| In order to study the rule of the nitrogen phosphorus potassium nutritive elements and heavy metals elements content with season change in Changde Xihu water and the bottom mud, sampling and checking contents of nitrogen phosphorus potassium nutrition and heavy metals elements with season change in three relatively independent water of the West Lake and bottom mud from July 2006 to May 2007, and analyzed influence of the nitrogen, phosphorus, potassium nutritive elements and heavy metals elements content to the lake water quality by the standard analytic method of National Environmental protection Bureau (1989) "Water And Waste water Examination And Analysis Standard" and "Soil Analysis method",The result showed that, both bottom mud and water nitrogen content are very high, the water total nitrogen content ranged from 30 to 80mg/L and the bottom mud alkaline lysis nitrogen content ranged from 150 to 300mg/L, distribution of nitrogen content in bottom mud and water is non-uniform, the nitrogen content of lake center is higher than that of other places, the nitrogen content tendency is drop from lake center to lake shore. The nitrogen phosphorus potassium contents is different with seasonal variation, the summer nitrogen phosphorus potassium contents are maximal and contents in autumn is lowest; The nitrogen/phosphorus ratios exceeds a national standard seriously, the phosphorus is a restrictive nutrition element in the wave; phosphorus contents in soil are high, nitrogen contents is low, the nitrogen is a restrictive nutrition element in soil. The lake displayed comparatively grave eutrophication. the effective phosphorus content of the water is lower significantly than that of the bottom mud, fluctuates from 0.008 to 0.4mg/L, it's content in spring and summer is higher than in autumn and winter, the content change is very obvious in ramification of lake region; The nitrogen/phosphorus ratio is 60 ~ 1000; The potassium is stable in the bottom mud and in the water body along with the seasonal variation, the winter content must be higher than other months.The experiment indicated that the phosphorus is the limit factor of the lake primary productive power, That the chemical fertilizer feeds fish in the lake district leads to pollution's aggravation of the lake water, It is key of management fertilizer applies rationally into the lake district.The lead and the cadmium content are safe in the lake water. Average lead content is 0.0710mg/L, Average cadmium content is 0.0048mg/L The content of copper and the zinc have surpassed the safe concentration, in which copper average content is 0. 0908mg/L, assumes tendency which reduces gradually. Zinc average content is 0. 5431mg/L ,also assumes the tendency which increases gradually, Indicates that there is not a serious pollution source of heavy metal in the lake nearby , but we must control the use of medicine. |
