquisition Date:</b> 1/25/2024</div><div><b><br /></b></div><div><b>Query Links:</b> https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Ammonia&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STORET</div><div><b><br /></b></div><div><b>Min. Value:</b> -99</div><div><b><br /></b></div><div><b>Max. Value:</b> 393000</div><div><b><br /></b></div><div><b>Units in Source/Original Dataset:</b> <Null>, % recovery, m, mg N/l******, mg/kg, mg/l, mg/L, mg/l as N, MPN, None, ppb, ppm, ug/l, ug/L, umol, umol/L</div><div><br /></div><div>Background</div><div>Ammonia is found naturally in the environment, produced by the decay of organic matter and animal waste (<a href="https://www.epa.gov/caddis/ammonia" target="_blank">USEPA 2024</a>). It is also a part of the nitrogen cycle, where it is produced by nitrogen-fixing bacteria and is essential for the synthesis of amino acids and other biological molecules. Ammonia exists primarily in two forms: un-ionized ammonia (NH3) and ionized ammonium (NH4+), with this dataset focusing on ammonia. The equilibrium between these forms is pH and temperature dependent.<br /></div><div><br /></div><div>In freshwater environments, ammonia can come from a variety of sources (<a href="https://www.epa.gov/caddis/ammonia" target="_blank">EPA 2024</a>, <a href="https://www.epa.gov/wqc/aquatic-life-criteria-ammonia" target="_blank">EPA 2013</a>), including but not limited to:</div><div><div><ul><li>Natural sources</li><ul><li>decomposition or breakdown of organic waste matter</li><li>gas exchange with the atmosphere</li><li>forest fires</li><li>animal and human waste</li><li>nitrogen fixation processes</li><li>lightning</li></ul><li>Anthropogenic sources</li><ul><li>agriculture include animal wastes:</li></ul><ul><li><i>concentrated animal feeding operations (CAFOs)</i></li><li><i>other livestock operations</i></li><li><i>aquaculture facilities</i></li><li><i>fertilizers applied to crop fields</i></li></ul><li>urban and suburban development</li><ul><li>fertilizers applied to golf courses and lawns</li><li>human wastewater</li><li>landfill wastes</li><li>nitrogenous vehicle emissions</li></ul><li>Industries</li><ul><li>coal-fired power plants and other industrial facilities</li><li>metal finishing and treating applications</li><li>pharmaceuticals and dyes</li><li>crude oil and in corrosion protection</li><li>metals extraction during mining</li></ul></ul></div></div><div><div>Ammonia is acutely toxic to animals and is normally excreted as ammonia or urea. When concentrations are too high, aquatic organisms cannot sufficiently excrete ammonia which then builds up in the internal tissues and blood, and potentially results in death. (<a href="https://www.epa.gov/wqc/aquatic-life-criteria-ammonia" target="_blank">EPA 2013</a>).</div><div><br /></div><div>Dissolved sulfate in freshwater is measured by Semi-Automated Colorimetry (<a href="https://www.epa.gov/esam/epa-method-3501-determination-ammonia-nitrogen-semi-automated-colorimetry" target="_blank">EPA 350.1</a>) or flow injection analysis automated colorimetric method (e.g., Lachat 10-107-06-3-D). Our quality Assurance/Quality Control (QA/QC) procedures were used to summarize reported values as well as the contributor’s laboratory processing and reporting procedures that were used by the contributor to ensure results of comparable measures that were used to summarize site data in the Freshwater Explorer. The WQP portal original dataset contains annotations for each sample to help understand the reliability and pedigree of the final reported values in the dataset.</div><div><br /></div><div><b>Dataset</b></div><div>This dataset focuses primarily on samples reported as ammonia. Unit conversions were normalized to mg/l as listed in Table 1.</div><div><br /></div><div>This dataset is a collection surface water ammonia samples collected across the United States from 2000-2023 from the Water Quality Portal (WQP), which integrates publicly available water quality data from the USGS National Water Information System (NWIS) and the EPA Water Quality Exchange (WQX) Data Warehouse. These water quality data records are provided by many federal, state, and tribal organizations and other partners. Because these data are from secondary sources, the U.S. EPA cannot ensure that the information is accurate, current, or complete. Therefore, users should verify the data from the original sources before drawing site specific conclusions.</div></div><div><br /></div><div><div><b>Quality Assurance/Quality Control (QA/QC) and identified issues</b></div><div>An automated Quality Assurance/Quality Control (QA/QC) protocol was developed using a mix of Python and R-scripts to remove or identify potentially erroneous values (outliers) in WQP. The quality of the WQP measured data was evaluated as follows. The quality of the WQP measured data was evaluated as follows.</div></div><div><br /></div><div><div><ul><li>Generally – do not delete data. Add a screening/flagging column to keep track of decision-making to remove records/observations.</li><li>Review the geographic/temporal scope and data types of the acquired data to the project objectives—it might not be necessary to process all data from a given data set. Map stations in a GIS to further refine and select data based on analysis selection criteria: geographic area, watersheds, bounding box, waterbody type, etc. This also provides the opportunity to conduct quality assurance checks based on spatial location (e.g., are the “estuarine” sites located near the coast).</li><li>Flag values outside of the known maximum and minimum ranges (0 – 250 mg/L) of ammonia in freshwater systems. </li><li>Flag values reported with units of measurements different than mg/L.</li><li>Convert all relevant ammonia values to mg/L or flag values where there is no direct path for unit conversion.</li><li>Identify and flag (gray circles) ammonia values > 250 mg/L.</li><li>Review and flag samples identified in the WQP with sample processing issues (e.g., suspected contamination, exceeding sampling hold time, no reported value).</li></ul></div></div><div style="text-align:center;"><img alt="Unit conversion to mg/L for measured ammonia samples." src="https://lh3.googleusercontent.com/pw/AP1GczNcD6U45OJ5QMNSZyy_m_JnG_gj2qQ82wmfBFOgVxfoykdDsXmf1g-1XFsPRQ2wnzEWXmMT6NwPDAZbv1B372iM70wb_eTL4nwbloJNlwbzYU2A-xcEnwJOvOOXxout8rEHtaBfO2y8KCRG2w-n_OzN7Q=w646-h397-s-no-gm?authuser=0" /><br /></div><div style="text-align:center;"><i>Table 1. Unit conversion to mg/L for measured ammonia samples.</i><br /></div><div style="text-align:left;"><br /></div><div style="text-align:left;"><div>Examples of errors found include negative ammonia values, units of measurements not consistent with surface water ammonia measurements (e.g., % recovery, m, mg/kg, MPN, None, ppb, ppm, umol/L), and values well above known ammonia ranges in freshwater systems. Users should verify the data from the original sources before drawing site specific conclusions. Individual contributing organizations can still be found in the final and original datasets if the end user would like to filter for only specific sampling partners.</div><div><br /></div><div>The resulting dataset is presented as summarized collection information for each unique sampling location and the original data flagging process helps to exclude unreliable and errant values from the final statistics. The R code developed to perform the QA/QC steps are available from <a href="mailto:cormier.susan@epa.gov" target="_blank">cormier.susan@epa.gov</a>.</div><div><br /></div><div><br /></div></div><div><div><b>Terms of Use</b></div><div><b>Freshwater Explorer Data Disclaimer</b></div><div>This data is intended for exploratory and discussion purposes. Although statutory provisions and U.S. Environmental Protection Agency (EPA) regulations contain legally binding requirements, these data and related information are not regulatory, nor do they change or substitute for any provisions or regulations. The information does not substitute for the Clean Water Act, a National Pollutant Discharge Elimination System permit, or EPA or state regulations applicable to permits; nor is this material a permit or regulation itself. Thus, it does not impose legally binding requirements on EPA, states, tribes, or the regulatory community. This information does not confer legal rights or impose legal obligations on any member of the public. Mention of any trade names, products, or services is not and should not be interpreted as conveying official EPA approval, endorsement, or recommendation.</div><div><br /></div><div>While EPA has used its best efforts to include complete and accurate information in this system, EPA cannot be held responsible for errors or omissions and is not liable for any direct, indirect, or consequential damages resulting from using this secondary information. Some potential sources of error have been assessed by the U.S. EPA resulting in the removal of some samples from the original data sets. However, all sources of potential error cannot be eliminated from the measured data reported in the Freshwater Explorer or the data used to develop predictive models. Therefore, the U.S. EPA cannot fully ensure either the original data or the values calculated from them. Conclusions and assessments drawn from the use of the Freshwater Explorer are the responsibility of the user.</div><div><br /></div><div>Please check sources, scale, accuracy, dates, and other available information. Please confirm that you are using the most recent copy of both data and metadata. Reliance on the information contained in this system by any party cannot be used as a defense in any administrative or judicial proceeding.</div><div><br /></div><div>This dataset may be revised periodically. EPA can revise this dataset without public notice to reflect changes in EPA policy, guidance, and advancements in the field of biological assessments. EPA welcomes public input on this document at any time. Send comments to FreshwaterExplorer@epa.gov, National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr, Cincinnati, OH 45268.</div></div><div><br /></div><div><b>Preferred citation:</b> Leppo, E., Wharton, C., and Cormier. S. 2024. U.S. EPA Freshwater Explorer v2 national measured dissolved ammonia metadata and dataset. USEPA. <a href="https://arcg.is/0OuDn80" target="_blank">https://arcg.is/0OuDn80</a><br /></div><div><br /></div><div><div><b>References</b></div><div>U.S. EPA. 1993. “Method 350.1: Nitrogen, Ammonia (Colorimetric, Automated Phenate),” Revision 2.0. Cincinnati, OH. <a href="https://www.epa.gov/esam/epa-method-3501-determination-ammonia-nitrogen-semi-automated-colorimetry" target="_blank">https://www.epa.gov/esam/epa-method-3501-determination-ammonia-nitrogen-semi-automated-colorimetry</a></div><div><br /></div><div>U.S. EPA. 2024. Ammonia. Causal Analysis/Diagnosis Decision Information System (CADDIS). <a href="https://www.epa.gov/caddis/ammonia" target="_blank">https://www.epa.gov/caddis/ammonia</a></div><div><br /></div><div>USEPA. 2013. Aquatic Life Ambient Water Quality Criteria for Ammonia – Freshwater. Office of Water. EPA 822-R-18-002. <a href="https://www.epa.gov/sites/default/files/2015-08/documents/aquatic-life-ambient-water-quality-criteria-for-ammonia-freshwater-2013.pdf" target="_blank">https://www.epa.gov/sites/default/files/2015-08/documents/aquatic-life-ambient-water-quality-criteria-for-ammonia-freshwater-2013.pdf</a></div></div><div><br /></div>
Copyright Text: Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021. https://doi.org/10.5066/P9QRKUVJ.
