A quality-assurance assessment for constituents reported by the National Atmospheric Deposition Program and the National Trends Network
A continuing quality-assurance program has been operated by the U.S. Geological Survey to evaluate any bias introduced by routine handling, shipping, and laboratory analyses of wet-deposition samples collected in the National Atmospheric Deposition Program (NADP) and National Trends Network (NTN). Blind-audit samples having a variety of constituent concentrations and values were selected. Only blind-audit samples with constituent concentrations and values less than the 95th-percentile concentration for natural wet-deposition samples were included in the analysis. Of the major ions, there was a significant increase of Ca2+, Mg2+, Na2+, K+, SO42− and Cl−1 in samples handled according to standard protocols and shipped in NADP/NTN sample-collection buckets. For 1979–1987, graphs of smoothed data showing the estimated contamination in blind-audit samples indicate a decrease in the median concentration and ranges of Ca2+, Mg2+ and SO42− contamination of blind-audit samples shipped in sample-collection buckets. Part of the contamination detected in blind-audit samples can be attributed to contact with the sample-collection bucket and lid; however, additional sources also seem to contaminate the blind-audit sample. Apparent decreases in the magnitude and range of sample contamination may be caused by differences in sample-collection bucket- and lid-washing procedures by the NADP/NTN Central Analytical Laboratory. Although the degree of bias is minimal for most constituents, summaries of the NADP/NTN data base may contain overestimates of Ca2+, Mg2+, Na−, K+ and SO42− and Cl− concentrations, and underestimates of H+ concentrations.
Citation Information
Publication Year | 1989 |
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Title | A quality-assurance assessment for constituents reported by the National Atmospheric Deposition Program and the National Trends Network |
DOI | 10.1016/0004-6981(89)90063-2 |
Authors | R.B. See, L.J. Schroder, T. C. Willoughby |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Atmospheric Environment |
Index ID | 70015738 |
Record Source | USGS Publications Warehouse |