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Layer: Alkalinity (ID:1)

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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&amp;characteristicName=Alkalinity&amp;startDateLo=01-01-2000&amp;startDateHi=12-31-2023&amp;mimeType=csv&amp;sorted=no&amp;dataProfile=narrowResult&amp;providers=NWIS&amp;providers=STEWARDS&amp;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> &lt;Null&gt;, 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 &lt; -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., &lt;Null&gt;, 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.

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