According to a recent study by the U.S. Geological Survey (USGS), inorganic trace elements, such as fluoride, arsenic, molybdenum, and boron, were detected at high concentrations in 42 percent of groundwater used for public supply in the southern desert areas, inlcuding Borrego Valley, of the state of California.

The study is part of the State Water Resources Control Board GAMA Program Priority Basin Project, for which the USGS California Water Science Center is the technical lead. These findings are significant because elsewhere in the state, high concentrations of trace elements generally are found in only 6 to 28 percent of the groundwater used for public supply. The four elements are naturally present in rocks, soils and the water that comes in contact with them.

High concentrations generally are the result of natural processes, but human activities may have some influence. Further, high concentrations are considered above the Environmental Protection Agency's (EPA) or California Department of Public Health's established Maximum Contaminant Levels or other non-regulatory health-based levels for chemical constituents or elements not having MCLs. Moderate concentrations are considered greater than one-tenth the MCL.

"Local water distributors, regional agencies, as well as the U.S. EPA, are aware of the presence of arsenic, fluoride, boron, and other trace elements in groundwater in the desert region, and are actively working to manage local groundwater resources and assure that water delivered to consumers meets water-quality standards," said Dr. Miranda Fram, chief of the USGS Groundwater Ambient Monitoring and Assessment program. "This quantitative assessment of where, what and how much contamination is in the groundwater will help agencies better manage groundwater resources."

Nitrate was detected at high concentrations in less than 3 percent of groundwater used for public supply. Household, commercial, industrial, and agricultural products and pesticides were detected at moderate concentrations in about 5 percent of the groundwater tested.

In cooperation with the SWRCB, the USGS is monitoring and assessing groundwater quality in 120 priority basins and groundwater outside of basins to better understand the natural and human factors affecting groundwater quality in California. The main goals of the GAMA Program Priority Basin Project are to improve comprehensive statewide groundwater monitoring and to increase the availability of groundwater-quality information to the public.

[출처 = Water World/ 2014년 4월 25일]