Primary Study On Pollution Control Of Agricultural Non-point Source By Means Of Riparian Buffer In Shanghai

Agricultural non-point source pollution has become a majority of water contamination. Many studies have shown that riparian buffer can effectively reduce nutrient transport from agricultural fields under certain landscape conditions.Based on investigating numerous references in literature both at home and abroad, collection of statistical data and field survey, this paper conducts a primary study on pollution control of agricultural non-point source by means of riparian buffer in shanghai for the first time. The research site is located at the sijng town, Sungkiang in shanghai. Water quality sampling of the wells began in April 2002 and proceeded approximately monthly through December 2003.By the means of soil and vegetation treatment system, riparian buffers are established between field agriculture and stream in order to reduce contamination flowing stream. The study contents are as follows: 1) analysis on condition of riparian buffers; 2) rebuilding engineer of riparian buffers and design of riparian buffers system; 3) analysis on effect of riparian buffers; 4) maintenance and management mode; 5) analysis on economy benefit of riparian buffer.Riparian buffers are established at 5m buffer wide, perpendicular to stream for a total of 4 plots on the each side of stream. Each plot is 12m long, 5m wide. A groundwater monitoring well nest is installed at the field buffer edge and the stream edge in the middle of each riparian buffer plot. Wells are installed at two well depths per well nest, respectively 1m and 0.7m. Samples are analyzed for nitrate nitrogen, ammonium nitrogen, total nitrogen, and total phosphor to compare the effect of vegetation type, different field slope and different season. Main research results and conclusion of the study are as follows:1) Percent total nitrogen is higher in the deep wells 1m than the wells 0.7m,by 11.43%. Percent nitrate nitrogen, ammonium nitrogen and total phosphor was not a significantly variable at the different depths.2) Vegetation type results in significant difference in nitrate removal. LoLium perenne L is most effective on reducing nitrate nitrogen concentration , accounting to 90%.For total phosphor, natural vegetation is most effective, reaching 61.01%.3) The riparian buffer effectiveness is relate to field slope.8% slope buffer is more effectivethan the 5% slope buffers at decreasing nitrogen .The slope does not seem to play a important key on phosphor concentration decrease.4) A higher percent nitrogen and phosphor decrease is observed in spring compared to autumn and winter. Reasons may be attributed to growth of vegetation. Percent total nitrogen and total phosphor decrease is impacted more by season. It is important to improve buffer effectiveness by changing vegetation type in different season.5) Spreading different concentration organic and inorganic fertilizer on samples, result shows that the higher fertilizer concentration, the more buffer effectiveness.Based on experimentation study and advanced experience both at home and abroad , the study advances some suggestion on buffer design pattern and management pattern in shanghai ,and access the environment benefit of riparian buffer . 5m buffers were documented as reducing the amount of nitrogen and phosphor lost from fields as much as 30 to 70% above. Riparian buffers are of important application patential.The present this is only primary study on riparian buffer effectiveness. The study on absorption of pesticides will be tested in future. These may offer guide and reference to establish riparian buffer controlling agricultural non-point source in shanghai and other plain districts.