Purifying Effects of Nitrogen in Wangyu River Water through Natural Wetlands

In order to study the purifying effects and influences on nitrogen caused by natural riparian wetlands in the river course, Cao Lake and Ezhen Lake in Wangyu River were selected as the main research regions. Samplings in the transfer period with a large flow in May, 2010 were taken in the sites over the whole wetland area and along the main river course, respectively. Observations on the physicochemical indexes such as water temperature, pH, dissolved oxygen(DO), turbidity, suspended solid(SS), total nitrogen (TN), total dissolved nitrogen(DTN), ammonia, nitrate and nitrite were performed to analyze the concentration and chemical forms variations, regional difference of nitrogen nutrient in the river water column. Results are showed as follows: (1) As the water flowed through Cao Lake and Ezhen Lake, the TN、DTN and nitrate showed a trend of descending (descending proportion: 10.45%, 17.85%, 7.62% in Ehen Lake, 9.09%, 7.17%, 7.60% in Cao Lake). The overall removal effects of nitrogen in Ezhen Lake was better than that in Cao Lake, but the retaining effect of ammonia in Cao Lake was better than that in Ezhen Lake. (2) The nitrogen existed in the water mainly in the forms of DTN and the rates on TN were 88.0% and 91.4%, respectively, higher than that of particle nitrogen, but the rates would decrease for the sedimentation of particle nitrogen in the vertical distribution.(3) Water temperature, pH and DO were the dominant factors that affected the purifying effects of nitrogen in the riparian areas. The research showed the obvious retaining effects of nitrogen and evident influences on the nutrients forms variations in the river water column. The results could provide theoretical foundation and technical support for nitrogen purification in the river course.