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Layer: Organic Carbon (ID:6)

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Name: Organic Carbon

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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&amp;characteristicName=Organic%20carbon&amp;startDateLo=01-01-2000&amp;startDateHi=12-31-2023&amp;mimeType=tsv&amp;dataProfile=narrowResult&amp;providers=NWIS&amp;providers=STEWARDS&amp;providers=STORET" target="_blank">https://www.waterqualitydata.us/#sampleMedia=Water&amp;characteristicName=Organic%20carbon&amp;startDateLo=01-01-2000&amp;startDateHi=12-31-2023&amp;mimeType=tsv&amp;dataProfile=narrowResult&amp;providers=NWIS&amp;providers=STEWARDS&amp;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> &lt;Null&gt;, %, 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., &lt;Null&gt;, 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 &amp; 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.

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