环太湖丘陵地区农田磷素随地表径流输出特征

Agricultural Phosphorus Losses with Overland Runoff in Hilly Area Around Tai Lake

太湖水质污染问题比较严重,其中农业非点源污染对太湖富营养化有着相当大的贡献,为此采用现场采样及室内分析方法,对环太湖丘陵地区进行了自然降雨条件下农田磷素随地表径流输出特征的研究。结果表明,TP和PO4-P浓度的变化趋势表现出随流量变化的特征,浓度峰值均发生在或稍滞后于径流峰值,次降雨事件中,悬浮态磷素流失量显著高于溶解态磷素,尤以悬浮态磷酸盐最为显著。此外,径流中磷酸盐含量显著高于有机磷含量,径流有机磷含量表现随时间快速下降的趋势,有机磷主要以溶解态形式输出,以悬浮态形式输出的量极少。

Tai Lake Basin covers Jiangsu, Zhejiang and Anhui Provinces and Shanghai Municipality located in the east of China, is one of the most developed industrial and agricultural areas with a dense population and a large shallow lake seated within the Basin. The transport of phosphorus especially bioavailable P （BAP） in agricultural runoff can accelerate the eutrophication of surface waters in the basin, so, it is important to study the characteristics of agricultural phosphorus losses with overland runoff around the Lake. The study was conducted on Meilin watershed in the hilly area around Tai Lake to evaluate various P forms losses with runoff under natural rainfall. The samples were collected at outlet of the watershed with different time-interval in different period of runoff, and parts of the samples were filtered （0.45 μm） before tested. The results indicated that the peek of total phosphorus （TP） and phosphate concentration occurred at or a little lagged behind that of runoff. The losses of suspended phosphorus especially phosphate which accounted for 77.5% of the total amount, was significantly higher than that of dissolved forms during each runoff events. In addition, the concentration of phosphate in runoff was higher than that of organophosphorus, up to 0.132 mg. L^-1, being 6 times of organic phosphorus which decreased rapidly with time. Dissolved form accounted for 91% of the total organic phosphorus, and suspended phosphorus was only a little part.