三峡水库中下游水体氮磷时空变化与机制分析

2010年每月定期测定了位于三峡水库中下游的云阳、巫山、秭归和三斗坪段的TN、NH4 N、NO3 N和TP浓度。结果表明：4个段面水质中的TN、NH4 N、NO3 N和TP浓度空间差异不显著，但季节变化显著，TN和TP的季节变化呈单峰格局，分别在5月和7月达到最大值；NH4 N的季节变化则呈双峰格局，主要的峰值出现在7、8月，次要的峰值出现在3、4月。4个地点低水位期（3~8月）的TN、NH4 N、NO3 N和TP浓度都高于高水位期（9月~次年2月）。主要因为在低水位期，长江上游和三峡库区的降雨量大，入库流量显著增加，污染物主要来自长江上游入库的非点源污染和水库两岸农田施用农药化肥造成的面源污染。三峡水库三期蓄水后，水库水质与前两期蓄水后的水质变化不大，水质仍然保持良好，高水位期为Ⅲ类水质，低水位期为Ⅳ类水质

TEMPORAL AND SPATIAL VARIATION ON NITROGEN AND PHOSPHORUS IN THE MIDDLE AND LOWER REACHES OF THE THREE GORGES RESERVOIR

The contents of TN,NH4-N,NO3-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,NH4-N,NO3-N and TP among the four sites,but significant seasonal variations were observed in TN,NH4-N,NO3-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 NH4-N with the minor peak in March and April and the major one in July and August.The contents of TN,NH4-N,NO3-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.