USGS Blind Sample Project: monitoring and evaluating laboratory analytical quality

Ludtke, Amy S.; Woodworth, Mark T.

doi:10.3133/fs13697

Cited by 10 publications

(8 citation statements)

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“…Accuracy of analyses was evaluated based on results of repeated measurements of USGS standard reference samples and certified high‐purity standards traceable to the National Institute of Standards, and by participation in blind‐audit performance tests conducted by the USGS [ Ludtke and Woodworth , 1997] and by Environment Canada [ Blum and Alkema , 2000]. Accuracy of analyses was better than 1 μmol L −1 or 1.5% for all constituents.…”

Section: Methodsmentioning

confidence: 99%

Changes in the chemistry of lakes and precipitation in high‐elevation national parks in the western United States, 1985–1999

Clow

Sickman²,

Striegl

et al. 2003

Water Resources Research

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[1] High-elevation lakes in the western United States are sensitive to atmospheric deposition of sulfur and nitrogen due to fast hydrologic flushing rates, short growing seasons, an abundance of exposed bedrock, and a lack of well-developed soils. This sensitivity is reflected in the dilute chemistry of the lakes, which was documented in the U.S. Environmental Protection Agency's Western Lake Survey of 1985. Sixty-nine lakes in seven national parks sampled during the 1985 survey were resampled during fall 1999 to investigate possible decadal-scale changes in lake chemistry. In most lakes, SO 4 concentrations were slightly lower in 1999 than in 1985, consistent with a regional decrease in precipitation SO 4 concentrations and in SO 2 emissions in the western United States. Nitrate concentrations also tended to be slightly lower in 1999 than in 1985, in contrast with generally stable or increasing inorganic N deposition in the west. Differences in alkalinity were variable among parks but were relatively consistent within each park. Possible effects of annual and seasonal-scale variations in precipitation amount on lake chemistry were evaluated based on climate data available for the parks and an analysis of climatic effects at two research watersheds with long-term records. Results suggest that rain prior to sampling in 1985 may have caused elevated NO 3 in some lakes due to direct runoff of precipitation and flushing of NO 3 from alpine soils, which may explain some of the decrease in NO 3 concentrations observed in survey lakes.

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Section: Methodsmentioning

confidence: 99%

Changes in the chemistry of lakes and precipitation in high‐elevation national parks in the western United States, 1985–1999

Clow

Sickman²,

Striegl

et al. 2003

Water Resources Research

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“…Time series plots of stream water concentrations were inspected visually for step functions, which can indicate changes in analytical bias due to methods changes. The USGS central laboratory has routinely incorporated blind-audit samples into each analytical run since the early 1980s, and the results are reported by the USGS Branch of Quality Assurance [Ludtke and Woodworth, 1997]. The bias of results for blind-audit samples analyzed by the central laboratory between 1985 and 1996 were tested for trends and inspected for step functions.…”

Section: Data Screeningmentioning

confidence: 99%

“…This illustrates the importance of routine analyses of blind samples that have a matrix similar to that of the natural waters being monitored. Other quality-assurance measures, including submittal of field blanks, analysis of spiked samples, and documentation of changes in sampling or analytical procedures are also important [Ludtke and Woodworth, 1997].…”

Section: Implications For Long-term Monitoring Programsmentioning

confidence: 99%

Long‐term trends in stream water and precipitation chemistry at five headwater basins in the northeastern United States

Clow¹,

Mast²

1999

Water Resources Research

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“…Sulphate (SO 4 ), nitrate (NO 3 ) and chloride (Cl) were measured by ion chromotography on filtered samples. Accuracy of analyses generally was better than š5% on the basis of repeated analyses of standard reference waters obtained from the US Geological Survey (Ludtke and Woodworth, 1997). Detailed discussions of discharge measurements; stream-water chemistry sampling and analysis methods; and precision, accuracy and detection limits of analyses are provided in Sueker (1996).…”

Section: Flow Measurements Sample Collection and Analysesmentioning

confidence: 99%

Effect of basin physical characteristics on solute fluxes in nine alpine/subalpine basins, Colorado, USA

Sueker¹,

Clow

Ryan

et al. 2001

Hydrological Processes

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Abstract:Alpine/subalpine basins may exhibit substantial variability in solute fluxes despite many apparent similarities in basin characteristics. An evaluation of controls on spatial patterns in solute fluxes may allow development of predictive tools for assessing basin sensitivity to outside perturbations such as climate change or deposition of atmospheric pollutants. Relationships between basin physical characteristics, determined from geographical information system (GIS) tools, and solute fluxes and mineral weathering rates were explored for nine alpine/subalpine basins in Rocky Mountain National Park, Colorado, using correlation analyses for 1993 and 1994 data. Stream-water nitrate fluxes were correlated positively with basin characteristics associated with the talus environment; i.e., the fractional amounts of steep slopes (½ 30°), unvegetated terrain and young debris (primarily Holocene till) in the basins, and were correlated negatively with fractional amounts of subalpine meadow terrain. Correlations with nitrate indicate the importance of the talus environment in promoting nitrate flux and the mitigating effect of areas with established vegetation, such as subalpine meadows. Total mineral weathering rates for the basins ranged from about 300 to 600 mol ha 1 year 1 . Oligoclase weathering accounted for 30 to 73% of the total mineral weathering flux, and was positively correlated with the amount of old debris (primarily Pleistocene glacial till) in the basins. Although calcite is found in trace amounts in bedrock, calcite weathering accounted for up to 44% of the total mineral weathering flux. Calcite was strongly correlated with steep slope, unvegetated terrain, and young debris-probably because physical weathering in steep-gradient areas exposes fresh mineral surfaces that contain calcite for chemical weathering. Oligoclase and calcite weathering are the dominant sources of alkalinity in the basins. However, atmospherically deposited acids consume much of the alkalinity generated by weathering of calcite and other minerals in the talus environment. Published in

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USGS Blind Sample Project: monitoring and evaluating laboratory analytical quality

Cited by 10 publications

References 0 publications

Changes in the chemistry of lakes and precipitation in high‐elevation national parks in the western United States, 1985–1999

Changes in the chemistry of lakes and precipitation in high‐elevation national parks in the western United States, 1985–1999

Long‐term trends in stream water and precipitation chemistry at five headwater basins in the northeastern United States

Effect of basin physical characteristics on solute fluxes in nine alpine/subalpine basins, Colorado, USA

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