Distribution and mobility of selenium and other trace elements in shallow groundwater of the western San Joaquin Valley, California

As part of a comprehensive study on the hydrology and geochemistry of the San Joaquin valley, Calif., the concentrations of major ions and trace elements in shallow groundwater underlying the irrigated area of the valley were determined. The concentrations of major ions were similar in the 2 principle geological zones (the alluvial fan and basin trough), but selenium concentrations were significantly higher in the alluvial-fan zone than in the basin-trough zone. The principal factors affecting the selenium concentrations in the shallow groundwater were the degree of groundwater salinity and the geological source of the alluvial soil material. There are 33 references.