Metal accumulation by bermudagrass grown on four diverse soils amended with secondarily treated sewage effluent

Land treatment is increasingly being utilized as a method of waste disposal for both sewage effluent and sludges. While there has been considerable attention directed toward the fate of metallic constituents of sewage sludges, there have been fewer studies of the fate and mobility of metals appled to soils in sewage effluent. This study was undertaken utilizing secondarily treated sewage effluent amended to contain less than 1 mg l^?1 each of Cd, Cu, Ni, Pb, and Zn. The effluent was applied weekly for a period of 1 yr on large undisturbed monoliths of four diverse soils enclosed in lysimeters and sprigged to common bermudagrass (Cynodon dactylon L.). Soil samples were collected periodically and extracted with DTPA to measure plant available metals. Vegetation was harvested, weighed, subsampled and analyzed for total metal content. Total plant uptake of Cd, Cu, Pb, and Ni during the year was less than 1% of that applied. Vegetative uptake of Zn was as high as 2%. Metal uptake was greatest in the soil with the lowest initial pH. Heavy metal concentrations in plant tissue exhibited a cyclic trend. A similar increasing cyclic trend was evident in the DTPA extractable metals in the surface 0 to 12.5 cm of the treated soils. Decreases in plant and DTPA extractable metals occurred when the soils dried, allowing O₂ to enter. Vegetative concentrations of Cd, Cu, and Ni exceeded normal ranges of 0.2 to 0.8, 4 to 15, and 1.0 mg kg^?1, respectively, for vegetation while Pb and Zn were near normal. Only Cd concentration of vegetation posed a threat to grazing animals.