An incubation experiment was conducted to evaluate the potential for water contamination with sludge-
derived organic substances and copper following land application of alkaline-stabilised sewage sludge. Two
contrasting sludge-amended soils were studied. Both soils were previously treated with urban and rural
alkaline biosolids separately at sludge application rates of 0, 30 and 120 t ha-1 fresh product. The air-dried
soil/sludge mixtures were wetted with distilled water, maintained at 40 % of water-holding capacity and
equilibrated for three weeks at 4 ℃ before extraction. Subsamples were extracted with either distilled water
or 0.5 mol L-1 K2SO4 solution. The concentrations of organic C in the aqueous and chemical extracts
were determined directly with a total organic carbon (TOC) analyser. The concentrations of Cu in the two
extracts were also determined by atomic absorption spectrophotometry The relationship between the two
extractable organic C fractions was examined, together with t
