Geogenic Sources of Benzene in Aquifers Used for Public Supply, California

• Published in: Environmental science & technology 2012-08, Vol.46 (16), p.8689-8697
• Main Authors: Landon, Matthew K, Belitz, Kenneth
• Format: Article
• Language: English
• Subjects: Applied sciences; Aquifers; Benzene - analysis; California; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental monitoring; Exact sciences and technology; Groundwater; Groundwaters; Hydrocarbons; Natural water pollution; Pollution; Pollution, environment geology; Water Pollutants, Chemical - analysis; Water Supply; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es302024c

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 (12 417 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 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