Flocculation of sewage sludge with FeCl3 modifies the bioavailability of potentially toxic elements when added to different soils

摘要

Land application of sewage sludge (SS) is a convenient way of disposal compared to incineration or landfill, but can result in accumulation of potentially toxic elements (PTE) in agricultural soils. The environmental risk associated with PTE accumulation in soils that received several SS applications depends mainly on soil pH and SS treatments. We studied the effects of addition to soil of SS treated and untreated with FeCl3 on the biological availability of Zn, Ni, Cd and Cu to oilseed rape (Brassica napus). The plants were grown on an acid and a neutral soil in a greenhouse incubation experiment. The following treatments were carried out: (i) unamended control soil, (ii) sewage sludge amended soils kept bare throughout the experiment and (iii) sewage sludge amended soil planted with oilseed rape. Amended soils received either untreated SS or FeCl3 treated SS at a rate equivalent to 75 t d.w. ha(-1) y(-1).