Occurrence of Naturally High Cadmium Levels in Soils and Its Accumulation by Vegetation

Abstract

Abstract A survey of soils in the Santa Monica Mountains of Los Angeles and Venture Counties, Calif., was conducted to determine the relationship between parent materials and soil Cd contents. Twenty‐four series were sampled and analyzed for Cd after digestion in 4 N HNO 3 . Residual soils developed from shale parent materials had the greatest Cd concentrations, with a mean of 7.5 µ g/g, whereas soils developed from sandstone and basalt had the lowest Cd concentrations, with a mean of 0.84 µ g/g. Alluvial soils with parent materials from mixed sources had an intermediate mean Cd content of 1.5 µ g/g. A more extensive survey of the dominant soil series of the area was carried out and the Millsholm series, mapped in 30% of the area, was found to have a mean Cd content of 7.3 µ g/g. A greenhouse vegetable study conducted with seven soils from the area, representing a range of Cd concentrations, showed that the Cd present naturally in these soils was absorbed by the vegetables in amounts sufficient to be of public health concern.