Layer: pH (ID:7)

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Name: pH

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Description: <div>Data Date Range: 01/2000 – 12/2023 Acquisition Date: 1/25/2024 Query Links: https://www.waterqualitydata.us/#sampleMedia=Water&characteristicName=pH&startDateLo=01-01-2000&startDateHi=12-31-2023&mimeType=csv&dataProfile=narrowResult&providers=NWIS&providers=STORET Min. Value: -2689.41 Max. Value: 9999999 Units in Source/Original Dataset: <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 BackgroundHydrogen 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). In freshwater environments, the pH regime for a waterbody can arise from natural and anthropogenic influences including but not limited to: <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;">Natural Sources<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;"><ul><li>Groundwater from peatlands (low pH)</li><li>Blackwater systems with high organic matter (low pH)</li><li>Organic acids (e.g., tannic acid from leaf decay) (low pH)</li><li>Photosynthesis reducing CO2 (high pH)</li><li>naturally occurring geology and minerals (high or low pH)</li></ul> <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;">Anthropogenic Sources <ul> <li>Mining and waste piles</li> <li>Power plants and other sources of acidic gases</li> <li>Industrial effluents</li> <li>Landfill leachate</li> <li>Confined animal feeding operations, dairy runoff</li> <li>Instream oxidation or reduction processes</li> <li>Recent draining of naturally inundated wetlands or floodplains</li> </ul> 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. 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. Dataset This dataset focuses primarily on samples reported as pH reported as standard unis without any conversion to the original data (Table 1). 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. Quality Assurance/Quality Control (QA/QC) and identified issues 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.<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 missing values – Identify and flag entries with missing pH values.</li><li>Check for outliers – Detect potential outliers that deviate from expected pH ranges (pH typically ranges from 0 to 14).</li><li>Check for incorrect units in the ResultMeasure/MeasureUnitCode variable and flag entries where the unit is different than International System of Units (SI) (Table 1).</li><li>Check for flagged values in the ResultStatusIdentifier column by the Water Quality Portal that should not be used.</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><li>Visualize data – Plot the distribution of the pH data (boxplot, histogram).</li><li>Flag invalid entries – Flag entries that fall outside a typical pH range (for example, less than 0 or greater than 14).</li></ul> </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>Table 1. Unit conversion to SI for measured pH samples. Examples of errors found include negative pH values, units of measurements not consistent with pH measurements (Table 1), 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. 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 Terms of Use Freshwater Explorer Data Disclaimer 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. 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. 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. 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. Preferred citation: Leppo, E., Wharton, C., and Cormier. S. 2024. U.S. EPA Freshwater Explorer v2 national measured nutrient metadata and dataset. USEPA. https://arcg.is/0OuDn80 References U.S. EPA. 2024. pH. Causal Analysis/Diagnosis Decision Information System (CADDIS). <a href="https://www.epa.gov/caddis/ph">https://www.epa.gov/caddis/ph</a> 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>

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.

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Last Edit Date: 10/9/2024 7:07:24 PM

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