Description: <div><div><b>Description: </b>National Measured Dissolved Calcium Data derived from data stored in the U.S. EPA Water Quality Portal.</div><div><b>Data Date Range:</b> 01/2000 – 12/2023</div><div><b>Acquisition Date:</b> 1/25/2024</div><div><b>Query Links:</b> <a href="https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Calcium&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET" target="_blank">https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Calcium&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET</a></div><div><b>Min. Value:</b> -214.934</div><div><b>Max. Value:</b> 23000000</div><div><b>Units in Original/Source Dataset:</b> <Null>, %, % recovery, count, lb/day, mg/g, mg/kg, mg/l, mg/L, mg/l CaCO3, mg/l CaCO3**, mg/m2, MPN, ppb, ppm, ueq/L, ug/g, ug/kg, ug/L, ug/l, umol/L</div></div><div><br /></div><div><div><b>Background</b></div><div>Dissolved calcium in freshwater can have both positive and negative effects on aquatic life and other uses of water. Some natural and anthropogenic sources of calcium ions are weathering of rocks and minerals, particularly limestone and sandstone, which releases calcium ions into the water. Anthropogenic activities that increase calcium in streams include agricultural runoff, dissolution of mine waste, demineralization of concrete, wastewater discharge, and industrial processes. Dissolved calcium can somewhat reduce metal toxicity (e.g., <a href="https://www.epa.gov/wqs-tech/copper-biotic-ligand-model" target="_blank">EPA 2024a</a>), but excess levels can also be associated with ionic stress for aquatic life (<a href="https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=233809" target="_blank">EPA 2011</a>). It can lead to scaling and deposits in water infrastructure, affecting water supply systems (<a href="https://www.epa.gov/sites/default/files/2018-10/documents/quality-criteria-water-1976.pdf" target="_blank">EPA 1976</a>; USEPA 2024b). </div><div><br /></div><div>Dissolved calcium ion concentration is in freshwater is typically measured by atomic absorption spectroscopy (EPA 6010D, (USEPA 2014) or inductively-coupled plasma atomic emission spectroscopy (ICP-AES) (EPA 200.7(USEPA 1994). Therefore, data reliability depends upon analytical quality and then data transcription into the water quality exchange. </div><div><br /></div><div><b>Dataset</b></div><div>This dataset focuses primarily on samples reported as dissolved calcium cations. Unit conversions were normalized to mg/l as listed in Table 1. </div><div><br /></div><div>This dataset is a collection surface water disolved calcium samples collected across the United States from 2000-2023 from the Water Quality Portal (WQP), which integrates publicly available water quality data from the USGS National Water Information System (NWIS) and the EPA Water Quality Exchange (WQX) Data Warehouse. These water quality data records are provided by many federal, state, and tribal organizations and other partners. Because these data are from secondary sources, the U.S. EPA cannot ensure that the information is accurate, current, or complete. Therefore, users should verify the data from the original sources before drawing site specific conclusions.</div></div><div><br /></div><div><div><b>Quality Assurance/Quality Control (QA/QC) and identified issues</b></div><div>An automated Quality Assurance/Quality Control (QA/QC) protocol was developed using a mix of Python and R-scripts to remove or identify potentially erroneous values (outliers) appearing in the WQP data. The quality of the WQP measured data was evaluated as follows. </div></div><div><div><ul><li>Generally – do not delete data. Add a screening/flagging column to keep track of decision-making to remove records/observations.</li><li>Review the geographic/temporal scope and data types of the acquired data to the project objectives—it might not be necessary to process all data from a given data set. Map stations in a GIS to further refine and select data based on analysis selection criteria: geographic area, watersheds, bounding box, waterbody type, etc. This also provides the opportunity to conduct quality assurance checks based on spatial location (e.g., are the “estuarine” sites located near the coast).</li><li>Flag values reported with units of measurements different than mg/L.</li><li>Review and flag samples identified in the WQP with sample processing issues (e.g., suspected contamination, exceeding sampling hold time, no reported value, below reporting value). Many of the samples that met these criteria were already found and identified by WQP QA/QC data process.</li><li>Convert all relevant calcium values to mg/L or flag values where there is no direct path for unit conversion Table 1.</li><li>Flag values outside of the known maximum and minimum (0.05 – 500) ranges of dissolved calcium in freshwater systems. This range falls within the range of dissolved calcium values observed in freshwater systems. This dataset contains well samples along with stream collected samples and map range values were widened to include those locations (USEPA, 2022).</li><li>Review and flag samples identified in the WQP with sample processing issues so that value is not used in summarization calculation (e.g., suspected contamination, exceeding sampling hold time, no reported value, below reporting value). </li><li>Parse/filter out various measurement compositions (Total vs Dissolved) for summarization to use only data denoted as Dissolved.</li><li>Summary statistics – Calculate basic statistics (mean, median, standard deviation, range, last measurement, maximum, minimum).</li></ul></div></div><div><br /></div><div style="text-align:center;"><img alt="Unit conversion to mg/L for measured dissolved calcium samples." src="https://lh3.googleusercontent.com/pw/AP1GczPCzbmWZpeDgIjetwFTogMDQYvYPPQdRzst8nkcblCi-Ovq4YT2cyZPPuqCZabcnhmVDtVwLS0czeFsmhKbtxKqLNbsnWRYLpI3oM6QQIWKhLxUlkbWy_5C3X4w_0J8lmt811M1EsCPHkrn9nsD_61Mig=w676-h700-s-no-gm?authuser=0" /><br /></div><div style="text-align:center;"><i>Table 1. Unit conversion to mg/L for measured dissolved calcium samples.</i></div><div style="text-align:center;"><i><br /></i></div><div style="text-align:left;"><div style>Examples of errors found include negative calcium values, units of measurements not consistent with calcium measurements (e.g., <Null>, %, % recovery, count, lb/day, mg/m2, MPN,), and values well above known dissolved calcium ranges in freshwater systems. Users should verify the data from the original sources before drawing site specific conclusions. Individual contributing organizations can still be found in the final and original datasets if the end user would like to filter for only specific sampling partners.</div><div style><br /></div><div style>The resulting dataset is presented as a summarized collection information for each unique sampling location and the original data flagging process helps to exclude unreliable and errant values from the final statistics. The R code developed to perform the QA/QC steps are available from <a href="mailto:cormier.susan@epa.gov" target="_blank">cormier.susan@epa.gov</a>.</div><div style="font-style:italic;"><br /></div><div style><div style><b>Terms of Use</b></div><div style><b><br /></b></div><div style><b>Freshwater Explorer Data Disclaimer</b></div><div style><br /></div><div style>This data is intended for exploratory and discussion purposes. Although statutory provisions and U.S. Environmental Protection Agency (EPA) regulations contain legally binding requirements, these data and related information are not regulatory, nor do they change or substitute for any provisions or regulations. The information does not substitute for the Clean Water Act, a National Pollutant Discharge Elimination System permit, or EPA or state regulations applicable to permits; nor is this material a permit or regulation itself. Thus, it does not impose legally binding requirements on EPA, states, tribes, or the regulatory community. This information does not confer legal rights or impose legal obligations on any member of the public. Mention of any trade names, products, or services is not and should not be interpreted as conveying official EPA approval, endorsement, or recommendation.</div><div style><br /></div><div style>While EPA has used its best efforts to include complete and accurate information in this system, EPA cannot be held responsible for errors or omissions and is not liable for any direct, indirect, or consequential damages resulting from using this secondary information. Some potential sources of error have been assessed by the U.S. EPA resulting in the removal of some samples from the original data sets. However, all sources of potential error cannot be eliminated from the measured data reported in the Freshwater Explorer or the data used to develop predictive models. Therefore, the U.S. EPA cannot fully ensure either the original data or the values calculated from them. Conclusions and assessments drawn from the use of the Freshwater Explorer are the responsibility of the user.</div><div style><br /></div><div style>Please check sources, scale, accuracy, dates, and other available information. Please confirm that you are using the most recent copy of both data and metadata. Reliance on the information contained in this system by any party cannot be used as a defense in any administrative or judicial proceeding.</div><div style><br /></div><div style>This dataset may be revised periodically. EPA can revise this dataset without public notice to reflect changes in EPA policy, guidance, and advancements in the field of biological assessments. EPA welcomes public input on this document at any time. Send comments to FreshwaterExplorer@epa.gov, National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr, Cincinnati, OH 45268.</div><div style><br /></div><div style><b>Preferred citation:</b> Leppo, E., Wharton, C., and Cormier. S. 2024. U.S. EPA Freshwater Explorer v2 national measured dissolved calcium metadata and dataset. USEPA. https://arcg.is/0OuDn80</div><div style><br /></div><div style><b>Original data sources:</b> https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Calcium&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET</div><div style><br /></div><div style><b>References</b></div><div style>USEPA. 1976. Quality Criteria for Water. EPA 440-9-76-023. <a href="https://www.epa.gov/sites/default/files/2018-10/documents/quality-criteria-water-1976.pdf" target="_blank">https://www.epa.gov/sites/default/files/2018-10/documents/quality-criteria-water-1976.pdf</a>.</div><div style><br /></div><div style>U.S. EPA. 1994. “Method 200.7: Determination of Metals and Trace Elements in Water and Wastes by Inductively Coupled Plasma-Atomic Emission Spectrometry,” Revision 4.4. Cincinnati, OH. </div><div style><br /></div><div style>USEPA. 2011A Field-Based Aquatic Life Benchmark for Conductivity In Central Appalachian Streams (Final Report). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-10/023F. <a href="https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=233809" target="_blank">https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=233809</a>.</div><div style><br /></div><div style>USEPA. 2014. "Method 6010D (SW-846): Inductively Coupled Plasma-Atomic Emission Spectrometry," Revision 4. Washington, DC. <a href="https://www.epa.gov/esam/epa-method-6010d-sw-846-inductively-coupled-plasma-atomic-emission-spectrometry" target="_blank">https://www.epa.gov/esam/epa-method-6010d-sw-846-inductively-coupled-plasma-atomic-emission-spectrometry</a>.</div><div style><br /></div><div style>USEPA. 2022. National Rivers and Streams Assessment 2023 - 2024: Laboratory Operations Manual. EPA841-B-22-008. U.S. Environmental Protection Agency, Office of Water, Washington, DC. <a href="https://www.epa.gov/system/files/documents/2023-06/NRSA2324_LOM_v1.0.pdf" target="_blank">https://www.epa.gov/system/files/documents/2023-06/NRSA2324_LOM_v1.0.pdf</a></div><div style><br /></div><div style>USEPA. 2024a. Copper Biotic Ligand Model. Water Quality Standards: Regulations and Resources. <a href="https://www.epa.gov/wqs-tech/copper-biotic-ligand-model" target="_blank">https://www.epa.gov/wqs-tech/copper-biotic-ligand-model</a></div><div style><br /></div><div style>USEPA. 2024b. Secondary Drinking Water Standards: Guidance for Nuisance Chemicals. <a href="https://www.epa.gov/sdwa/secondary-drinking-water-standards-guidance-nuisance-chemicals" target="_blank">https://www.epa.gov/sdwa/secondary-drinking-water-standards-guidance-nuisance-chemicals</a>.</div><div style="font-style:italic;"><br /></div></div></div>
Copyright Text: Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021. https://doi.org/10.5066/P9QRKUVJ.
