| Abstract: | Analyses of 42 sewage sludges from rural and industrial towns in England and Wales show very large concentrations of certain trace elements. Total contents of 5% Zn, nearly 1% Cr and Cu and 0.5 % Ni were found in certain dried sludges. Total contents of Cu, Sn and Zn and, to a lesser extent, Ag, Bi and Pb were much greater than the levels of these elements in soils. Total Cr and Ni were very high in a small number of samples. Acetic acid-soluble Zn and Cu levels were generally very much greater than in soils. Overall, Mn, Ni and Zn had considerably higher percentage solubilities than Cr, Cu, Mo, Pb, Sn and V. Zinc, Cu and Ni appear to be the elements most likely to give rise to toxicity problems in plants due to the use of sewage sludge as a soil additive. |
