Abstract: The accumulation of heavy metals in the sediment of rivers and lakes has become a major environmental problem in China. On the basis of reducing the water content of sediment by adding quicklime and preliminarily solidifying by sawdust ash, the polluted sludge from a river in Tianjin was further solidified by adding cement or mineral powder plus cement as a demonstration. The leaching concentrations of heavy metals in the test samples were examined using atomic absorption spectrometry, and the curing effects of cement and mineral powder plus cement were compared. Results unveiled that treated by a dosage of 9% quicklime for two days, the contaminated sludge saw an obviously reduction in moisture content. The leaching concentrations of Ni²⁺, Hg²⁺, Pb²⁺ and Cd²⁺ in the contaminated sediment declined by 71.61%, 84.85%, 58.49%, and 77.78% respectively when the content of saw dust was 10%, cement was 20%, and ore powder replacing 40% of the cement, which all met the requirements of relevant technical specifications. To test the planting effect of solidified soil,Eleusine indica and Malachium aquaticum were selected for indoor planting experiment for 60 days. The photosynthesis, root development and growth rate of the two plants were normal. It can be concluded that the contaminated sediment solidified by 9% quicklime, 10% sawdust ash, 20% cement and 40% mineral powder for replacing cement can be used for greening planting.

Key words: heavy metal, quick lime, sawdust, cement, mineral powder, greening planting