Description: <div><b>Description:</b> National Measured Chlorophyll a Data derived from data stored in the U.S. EPA Water Quality Portal.</div><div><b>Data Date Range:</b> 01/2000 – 12/2023</div><div><b>Acquisition Date:</b> 1/25/2024</div><div><b>Query Links:</b> <a href="https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Chlorophyll%20a&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET" target="_blank">https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Chlorophyll%20a&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET</a></div><div><b>Min. Value:</b> -200</div><div><b>Max. Value:</b> 999.999</div><div><b>Units in Source/Original Dataset:</b> <Null>, #/L, g/m2, IVFU, m, mg, mg/cm2, mg/cm3, None, mg/l, mg/L, mg/m2, mg/m3, ppb, ppm, ug/L, ug/l, ug/net, RFU, ug, ug/cm2</div><div><br /></div><div><div><b>Background</b></div><div>Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light. It is a critical pigment found in all photosynthetic organisms, including algae and cyanobacteria, and it is often used as an indicator of the amount of algae (or phytoplankton) in freshwater systems. High levels of chlorophyll a can indicate eutrophic conditions, where nutrient enrichment (often from agricultural runoff or sewage discharge) leads to excessive algal growth. Measuring chlorophyll a concentrations helps assess the trophic state of the waterbody (USEPA 2022, USEPA 2024). Rates of increase can be used to predict fish die offs from hypoxia (low oxygen levels) as plant material decays and the probability of cyanobacterial blooms that are toxic to wildlife and people.</div><div><br /></div><div>Chlorophyll a is typically measured by extraction in 90% acetone and analyzed by fluorometry (<a href="https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=309417" target="_blank">EPA 445.0</a>, <a href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=309415&Lab=NERL" target="_blank">EPA 446.0</a>)</div></div><div><br /></div><div><div><b>Dataset</b></div><div>This dataset is a collection chlorophyll a samples, collected and summarized across the United States from 2000-2023 from the Water Quality Portal (WQP), which integrates publicly available water quality data from the USGS National Water Information System (NWIS) and the EPA Water Quality Exchange (WQX) Data Warehouse. These water quality data records are provided by many federal, state, and tribal organizations and other partners. As such, the U.S. EPA cannot ensure that the information is accurate, current or complete. Therefore, users should verify the data from the original sources before drawing site specific conclusions.</div></div><div><br /></div><div><div><b>Quality Assurance/Quality Control (QA/QC) and identified issues</b></div><div>An automated Quality Assurance/Quality Control (QA/QC) protocol was developed using a mix of Python and R-scripts to remove or identify potentially erroneous values (outliers) in WQP. The quality of the WQP measured data was evaluated as follows.</div></div><div><div><ul><li>Generally – do not delete data. Add a screening/flagging column to keep track of decision-making to remove records/observations.</li><li>Review the geographic/temporal scope and data types of the acquired data to the project objectives—it might not be necessary to process all data from a given data set. Map stations in a GIS to further refine and select data based on analysis selection criteria: geographic area, watersheds, bounding box, waterbody type, etc. This also provides the opportunity to conduct quality assurance checks based on spatial location (e.g., are the “estuarine” sites located near the coast).</li><li>Flag values reported with units of measurements different than µg/L and that have no conversion factor. </li><li>Convert all relevant chlorophyll a values to mg/L and flag values where there is no direct path for unit conversion Table 1.</li><li>Flag values outside of the range of values that have been observed in surface water samples across the continental United States (0– 11,000 µg/L)(USEPA, 2022).</li><li>Review and flag samples identified in the WQP with sample processing issues (e.g., suspected contamination, exceeding sampling hold time, no reported value, below reporting value).</li></ul><div style="text-align:center;"><img alt="Unit conversion to mg/L for measured chlorophyll A." src="https://lh3.googleusercontent.com/pw/AP1GczMOwz4jqBUkDURom7xq07znu-lYzJlVqY92frLSaDzTmHEesjVnhyIhIwocflWM1Oc4Y4oOGSpn4tqxMNzQSDT2g-LPnXcslvOpU3NUpBaE-WOpCZzgznfhsJs5S1zeBJ8CRnF3G6gpo_t5ZseWQ-lfEQ=w884-h348-s-no-gm?authuser=0" /></div></div></div><div style="text-align:center;">Table 1. Unit conversion to mg/L for measured chlorophyll a samples.</div><div style="text-align:center;"><br /></div><div style="text-align:left;"><div>Examples of errors found include negative chlorophyll a values, units of measurements not consistent with chlorophyll a measurements (Table 1), and values well above known chlorophyll a ranges in freshwater systems. Users should verify the data from the original sources before drawing site specific conclusions. Individual contributing organizations can still be found in the final and original datasets if the end user would like to filter for only specific sampling partners.</div><div><br /></div><div>The resulting dataset is presented as summarized collection information for each unique sampling location and the original data flagging process helps to exclude unreliable and errant values from the final statistics. The data set is set to be updated on an annual basis to account for sample additions and updates continually being added to the WQP. The R code developed to perform the QA/QC steps are available from <a href="mailto:cormier.susan@epa.gov" target="_blank">cormier.susan@epa.gov</a></div><div><br /></div><div><br /></div></div><div><div><b>Terms of Use</b></div><div><b><br /></b></div><div><b>Freshwater Explorer Data Disclaimer</b></div><div><br /></div><div>This data is intended for exploratory and discussion purposes. Although statutory provisions and U.S. Environmental Protection Agency (EPA) regulations contain legally binding requirements, these data and related information are not regulatory, nor do they change or substitute for any provisions or regulations. The information does not substitute for the Clean Water Act, a National Pollutant Discharge Elimination System permit, or EPA or state regulations applicable to permits; nor is this material a permit or regulation itself. Thus, it does not impose legally binding requirements on EPA, states, tribes, or the regulatory community. This information does not confer legal rights or impose legal obligations on any member of the public. Mention of any trade names, products, or services is not and should not be interpreted as conveying official EPA approval, endorsement, or recommendation.</div><div><br /></div><div>While EPA has used its best efforts to include complete and accurate information in this system, EPA cannot be held responsible for errors or omissions and is not liable for any direct, indirect, or consequential damages resulting from using this secondary information. Some potential sources of error have been assessed by the U.S. EPA resulting in the removal of some samples from the original data sets. However, all sources of potential error cannot be eliminated from the measured data reported in the Freshwater Explorer or the data used to develop predictive models. Therefore, the U.S. EPA cannot fully ensure either the original data or the values calculated from them. Conclusions and assessments drawn from the use of the Freshwater Explorer are the responsibility of the user.</div><div><br /></div><div>Please check sources, scale, accuracy, dates, and other available information. Please confirm that you are using the most recent copy of both data and metadata. Reliance on the information contained in this system by any party cannot be used as a defense in any administrative or judicial proceeding.</div><div><br /></div><div>This dataset may be revised periodically. EPA can revise this dataset without public notice to reflect changes in EPA policy, guidance, and advancements in the field of biological assessments. EPA welcomes public input on this document at any time. Send comments to FreshwaterExplorer@epa.gov, Center for Environmental Measurement and Modeling, Office of Research and Development, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr, Cincinnati, OH 45268.</div></div><div><br /></div><div><div><b>Preferred citation:</b> Leppo, E., Wharton, C., and Cormier. S. 2024. U.S. EPA Freshwater Explorer v2 national measured dissolved calcium metadata and dataset. USEPA. <a href="https://arcg.is/0OuDn80" target="_blank">https://arcg.is/0OuDn80</a></div><div><br /></div><div><b>References</b></div><div>Arar, E. J. Method 446.0: In Vitro Determination of Chlorophylls a, b, c + c and Pheopigments in 1 2Marine And Freshwater Algae by Visible Spectrophotometry. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-15/005, 1997. <a href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=309415&Lab=NERL" target="_blank">https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=309415&Lab=NERL</a></div><div><br /></div><div>Arar, E. J. and G. B. COLLINS. Method 445.0 In Vitro Determination of Chlorophyll a and Pheophytin a in Marine and Freshwater Algae by Fluorescence. U.S. Environmental Protection Agency, Washington, DC, 1997. <a href="https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=309417" target="_blank">https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=309417</a></div><div><br /></div><div>USEPA. 2024. National Aquatic Resource Surveys. Indicators: Chlorophyll a. <a href="https://www.epa.gov/national-aquatic-resource-surveys/indicators-chlorophyll" target="_blank">https://www.epa.gov/national-aquatic-resource-surveys/indicators-chlorophyll</a>.</div><div><br /></div><div>USEPA. 2022. National Rivers and Streams Assessment 2023 - 2024: Laboratory Operations Manual. EPA841-B-22-008. U.S. Environmental Protection Agency, Office of Water, Washington, DC. <a href="https://www.epa.gov/system/files/documents/2023-06/NRSA2324_LOM_v1.0.pdf" target="_blank">https://www.epa.gov/system/files/documents/2023-06/NRSA2324_LOM_v1.0.pdf</a></div></div>
Copyright Text: Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021. https://doi.org/10.5066/P9QRKUVJ.
Description: <div><div><b>Description:</b> National Measured Dissolved Chloride Data derived from data stored in the U.S. EPA Water Quality Portal.</div><div><b>Data Date Range:</b> 01/2000 – 12/2023</div><div><b>Acquisition Date:</b> 1/25/2024</div><div><b>Query Links: </b><a href="https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Chloride&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET" target="_blank">https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Chloride&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET</a></div><div><b>Min. Value:</b> -1.05</div><div><b>Max. Value:</b> 2360000</div><div><b>Units in Source/Original Dataset:</b> <Null>, %, % recovery, count, mg/kg, mg/l, mg/L, mg/l CaCO3**, mg/m2, mmol/L, None, NTU, ueq/L, ppm, umol, umol/L, ug/L, ug/l</div></div><div><br /></div><div><div><b>Background</b></div><div>Dissolved chloride in freshwater refers to chloride ions (Cl⁻) that are present in a dissolved state within water bodies such as rivers, lakes, and streams (<a href="https://www.epa.gov/sites/default/files/2018-08/documents/chloride-aquatic-life-criteria-1988.pdf" target="_blank">USEPA 1988</a>). Chloride is a common anion (Cl⁻) found in various salts of sodium, calcium, magnesium, and potasium (<a href="https://stormwater.pca.state.mn.us/index.php/How_salt_works_and_overview_of_deicing_chemicals" target="_blank">MPCA 2022</a>). In freshwater environments, chloride can come from a variety of sources (<a href="https://www.nature.com/articles/sdata2017101" target="_blank">Dugan et al. 2017</a>), including but not limited to:</div></div><div><ul><li>Natural Sources:</li><ul><li>Weathering of rocks and minerals.</li><li>Sea spray in coastal areas.</li><li>Volcanic activity.</li></ul><li>Anthropogenic Sources:</li><ul><li>Road de-icing salts </li><li>Agricultural runoff containing fertilizers.</li><li>Wastewater </li><li>Industrial processes and effluents.</li><li>Coal combustion</li></ul></ul></div><div>High levels of chloride can alter buffering of water resources, increase transport and bioavailability of metals, increase corrosion, and harm aquatic life (<a href="https://www.nature.com/articles/sdata2017101" target="_blank">Dugan et al. 2017</a>; <a href="https://pubs.acs.org/doi/pdf/10.1021/acs.est.8b04709" target="_blank">Pieper, et al. 2018</a>).<br /></div><div><br /></div><div>Disolved chloride in freshwater can be measured using various methods such as: ion chromatography (<a href="https://www.epa.gov/sites/default/files/2015-06/documents/epa-300.1.pdf" target="_blank">USEPA 300.1</a>); automatic titration (<a href="https://cdn.standards.iteh.ai/samples/81377/c6541ded1cf14db9833072aa784a65aa/ASTM-D512-12.pdf" target="_blank">ASTM D512-12</a>), and electrochemical sensors (<a href="https://www.epa.gov/hw-sw846/sw-846-test-method-9212-potentiometric-determination-chloride-aqueous-samples-ion" target="_blank">USEPA 1996-EPA SW-846 Test Method 9212</a>). Our Quality Assurance/Quality Control (QA/QC) procedures as well as the contributor’s laboratory processing and reporting procedures were used to summarize reported values. The WQP portal original dataset contains annotations for each sample to help understand the reliability of flagged values in the dataset.<br /></div><div><br /></div><div><div><b>Dataset</b></div><div>This dataset focuses primarily on samples reported as dissolved chloride anions. Unit conversions were normalized to mg/l as listed in <b>Table 1.</b> </div><div><br /></div><div>This dataset is a collection surface water dissolved chloride samples collected across the United States from 2000-2023 from the Water Quality Portal (WQP), which integrates publicly available water quality data from the USGS National Water Information System (NWIS) and the EPA Water Quality Exchange (WQX) Data Warehouse. These water quality data records are provided by many federal, state, and tribal organizations and other partners. Because these data are from secondary sources, the U.S. EPA cannot ensure that the information is accurate, current, or complete. Therefore, users should verify the data from the original sources before drawing site specific conclusions.