Study On Improving The Sedimentation Of Taihu Lake By Using Vermicompost

In recent years, with the development of economy and the increase of population, a large amount of industrial wastewater, sewage and agricultural waste water has been discharged into water bodies. Contaminants and nutrients in sewage accumulate in the sediment of rivers, lakes and harbors, making sediment a potentially huge endogenous pollutant source. Without timely treatment, this will seriously affect the water quality of the environment and even threaten people’s daily lives. Sediment dredging is a common method for water pollution control, by removing pollutant containing sediment from the water. However, the sediment dredged from the river is massive andhigh in moisture content and contaminants. If simply stacked without any treatment, it will not only occupy a lot of space, but also cause secondary pollution due to rainfall. Moreover, the beneficial ingredients in the sediment can not be fully utilized, leading to a waste of resources.In this study, Vermicompost mixed with sediment from Lake Tai was incubated, followed by determination ofphysical and chemical properties, microbial and enzyme activities, as well as the effects on vegetable growth. Vermicompost mixed with dredged sediment at different ratios (0%,5%,10%,15%,20%g/g) were mixed, stabilized for a certain period, and used to the cultivation of Chinese white cabbage.Basic soil physical and chemical properties, nutrient status and soil microbial biomass and enzyme activities before and after planting were determined. Growth characteristics and nutrient contents of the cabbage seedlings were studied to find the optimal ratio of vermicompost to sediment and thus the improving effects of vericompost.The results based on statistical analysis are as follows:1. Adding appropriate amount of vermicompost can improve the basic physical and chemical properties of the sediment. After the addition, soil bulk density was reduced significantly, while porosity water holding capacity and aeration increased, which provided cabbage roots with balanced growth factors, including optimal water, fertilizer, gas. The results showed that prove that plant cultivation could improve soil physical and chemical properties. With the growth of Chinese white cabbage, the sediment showed a better structure with a decrease in the conductivity and bulk density and an increase in porosity. The treatment with 10% vermicompost had the best improving efficiency.2. Higer ratio of vermicompost addition was more beneficial for nutrient uptake and use efficiency of Chines white cabbage. As compared with control, the treatments with vermicompost addition improved vegetable growth and nutrient uptake significantly. Overall, the optimal growth and nutrient uptake were achieved when vermicompost addition was adjusted at ratio of 10%-15%.3. The addition of vermicompost into the dredged sediment increase microbial biomass to a certain extent, with enzyme activity increased as well. With the increase of vermicompost addition, soil urease activity, phosphatase activity, dehydrogenase activity, and catalase activity showed an increasing trend, which would further improve soil fertility status. The highest microbial biomass and enzyme activity were achieved with 10% vermicompost addition.4. Nutrient contents of various eluents from the sediment were significantly increased with increasing ratio of vermicompost, which provided a good growth condition for cabbage. However, too much vermicompost caused excess nutrients in sediment, leading to nutrient loss and even environmental pollution when released. Collectively, the treatment with 10% of vermicompost addition showed a higher stability, with moderate nutrient contents in the eluent.5. Adding the appropriate amount of vermicompost promoted root growth of cabbage seedlings, thus increased nutrient absorption.. The promoting efficiency decreased with too much vermicompost addition. Adding appropriate amount of vermicompost increased cabbage height, and reduced the nitrate content. Chlorophyll content and carotenoid content of cabbage increased, which enhanced the photosynthetic capacity and improved the absorption of nitrogen, phosphorus and other nutrients. The cabbage growth was thus promoted.5% -10% vermicompost addition resulted in the best cabbage growth, with the highest plant height chlorophyll content and nutrient uptake.In conclusion, the best improving effect was achieved when adding vermicompost into sediment of lake Taiat a ratio of 10%,As this simulation experiment was carried out under laboratory conditions, which differs in temperature, humidity, irrigation and other conditions from the field.