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Geogenic sources of benzene in aquifers used for public supply, California

Environmental Science and Technology

By:
,
DOI: 10.1021/es302024c

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Abstract

Statistical evaluation of two large statewide data sets from the California State Water Board's Groundwater Ambient Monitoring and Assessment Program (1973 wells) and the California Department of Public Health (12417 wells) reveals that benzene occurs infrequently (1.7%) and at generally low concentrations (median detected concentration of 0.024 μg/L) in groundwater used for public supply in California. When detected, benzene is more often related to geogenic (45% of detections) than anthropogenic sources (27% of detections). Similar relations are evident for the sum of 17 hydrocarbons analyzed. Benzene occurs most frequently and at the highest concentrations in old, brackish, and reducing groundwater; the detection frequency was 13.0% in groundwater with tritium <1 pCi/L, specific conductance >1600 μS/cm, and anoxic conditions. This groundwater is typically deep (>180 m). Benzene occurs somewhat less frequently in recent, shallow, and reducing groundwater; the detection frequency was 2.6% in groundwater with tritium ≥1 pCi/L, depth <30 m, and anoxic conditions. Evidence for geogenic sources of benzene include: higher concentrations and detection frequencies with increasing well depth, groundwater age, and proximity to oil and gas fields; and higher salinity and lower chloride/iodide ratios in old groundwater with detections of benzene, consistent with interactions with oil-field brines.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Geogenic sources of benzene in aquifers used for public supply, California
Series title:
Environmental Science and Technology
DOI:
10.1021/es302024c
Volume
46
Issue:
16
Year Published:
2012
Language:
English
Publisher:
ACS Publications
Publisher location:
Washington, D.C.
Contributing office(s):
California Water Science Center
Description:
8 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Science and Technology
First page:
8689
Last page:
8697
Number of Pages:
9
Country:
United States
State:
California