</div></div><div><br /></div><div><div><b>Quality Assurance/Quality Control (QA/QC) and Identified Issues</b></div><div>An automated Quality Assurance/Quality Control (QA/QC) protocol was developed using a mix of Python and R-scripts to remove or identify potentially erroneous values (outliers) in WQP final value, reporting units, and sample lab notes. The quality of the WQP measured data was evaluated as follows.</div></div><div><div><ul><li>Generally – do not delete data. Add a screening/flagging column to keep track of decision-making to remove records/observations.</li><li>Review the geographic/temporal scope and data types of the acquired data to the project objectives—it might not be necessary to process all data from a given data set. Map stations in a GIS to further refine and select data based on analysis selection criteria: geographic area, watersheds, bounding box, waterbody type, etc. This also provides the opportunity to conduct quality assurance checks based on spatial location (e.g., are the “estuarine” sites located near the coast).</li><li>Flag values reported with units of measurements different than mg/L that have no conversion factor.</li><li>Convert all relevant dissolved chloride values to mg/L or flag values where there is no direct path for unit conversion Table 1.</li><li>Flag values outside of the known maximum and minimum (0 – 19000) ranges of dissolved chloride in freshwater systems (USEPA, 2022).</li><li>Review and flag samples identified in the WQP with sample processing issues (e.g., suspected contamination, exceeding sampling hold time) that don’t meet the requirements or thresholds of end use.</li><li>Flag samples based on the WAP’s Result Status Identifier denoting the sample was rejected based on WQP internal QA/QC processing of the data.</li><li>Check for flagged values in the ResultStatusIdentifier column by the Water Quality Portal that should not be used.</li><li>Summary statistics – Calculate basic statistics (mean, median, standard deviation, range, last measurement, maximum, minimum).</li></ul>Review and flag samples identified in the WQP with sample processing issues (e.g., suspected contamination, exceeding sampling hold time, no reported value, below reporting value). Many of the samples that met these criteria were already found and identified by WQP QA/QC data process.<br /></div></div><div style="text-align:center;"><br /></div><div style="text-align:center;"><img alt="Table 1. Unit conversion to mg/L for measured dissolved chloride samples." src="https://lh3.googleusercontent.com/pw/AP1GczNNsJ7LL1pA53YsJoAqW9loowEc1vtvieMcN60WRQXrL0GQQfCLwdmlTh1fGLbFFcVVIp61fQHhQ86jG9mE_FfRVuCa4LX3EvVbhp1Pq0fLiWt8i3GF22TvQm33YTkbZPS7CyWZ9TDfqTOEqPlgjTo9og=w728-h528-s-no-gm?authuser=0" /><br /></div><div style="text-align:center;">Table 1. Unit conversion to mg/L for measured dissolved chloride samples.<br /></div><div style="text-align:center;"><br /></div><div style="text-align:left;"><div>Examples of errors found include negative chloride values, units of measurements not consistent with chloride measurements (e.g., <Null>, %, % recovery, count, mg/kg, mg/l, mg/L, mg/l CaCO3**, mg/m2, mmol/L, None, NTU, ueq/L, ppm, umol, umol/L, ug/L, ug/l) <b>Table 1</b>, and values well above known dissolved chloride ranges in freshwater systems (<19,000 mg/L) (USEPA, 2022). Users should verify the data from the original sources before drawing site specific conclusions. Individual contributing organizations can still be found in the final and original datasets if the end user would like to filter for only specific sampling partners.</div><div><br /></div><div>The resulting dataset is presented as summarized collection of information for each unique sampling location and the original data flagging process helps to exclude unreliable and errant values from the final statistics. The R code developed to perform the QA/QC steps are available from <a href="mailto:cormier.susan@epa.gov" target="_blank">cormier.susan@epa.gov</a></div><div><br /></div><div><br /></div><div><div><b>Terms of Use</b></div><div><b><br /></b></div><div><b>Freshwater Explorer Data Disclaimer</b></div><div>This data is intended for exploratory and discussion purposes. Although statutory provisions and U.S. Environmental Protection Agency (EPA) regulations contain legally binding requirements, these data and related information are not regulatory, nor do they change or substitute for any provisions or regulations. The information does not substitute for the Clean Water Act, a National Pollutant Discharge Elimination System permit, or EPA or state regulations applicable to permits; nor is this material a permit or regulation itself. Thus, it does not impose legally binding requirements on EPA, states, tribes, or the regulatory community. This information does not confer legal rights or impose legal obligations on any member of the public. Mention of any trade names, products, or services is not and should not be interpreted as conveying official EPA approval, endorsement, or recommendation.</div><div><br /></div><div>While EPA has used its best efforts to include complete and accurate information in this system, EPA cannot be held responsible for errors or omissions and is not liable for any direct, indirect, or consequential damages resulting from using this secondary information. Some potential sources of error have been assessed by the U.S. EPA resulting in the removal of some samples from the original data sets. However, all sources of potential error cannot be eliminated from the measured data reported in the Freshwater Explorer or the data used to develop predictive models. Therefore, the U.S. EPA cannot fully ensure either the original data or the values calculated from them. Conclusions and assessments drawn from the use of the Freshwater Explorer are the responsibility of the user.</div><div><br /></div><div>Please check sources, scale, accuracy, dates, and other available information. Please confirm that you are using the most recent copy of both data and metadata. Reliance on the information contained in this system by any party cannot be used as a defense in any administrative or judicial proceeding.</div><div><br /></div><div>This dataset may be revised periodically. EPA can revise this dataset without public notice to reflect changes in EPA policy, guidance, and advancements in the field of biological assessments. EPA welcomes public input on this document at any time. Send comments to FreshwaterExplorer@epa.gov, Center for Environmental Measurement and Modeling, Office of Research and Development, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr, Cincinnati, OH 45268.</div></div><div><br /></div><div><b>Preferred citation:</b> Leppo, E., Wharton, C., and Cormier. S. 2024. U.S. EPA Freshwater Explorer v2 national measured dissolved calcium metadata and dataset. USEPA. <a href="https://arcg.is/0OuDn80" target="_blank">https://arcg.is/0OuDn80</a><br /></div><div><br /></div><div><div><b>Original data sources: </b></div><div>USEPA. 2023. Source data set for National Measured Dissolved Chloride Data derived from data stored in the U.S. EPA Water Quality Portal. Accessible at: <a href="https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Chloride&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET" target="_blank">https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Chloride&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET</a></div></div><div><br /></div><div><div>References</div><div>ASTM. Draft Standard Test Methods for Chloride Ion in Water. D512 – 12. <a href="https://cdn.standards.iteh.ai/samples/81377/c6541ded1cf14db9833072aa784a65aa/ASTM-D512-12.pdf" target="_blank">https://cdn.standards.iteh.ai/samples/81377/c6541ded1cf14db9833072aa784a65aa/ASTM-D512-12.pdf</a>.</div><div><br /></div><div>Dugan, H.A., Summers, J.C., Skaff, N.K., Krivak-Tetley, F.E., Doubek, J.P., Burke, S.M., Bartlett, S.L., Arvola, L., Jarjanazi, H., Korponai, J. and Kleeberg, A., 2017. Long-term chloride concentrations in North American and European freshwater lakes. Scientific Data, 4(1), pp.1-11. <a href="https://www.nature.com/articles/sdata2017101" target="_blank">https://www.nature.com/articles/sdata2017101</a>.</div><div><br /></div><div>MPCA. 2024. Minnesota Stormwater Manual website. How salt works and overview of deicing chemicals. Level 2 - Pollutants/ChlorideLevel 2 - Management/Winter management. <a href="https://stormwater.pca.state.mn.us/index.php/How_salt_works_and_overview_of_deicing_chemicals" target="_blank">https://stormwater.pca.state.mn.us/index.php/How_salt_works_and_overview_of_deicing_chemicals</a>.</div><div><br /></div><div>Pieper, K.J., Tang, M., Jones, C.N., Weiss, S., Greene, A., Mohsin, H., Parks, J. and Edwards, M.A., 2018. Impact of road salt on drinking water quality and infrastructure corrosion in private wells. Environmental science & technology, 52(24), pp.14078-14087. <a href="https://pubs.acs.org/doi/pdf/10.1021/acs.est.8b04709" target="_blank">https://pubs.acs.org/doi/pdf/10.1021/acs.est.8b04709</a></div><div><br /></div><div>USEPA. 1988. Ambient Water Quality Criteria for Chloride-1988. Office of Water. EPA 44015-88-001. <a href="https://www.epa.gov/sites/default/files/2018-08/documents/chloride-aquatic-life-criteria-1988.pdf" target="_blank">https://www.epa.gov/sites/default/files/2018-08/documents/chloride-aquatic-life-criteria-1988.pdf</a></div><div><br /></div><div>USEPA. 1999. Pfaff, J., and Hautman, D. Method 300.1: Determination of inorganic anions in drinking water by ion. Revision 1.0. Office of Research and Development. <a href="https://www.epa.gov/sites/default/files/2015-06/documents/epa-300.1.pdf" target="_blank">https://www.epa.gov/sites/default/files/2015-06/documents/epa-300.1.pdf</a>.</div><div><br /></div><div>USEPA. 1996. SW-846 Test Method 9212: Potentiometric Determination of Chloride in Aqueous Samples with Ion-Selective Electrode, Part of Test Methods for Evaluating Solid Waste, Physical/Chemical Methods (pdf). <a href="https://www.epa.gov/sites/default/files/2015-12/documents/9212.pdf" target="_blank">https://www.epa.gov/sites/default/files/2015-12/documents/9212.pdf</a>.</div><div><br /></div><div>USEPA. 2022. National Rivers and Streams Assessment 2023 - 2024: Laboratory Operations Manual. EPA841-B-22-008. U.S. Environmental Protection Agency, Office of Water, Washington, DC. <a href="https://www.epa.gov/system/files/documents/2023-06/NRSA2324_LOM_v1.0.pdf" target="_blank">https://www.epa.gov/system/files/documents/2023-06/NRSA2324_LOM_v1.0.pdf</a></div></div><div><br /></div></div>
Copyright Text: Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021. https://doi.org/10.5066/P9QRKUVJ.
National Water Quality Monitoring Council, 2024, Water Quality Portal, accessed 01, 25, 2024, https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Chloride&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET, https://doi.org/10.5066/P9QRKUVJ.
Description: <div><div><b>Description:</b> National Measured Dissolved Organic Carbon Data derived from data stored in the U.S. EPA Water Quality Portal.</div><div><b>Data Date Range:</b> 01/2000 – 12/2023</div><div><b>Acquisition Date:</b> 1/16/2024</div><div><b>Query Links:</b> <a href="https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Organic%20carbon&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=tsv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET" target="_blank">https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Organic%20carbon&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=tsv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET</a></div><div><b>Min. Value:</b> -2.21</div><div><b>Max. Value:</b> 340000</div><div><b>Units in Dataset:</b> <Null>, %, g/kg, mg/kg, mg/l, mg/L, None, ug/L, ppm, ug/l, umol/L, umol, ug/mL</div></div><div><br /></div><div><div><b>Background</b></div><div>For a review, see Vogt et al 2023.</div><div><br /></div><div>Dissolved organic carbon (DOC) consists of a complex mixture of organic molecules derived from both terrestrial and aquatic sources, and anthropogenic sources. including decomposed plant and animal matter, as well as microbial byproducts (Vogt, et al. 2023, Thurman, 1985). In freshwater systems, DOC concentrations can vary widely, typically ranging from less than 1 mg/L in oligotrophic waters to over 50 mg/L in highly organic-rich environments like wetlands and peatlands (Mulholland, 2003).</div><div><br /></div><div>DOC acts as a major energy source for heterotrophic microorganisms, fueling microbial food webs and influencing overall ecosystem productivity (Cole et al., 2006). Additionally, DOC affects water quality by altering light penetration, influencing thermal stratification, and complexing with metals and other pollutants (Williamson et al., 1999). These properties can have cascading effects on aquatic organisms and ecosystem processes.</div><div><br /></div><div>Photochemical reactions induced by sunlight can break down DOC molecules, releasing nutrients and altering their bioavailability (Moran and Zepp, 1997). Microbial degradation further transforms DOC, releasing carbon dioxide and contributing to greenhouse gas emissions from freshwater ecosystems (Tranvik et al., 2009). </div><div><br /></div><div>Dissolved Organic Carbon in freshwater is typically measured by UV promoted persulfate oxidation to CO2 with infrared detection (APHA 5310-C, EPA 415.3). Walter is filtered through a 0.45 μm nominal pore size filter. The organic carbon is oxidized to form carbon dioxide (CO2 by one of two approaches: (a) combustion in an oxidizing gas and (b) UV promoted or heat catalyzed chemical oxidation with a persulfate solution. CO2 is then detected by a conductivity detector or by a nondispersive infrared (NDIR) detector.