Desert Groundwater Contamination

High levels of Inorganic elements found in Southern California but low levels of organics.

Published on: Jan 24, 2013

Eight inorganic elements including arsenic, boron, and fluoride were detected in high concentrations in the desert region of southern California in 35% of untreated groundwater used for public water supply, according to a study released by the U.S. Department of the Interior's U.S. Geological Survey (USGS).

The study also found that human-made organic chemical constituents and nitrates were found at high concentrations in less than 1% of the same desert region's aquifers. The study's findings are "important," a press release from the USGS stated, because in other parts of California, high concentrations of inorganic elements typically are found in 10% to 25% of the aquifer system used for public supply, nitrate in 1% to 8%, and human-made organic chemical constituents in up to 2%.

Human-made organic chemical constituents and nitrates were found at high concentrations in less than 1% of the same desert regions aquifers.
Human-made organic chemical constituents and nitrates were found at high concentrations in less than 1% of the same desert region's aquifers.

"High" concentrations are defined as above the Environmental Protection Agency's established Maximum Contaminant Levels (MCLs) or other non-regulatory health-based levels for constituents or elements not having MCLs. The USGS did not analyze treated tap water for this study.

The findings are part of a statewide study in which USGS scientists analyzed untreated groundwater from wells in the desert region between 2006 and 2008, looking for as many as 207 chemical constituents. California's desert region includes Antelope Valley, Coachella Valley, Indian Wells Valley, Owens Valley, Mojave River area and the Colorado River Basin.

Naturally occurring inorganic elements were found in high concentrations in 22% of Owens Valley, 30% of Antelope Valley, 28% of the Mojave area, 42% of Coachella Valley, 45% of Colorado River basins, and 62% of Indian Wells Valley. In these areas, one or more of the following eight inorganic elements was found at high concentrations: arsenic, boron, fluoride, gross-alpha radioactivity, molybdenum, strontium, vanadium, and uranium. High concentrations are generally the result of natural processes, but human activities may have an influence.

High concentrations of organic constituents such as solvents, gasoline components, and pesticides as well as nitrate were found in less than 1% of the desert region's aquifers. Perchlorate was found in high concentrations in 10% of Coachella Valley aquifers and was not found in high concentrations in other areas. High concentrations of organic constituents, nitrate, and perchlorate are typically associated with human activity.