CADMIUM, LEAD, ZINC, COPPER, AND NICKEL IN AGRICULTURAL SOILS OF THE UNITED-STATES-OF-AMERICA

Three thousand forty-five surface soil samples from 307 different soil series were analyzed for Pb, Cd, Zn, Cu, Ni, cation exchange capacity (CEC), organic C, and pH in the course of a study of trace element up take by major agricultural crops. The soil data from this study are su mmarized here statistically and in map form to show their interactions and generalized geographic distribution patterns. Amounts of all rive metal elements are generally low in the Southeast. A regional high of about 15 mg/kg Pb covers the Mississipi, Ohio, and Missouri River val leys. Higher values for other elements are generally concentrated in t he West and in the lower Mississippi River Valley. Maximum Cd levels w ere found in soils of the coast ranges of central and southern Califor nia. Copper levels are noticeably higher in organic soil areas of Flor ida, Oregon, and the Great Lakes. Nickel and Cu concentrations are hig h in serpentine soil areas of California. Nickel levels are also somew hat higher in the glaciated areas of the northern great plains and in northern Maine. For the entire dataset, the values of the minimum-maxi mum, 5th, 50th, and 95th percentiles are as follows: (mg/kg dry soil) Cd, <0.005 to 2.0, 0.036, 0.20, 0.78; Pb, 0.5 to 135, 4.0, 11, 23; Zn, 1.5 to 264, 8.0, 53, 126; Cu, 0.3 to 495, 3.8, 18.5, 95; Ni, 0.7 to 2 69, 4.1, 18.2, 57; pH (pH units) 3.9-8.9, 4.7, 6.1, 8.1; CEC (cmol/kg) 0.6 to 204, 2.4, 14.0, 135; and organic C % 0.09 to 63, 0.36, 1.05, 3 3.3. Metal levels generally increased with increasing clay concentrati on.