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Quality Assurance/Quality Control


All sample handling, analysis, storage, and data reporting adhere to QA/QC guidelines established in the Handbook of Methods for Acid Deposition Studies (EPA 600/4-87/026, September 1987) and the Standard Methods for the Examination of Water and Waste Water (20th edition). Within each analytical run, field and laboratory blanks are analyzed as well as duplicate samples and check standards (every 10 samples). All commercial standards are certified by the National Institute of Standards and Technology (Washington, DC).

Analytical Evaluation

Periodically, the Air Program Laboratory participates in exchange and analysis of unknown samples (USGS Analytical Evaluation Program). This program assesses the quality of our laboratory methods and procedures.

Results of U.S. Geological Analytical Evaluation Program--Spring 2009

Low Ionic Strength Precipitation/Snowmelt Sample
Analyte Most Probable Value (mg/L) Water Lab Reported Value (mg/L)

Percent Difference

(%)

Ca
0.415
0.4462
7.52
Cl
1.78
1.988
11.69
F
0.100
0.0907
-9.30
K
0.650
0.7346
13.02
Mg
0.057
0.0625
9.65
Na
0.230
0.2374
3.22
pH
4.88
4.784
-1.97
SO4
0.210
0.2033
-3.19
Cond.
14.0
13.63
-2.64

Results of U.S. Geological Analytical Evaluation Program--Fall 2009


Low Ionic Strength Precipitation/Snowmelt Sample
Analyte Most Probable Value (mg/L) Water Lab Reported Value (mg/L)

Percent Difference

(%)

Ca
0.741
0.779
5.13
Cl
1.05
1.042
-0.76
F
0.040
0.036
-10.00
K
0.080
0.091
13.75
Mg
0.340
0.351
3.24
Na
0.321
0.338
5.30
pH
6.70
6.67
-0.45
SO4
0.418
0.408
-2.39
Cond.
10.0
9.70
-3.00

Supplemental information and SRS Round Robin results can be viewed at http://bqs.usgs.gov/srs (Air Program Laboratory = Lab No. 422)