Abstract:

The contents of TN,NH4N,NO3N and TP were measured every month in the waters of Yunyang,Wushan,Zigui and Sandouping in the middle and lower reaches of the Three Gorges Reservoir in 2010.The results showed that no significant spatial difference was observed in TN,NH4N,NO3N and TP among the four sites,but significant seasonal variations were observed in TN,NH4N,NO3N and TP in 2010.The single peak pattern was observed in the seasonal dynamics of TN and TP,and reached the maximum in May and July,respectively.There were double peaks in the seasonal dynamics of NH4N with the minor peak in March and April and the major one in July and August.The contents of TN,NH4N,NO3N and TP in the low water table were higher than those in the high water table.The inlet water flow was significantly increased during the low water table period because of the strong rainfall in the upstream of the Yangtze River and the Three Gorges Reservoir region.The contaminants mainly came from the nonpoint source pollution of the inlet water flow and the areasource pollution of agriculture.The water quality was still kept well after the third time of impounding,and reached the grade Ⅲ during the high water table period and the grade Ⅳ during the low water table period