U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 02-4175
Sacramento, California 2002
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Organcochlorine compounds, semivolatile-organic compounds (SVOC), and trace elements were analyzed in reservoir sediment cores, streambed sediment, and fish tissue in the Santa Ana River Basin as part of the U.S. Geological Survey's National Water-Quality Assessment Program. Three reservoirs were sampled in areas that have different degrees of urbanization. Streambed sediment and fish tissue collected at 12 sites were divided into two groups, urban and nonurban. More organochlorine compounds were detected in reservoir sediment cores, streambed sediment and fish tissue, and at higher concentrations at urban sites than at nonurban sites. At all sites, except West Street Basin, concentrations of organochlorine compounds were lower than the probable-effect concentration (PEC). At the highly urbanized West Street Basin, chlordane and p,p´-DDE exceeded the PEC throughout the historical record. The less stringent threshold-effect concentration (TEC) was exceeded for six compounds at eight sites. Most of the organochlorine compounds detected in streambed sediment and fish tissue were at urban sites on the Santa Ana River as opposed to its tributaries, suggesting accumulation and persistence in the river.
More SVOCs were detected in reservoir sediment cores and streambed
sediment, and at higher concentrations, at urban sites than at nonurban sites. At all the
sites,
except West Street Basin, concentrations of SVOCs were lower than the PEC. At West Street
Basin,
chrysene, pyrene, and total polycyclic-aromatic hydrocarbons exceeded the PEC throughout the
historical record. The TEC was exceeded for 10 compounds at 3 sites. Most of the SVOCs were
detected in streambed sediment at urban sites on tributaries to the Santa Ana River rather than
the mainstem itself. The less frequent occurrence and lower concentrations in the Santa Ana
River
suggest that SVOCs are less persistent than organochlorine compounds, possibly as a result of
volatization, gradation, or dilution.
Most trace-element detections in reservoir sediment cores and streambed
sediment were at urban sites, and the concentrations were generally higher than at nonurban
sites.
Lead and zinc exceeded their PECs at West Street Basin throughout the historical record; copper
exceeded its PEC at Canyon Lake, an area of urban growth. The TEC was exceeded for 10 compounds
at
11 sites. Frequency of detection and concentration did not differ between tributary and Santa
Ana
River sites, which may be attributed to the fact that trace elements occur naturally. Four
trace
elements (arsenic, copper, mercury, and selenium) had higher concentrations in fish tissue at
nonurban sites than at urban sites.
Concentrations decreased over time for organochlorine compounds at all
three reservoirs, probably a result of the discontinued use of many of the compounds.
Decreasing
trends in SVOCs and trace elements were observed at West Street Basin, but increasing trends
were
observed at Canyon Lake. Concentrations of organochlorine compounds, SVOCs, and trace elements
were higher during periods of above average rainfall at both West Street Basin and Canyon
Lake.
Abstract
Introduction
Purpose and Scope
Acknowledgments
Study Design
Background Information
Site Selection
Reservoir Sites
Streambed-Sediment and Fish-Tissue Sites
Description of Analytes
Methods of Sample Collection, Sample Processing and Data Analysis
Sample Collection and Processing
Data Analysis
Effects of Urbanization and Long-Term Rainfall on Occurrence and Trends
Organochlorine Compounds
Reservoir Sediment Cores
Streambed Sediment
Fish Tissue
Semivolatile-Organic Compounds
Reservoir Sediment Cores
Streambed Sediment
Trace Elements
Reservoir Sediment Cores
Streambed Sediment
Fish Tissue
Summary and Conclusions
References Cited
Appendix
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