The environmental impact of heavy metals from sewage sludge in ferralsols (Sao Paulo, Brazil)

The spreading of sewage sludge on acidic ferralsol soil was simulated in a column experiment in order to estimate the potential impact on water and so il quality. Drainage and runoff water were sampled daily over a 2-month exp eriment and analysed for Fe, Ni, Cu, Pb and DOG. Results show a clear influ ence of the sludge on the water quality, especially at the start of the exp eriment, increasing the export of Cu, Ni, Ph and in DOC from the soil, main ly in dissolved form. Nickel was usually the most mobile element in the slu dge and in the soil. In the soil, Pb mobility was complex and increased dra stically with time compared to the other elements. No significant increase in soil heavy metal content due to the sludge spreading was recorded on thi s time scale. (C) 2001 Elsevier Science B.V. All rights reserved.