</div><div><br /></div><div>Quality Assurance/Quality Control (QA/QC) procedures were used to summarize reported values as well as the laboratory processing and reporting that were used by the contributor. The WQP portal original dataset contains annotations for each sample to help understand the reliability and pedigree of the final reported values in the dataset.</div></div><div><br /></div><div><div><b>Dataset</b></div><div>This dataset is a collection of dissolved organic carbon samples collected across the United States from 2000-2023 from the Water Quality Portal (WQP), which integrates publicly available water quality data from the USGS National Water Information System (NWIS) and the EPA Water Quality Exchange (WQX) Data Warehouse. These water quality data records are provided by many federal, state and tribal organizations and other partners. Because these data are from secondary sources , the U.S. EPA cannot ensure that the information is accurate, current, or complete. Therefore, users should verify the data from the original sources before drawing site specific conclusions.</div></div><div><br /></div><div><div><b>Quality Assurance/Quality Control (QA/QC) and Identified Issues</b></div><div>An automated Quality Assurance/Quality Control (QA/QC) protocol was developed using a mix of Python and R-scripts to remove or identify potentially erroneous values (outliers) in WQP. The quality of the measured data was evaluated as follows. </div></div><div><div><ul><li>Generally – do not delete data. Add a screening/flagging column to keep track of decision-making to remove records/observations.</li><li>Review the geographic/temporal scope and data types of the acquired data to the project objectives—it might not be necessary to process all data from a given data set. Map stations in a GIS to further refine and select data based on analysis selection criteria: geographic area, watersheds, bounding box, waterbody type, etc. This also provides the opportunity to conduct quality assurance checks based on spatial location (e.g., are the “estuarine” sites located near the coast).</li><li>Flag values reported with units of measurements different than mg/L.</li><li>Convert all relevant DOC values to mg/L. See conversion Table 1 below.</li><li>Flag values outside of the known maximum and minimum ranges of DOC in freshwater systems (0- 109mg/L). This range falls well beyond the natural range of DOC values observed in freshwater systems but accounts for areas of high anthropogenic input (USEPA, 2022).</li><li>Review and flag samples identified in the WQP with sample processing issues (e.g., suspected contamination, exceeding sampling hold time, no reported value, below reporting value). Many of the samples that met these criteria were already found and identified by WQP QA/QC data process.Parse/filter out various measurement compositions (Total vs Dissolved) for summarization to use only data denoted as Dissolved.</li><li>Summary statistics – Calculate basic statistics (mean, median, standard deviation, range, last measurement, maximum, minimum).</li></ul></div></div><div style="text-align:center;"><img alt="Table 1. Unit conversion to mg/L for measured dissolved organic carbon samples." src="https://lh3.googleusercontent.com/pw/AP1GczOppBWcFuzsGCe6vcI0y41cXVaR_eNB16YEwwtDy2GGMlMSH2rjd89yfyfc4OGu8FVj8stDJF8VDcX3b5LQZ2IO3MqnIXuPOBgbeGvB2nJi-tKgMNkQndjRqe3nr6KSID9-4cKg8FB9wncpGe9Qxqs89g=w770-h419-s-no-gm?authuser=0" /><br /></div><div style="text-align:center;"><i>Table 1. Unit conversion to mg/L for measured dissolved organic carbon samples.</i></div><div><br /></div><div><div>Examples of errors found include negative DOC values, units of measurements not consistent with DOC measurements (e.g., <Null>, g/kg, %, ppm) and entries as µg/L but reported as mg/L and vice versa. Users should verify the data from the original sources before drawing site specific conclusions. Individual contributing organizations can still be found in the final and original datasets if the end user would like to filter for only specific sampling partners.</div><div><br /></div><div>The resulting dataset is presented as summarized collection information for each unique sampling location and the original data flagging process helps to exclude unreliable and errant values from the final statistics, but errors in the dataset may still exist. Please refer to the original dataset before drawing final conclusions on site specific information. The R code developed to perform the QA/QC steps are available from <a href="mailto:cormier.susan@epa.gov" target="_blank">cormier.susan@epa.gov</a>.</div></div><div><br /></div><div><br /></div><div><div><b>Terms of Use</b></div><div><br /></div><div><b>Freshwater Explorer Data Disclaimer</b></div><div>This data is intended for exploratory and discussion purposes. Although statutory provisions and U.S. Environmental Protection Agency (EPA) regulations contain legally binding requirements, these data and related information are not regulatory, nor do they change or substitute for any provisions or regulations. The information does not substitute for the Clean Water Act, a National Pollutant Discharge Elimination System permit, or EPA or state regulations applicable to permits; nor is this material a permit or regulation itself. Thus, it does not impose legally binding requirements on EPA, states, tribes, or the regulatory community. This information does not confer legal rights or impose legal obligations on any member of the public. Mention of any trade names, products, or services is not and should not be interpreted as conveying official EPA approval, endorsement, or recommendation.</div><div><br /></div><div>While EPA has used its best efforts to include complete and accurate information in this system, EPA cannot be held responsible for errors or omissions and is not liable for any direct, indirect, or consequential damages resulting from using this secondary information. Some potential sources of error have been assessed by the U.S. EPA resulting in the removal of some samples from the original data sets. However, all sources of potential error cannot be eliminated from the measured data reported in the Freshwater Explorer or the data used to develop predictive models. Therefore, the U.S. EPA cannot fully ensure either the original data or the values calculated from them. Conclusions and assessments drawn from the use of the Freshwater Explorer are the responsibility of the user.</div><div><br /></div><div>Please check sources, scale, accuracy, dates, and other available information. Please confirm that you are using the most recent copy of both data and metadata. Reliance on the information contained in this system by any party cannot be used as a defense in any administrative or judicial proceeding.</div><div><br /></div><div>This dataset may be revised periodically. EPA can revise this dataset without public notice to reflect changes in EPA policy, guidance, and advancements in the field of biological assessments. EPA welcomes public input on this document at any time. Send comments to FreshwaterExplorer@epa.gov, National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr, Cincinnati, OH 45268.</div></div><div><br /></div><div><b>Preferred citation:</b> Leppo, E., Wharton, C., and Cormier. S. 2024. U.S. EPA Freshwater Explorer v2 national measured dissolved calcium metadata and dataset. USEPA. <a href="https://arcg.is/0OuDn80" target="_blank">https://arcg.is/0OuDn80</a><br /></div><div><br /></div><div><div><b>References</b></div><div>Cole, J.J., et al. (2006). Plumbing the global carbon cycle: integrating inland waters into the terrestrial carbon budget. Ecosystems, 9(1), 172-185.</div><div><br /></div><div>Moran, M.A., and Zepp, R.G. (1997). Role of photoreactions in the formation of biologically labile compounds from dissolved organic matter. Limnology and Oceanography, 42(6), 1307-1316.</div><div><br /></div><div>Mulholland, P.J. (2003). Large-scale patterns in dissolved organic carbon concentration, flux, and sources. Aquatic Ecosystems: Interactivity of Dissolved Organic Matter, 139-159. </div><div><br /></div><div>Potter, B B. and J. C. Wimsatt. 2005METHOD 415.3 - Measurement of total organic carbon, dissolved organic carbon and specific uv absorbance at 254 nm in source water and drinking water. U.S. Environmental Protection Agency, Washington, DC, 2005.</div><div><br /></div><div>Thurman, E.M. (1985). Organic geochemistry of natural waters. Springer Science & Business Media.</div><div><br /></div><div>Tranvik, L.J., et al. (2009). Lakes and reservoirs as regulators of carbon cycling and climate. Limnology and Oceanography, 54(6part2), 2298-2314.</div><div><br /></div><div>USEPA. 2022. National Rivers and Streams Assessment 2023 - 2024: Laboratory Operations Manual. EPA841-B-22-008. U.S. Environmental Protection Agency, Office of Water, Washington, DC. <a href="https://www.epa.gov/system/files/documents/2023-06/NRSA2324_LOM_v1.0.pdf" target="_blank">https://www.epa.gov/system/files/documents/2023-06/NRSA2324_LOM_v1.0.pdf</a></div><div><br /></div><div>Vogt, R.D., Porcal, P., Hejzlar, J., Paule-Mercado, M.C., Haaland, S., Gundersen, C.B., Orderud, G.I. and Eikebrokk, B., 2023. Distinguishing between sources of natural dissolved organic matter (DOM) based on its characteristics. Water, 15(16), p.3006.</div><div><br /></div><div>Williamson, C.E., et al. (1999). Dissolved organic carbon and nutrients as regulators of lake ecosystems: Resurrection of a more integrated paradigm. Limnology and Oceanography, 44(3part2), 795-803.</div></div><div><br /></div>
Copyright Text: Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021. https://doi.org/10.5066/P9QRKUVJ.
National Water Quality Monitoring Council, 2024, Water Quality Portal, accessed 02, 01, 2024, https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Organic%20carbon&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=tsv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET, https://doi.org/10.5066/P9QRKUVJ.
Description: <div><p><b><span style="font-size:12.0pt; line-height:107%;">Data Date
Range:</span></b><span style="font-size:12pt; line-height:107%;"> 01/2000 –
12/2023</span><br /></p>
<p><b><span style="font-size:12.0pt; line-height:107%;">Acquisition
Date:</span></b><span style="font-size:12.0pt; line-height:107%;"> 1/25/2024</span></p>
<p><b><span style="font-size:12.0pt; line-height:107%;">Query
Links</span></b><span style="font-size:12.0pt; line-height:107%;">: https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=pH&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STORET</span></p>
<p><b><span style="font-size:12.0pt; line-height:107%;">Min.
Value:</span></b><span style="font-size:12.0pt; line-height:107%;"> -2689.41</span></p>
<p><b><span style="font-size:12.0pt; line-height:107%;">Max.
Value:</span></b><span style="font-size:12.0pt; line-height:107%;"> 9999999</span></p>
<p><b><span style="font-size:12.0pt; line-height:107%;">Units in
Source/Original Dataset:</span></b><span style="font-size:12.0pt; line-height:107%;"> <Null>, ADMI value, #/100 gal, #/L, %, 0/00, count, days, deg C,
ft, in, kgal, m, mg/L, Molar, Mole/L, mS/cm, mV, ng, None, Normal, NTU, nu, std
units, ug/L, units/cm, uS/cm</span></p>
<p><b><span style="font-size:12.0pt; line-height:107%;">Background</span></b></p><p><span style="font-size:16px;">Hydrogen ions [H+] and bases like hydroxyl ions [OH-] measured as pH are naturally present in freshwater, but in excess they are harmful to aquatic life and other beneficial uses. For a review see USEPA (2024). </span></p><p><span style="line-height:107%; font-size:16px;"></span></p><p><span style="font-size:16px;">In freshwater environments, the pH regime for a waterbody can arise from natural and anthropogenic influences including but not limited to: </span></p>
<p style="margin-bottom:0in; background-image:initial; background-position:initial; background-size:initial; background-repeat:initial; background-attachment:initial; background-origin:initial; background-clip:initial;"><b><span style="font-size:12.0pt; line-height:107%; color:#1B1B1B;">Natural Sources</span></b></p><p style="margin-bottom:0in; background-image:initial; background-position:initial; background-size:initial; background-repeat:initial; background-attachment:initial; background-origin:initial; background-clip:initial;"></p><ul><li><span style="font-size:12pt;">Groundwater
from peatlands (low pH)</span></li><li><span style="font-size:12pt;">Blackwater
systems with high organic matter (low pH)</span></li><li><span style="font-size:12pt; line-height:107%;">Organic acids
(e.g., tannic acid from leaf decay)</span><span style="font-size:12pt; line-height:107%; color:black;"> (low pH)</span></li><li><span style="font-size:12pt;">Photosynthesis
reducing CO</span><sub>2</sub><span style="font-size:12pt;"> (high pH)</span></li><li><span style="color:black; font-size:12pt;">naturally occurring
geology and minerals (high or low pH)</span></li></ul><p></p>
<p style="margin-bottom:0in; background-image:initial; background-position:initial; background-size:initial; background-repeat:initial; background-attachment:initial; background-origin:initial; background-clip:initial;"><b><span style="font-size:12.0pt; line-height:107%; color:#1B1B1B;">Anthropogenic Sources</span></b></p>
<ul>
<li><span style="font-size:12.0pt; line-height:107%;">Mining and
waste piles</span></li>
<li><span style="font-size:12.0pt; line-height:107%;">Power plants and other sources of acidic gases</span></li>
<li><span style="font-size:12.0pt; line-height:107%;">Industrial effluents</span></li>
<li><span style="font-size:12.0pt; line-height:107%;">Landfill leachate</span></li>
<li><span style="font-size:12.0pt;">Confined animal feeding operations, dairy runoff</span></li>
<li><span style="font-size:12.0pt; line-height:107%;">Instream
oxidation or reduction processes</span></li>
<li><span style="font-size:12.0pt; line-height:107%;">Recent draining
of naturally inundated wetlands or floodplains</span></li>
</ul>
<p style="margin-bottom:0in;"><span style="font-size:12.0pt; line-height:107%;"> </span><span style="font-size:12pt;">Although living organisms occur over a wide range of pH
conditions, most thrive in circumneutral pH, between 6.5 and 8.5. Direct effects are associated with the
inability to maintain internal pH homeostasis.
