External Quality Assurance Project Report for the National Atmospheric Deposition Program’s National Trends Network and Mercury Deposition Network, 2017–18

Scientific Investigations Report 2020-5084
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Abstract

The U.S. Geological Survey (USGS) Precipitation Chemistry Quality Assurance project (PCQA) operated five distinct programs to provide external quality-assurance monitoring for the National Atmospheric Deposition Program’s (NADP) National Trends Network and Mercury Deposition Network during 2017–18. The National Trends Network programs included (1) a field audit program to evaluate sample contamination and stability, (2) an interlaboratory comparison program to evaluate analytical laboratory performance, and (3) a colocated sampler program to evaluate variability attributed to automated precipitation samplers. The Mercury Deposition Network programs include the (4) system blank program and (5) an interlaboratory comparison program. The results indicate consistently low levels of sample contamination, generally strong analytical laboratory performance, and low overall variability in concentration data imparted by field equipment. The NADP operations moved from its 40-year home at the Illinois State Water Survey to the Wisconsin State Laboratory of Hygiene in June 2018. The PCQA programs were modified and (or) temporarily curtailed during the transition in 2018. Bias and variability of sample analysis results were evaluated for the two Central Analytical Laboratories, and ongoing monitoring will be helpful to differentiate true environmental signals from the effects of changing laboratory conditions and performance. Results of quality assurance sample analyses are provided to document that NADP data continue to be of sufficient quality for the analysis of spatial distributions and time trends for chemical constituents in wet deposition.

Suggested Citation

Wetherbee, G.A., and Martin, R., 2020, External quality assurance project report for the National Atmospheric Deposition Program’s National Trends Network and Mercury Deposition Network, 2017–18: U.S. Geological Survey Scientific Investigations Report 2020–5084, 31 p., https://doi.org/10.3133/sir20205084.

ISSN: 2328-0328 (online)

Table of Contents

  • Abstract
  • Introduction
  • Statistical Methods
  • National Trends Network Quality Assurance Programs
  • Mercury Deposition Network Quality Assurance Programs
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title External quality assurance project report for the National Atmospheric Deposition Program’s National Trends Network and Mercury Deposition Network, 2017–18
Series title Scientific Investigations Report
Series number 2020-5084
DOI 10.3133/sir20205084
Year Published 2020
Language English
Publisher U.S. Geological Survey
Publisher location Reston VA
Contributing office(s) WMA - Observing Systems Division
Description Report: vii, 31 p.; 2 Data Releases
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
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