三峡水库库首初期蓄水前后理化因子的比较研究

COMPARATIVE RESEARCH ON PHYSICOCHEMICAL FACTORS IN THE FRONT OF THREE GORGES RESERVOIR BEFORE AND AFTER THE INITIATE IMPOUNDING

根据2002—2004年对三峡水库库首的监测,对该水域的理化特征及其动态进行了比较分析,并对三峡水库初期蓄水前后的数据进行了差异显著性分析。结果显示主要理化指标空间差异不大,主要随季节变化。部分理化指标在蓄水前后有显著差异。其中TN、TP在蓄水后与蓄水前同期比较有明显降低,分别由蓄水前的周年平均值2.38mg/L、0.274mg/L下降到蓄水后的1.62mg/L0、.132mg/L。在无机氮组成中,NO3-N高达91.25%,而NO2-N仅占1.05%,这表明调查水域有较强的自净能力。透明度、浊度月变化很大,且呈良好的负相关,并在7—9月分别有显著降低与升高,表明本地区水土流失在降雨季节十分剧烈。而TP也随库区水体中悬浮物增高而显著增高,表明流失水土受磷污染严重。但由于同时期PO4-P反而是降低的,则说明此污染并不能有效转化为PO4-P。对营养状态指数(TSIM)的评价表明,尽管蓄水后库首水质污染较之蓄水前有明显降低,但仍呈中营养化水平。与国内其他大型水库比较,结果显示TP、NO3-N都远远高于被比较水库。

Based on the routine monitoring in the front region of Three Gorges reservoir from 2002 to 2004, the physicochemical indices were analyzed, and the significant tests for the investigated data before and after the initial impounding were carried out. The results indicated that the major physicochemical indices were not significant differencds spatially, but mainly vary with time. Some indices were significantly different before and after impounding. Among them, the annual averages of TN,TP reduced from 2.38mg/L,0.274mg/L before impounding to 1.62mg/L,0. 132mg/L after impounding respectively. Among inorganic nitrogens, NO3-N was as high as 91.25 %, while NO2-N was only 1.05 %, indicating that the Three Gorges Reservoir has great self-purification capacity. The results also showed that monthly averages of transparency and turbidity changed greatly, the two indices were negatively related, and transparency decreased and turbidity increased significantly during July to September, which implied that there were heavy soil erosion during rainfall seasons in this area. Meanwhile, TP also increased significantly along with turbidity increase, indicating that phosphorus pollution is heavy in the soil erosion area. However, since PO4-P deceased at the same time, it also indicated that this phosphorus pollution could not be effectively changed to PO4-P. Based on the evaluation of the trophic state indices （TSIM）, the front region of the Three-Gorges reservoir was still middle eutrophical due to huge pollution basis （TSIM 〉 37）, although the water pollution reduced much after the impounding. At last, we compared the major physicochemical indices with those of other large local reservoirs, the results showed that concentrations of TP,NO3-N in the studying area were much greater.