Indirectly, low pH, i.e., <6 SU, dissolves metals that are toxic.</span></p>
<p><span style="font-size:12.0pt; line-height:107%;">The pH in
freshwater is typically measured using methods such as electronic and portable
pH meters, pH test strips, chemical test kits, and digital colorimeters. Although vales values greater than 14 and less
than 0 are possible but were constrained to the 0-14 range for this dataset.</span></p>
<p><b><span style="font-size:12.0pt; line-height:107%;">Dataset</span></b></p>
<p><span style="font-size:12.0pt; line-height:107%;">This dataset
focuses primarily on samples reported as pH reported as standard unis without
any conversion to the original data (<b>Table 1</b>). </span></p>
<p><span style="font-size:12.0pt; line-height:107%;">This dataset
is a collection surface water pH samples collected across the United States
from 2000-2023 from the Water Quality Portal (WQP), which integrates publicly
available water quality data from the USGS National Water Information System
(NWIS) and the EPA Water Quality Exchange (WQX) Data Warehouse. These water
quality data records are provided by many federal, state and tribal
organizations and other partners. Because these data are from secondary
sources, the U.S. EPA cannot ensure that the information is accurate, current
or complete. Therefore, users should verify the data from the original sources
before drawing site specific conclusions. </span></p>
<p><b><span style="font-size:12.0pt; line-height:107%;">Quality
Assurance/Quality Control (QA/QC) and identified issues</span></b></p>
<p><span style="font-size:12.0pt; line-height:107%;">An automated
Quality Assurance/Quality Control (QA/QC) protocol was developed using a mix of
Python and R-scripts to remove or identify potentially erroneous values
(outliers) in WQP. The quality of the WQP measured data was evaluated as
follows.</span></p><p></p><ul><li><span style="font-size:16px;">Generally – do not delete data. Add a screening/flagging column to keep track of decision-making to remove records/observations.</span></li><li><span style="font-size:16px;">Review the geographic/temporal scope and data types of the acquired data to the project objectives—it might not be necessary to process all data from a given data set. Map stations in a GIS to further refine and select data based on analysis selection criteria: geographic area, watersheds, bounding box, waterbody type, etc. This also provides the opportunity to conduct quality assurance checks based on spatial location (e.g., are the “estuarine” sites located near the coast).</span></li><li><span style="font-size:16px;">Check for missing values – Identify and flag entries with missing pH values.</span></li><li><span style="font-size:16px;">Check for outliers – Detect potential outliers that deviate from expected pH ranges (pH typically ranges from 0 to 14).</span></li><li><span style="font-size:16px;">Check for incorrect units in the <i>ResultMeasure/MeasureUnitCode</i> variable and flag entries where the unit is different than International System of Units (SI) (<b>Table 1</b>).</span></li><li><span style="font-size:16px;">Check for flagged values in the <i>ResultStatusIdentifier</i> column by the Water Quality Portal that should not be used.</span></li><li><span style="font-size:16px;">Review and flag samples identified in the WQP with sample processing issues (e.g., suspected contamination, exceeding sampling hold time, no reported value, below reporting value). Many of the samples that met these criteria were already found and identified by WQP QA/QC data process.</span></li><li><span style="font-size:16px;">Summary statistics – Calculate basic statistics (mean, median, standard deviation, range, last measurement, maximum, minimum).</span></li><li><span style="font-size:16px;">Visualize data – Plot the distribution of the pH data (boxplot, histogram).</span></li><li><span style="font-size:16px;">Flag invalid entries – Flag entries that fall outside a typical pH range (for example, less than 0 or greater than 14).</span></li></ul><span style="font-size:16px;"><br /></span></div><div><div><div style="text-align:center;"><img alt="Figure 1. Unit conversion to SI for measured pH samples." src="https://lh3.googleusercontent.com/pw/AP1GczPuOnJy9dicT5ZmirqR_lLSJeJqc6wb5nXONrBOImG_wbqtPQpwOJH-pIt2cFMUO2d2JCVetcsfU24_1OCmgpnKN0ap0gC3jxxLUT8E-95CW4susDkeyRUwZtaBaNkcYf_CqD_FM_AlrM1filw33J1zkg=w624-h608-s-no-gm?authuser=0" /></div></div></div><div><p style="text-align:center;"><i><b><span style="font-size:12.0pt;">Table </span><span style="font-size:12.0pt;"><span style>1</span></span></b><span style="font-size:12.0pt;">. Unit conversion to SI for measured pH samples.</span></i></p>
<p><span style="font-size:12.0pt; line-height:107%;">Examples of
errors found include negative pH values, units of measurements not consistent
with pH measurements (<b>Table 1</b>), and values well above known pH ranges in
freshwater systems. Users should verify the data from the original sources
before drawing site specific conclusions. Individual contributing organizations
can still be found in the final and original datasets if the end user would
like to filter for only specific sampling partners.</span></p>
<p><span style="font-size:12.0pt; line-height:107%;">The
resulting dataset is presented as summarized collection of information for each
unique sampling location and the original data flagging process helps to
exclude unreliable and errant values from the final statistics. The R code
developed to perform the QA/QC steps are available from cormier.susan@epa.gov</span></p>
<p><b><span style="font-size:12.0pt; line-height:107%;"><br /></span></b></p><p><b><span style="font-size:12.0pt; line-height:107%;">Terms of
Use</span></b></p>
<p><b><i><span style="font-size:12.0pt; line-height:107%;">Freshwater
Explorer Data Disclaimer</span></i></b></p>
<p><span style="font-size:12.0pt; line-height:107%;">This data is
intended for exploratory and discussion purposes. Although statutory provisions
and U.S. Environmental Protection Agency (EPA) regulations contain legally
binding requirements, these data and related information are not regulatory,
nor do they change or substitute for any provisions or regulations. The
information does not substitute for the Clean Water Act, a National Pollutant
Discharge Elimination System permit, or EPA or state regulations applicable to
permits; nor is this material a permit or regulation itself. Thus, it does not
impose legally binding requirements on EPA, states, tribes, or the regulatory
community. This information does not confer legal rights or impose legal
obligations on any member of the public. Mention of any trade names, products,
or services is not and should not be interpreted as conveying official EPA
approval, endorsement, or recommendation.</span></p>
<p><span style="font-size:12.0pt; line-height:107%;">While EPA
has used its best efforts to include complete and accurate information in this
system, EPA cannot be held responsible for errors or omissions and is not
liable for any direct, indirect, or consequential damages resulting from using
this secondary information. Some potential sources of error have been assessed
by the U.S. EPA resulting in the removal of some samples from the original data
sets. However, all sources of potential error cannot be eliminated from the
measured data reported in the Freshwater Explorer or the data used to develop
predictive models. Therefore, the U.S. EPA cannot fully ensure either the
original data or the values calculated from them. Conclusions and assessments
drawn from the use of the Freshwater Explorer are the responsibility of the
user.</span></p>
<p><span style="font-size:12.0pt; line-height:107%;">Please check
sources, scale, accuracy, dates, and other available information. Please
confirm that you are using the most recent copy of both data and metadata.
Reliance on the information contained in this system by any party cannot be
used as a defense in any administrative or judicial proceeding.</span></p>
<p><span style="font-size:12.0pt; line-height:107%;">This dataset
may be revised periodically. EPA can revise this dataset without public notice
to reflect changes in EPA policy, guidance, and advancements in the field of
biological assessments. EPA welcomes public input on this document at any time.
Send comments to FreshwaterExplorer@epa.gov, Center for Environmental
Measurement and Modeling, Office of Research and Development, U.S.
Environmental Protection Agency, 26 W. Martin Luther King Dr, Cincinnati, OH
45268.</span></p>
<p><b><span style="font-size:12.0pt; line-height:107%;">Preferred
citation: </span></b><span style="font-size:12.0pt; line-height:107%;">Leppo, E.,
Wharton, C., and Cormier. S. 2024. U.S. EPA Freshwater Explorer v2 national
measured nutrient metadata and dataset. USEPA. <span style="color:#00B0F0;">https://arcg.is/0OuDn80</span></span></p>
<p><b><span style="font-size:12.0pt; line-height:107%;">References</span></b></p>
<p><span style="font-size:12.0pt; line-height:107%;">U.S. EPA.
2024. pH. Causal Analysis/Diagnosis Decision Information System (CADDIS). </span><a href="https://www.epa.gov/caddis/ph"><span style="font-size:12.0pt; line-height:107%;">https://www.epa.gov/caddis/ph</span></a></p>
<p><span style="font-size:12.0pt; line-height:107%;">USEPA. 2022.
National Rivers and Streams Assessment 2023 - 2024: Laboratory Operations
Manual. EPA841-B-22-008. U.S. Environmental Protection Agency, Office of Water,
Washington, DC.</span></p></div>
Copyright Text: Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021. https://doi.org/10.5066/P9QRKUVJ.
National Water Quality Monitoring Council, 2024, Water Quality Portal, accessed 01, 25, 2024, https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=pH&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STORET, https://doi.org/10.5066/P9QRKUVJ.
