Study On Source Analysis Of Non-point Pollution And Its Process Control Technology For Tiaoxi River In Taihu Lake Basin

Firstly, this study had discussed the current eutrophication situation of Tiaoxi River through field water quality monitoring. The ratio of nitrogen to phosphorus (N/P, an index of stoichiometry) was used to assess the nutrient conditions of Tiaoxi River which is the main inflow river of Taihu Lake. Furthermore, some strategies for water quality improvement were proposed elementary. The results from field monitoring data showed that:a. Nitrogen contents in Tiaoxi River were much higher than surface water quality standard in China but phosphorus pollution was light. The Nitrate and particulate phosphate were the main pollutants in Tiaoxi River, and nutrients concentrations presented the similarly seasonal variations, suggesting that Tiaoxi River was mainly influenced by agricultural non-point source pollution. b. The N/P ratio demonstrated that Tiaoxi River in spring and autumn was under the condition of phosphorus limitation. The water was suitable for algae growth in summer but not in winter because of the low temperature. Biomass growth was limited by phosphorus for the whole river, and linear regression showed that N/P ratio was mainly affected by phosphorus fluctuations. Thus, it would significantly improve the algal bloom risk of Taihu Lake, especially in summer.Secondly, water-saving irrigation(AWD) experiments coupled with fertilizer management(SSNM) were done. Results found that water-fertilizer management can effectively control nutrients losses by storm runoff:a. water-saving irrigation(AWD) could significantly reduce the times and amounts of irrigation and storm runoff; b. the combined technology (AWD+SSNM) could reduce the inputs and times of fertilizer; c. water management could effectively reduce the nutrients losses by storm runoff, and fertilizer management(SSNM) could strengthen the nutrient losses reduction function; d. nitrogen concentration of local precipitation was very high, and its estimated wet deposition of nitrogen in this area was 16.4 kg hm-2 yr-1.Again, field water sampling and online monitoring analysis for agricultural drainage, combined with the construction of ecological bed, were done in order to reflect the process control strategy for nutrients losses. Results revealed that:a. canna generalis and Pistia stratiotes gained good application effects; b. nitrogen pollution in farmland drainage was serious during rice cultivation period in summer, and analysis of N/P ratio showed that farmland drainage would cause serious influence on receiving waterbody; c. levels of nutrients concentration of farmland drainage were higher than receiving waterbody (Caoqiao creek) during rice fallow period, ammonia and phosphorus concentration had reached the III grade of national water quality standards, and analysis of N/P ratio showed that the former kind of waterbody was in a phosphrus-limitied status, and it would cause mild effects to receiving waterbody in winter when the temperature was very low.