太湖上游不同类型过境水氮素污染状况

Nitrogen pollution status of various types of passing-by water bodies in upper reaches of Taihu Lake

利用GPS定位,在春、夏、秋、冬4个季节,对地处太湖上游宜兴地区受农田径流、农村生活污水、水产养殖和畜禽养殖污水污染的过境水体氮素污染状况进行了调查,对不同类型水体中不同形态氮浓度的季节性变化特征进行了分析,比较了不同类型水体的15N自然丰度。结果表明:不同类型过境水氮素污染严重,人为影响强烈,不同的农业生产和人类活动具有不同的污染特征;受农田径流影响的河流,水体受铵态氮污染的风险较小,受硝态氮的污染较重;农村居民区河流主要受农村生活污水影响,水体铵态氮负荷较高;畜禽养殖场附近的河流受养殖污水的影响,水体的氮素污染最为严重,尤其是铵态氮负荷最高;相比之下,养殖鱼塘水体总氮最低,主要以有机氮为主;水体氮素污染受河流季节性环境演变的影响,表现为夏季浓度最低,冬季浓度最高;农田施肥是太湖氮污染的主要来源,但在丰水期生活污水和畜禽养殖废水也会成为太湖重要的污染源。

With the aid of Global Positioning System （ GPS）, this paper investigated the present nitrogen pollution status of passing-by water bodies in the agricultural area, rural residential area, fishpond area, and animal farming area of Yixing in the upper reaches of Taihu Lake in spring, summer, autumn and winter. The seasonal variations of the nitrogen concentration in the water bodies were analyzed, and the ^15N natural abundance in the water bodies was compared. The resuits showed that anthropogenic activities had intense effects on the nitrogen pollution, and vari- ous agricuhural and anthropogenic activities had different nitrogen pollution characters. The passing-by water bodies in agricultural area were more easily polluted by NO3^ --N than by NH4^ ＋ -N, and the NH4^ ＋-N concentration in passing-by water bodies was higher in rural residential area than in agricultural area due to the domestic sewage discharge. The passing-by water bodies in animal farming area was often heavily polluted by NH4 ＋ -N. Fishponds had the least nitrogen pollution, compared to other passing-by water bodies, and the main pollutant was organic nitrogen. The nitrogen pollution of the passing-by water bodies was also affected by the seasonal evolvement of environment, with the lowest nitrogen concentration in summer and the highest one in winter. Farmland fertilization was the main source of the nitrogen pollution in Taihu Lake, and domestic sewage and animal excreta were also the important nitrogen pollution sources when the water level was high.