THE EFFECT OF COVERING ON SEDIMENT IN A CANYON TYPE LAKE UNDER THE ANAEROBIC CONDITION

Active sediment cover system was constructed for the effective control of lake sediment pollution． Several covering materials were prepared according to different proportion of red mud，fly ash，clay and CaCO3 to investigate the effect on control sediment pollutant． The red mud after de-alkalization was the main material． Results showed that the coverage can stabilize the quality of the overlying water，improve the concentration of DO，and limit the COD and TP content． However，the control effect of NH3－N is weak in short term． Additionally，the coverage could decrease heavy metals ( Cu，Pb，Zn，Cr，Cd， Fe，Mn，Ca，Mg) re-released from sediment to overlying water． Considering two aspects of the control effect on endogenous contaminants and stability of the overlying water quality，material Ⅱ ( red mud 38. 9%，clay 14. 4%，fly ash 38. 9%，CaCO3 7. 8%) is most suitable for covering deep lake sediment due to obtaining raw materials conveniently，making simple，low economic cost，simple operation and good effect．