Quality-Control Results for Ground-Water and Surface-Water Data, Sacramento River Basin,
California, National Water-Quality Assessment, 1996-1998
By Cathy Munday, and Joseph L. Domagalski
U.S. GEOLOGICAL SURVEY
Water–Resources Investigations Report 02-4201
Sacramento, California 2003
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Abstract
Evaluating the extent that bias and variability affect the interpretation
of ground- and surface-water data is necessary to meet the objectives of the National Water-Quality Assessment
(NAWQA) Program. Quality-control samples used to evaluate the bias and variability include annual equipment blanks,
field blanks, field matrix spikes, surrogates, and replicates. This report contains quality-control results for the
constituents critical to the ground- and surface-water components of the Sacramento River Basin study unit of the
NAWQA Program. A critical constituent is one that was detected frequently (more than 50 percent of the time in blank
samples), was detected at amounts exceeding water-quality standards or goals, or was important for the interpretation
of water-quality data. Quality-control samples were collected along with ground- and surface-water samples during the
high intensity phase (cycle 1) of the Sacramento River Basin NAWQA beginning early in 1996 and ending in 1998.
Ground-water field blanks indicated contamination of varying levels of significance when
compared with concentrations detected in environmental ground-water samples for ammonia, dissolved organic carbon,
aluminum, and copper. Concentrations of aluminum in surface-water field blanks were significant when compared with
environmental samples. Field blank samples collected for pesticide and volatile organic compound analyses revealed
no contamination in either ground- or surface-water samples that would effect the interpretation of environmental
data, with the possible exception of the volatile organic compound trichloromethane (chloroform) in ground water.
Replicate samples for ground water and surface water indicate that variability resulting from
sample collection, processing, and analysis was generally low. Some of the larger maximum relative percentage differences
calculated for replicate samples occurred between samples having lowest absolute concentration differences and(or) values
near the reporting limit.
Surrogate recoveries for pesticides analyzed by gas chromatography/mass spectrometry (GC/MS),
pesticides analyzed by high performance liquid chromatography (HPLC), and volatile organic compounds in ground- and
surface-water samples were within the acceptable limits of 70 to 130 percent and median recovery values between 82 and
113 percent. The recovery percentages for surrogate compounds analyzed by HPLC had the highest standard deviation, 20
percent for ground-water samples and 16 percent for surface-water samples, and the lowest median values, 82 percent for
ground-water samples and 91 percent for surface-water samples. Results were consistent with the recovery results described
for the analytical methods.
Field matrix spike recoveries for pesticide compounds analyzed using GC/MS in ground- and
surface-water samples were comparable with published recovery data. Recoveries of carbofuran, a critical constituent
in ground- and surface-water studies, and desethyl atrazine, a critical constituent in the ground-water study, could
not be calculated because of problems with the analytical method. Recoveries of pesticides analyzed using HPLC in ground-
and surface-water samples were generally low and comparable with published recovery data. Other methodological problems
for HPLC analytes included nondetection of the spike compounds and estimated values of spike concentrations.
Recovery of field matrix spikes for volatile organic compounds generally were within the
acceptable range, 70 and 130 percent for both ground- and surface-water samples, and median recoveries from 62 to 127
percent. High or low recoveries could be related to errors in the field, such as double spiking or using spike solution
past its expiration date, rather than problems during analysis. The methodological changes in the field spike protocol
during the course of the Sacramento River Basin study, which included decreasing the amount of spike solution added to
volatile organic compound samples and changing the method of spike delivery, had no apparent effect on recovery results.
CONTENTS
Abstract
Introduction
Quality-Control Sample Types
Blank Samples
Field Blanks
Equipment Blanks
Trip Blanks
Source Solution Blanks
Ambient Blanks
Spiked Samples
Replicate Samples
Analysis
Quality-Assurance and Quality-Control Design
Ground Water
Blank Samples
Major Ions
Dissolved Organic Carbon
Nutrients
Trace Elements
Arsenic
Aluminum
Copper
Chromium
Cadmium
Barium
Pesticides in Filtered Water Analyzed by Gas Chromatography/Mass Spectrometry
Pesticides in Filtered Water Analyzed by High Performance Liquid Chromatography
Volatile Organic Compounds
Replicate Samples
Surrogate Recovery
Field Spiked Samples
Pesticides in Filtered Water Analyzed by Gas Chromatography/Mass Spectrometry
Pesticides in Filtered Water Analyzed by High Performance Liquid Chromatography
Volatile Organic Compounds
Surface Water
Blank Samples
Major Ions
Dissolved Organic Carbon
Suspended Organic Carbon
Nutrients
Trace Elements
Aluminum
Chromium, Copper, Manganese, Nickel, Zinc, and Iron
Total Mercury
Methylmercury
Pesticides in Filtered Water Analyzed by Gas Chromatography/Mass Spectrometry
Pesticides in Filtered Water Analyzed by High Performance Liquid Chromatography
Volatile Organic Compounds
Replicate Samples
Surrogate Recovery
Field Spiked Samples
Pesticides in Filtered Water Analyzed by Gas Chromatography/Mass Spectrometry
Pesticides in Filtered Water Analyzed by High Performance Liquid Chromatography
Volatile Organic Compounds
Summary and Conclusion
References Cited
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Water Resources of California
