Heavy metals extractable from a calcareous soil treated with sewage sludge

Abstract

Four chemically extractable elements available to plants, i.e. Cu, Mn, Fe and Zn, occurring in a calcareous soil treated with Riyadh digested sewage sludge were investigated by glasshouse and incubation experiments. The results indicate that Riyadh sewage sludge is apparently a good source of elements for plant growth. The plant-available and H 2O-, HCl- and DTPA-extractable metals found in sludge-treated soil were considerably higher than those found in soil alone. Fluctuations in the concentrations of chemically extractable metals with time were observed, indicating that more than one reaction process is operating and leading to more stable forms. It was concluded that cropland utilisation of Riyadh digested sewage sludge, on the calcareous soils commonly found in Saudi Arabia, is unlikely to give rise to the heavy metal problems associated with disposal on acid soils.