U.S. Geological Survey Precipitation Chemistry Quality Assurance Project Data 2021 – 2022
Dates
Publication Date
2023-08-30
Start Date
2021-01-01
End Date
2022-12-31
Citation
Wetherbee, G.A., 2023, U.S. Geological Survey Precipitation Chemistry Quality Assurance Project Data 2021 – 2022: U.S. Geological Survey data release, https://doi.org/10.5066/P9OZ5GL1.
Summary
The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) was initiated in 1978 by the Association of State Agricultural Experiment Stations to monitor long-term atmospheric chemistry and the effects pollutants have on aquatic and terrestrial systems. As of fall 2023, precipitation was being collected at approximately 260 NTN sites in the United States, including Puerto Rico and the U.S. Virgin Islands, and additionally Bermuda and Canada. Beginning in 1996, the NADP/Mercury Deposition Network (MDN) has monitored mercury (Hg) in precipitation, and includes approximately 80 sites in the United States including Puerto Rico, plus Canada and Taiwan. The U.S. Geological Survey started the Precipitation Chemistry Quality [...]
Summary
The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) was initiated in 1978 by the Association of State Agricultural Experiment Stations to monitor long-term atmospheric chemistry and the effects pollutants have on aquatic and terrestrial systems. As of fall 2023, precipitation was being collected at approximately 260 NTN sites in the United States, including Puerto Rico and the U.S. Virgin Islands, and additionally Bermuda and Canada. Beginning in 1996, the NADP/Mercury Deposition Network (MDN) has monitored mercury (Hg) in precipitation, and includes approximately 80 sites in the United States including Puerto Rico, plus Canada and Taiwan. The U.S. Geological Survey started the Precipitation Chemistry Quality Assurance Project (PCQA) for NADP/NTN in 1978 and for NADP/MDN in 2004. The quality-assurance programs assess and document the quality of wet-deposition data for NADP/NTN and NADP/MDN. During 2021-2022, the NADP Central Analytical Laboratory (CAL) and the Mercury Analytical Laboratory (HAL) were located at the Wisconsin State Laboratory of Hygiene at the University of Wisconsin, Madison (UW). The CAL analyzed all weekly precipitation samples collected by NADP/NTN, and the HAL analyzed all weekly total mercury samples from the MDN. In 2023, these two laboratories were combined and rebranded as the National Atmospheric Laboratory (NAL).
The PCQA verifies the quality of NADP data-collection processes for both the National Trends Network (NTN) and Mercury Deposition Network (MDN). PCQA data are available in separate tables for each quality-assurance program: (1) NTN Interlaboratory-Comparison, (2) MDN Interlaboratory-comparison program, (3) NTN Field-Audit program, (4) MDN System-Blank program, and (5) Co-located Sampler program. The Interlaboratory-Comparison programs (1 & 2) compare the variability and bias of the NADP National Atmospheric Laboratory’s chemical results to other labs that measure low-ionic strength samples, including labs that serve international precipitation monitoring networks. The Field Audit and System Blank programs (3 & 4) quantify the contamination and stability of NADP NTN and MDN samples, respectively by analysis and comparison of equipment rinse samples to unaltered parent solutions. The Co-located Sampler program uses identical, NTN collectors located within 5 meters of each other to obtain replicate samples that are used to calculate the overall variability of NTN sample data. Measured parameters include precipitation depth, pH, specific conductance, and ion concentrations for calcium, magnesium, sodium, potassium, ammonium, chloride, nitrate, sulfate, phosphate, and total mercury. Periodically, the PCQA prepares an interpretive report of the QA data. These data support the 2021-2022 USGS External QA Report for the NADP NTN and MDN.
Data users should consult the metadata file for explanations of the data fields. All negative values for chemical constituents are the negatives of the analytical detection limits. For example, a concentration value reported as less than 0.005 milligrams per liter is reported in the data files as -0.005. Data users may also consult the NADP website for data descriptions as well as USGS external quality assurance reports, which are availble from the online USGS Publications Warehouse.
Deyette, N.A., Wetherbee, G.A., and Martin, R., 2024, External quality-assurance project report for the National Atmospheric Deposition Program National Trends Network and Mercury Deposition Network, 2021–22: U.S. Geological Survey Scientific Investigations Report 2024–5054, 34 p., https://doi.org/10.3133/sir20245054.
For more information, contact the USGS, Water Mission Area, Observing Systems Division Director: https://www.usgs.gov/staff-profiles/janice-fulford.
Purpose
The Precipitation Chemistry Quality Assurance Project (PCQA) results gives users of National Atmospheric Deposition Program (NADP) data the assurance that measurements are representative of environmental conditions. The PCQA programs test the NADP measurements to ensure that the data are of sufficient quality for use in identification and quantification of spatial and temporal trends in atmospheric wet-deposition chemistry. These data are for a quality-control testing project. Therefore, most of these data are not representative measurements of the environment and should not be used as such, except for the Co-located Sampler data, which are true environmental measurements. Test solutions were prepared in the USGS Quality Systems Branch for the USGS Hydrologic Networks Branch in Bldg. 95, Room 2471 at the Denver Federal Center, Denver, Colorado. Test solutions were shipped to NADP sites for processing, and then the processed samples were shipped to the NADP laboratories at the University of Wisconsin, Madison for chemical analysis. Test solutions were also split among several identical, clean bottles and sent to chemical analysis laboratories, including the NADP laboratories for inter-laboratory comparison. Co-located samplers were installed at existing NADP National Trends Network sites to collect replicate weekly composite samples of precipitation for evaluation of the overall variability in NADP chemical data. All data were returned to the USGS Precipitation Chemistry Quality Assurance Project for compilation, assessment of results, permanent curation, and communication to the NADP and general public. The PCQA programs are continually evolving as described in the USGS reports, including: 1. Programs and Analytical Methods for the U.S. Geological Survey Acid Rain Quality-Assurance Project (See and others, 1990); 2. USGS Open-File Report 2005-1024, External Quality-Assurance Programs Managed by the U.S. Geological Survey in Support of the National Atmospheric Deposition Program/National Trends Network (Latysh and Wetherbee, 2005); 3. USGS Open-File Report 2007-1170, External Quality Assurance Programs Managed by the U.S. Geological Survey in Support of the National Atmospheric Deposition Program/Mercury Deposition Network (Latysh and Wetherbee, 2007); and 4. USGS Open-File Report 2016-1213, Updated Operational Protocols for the U.S. Geological Survey Precipitation Chemistry Quality Assurance Project in Support of the National Atmospheric Deposition Program (Wetherbee and Martin, 2017).