摘要
A glasshouse pot experiment was conducted to study changes in the solubility of copper and zinc in the soil plant system following heavy application of sewage sludge and partial sterilisation of the sludge/soil mixture. A slightly acid sandy loam was mixed with alkaline stabilised and composted urban sewage sludge solids (`Agri Soil', 180 t hm -2 ), and the soil/sludge mixture was γ irradiated (10 kGy). The contrasts without the application of sewage sludge and γ irradiation were also included in the experiment. Perennial ryegrass (Lolium perenne cv. Magella) was grown on irradiated and unirradiated soils for 50 days. Soil solution samples were obtained using soil suction samplers immediately before plant transplantation and every ten days thereafter. The soil solution samples were used directly for determination of Cu and Zn, together with pH, electrical conductivity (EC) and absorbance at wavelength 360 nm (A 360 ). Application of Agri Soil led to a substantial increase in dissolved Cu and a significant decrease in dissolved Zn in the soil solution and these effects were accompanied by increased soil solution pH, EC and A 360 . The alkaline sludge product (Agri Soil) in combination with γ irradiation also led to a pronounced elevation of Cu and A 360 but a marked decline in EC, indicating an increase in dissolved organic compounds and a decrease in the ionic strength of the soil solution. The dissolved Cu and Zn, EC and A 360 usually decreased while the pH increased after plant growth for 50 days.
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