Description: <div><div><b>Description:</b> National Measured Dissolved Sulfate Data derived from data stored in the U.S. EPA Water Quality Portal.</div><div><b>Data Date Range:</b> 01/2000 – 12/2023</div><div><b>Acquisition Date</b>: 1/17/2024</div><div><b>Query Links:</b> <a href="https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Sulfate&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET" target="_blank">https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Sulfate&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET</a></div><div><b>Min. Value:</b> -13.7</div><div><b>Max. Value:</b> 3420000</div><div><b>Units in Dataset:</b> <Null>, %, % recovery, mg/kg, mg/l, mg/L, mg/l CaCO3**, mg/m2, MPN, None, NTU, ppm, ueq/L, ug/L, umol/L, count</div></div><div><br /></div><div><div><b>Background</b></div><div>Sulfate is naturally present in freshwater but in excess is harmful to aquatic life and other beneficial uses. For a review see <a href target="_blank">Zak et al. (2021)</a>.</div></div><div><br /></div><div>In freshwater environments, chloride can come from a variety of sources (<a href="https://www.epa.gov/sites/default/files/2014-09/documents/support_cc1_sulfate_dwreport.pdf" target="_blank">Wang and Zhang, 2019</a>; EPA 2003), including but not limited to:<br /></div><div><div><ul><li>Natural Sources:</li><li>Weathering of rocks and minerals.</li><li>Volcanic activity. </li><li>Oxidation of sulfide minerals, </li><li>Decomposition of organic matter</li><li>Anthropogenic Sources:</li><li>Agricultural runoff containing fertilizers.</li><li>Wastewater and sewage</li><li>Synthetic detergents</li><li>Industrial processes and effluents.</li><li>Mine drainage</li><li>Burning of fossil fuels</li></ul></div></div><div><div>Sulfate is an essential nutrient for some aquatic plants and microorganisms, particularly sulfate-reducing bacteria (Muyzer and Stams, 2008). These bacteria play a crucial role in the sulfur cycle, reducing sulfate to sulfide in anaerobic conditions. This process can affect the availability of other nutrients and influence the overall chemical balance of the aquatic system (Lamers et al., 2013). For example, acid deposition results in dissolution of calcium carbonates reducing the buffering capacity of soils and freshwater systems in soils (Driscoll et al. 2001; Likens et al. 2002).</div><div><br /></div><div>Monitoring and managing sulfate levels in freshwater systems is important for maintaining ecological balance and water quality. High sulfate concentrations can impact the taste and odor of drinking water, and in some cases, may have laxative effects on humans and animals (World Health Organization, 2004). Additionally, elevated sulfate levels can contribute to the formation of scale in pipes and industrial equipment, causing economic concerns for water treatment and distribution systems (Snoeyink and Jenkins, 1980).</div><div><br /></div><div>Dissolved sulfate in freshwater is typically measured by ion chromatography (<a href="https://www.epa.gov/sites/default/files/2015-06/documents/epa-300.1.pdf" target="_blank">EPA 300.1</a>). Our Quality Assurance/Quality Control (QA/QC) procedures as well as the contributor’s laboratory processing and reporting procedures were used to summarize reported values. The WQP portal original dataset contains annotations for each sample to help understand the reliability and flagging process.</div></div><div><br /></div><div><div><b>Dataset</b></div><div>This dataset focuses primarily on samples reported as dissolved sulfate anions. Unit conversions were normalized to mg/l as listed in <b>Table 1</b>. </div><div><br /></div><div>This dataset is a collection of dissolved sulfate samples collected across the United States from 2000-2023 from the Water Quality Portal (WQP), which integrates publicly available water quality data from the USGS National Water Information System (NWIS) and the EPA Water Quality Exchange (WQX) Data Warehouse. These water quality data records are provided by many federal, state, and tribal organizations and other partners. Because these data are from secondary sources, the U.S. EPA cannot ensure that the information is accurate, current, or complete. Therefore, users should verify the data from the original sources before drawing site specific conclusions. </div><div><br /></div><div><b>Quality Assurance/Quality Control (QA/QC) and Identified Issues</b></div><div>An automated Quality Assurance/Quality Control (QA/QC) protocol was developed using a mix of Python and R-scripts to remove or identify potentially erroneous values (outliers) in WQP. The quality of the WQP measured data was evaluated as follows. The quality of the WQP measured data was evaluated as follows.</div></div><div><div>•<span style> </span>Generally – do not delete data. Add a screening/flagging column to keep track of decision-making to remove records/observations.</div><div>•<span style> </span>Review the geographic/temporal scope and data types of the acquired data to the project objectives—it might not be necessary to process all data from a given data set. Map stations in a GIS to further refine and select data based on analysis selection criteria: geographic area, watersheds, bounding box, waterbody type, etc. This also provides the opportunity to conduct quality assurance checks based on spatial location (e.g., are the “estuarine” sites located near the coast).</div><div>•<span style> </span>Flag values reported with units of measurements different than mg/L.</div><div>•<span style> </span>Review and flag samples identified in the WQP with sample processing issues (e.g., suspected contamination, exceeding sampling hold time, no reported value, below reporting value). Many of the samples that met these criteria were already found and identified by WQP QA/QC data process.</div><div>•<span style> </span>Convert all relevant dissolved sulfate values to mg/L. See conversion Table 1 below.</div><div>•<span style> </span>Flag values outside of the known maximum and minimum ranges of dissolved sulfate in freshwater systems (0- 33,000mg/L). This range falls within the range of dissolved sulfate values observed in freshwater systems. This dataset contains well samples along with stream collected samples and map range values were widened to include those locations (USEPA, 2022).</div><div>•<span style> </span>Identify and denote (gray circles) dissolved sulfate values > 33,000 mg/L - these values likely represent areas of naturally high sulfate due to geologic makeup or could denote areas active contamination from point and non-point sources (USEPA, 2022).</div><div>•<span style> </span>Check for flagged values in the ResultStatusIdentifier column by the Water Quality Portal that should not be used.</div><div>•<span style> </span>Parse/filter out various measurement compositions (Total vs Dissolved) for summarization to use only data denoted as Dissolved.</div><div>•<span style> </span>Summary statistics – Calculate basic statistics (mean, median, standard deviation, range, last measurement, maximum, minimum).</div></div><div><br /></div><div style="text-align:center;"><img alt="Table 1. Unit conversion to mg/L for measured dissolved sulfate samples." src="https://lh3.googleusercontent.com/pw/AP1GczNfRBgc6z1iW5lG3uMtvup2YNv_2wemVWxn-WfOMX1O1xI2hdPaet-L1xseghJKDlH5Ut-gmmxgiC7Vcl8pzqchCh0Eobh4WexixTviJMnM7q3AsazWQnm1ewICFF_ei5aPYVwS94dwPBBSXlSpAh3PDw=w741-h575-s-no-gm?authuser=0" /><br /></div><div style="text-align:center;"><i>Table 1. Unit conversion to mg/L for measured dissolved sulfate samples.</i></div><div style="text-align:center;"><br /></div><div style="text-align:left;"><div>Examples of errors found include negative dissolved sulfate values, units of measurements not consistent with dissolved sulfate measurements (e.g., <Null>, g/kg, %, ppm) and entries as µg/L but reported as mg/L and vice versa. Users should verify the data from the original sources before drawing site specific conclusions. Individual contributing organizations can still be found in the final and original datasets if the end user would like to filter for only specific sampling partners.</div><div><br /></div><div>The resulting dataset is presented as summarized collection of information for each unique sampling location and the original data flagging process helps to exclude unreliable and errant values from the final statistics. The R code developed to perform the QA/QC steps are available from <a href="mailto:cormier.susan@epa.gov" target="_blank">cormier.susan@epa.gov</a></div><div><br /></div></div><div><div><b>Terms of Use</b></div><div><br /></div><div><b>Freshwater Explorer Data Disclaimer</b></div><div>This data is intended for exploratory and discussion purposes. Although statutory provisions and U.S. Environmental Protection Agency (EPA) regulations contain legally binding requirements, these data and related information are not regulatory, nor do they change or substitute for any provisions or regulations. The information does not substitute for the Clean Water Act, a National Pollutant Discharge Elimination System permit, or EPA or state regulations applicable to permits; nor is this material a permit or regulation itself. Thus, it does not impose legally binding requirements on EPA, states, tribes, or the regulatory community. This information does not confer legal rights or impose legal obligations on any member of the public. Mention of any trade names, products, or services is not and should not be interpreted as conveying official EPA approval, endorsement, or recommendation.</div><div><br /></div><div>While EPA has used its best efforts to include complete and accurate information in this system, EPA cannot be held responsible for errors or omissions and is not liable for any direct, indirect, or consequential damages resulting from using this secondary information. Some potential sources of error have been assessed by the U.S. EPA resulting in the removal of some samples from the original data sets. However, all sources of potential error cannot be eliminated from the measured data reported in the Freshwater Explorer or the data used to develop predictive models. Therefore, the U.S. EPA cannot fully ensure either the original data or the values calculated from them. Conclusions and assessments drawn from the use of the Freshwater Explorer are the responsibility of the user.</div><div><br /></div><div>Please check sources, scale, accuracy, dates, and other available information. Please confirm that you are using the most recent copy of both data and metadata. Reliance on the information contained in this system by any party cannot be used as a defense in any administrative or judicial proceeding.</div><div><br /></div><div>This dataset may be revised periodically. EPA can revise this dataset without public notice to reflect changes in EPA policy, guidance, and advancements in the field of biological assessments. EPA welcomes public input on this document at any time. Send comments to FreshwaterExplorer@epa.gov, Center for Environmental Measurement and Modeling, Office of Research and Development, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr, Cincinnati, OH 45268.</div></div><div><br /></div><div><b>Preferred citation:</b> Leppo, E., Wharton, C., and Cormier. S. 2024. U.S. EPA Freshwater Explorer v2 national measured dissolved calcium metadata and dataset. USEPA. <a href="https://arcg.is/0OuDn80" target="_blank">https://arcg.is/0OuDn80</a><br /></div><div><br /></div><div><div><b>References</b></div><div>Driscoll, C. T., et al. (2001). Acidic deposition in the northeastern United States: Sources and inputs, ecosystem effects, and management strategies. BioScience, 60(1), 10-22. <a href="https://academic.oup.com/bioscience/article/51/3/180/256122" target="_blank">https://academic.oup.com/bioscience/article/51/3/180/256122</a></div><div><br /></div><div>Lamers, L. P., et al. (2013). Sulfide as a soil phytotoxin—a review. Frontiers in Plant Science, 4, 268. <a href="https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2013.00268/full" target="_blank">https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2013.00268/full</a></div><div><br /></div><div>Likens, G. E., et al. (2002). The biogeochemistry of sulfur at Hubbard Brook. Biogeochemistry, 60(3), 235-316. <a href="https://link.springer.com/content/pdf/10.1023/A:1020972100496.pdf" target="_blank">https://link.springer.com/content/pdf/10.1023/A:1020972100496.pdf</a></div><div><br /></div><div>Muyzer, G., & Stams, A. J. (2008). The ecology and biotechnology of sulphate-reducing bacteria. Nature Reviews Microbiology, 6(6), 441-454. <a href="https://www.nature.com/articles/nrmicro1892" target="_blank">https://www.nature.com/articles/nrmicro1892</a></div><div><br /></div><div>Snoeyink, V. L., & Jenkins, D. (1980). Water Chemistry. John Wiley & Sons. New York, 384.</div><div><br /></div><div>USEPA. 2003. Contaminant Candidate List Regulatory Determination Support Document for Sulfate. EPA-815-R-03-16. <a href="https://www.epa.gov/sites/default/files/2014-09/documents/support_cc1_sulfate_dwreport.pdf" target="_blank">https://www.epa.gov/sites/default/files/2014-09/documents/support_cc1_sulfate_dwreport.pdf</a></div><div><br /></div><div>USEPA. 2022. National Rivers and Streams Assessment 2023 - 2024: Laboratory Operations Manual. EPA841-B-22-008. U.S. Environmental Protection Agency, Office of Water, Washington, DC. <a href="https://www.epa.gov/system/files/documents/2023-06/NRSA2324_LOM_v1.0.pdf" target="_blank">https://www.epa.gov/system/files/documents/2023-06/NRSA2324_LOM_v1.0.pdf</a></div><div><br /></div><div>Wang, H. and Zhang, Q., 2019. Research advances in identifying sulfate contamination sources of water environment by using stable isotopes. International journal of environmental research and public health, 16(11), p.1914. https://www.mdpi.com/1660-4601/16/11/1914/pdf</div><div>World Health Organization. (2004). Sulfate in Drinking-water: Background Document for development of WHO Guidelines for Drinking-water Quality. WHO/SDE/WSH/03.04/114. <a href="https://cdn.who.int/media/docs/default-source/wash-documents/wash-chemicals/sulfate.pdf?sfvrsn=b944d584_4" target="_blank">https://cdn.who.int/media/docs/default-source/wash-documents/wash-chemicals/sulfate.pdf?sfvrsn=b944d584_4</a></div><div><br /></div><div>Zak, D., Hupfer, M., Cabezas, A., Jurasinski, G., Audet, J., Kleeberg, A., McInnes, R., Kristiansen, S.M., Petersen, R.J., Liu, H. and Goldhammer, T., 2021. Sulphate in freshwater ecosystems: A review of sources, biogeochemical cycles, ecotoxicological effects and bioremediation. Earth-Science Reviews, 212, p.103446. <a href="https://www.sciencedirect.com/science/article/pii/S001282522030492X" target="_blank">https://www.sciencedirect.com/science/article/pii/S001282522030492X</a></div></div>
Copyright Text: National Water Quality Monitoring Council, 2024, Water Quality Portal, accessed 01, 17, 2024, https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Sulfate&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET, https://doi.org/10.5066/P9QRKUVJ.
