External Quality-Assurance Results for the National Atmospheric Deposition Program National Trends Network, 1995-96

By Gordon, John D.

Book Id: WPLBN0000079200
Format Type: PDF eBook:
File Size: 4.23 MB
Reproduction Date: 2007

Title:	External Quality-Assurance Results for the National Atmospheric Deposition Program National Trends Network, 1995-96
Author:	Gordon, John D.
Volume:
Language:	English
Subject:	Ecology, Natural resource issues, Environemtal protection
Collections:	Environmental Awareness Library Collection
Historic Publication Date:
Publisher:	United States Environmental Protection Agency


Citation APA MLA Chicago D. Gordo, B. J. (n.d.). External Quality-Assurance Results for the National Atmospheric Deposition Program National Trends Network, 1995-96. Retrieved from http://www.gutenberg.cc/

Description
Excerpt: The U.S. Geological Survey operated four external quality-assurance programs for the National Atmospheric Deposition Program/ National Trends Network (NADP/NTN) in 1995 and 1996: the intersite-comparison program, the blind-audit program, the interlaboratory- comparison program, and the collocatedsampler program. The intersite-comparison program assessed the precision and bias of pH and specific-conductance determinations made by NADP/NTN site operators. The analytical bias introduced during routine handling, processing, and shipping of wet-deposition samples and precision of analyte values was estimated by using a blind-audit program. An interlaboratory-comparison program was used to evaluate differences between analytical results and to estimate the analytical precision of five North American laboratories that routinely analyzed wet deposition. A collocatedsampler program was used to estimate the precision of the overall precipitation collection and analysis system from initial sample collection through final storage of the data.

Table of Contents
CONTENTS Abstract................................................................................................................................................................................. 1 Introduction .......................................................................................................................................................................... 3 Statistical Approach.............................................................................................................................................................. 3 External Quality-Assurance Results ..................................................................................................................................... 4 Intersite-Comparison Program ................................................................................................................................... 4 Results for Intersite-Comparison Study Numbers 35-38 .................................................................................. 4 Intersite-Comparison Study Follow-up Program .............................................................................................. 12 Blind-Audit Program .................................................................................................................................................. 15 Assessing Analytical Bias ................................................................................................................................ 18 Paired Blind-Audit Sample Differences ............................................................................................................ 18 Statistical Significance ............................................................................................................................ 22 Analyte Concentration Effects................................................................................................................. 22 Ultrapure Sample Analyses ..................................................................................................................... 22 Percent Differences................................................................................................................................. 29 Sample Volume Effects........................................................................................................................... 30 Interlaboratory-Comparison Program......................................................................................................................... 37 Laboratory Precision......................................................................................................................................... 39 Interlaboratory Bias .......................................................................................................................................... 40 Intralaboratory Bias .......................................................................................................................................... 41 National Institute of Standards and Technology Standard Reference Samples....................................... 41 Ultrapure Deionized-Water Samples ....................................................................................................... 53 Collocated-Sampler Program ..................................................................................................................................... 53 Comparison of Laboratory and Network Error ..................................................................................................................... 64 Summary............................................................................................................................................................................... 67 References Cited................................................................