Investigation of Differences between Field and Laboratory pH Measurements of National Atmospheric Deposition Program/National Trends Network Precipitation Samples

Latysh, Natalie; Gordon, John

doi:10.1023/b:wate.0000022971.59349.fc

Cited by 8 publications

(7 citation statements)

References 23 publications

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“…Many technical questions about the integrity and representativeness of NTN measurements have been addressed by PCQA throughout the past 33 years of network operation. Results of studies to address NTN sample integrity were completed by others (1987 and, See and others (1989), others (1989 and, Gordon (1997 and1999), and Latysh and Gordon (2004). MDN has been the subject of quality assurance studies by Vermette and others (1995) and Wetherbee and others (2004Wetherbee and others ( , 2005Wetherbee and others ( , 2006Wetherbee and others ( , 2009Wetherbee and others ( , and 2010.…”

Section: Precipitation Chemistry Quality Assurancementioning

confidence: 99%

Effects of equipment performance on data quality from the National Atmospheric Deposition Program/National Trends Network and the Mercury Deposition Network

Wetherbee¹,

Rhodes²

2013

Open-File Report

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The U.S. Geological Survey Branch of Quality Systems operates the Precipitation Chemistry Quality Assurance project (PCQA) to provide independent, external qualityassurance for the National Atmospheric Deposition Program (NADP). NADP is composed of five monitoring networks that measure the chemical composition of precipitation and ambient air. PCQA and the NADP Program Office completed five short-term studies to investigate the effects of equipment performance with respect to the National Trends Network (NTN) and Mercury Deposition Network (MDN) data quality: sample evaporation from NTN collectors; sample volume and mercury loss from MDN collectors; mercury adsorption to MDN collector glassware, grid-type precipitation sensors for precipitation collectors, and the effects of an NTN collector wind shield on sample catch efficiency. Sample-volume evaporation from an NTN Aerochem Metrics (ACM) collector ranged between 1.1-33 percent with a median of 4.7 percent. The results suggest that weekly NTN sample evaporation is small relative to sample volume. MDN sample evaporation occurs predominantly in western and southern regions of the United States (U.S.) and more frequently with modified ACM collectors than with N-CON Systems Inc. collectors due to differences in airflow through the collectors. Variations in mercury concentrations, measured to be as high as 47.5 percent per week with a median of 5 percent, are associated with MDN sample-volume loss. Small amounts of mercury are also lost from MDN samples by adsorption to collector glassware irrespective of collector type. MDN 11-grid sensors were found to open collectors sooner, keep them open longer, and cause fewer lid cycles than NTN 7-grid sensors. Wind shielding an NTN ACM collector resulted in collection of larger quantities of precipitation while also preserving sample integrity.

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Section: Precipitation Chemistry Quality Assurancementioning

confidence: 99%

Effects of equipment performance on data quality from the National Atmospheric Deposition Program/National Trends Network and the Mercury Deposition Network

Wetherbee¹,

Rhodes²

2013

Open-File Report

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“…The zvalue incorporated the difficulty of measuring lower hydrogenion concentrations by incorporating the f-pseudosigma, which is calculated using the interquartile range of all observations. The interquartile range for intersite-comparison solutions increased with increasing pH values due to the greater difficulty in accurately measuring higher pH solutions (Latysh and Gordon, 2004).…”

Section: Intersite-comparison Followup Studymentioning

confidence: 99%

“…The intersite-comparison program was designed to assess the accuracy and reliability of field pH and specificconductance (SC) measurements performed by site operators. Chemical changes between field and laboratory measurements render the initial assessment of precipitation chemistry important (Latysh and Gordon, 2004). In January 2003, the blindaudit program was replaced by the sample-handling evaluation program.…”

Section: Introductionmentioning

confidence: 99%

External quality-assurance programs managed by the U.S. Geological Survey in support of the National Atmospheric Deposition Program/National Trends Network

Latysh¹,

Wetherbee²

2005

Open-File Report

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The U.S. Geological Survey, Branch of Quality Systems, operates the external quality-assurance programs for the National Atmospheric Deposition Program/National Trends Network (NADP/NTN). Beginning in 1978, six different programs have been implemented-the intersite-comparison program, the blind-audit program, the sample-handling evaluation program, the field-audit program, the interlaboratorycomparison program, and the collocated-sampler program. Each program was designed to measure error contributed by specific components in the data-collection process. The intersite-comparison program, which was discontinued in 2004, was designed to assess the accuracy and reliability of field pH and specific-conductance measurements made by site operators. The blind-audit and sample-handling evaluation programs, which also were discontinued in 2002 and 2004, respectively, assessed contamination that may result from sampling equipment and routine handling and processing of the wet-deposition samples. The field-audit program assesses the effects of sample handling, processing, and field exposure. The interlaboratorycomparison program evaluates bias and precision of analytical results produced by the contract laboratory for NADP, the Illinois State Water Survey, Central Analytical Laboratory, and compares its performance with the performance of international laboratories. The collocated-sampler program assesses the overall precision of wet-deposition data collected by NADP/NTN. This report documents historical operations and the operating procedures for each of these external quality-assurance programs. USGS quality-assurance information allows NADP/NTN data users to discern between actual environmental trends and inherent measurement variability.

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“…The effects of handling, storage, filtration, refrigeration and transport of liquid precipitation samples have been documented (e.g., Bigelow et al, 1989;Latysh & Gordon, 2004;Tang et al, 1987). However, studies examining these aspects of lake and stream water sampling are less common.…”

Section: Introductionmentioning

confidence: 98%

Evaluation of Storage and Filtration Protocols for Alpine/Subalpine Lake Water Quality Samples

Korfmacher

Musselman

2006

Environ Monit Assess

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Many government agencies and other organizations sample natural alpine and subalpine surface waters using varying protocols for sample storage and filtration. Simplification of protocols would be beneficial if it could be shown that sample quality is unaffected. In this study, samples collected from low ionic strength waters in alpine and subalpine lake inlets and outlets in the western United States were used to evaluate (1) effects of refrigerated storage time on the chemistry of unfiltered samples, and (2) differences in sample filtration protocols. No analytes exhibited significant changes when stored less than 48 h. Six analytes (pH, sodium, ammonium, potassium, chloride, sulfate) exhibited statistically significant (but small) changes when storage time exceeded 48 h. Two analytes (calcium, nitrate) were significantly higher when samples were field filtered than when filtered in the laboratory, but the differences were also small. For waters similar to those in this test, unfiltered refrigerated samples may be stored up to 48 h without compromising sample quality. The small differences between field and lab filtration do not justify the expense, training, and contamination risk of field filtration.

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Investigation of Differences between Field and Laboratory pH Measurements of National Atmospheric Deposition Program/National Trends Network Precipitation Samples

Cited by 8 publications

References 23 publications

Effects of equipment performance on data quality from the National Atmospheric Deposition Program/National Trends Network and the Mercury Deposition Network

Effects of equipment performance on data quality from the National Atmospheric Deposition Program/National Trends Network and the Mercury Deposition Network

External quality-assurance programs managed by the U.S. Geological Survey in support of the National Atmospheric Deposition Program/National Trends Network

Evaluation of Storage and Filtration Protocols for Alpine/Subalpine Lake Water Quality Samples

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