Purification Effect Of Buffer Zones On Surface Runoff In Zhu Shan Bay Taihu Lake

Lake Buffer is an isolation habitat, which is located between land and lake. It is the space expanding from the lakeside to land. The healthy lake vegetation buffer is an important area for improving soil habitat, intercepting the non-point source pollutants for land, preventing and controlling of water pollution, improving the lake water quality. In recent years, human activities cause some ecological environment problems such as the degeneration of Lake Buffer, biodiversity decreasing and the Eutrophication increasing, therefore, ecological system restoration is very urgent. study of the effects of different Herbaceous vegetations on the soil improvement and purification of the surface runoff pollutants, is the theoretical basis of the vegetation buffer restoration and construction in Taihu. In addition, it will provide a scientific basis for the recovery of lakes buffers of same type domestically.Based on herbaceous plants as the research object, First, four different herbage vegetation buffer zones with the white clover, safflower sorrel, water chestnut and Bermuda grass were built. Based on the plants and soil sampling analysis, the influence of different herbs buffer on soil benefit were studied. The horseshoe gold and Bermuda grass were selected for indoor buffer simulation experiment, to study the purification effect of the different width and different slope on the surface runoff and seepage, study the growth characteristics of horseshoe gold and Bermuda grass, and analyze the relationship between the structure characteristics and the purifying effect of different plant root system. The research results are as follows:(1) Due to the characteristics of the plants, plant height and biomass have significant difference with different herbs and season. The biggest plant height and biomass was white clover, the smallest is the horseshoe gold. Soil temperature and moisture difference of different plant buffer is not big, while soil compactness and soil bulk density difference is larger. Comparing the soil compactness:horseshoe gold<Bermuda grass<white clover<safflower sorrel.(2) The content of organic matter in soil including TN, NH4-N, NO3-N decreased with the increase of soil depth in different herbs buffer zones. The TP content increased, and then decreased with soil depth increases in Different herbs buffer soil. In soil organic matter, the annual average of TN and TP content were similar, but the content have significant difference in different seasons.(3) Compared with the blank buffer, the purification effect of herb buffer is obvious on the removal of nitrogen and phosphorus from the surface runoff pollutants. In terms of the removal rate of TN in runoff, chestnut gold and Bermuda grass were26.70%and24.69%respectively, the maximum removal rate of TP in runoff were21.95%and20.15%respectively. The seepage pollutant removal rate were greater than runoff pollutants removal rate in different plant buffer zones, in terms of the removal of TN from seepage, water chestnut and Bermuda grass were40.97%and38.59%respectively, in terms of TP removal, the rate were35.81%and36.19%, respectively.(4) The removal rate of herbs buffer for surface runoff and seepage increased gradually with the flow, which means the purification effect increased as buffer width increased. Buffer slope had great influence on purifying effect, the greater the slope, the lower the surface runoff and seepage removal rate, and the smaller of the slope, the better the purification effect.(5) The total root length, total surface area and total root growth of horseshoe gold and Bermuda grass were exponentially increasing as time went on. When the plants kept growing for75days, the total root length, root surface area and total root number, and average root diameter of horseshoe gold were greater than that of Bermuda grass. The more advanced the plant roots, the lager root number, the stronger nutrient absorption ability, therefore, the horseshoe gold plant buffer for surface runoff purification effect is better than Bermuda grass buffer.