Description: <div><div><b>Description:</b> National Measured Total Nitrogen Data derived from data stored in the U.S. EPA Water Quality Portal.</div><div><b>Forms Retained:</b> Total Nitrogen</div><div><b>Data Date Range:</b> 01/2000 – 12/2023</div><div><b>Acquisition Date:</b> 1/22/2024</div><div><b>Query Links:</b> <a href="https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Nitrogen&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET" target="_blank">https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Nitrogen&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET</a></div><div><b>Min. Value:</b> -9</div><div><b>Max. Value:</b> 53200</div><div><b>Units in Source/Original Dataset:</b> <Null>, #/100mL, %, cm3/g @STP, cm3/g STP, mg N/l******, mg/l, mg/L, MPN/100mL, None, NTU, ppb, ppm, ug, ug/L, umol/ umol/L, uS/cm</div></div><div><br /></div><div><div><b>Background</b></div><div>Total nitrogen (TN) in freshwater refers to the sum of all nitrogen species present, including organic nitrogen, ammonia (NH₄⁺/NH₃), nitrate (NO₃⁻), and nitrite (NO₂⁻). It plays a critical role in aquatic ecosystems by supporting primary production, as nitrogen is an essential nutrient for the growth of phytoplankton and aquatic plants. However, excessive nitrogen levels can lead to eutrophication, a process where nutrient over-enrichment promotes excessive algal growth, which can result in oxygen depletion, harmful algal blooms (HABs), and declines in biodiversity (Smith et al., 1999).</div><div><br /></div><div>Nutrient species such as nitrogen are often reported in several forms. For example, nitrate may be reported as nitrate (NO3), nitrate as N or nitrate nitrogen (NO3-N), or nitrate ion (NO3- or Nitrate as NO3). Nitrate as nitrogen is an especially common way of reporting nitrate concentrations. Nitrate as nitrogen means that the concentration is provided in terms of the element nitrogen, isolating the nitrogen portion of the nitrate rather than the nitrate portion including the oxygen. Nitrate as nitrogen is determined by dividing the atomic weight of nitrogen (14.0067) by the molecular weight of a nitrate ion (62.0049). For example, a nitrate concentration reported as 62 mg/L nitrate ion can also be expressed as 14 mg/L nitrate as nitrogen. Analysts should verify that nutrient concentrations are converted to comparable formats (generally in elemental form as nitrogen).</div></div><div><br /></div><div><div><b>Dataset</b></div><div>This dataset focuses primarily on samples reported as total nitrogen and no speciation aggregations or conversions were performed. In some cases, components of a desired parameter are monitored and reported instead of the desired parameter. To take full advantage of available monitoring data, one might want to convert from one parameter to another. For example, if nitrate+nitrite data are desired, you might first use any reported values for “nitrate+nitrite” and then secondarily sum other reported values of “nitrate” and “nitrite” when each are reported separately. Total nitrogen values could be obtained using a similar procedure. Many analyses report both total nitrogen and components of total nitrogen, so summation will be needed only in cases where total nitrogen is not reported. When several nutrient species are reported, an opportunity to check that the component species are less than the totals should be used (e.g., SRP < TP, NH3N < TKN). A 2012 USGS report assessing precision and bias of total nitrogen sampling found that measuring total nitrogen directly to be the most accurate (priority 1 and 2), followed by summing dissolved and particulate nitrogen (priority 3), followed by summing TKN and nitrate + nitrite (priority 4) (Table 1)(Rus, 2012).</div></div><div><br /></div><div>Table 1. Total Nitrogen Prioritization<br /></div><div style="text-align:left;"><img alt="Nitrogen Priority" src="https://lh3.googleusercontent.com/pw/AP1GczM_REmTSRtpmyewaPmjtOx__MjBdE_rEo5FVeQ8nmNMVNeLgKxIND-4bWhXqMgR8ePhrQxSe1xCqQQcP5TS9J-RF0RgYHXlo0ud_pWYQ6EOPAfPQ8HYoZEnkMj9A79wsInHb4ha76u8yqZl9KaH8bvwGw=w764-h183-s-no-gm?authuser=0" /><br /></div><div style="text-align:left;"><br /></div><div style="text-align:left;">This dataset is a collection of surface water total nitrogen samples collected across the United States from 2000-2023 from the Water Quality Portal (WQP), which integrates publicly available water quality data from the USGS National Water Information System (NWIS) and the EPA Water Quality Exchange (WQX) Data Warehouse. These water quality data records are provided by many federal, state, and tribal organizations and other partners. Because these data are from secondary sources, the U.S. EPA cannot ensure that the information is accurate, current, or complete. Therefore, users should verify the data from the original sources before drawing site specific conclusions.<br /></div><div style="text-align:left;"><br /></div><div style="text-align:left;"><div>Quality Assurance/Quality Control (QA/QC) and Identified Issues </div><div>An automated Quality Assurance/Quality Control (QA/QC) protocol was developed using a mix of Python and R-scripts to remove or identify potentially erroneous values and outliers from the WQP data download. The quality of the WQP measured data was evaluated as follows.</div><div><div><ul><li>Generally – do not delete data. Add a screening/flagging column to keep track of decision-making to remove records/observations.</li><li>Review the geographic/temporal scope and data types of the acquired data to the project objectives—it might not be necessary to process all data from a given data set. Map stations in a GIS to further refine and select data based on analysis selection criteria: geographic area, watersheds, bounding box, waterbody type, etc. This also provides the opportunity to conduct quality assurance checks based on spatial location (e.g., are the “estuarine” sites located near the coast).</li><li>Check for duplicate entries. Identify and screen those samples that are duplicates. Check for samples or results that do not have stations.</li><li>Interpret data qualifiers and comments (spiked, blanks, duplicates, etc.)</li><ul><li>ActivityTypeCode – e.g., Quality Control Samples</li><li>ResultCommentText – e.g., Sample beyond holding time, sample temperature elevated</li><li>ResultLaboratoryCommentText – e.g., diluted sample: method hi range exceeded, holding time exceeded</li></ul><li>Check for missing values – Identify and flag entries with missing total nitrogen values.</li><li>Check for outliers – Detect potential outliers that deviate from expected total nitrogen ranges from surface samples collected across the continental United States (0 to 90) (USEPA, 2022).</li><li>Check for incorrect units in the ResultMeasure/MeasureUnitCode variable and flag entries where the unit is different than mg/L (Table 2).</li><li>Convert all relevant total nitrogen values to mg/L (Table 2).</li><li>Review and flag samples identified in the WQP with sample processing issues (e.g., suspected contamination, exceeding sampling hold time, no reported value, below reporting value). Many of the samples that met these criteria were already found and identified by WQP QA/QC data process.</li><li>Summary statistics – Calculate basic statistics (mean, median, standard deviation, range, last measurement, maximum, minimum).</li></ul></div></div><div style="text-align:center;"><img alt="Unit conversion to mg/l for measured total nitrogen samples." src="https://lh3.googleusercontent.com/pw/AP1GczMiu4KaD-lJLaTCzmAO6f93eoNL5gS-kEa_UgamlQ1M-9kRuL2PMjZbErDMx3gBHdejK0sSBeGIChX9EMY69yPeraFR4fzKxeqX--exB_t2Rn044uOMRV9Fm2Zqd1XaTD0j4kOmWUIyFKcxbDsU8MlLbQ=w670-h568-s-no-gm?authuser=0" /><br /></div><div style="text-align:center;"><i><b>Table 2</b>. Unit conversion to mg/l for measured total nitrogen samples.<br /></i></div><div style="text-align:center;"><br /></div><div style="text-align:left;"><div>Examples of errors found in the source dataset include negative alkalinity values, units of measurements not consistent with alkalinity measurements (e.g., <Null>, CaCO3, ppm) and entries suspected to be µg/L but reported as mg/L based on the natural and anthropogenic ranges of alkalinity. Users should verify the data from the original sources before drawing site specific conclusions. Generally source specific issues within the dataset will become apparent as QC steps are performed and data Individual contributing organizations can be found in the final and original datasets if the end user would like to filter for specific sampling partners.</div><div><br /></div><div>The resulting dataset is presented as a summarized collection of information for each unique sampling location and the original data flagging process helps to exclude unreliable and errant values from the final statistics. The R code developed to perform the QA/QC steps are available from <a href="mailto:cormier.susan@epa.gov" target="_blank">cormier.susan@epa.gov</a></div></div><div><br /></div><div><br /></div><div><div><b>Terms of Use</b></div><div><b><br /></b></div><div><b>Freshwater Explorer Data Disclaimer</b></div><div>This data is intended for exploratory and discussion purposes. Although statutory provisions and U.S. Environmental Protection Agency (EPA) regulations contain legally binding requirements, these data and related information are not regulatory nor do they change or substitute for any provisions or regulations. The information does not substitute for the Clean Water Act, a National Pollutant Discharge Elimination System permit, or EPA or state regulations applicable to permits; nor is this material a permit or regulation itself. Thus, it does not impose legally binding requirements on EPA, states, tribes, or the regulatory community. This information does not confer legal rights or impose legal obligations on any member of the public. Mention of any trade names, products, or services is not and should not be interpreted as conveying official EPA approval, endorsement, or recommendation.</div><div><br /></div><div>While EPA has used its best efforts to include complete and accurate information in this system, EPA cannot be held responsible for errors or omissions and is not liable for any direct, indirect, or consequential damages resulting from using this secondary information. Some potential sources of error have been assessed by the U.S. EPA resulting in the removal of some samples from the original data sets. However, all sources of potential error cannot be eliminated from the measured data reported in the Freshwater Explorer or the data used to develop predictive models. Therefore, the U.S. EPA cannot fully ensure either the original data or the values calculated from them. Conclusions and assessments drawn from the use of the Freshwater Explorer are the responsibility of the user.</div><div><br /></div><div>Please check sources, scale, accuracy, dates, and other available information. Please confirm that you are using the most recent copy of both data and metadata. Reliance on the information contained in this system by any party cannot be used as a defense in any administrative or judicial proceeding.</div><div><br /></div><div>This dataset may be revised periodically. EPA can revise this dataset without public notice to reflect changes in EPA policy, guidance, and advancements in the field of biological assessments. EPA welcomes public input on this document at any time. Send comments to FreshwaterExplorer@epa.gov, Center for Environmental Measurement and Modeling, Office of Research and Development, U.S. Environmental Protection Agency, 26 W. Martin Luther King Dr, Cincinnati, OH 45268.</div></div><div><br /></div></div><div><div><b>Credits (Attribution)</b></div><div><br /></div><div><b>Preferred Citation:</b> Leppo, E., Wharton, C., and Cormier. S. 2024. U.S. EPA Freshwater Explorer v2 national measured alkalinity metadata and dataset. USEPA. <a href="https://arcg.is/0OuDn80" target="_blank">https://arcg.is/0OuDn80</a></div></div><div><br /></div><div><b>Original data sources:</b> Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021. https://doi.org/10.5066/P9QRKUVJ. National Water Quality Monitoring Council, 2024 Water Quality Portal, accessed 01, 16, 2024, <a href="https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Alkalinity&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&sorted=no&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET, https://doi.org/10.5066/P9QRKUVJ." target="_blank">https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=Alkalinity&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&sorted=no&dataProfile=narrowResult&providers=NWIS&providers=STEWARDS&providers=STORET, https://doi.org/10.5066/P9QRKUVJ.</a><br /></div><div><br /></div><div><div><b>References</b></div><div>Hunt, D.T.E. and A.L. Wilson. 1986. The Chemical Analysis of Water: General Principles and Techniques. 2nd ed. Royal Society of Chemistry, London, England.</div><div><br /></div><div>Youden, W.J. 1969. Ranking laboratories by round-robin tests. In Precision Measurement and Calibration. H.H. Ku, ed. NBS Special Publication 300, Vol. 1. U.S. GPO Washington, D.C.</div><div><br /></div><div>Hillman, D.C., J.F. Potter, and S.J. Simon. 1986. National Surface Water Survey, Eastern Lake Survey-Phase I, Analytical Methods Manual. EPA/600/4-86/009. U.S. Environmental Protection Agency, Las, Vegas, NV.</div><div><br /></div><div>U.S. EPA, 1987. Handbook of Methods for Acid Deposition Studies: Laboratory Analyses for Surface Water Chemistry. EPA/600/4-87/026. U.S. Environmental Protection Agency, Office of Research and Development, Washington D.C.</div><div><br /></div><div>Oblinger Childress, C. J., W. T. Foreman, B. F. Connor, and T. J. Maloney. 1999. New reporting procedures based on long-term method detection levels and some considerations for interpretations of water-quality data provided by the U.S. Geological Survey National Water Quality Laboratory. Open-File Report 99-193, US Geological Survey, Reston, Virginia.</div><div><br /></div><div>Rus, D.L., Patton, C.J., Mueller, D.K., and Crawford, C.G. 2012. Assessing Total Nitrogen in Surface-Water Samples-Precision and Bias of Analytical and Computational Methods. U.S. Geological Survey Scientific Investigation Report 2012-5281. 38 p. <a href="https://pubs.usgs.gov/sir/2012/5281/sir12_5281.pdf" target="_blank">https://pubs.usgs.gov/sir/2012/5281/sir12_5281.pdf</a></div><div><br /></div><div>Smith, V. H., Tilman, G. D., & Nekola, J. C. (1999). Eutrophication: impacts of excess nutrient inputs on freshwater, marine, and terrestrial ecosystems. Environmental Pollution, 100(1-3), 179-196.</div><div><br /></div><div>USEPA. 2022. National Rivers and Streams Assessment 2023 - 2024: Laboratory Operations Manual. EPA841-B-22-008. U.S. Environmental Protection Agency, Office of Water, Washington, DC.</div><div><br /></div><div>USGS. 2024. Alkalinity Calculation Methods. <a href="https://or.water.usgs.gov/alk/methods.html" target="_blank">https://or.water.usgs.gov/alk/methods.html</a></div></div>
Copyright Text: Water Quality Portal. Washington (DC): National Water Quality Monitoring Council, United States Geological Survey (USGS), Environmental Protection Agency (EPA); 2021. https://doi.org/10.5066/P9QRKUVJ.