Treatment with biosolids affects soil availability and plant uptake of potentially toxic elements

Sewage sludge can be applied to soils without treatment or after biological treatments. We hypothesized that non-digested biosolids have more available potentially toxic elements (PTE) than digested ones. To test the hypothesis six field experiments with maize (Zea mays L.) were carried out on farms located in Buenos Aires province, Argentina. Treatments were non-digested or digested biosolids and controls. Cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) were determined with ICP/ES in the used biosolids; in soils (EDTA extractable and total concentration) and in maize (grains and straw). Total Cr, Cu, Ni and Zn, and EDTA extractable Cu and Zn were significantly higher in soils treated with non-digested biosolids. The concentration of Cd, Cr, Cu and Zn in maize plants and Cd concentration in grains were significantly higher in the non-digested biosolid treatment. Soils receiving non-digested biosolids, exhibited higher PTE crop availability in general terms. This fact partially supports the proposed hypothesis. In the non-digested treatments, Cd, one of the most hazardous PTE, was significantly higher in maize plants and grains.