Quality-assurance data for routine water analysis in the National Water-Quality Laboratory of the U.S. Geological Survey for water year 1987 /

Abstract

The U.S. Geological Survey maintains a quality-assurance program based on the analysis of reference sam¬ ples for its National Water-Quality Laboratory located in Denver, Colorado. Reference samples containing selected inorganic constituents are prepared at the Survey's Water Quality Services Unit in Ocala, Florida, disguised as rou¬ tine samples, and sent daily or weekly, as appropriate, to the laboratory through other Survey offices. Nutrient sam¬ ples and precipitation samples also were submitted as samples of unknown concentration. The results are stored permanently in the National Water Data Storage and Retrieval System (WATSTORE), the Survey's data base for all water data. These data are analyzed statistically for precision and bias. The results of these statistical analyses are discussed for data collected during water-year 1987. An overall evaluation of the major and trace constituent data for water-year 1987 indicated a lack of precision in the National Water-Quality Laboratory for the determination of 6 out of 58 constituents: chloride; chromium; iron, total recoverable; zinc, dissolved (atomic absorption spectroscopy); zinc, (inductively coupled plasma emission spectroscopy); and zinc, total recoverable. There were fewer constituents having positive or negative bias during water-year 1987 than during water-year 1986. A lack of precision was indicated in the determination of three of the six nutrient constituents: nitrate + nitrite nitrogen as N, orthophosphate as R and phosphorus as R A biased condition was indicated in the determination of ammonia + organic nitrogen as N. There was acceptable precision in the determination of all 10 precipitation-level constituents. One precipita¬ tion-level constituent, sodium, indicated a biased condition.

Quality-assurance results for routine water analyses in US Geological Survey laboratories, water year 1997

“…This report describes the results of a qualityassurance program used to monitor the quality of analytical inorganic, nutrient, and low ionic-strength procedures at the NWQL and inorganic and nutrient procedures at the QWSU. Previous reports (Peart and Thomas, 1983a, 1983b, 1984Peart and Sutphin, 1987;Lucey and Peart, 1988, 1989a, 1989bLucey, 1989;Maloney and others, 1992Maloney and others, , 1993Maloney and others, , 1994 document results from February 1981 through September 1991. Some of the previous reports contain quality-assurance information for organic determinations.…”

Water-quality assessment of the Connecticut, Housatonic, and Thames River Basins study unit: Analysis of available data on nutrients, suspended sediments, and pesticides, 1972-92

“…Friedman and Erdmann (1982) and Pritt and Raese (1992) have described quality-assurance practices at the NWQL. Since 1981, the NWQL has issued a series of reports (Lucey, 1989) that evaluate the precision and bias for inorganic major ion and trace metal constituent data. Dempster and Merk (1991) have described quality assurance for the NWIS data base.…”

Correction of stream quality trends for the effects of laboratory measurement bias

“…A second USGS quality assurance program, the blind sample (BS) program, uses dilutions and mixtures of SRWS reference samples to expand the range of reference concentrations [Lucey and Peart, 1989]. The large number of unique reference samples produced in the BS program makes possible regular monitoring of the accuracy and precision of USGS water quality laboratory measurements.…”