Investigation on Nutrients in two Megalobrama hoffmanni spawning grounds of Xijiang River from 2003 to 2006 and Ecological Risk Assessment
西江广东鲂产卵场水质营养盐现状与评价

From 2003 to 2006, we had surveyed the nutrient salts in the Megalobrama hoffmanni main spawning grounds located in Feng Kai Qingpitang and Luo Pang in Xijiang river, and there were 6 sites in the spawning sites. Based on these data,the character of nutrients distribution and the status of eutrophication were analyzed. The results show that, in both waters the DO are all sufficient, and COD has the low level which the organic pollution of oxygen consumption is small and the inorganic phosphorus concentrations are lower than grade 3 surface water quality standard. But the level of DIN in the water is all above normal, nearly four years of single factor index exceeded 1, the DIN in the water meanly exceeded grade 3 surface water quality standard, and even exceeded grade 5 quality standard at some sites. The two spawning grounds are mainly polluted by nitrogen nutrient. Using nutrition index method and the organic pollution index evaluation method for two spawning grounds comprehensive evaluation, the results told us that the comprehensive quality about the two spawning grounds achieve optimum nutrition standards to clean water.