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External Quality-Assurance Project Report for the National Atmospheric Deposition Program’s National Trends Network and Mercury Deposition Network, 2019–20

Scientific Investigations Report 2023-5045
By: , , and 
https://doi.org/10.3133/sir20235045

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Abstract

The U.S. Geological Survey Precipitation Chemistry Quality Assurance project (PCQA) operated four distinct programs to provide external quality-assurance monitoring for the National Atmospheric Deposition Program’s (NADP) National Trends Network (NTN) and Mercury Deposition Network (MDN) during 2019–20. The NTN programs included (1) a field audit program to evaluate sample contamination and stability, and (2) an interlaboratory comparison program to evaluate analytical laboratory performance. The MDN programs included the (3) system blank program to evaluate sample contamination and stability, and (4) an interlaboratory comparison program. The results indicated increased levels of sample contamination compared to previous years for NTN samples and decreased contamination in MDN samples. Strong analytical laboratory performance with low overall variability and bias in concentration data were indicated for the NTN’s Central Analytical Laboratory. A positive bias in the hydrogen ion concentrations in NTN samples during 2019 was eliminated by correction of a pH calibration protocol during 2020. The MDN’s Mercury Analytical Laboratory performance declined in 2020 compared to 2019 as indicated by increased variability in analytical results and a negative bias of approximately -1 nanogram per liter in the concentrations of total mercury. Slight perturbations in contamination levels in NTN samples and in analytical performance for MDN are considered small. The PCQA results indicate that NADP data continue to be of sufficient quality for applications in independent research and NADP data products, including spatial interpolations and time trends for chemical constituents in wet deposition. Small shifts in data quality indicated by the 2019–20 PCQA results are intended to be used for interpretation of the NADP data products.

Suggested Citation

Wetherbee, G.A., Martin, RA., and Liethen, A., 2023, External quality-assurance project report for the National Atmospheric Deposition Program’s National Trends Network and Mercury Deposition Network, 2019–20: U.S. Geological Survey Scientific Investigations Report 2023–5045, 29 p., https://doi.org/10.3133/sir20235045.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Purpose and Scope
  • Statistical Methods
  • National Trends Network Quality Assurance Programs
  • Mercury Deposition Network Quality Assurance Programs
  • Data Quality Assessment
  • 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, 2019–20
Series title Scientific Investigations Report
Series number 2023-5045
DOI 10.3133/sir20235045
Year Published 2023
Language English
Publisher U.S. Geological Survey
Publisher location Reston VA
Contributing office(s) WMA - Observing Systems Division
Description Report: vii, 29 p.; 3 Data Releases
Country United States
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details