The Investigation And Restoration Research Of Shiwuli River’s Sediment

Shiwuli River is the key rehabilitation region in the northwest of Chaohu Lake. Sediments are special composition in ecosystem which plays an important role in the substance circulation; therefore, the restoration has become an urgent problem to be solved. Phytoremediation is one of the most economy and effective way among variety of methods in the polluted sediment recovering, and has caused the extensive concern in the academic circles. Based on the analysis of aquatic plant recovery and the basal research at home and abroad, the main work finished is as follows:(1)The concentration of total nitrogen, total phosphorus, total organic matter and heavy metals (Cu,Zn,Pb,Cd,Cr) are measured based on the ten sampling points in Shiwuli River. The single factor index method and potential ecological risk assessment are used to further evaluate and analyze the situation of sediment pollution.(2) Study the effect of aquatic plant restoration. In order to provide a theoretical basis for further development of the aquatic plants in the recovery of the sediment, we choose 6 kinds of aquatic plants:Potamogeton lucens L., Vallisneria natans, Elodea canadensis, Trapa bispinosa Roxb, Nymphaea L.and Iris tectorum Maxim, and study the absorbing ability of total nitrogen, total phosphorus, and heavy metals for futher research.(3) Building an aquatic plant community in Shiwuli River for sediment remediation. Based on the study above and the principle of community configuration, combining with different functions and water conservancy conditions in channel segment, several aquatic plant communities were constructed to restore the sediment.Through the study above, we concluded as follows:(1)There are different levels of overweight and quite obvious synchronous change trend of the content of total nitrogen, total phosphorus and total organic matter in Shiwuli River’s sediments, the content of total nitrogen, total phosphorus and total organic matter is lower in upstream base than midstream and downstream. The content of heavy metal Cu, Zn, Pb, Cd and Cr all has different levels of overweight. Overall, the comprehensive risk index of heavy metals in middle reaches of the river is almost the same as either upstream or downstream river.(2)Potamogeton lucens L., Vallisneria natans, Elodea canadensis, Trapa bispinosa Roxb, Nymphaea, and Iris tectorum Maxim are effective to remove the content of total nitrogen, total phosphorus and heavy metals (Cu, Zn, Pb, Cd, Cr). But different plants have different absorption and accumulation abilities. The dead rotten plants can increase the content of sediment of total nitrogen, total phosphorus, but in the process of tending to balance, the content of total nitrogen, total phosphorus with plants is lower than without plants.(3)According to the reasons of sediments pollution in Shiwuli River’s and function planning in different channel segments, combined with the characteristics of aquatic plant species, the recovering sediment is established with high efficiency、economics and landscaping, better ecological protection and comprehensive benefits. These communities can be chosen based on channel conditions and functional requirements in the Shiwuli River basal restoration practices.