Summary of external quality assurance programs and results for the NADP/NTN
- Geological Survey, Denver, CO (United States)
The U.S. Geological Survey utilizes several programs to document and improve the quality of NADP/NTN data. The contribution of sample collection and shipping container surfaces to wet deposition sample chemistry and routine sample handling effects are evaluated with a blind audit program. The results of the blind audit program indicate that the median amount of SO{sub 4}{sup 2-} contamination attributable to handling and container contact has decreased from 0.04 mg/L in 1992 to 0.01 mg/L in 1995. Median percent bias in laboratory hydrogen ion concentration measurements due to handling and container contamination decreased from -9.76 {mu}eq/L in 1992 to -0.10 {mu}/L in 1995. An intersite comparison program evaluates onsite pH and specific conductance determinations. The median percent difference between the reported and expected pH value approximated 0% in every intersite comparison study, an indication that onsite pH measurements have consistently been unbiased. An interlaboratory comparison program compares the results from the NADP/NTN contract laboratory with results from other North American laboratories routinely analyzing wet deposition samples. The interlaboratory comparison program results in 1994-95 indicate cation precision estimates at the 50{sup th} percentile were quite similar between laboratories, with median absolute differences less than or equal to 0.004 mg/L. Anion precision estimates at the 50{sup th} percentile exhibited greater variability, but the median absolute differences were less than or equal to 0.014 mg/L. Network precision is estimated by the typical random error associated with differences between the existing and collocated collection equipment. For SOP{sub 4}{sup 2-} and NO{sub 3}{sup -}, random error in network measurements has consistently been less than 7%.
- OSTI ID:
- 617896
- Report Number(s):
- CONF-970145-; TRN: 98:002057-0065
- Resource Relation:
- Conference: 2. joint conference on acid rain and electric utilities, Scottsdale, AZ (United States), 20-22 Jan 1997; Other Information: PBD: 1997; Related Information: Is Part Of Acid rain & electric utilities II; PB: 1047 p.
- Country of Publication:
- United States
- Language:
- English
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