以野外观测的12场降雨径流污染数据为基础,分析川中丘陵区村镇的降雨径流污染物之间及与降雨特征的相关关系.结果表明,村镇降雨径流中TN、TP、COD、SS的EMCs(事件平均浓度)分别为21.31,3.00,526,1941 mg/L.TN和TP的EMCs与降雨特征(最大雨强、降雨量、径流量、径流时间、降雨时间)存在负相关关系,氮和磷污染物因初期径流冲刷而具有较高的浓度,但随着雨量、径流量的增大而发生稀释或污染源耗竭效应;TN和TP二者的EMCs存在显著的正相关关系,说明氮和磷的主要污染源相同.COD和SS的EMCs与降雨特征无显著相关关系,且COD和SS的EMCs存在显著的正相关关系,说明COD和SS的污染源较均匀分布于集水区,来源充足,控制颗粒物污染,可以较好地控制村镇COD输出.TN、TP、COD、SS的EMCs和FF30(由占总径流量30%的初期径流所运移的负荷)之间存在显著的负相关关系,表明初期径流运移的负荷较大,有将近40%的污染负荷为占总径流量30%的初期径流所运移.村镇降雨径流污染普遍存在中等初期冲刷效应.
To investigate the correlation among stormwater runoff pollutants in a rural township in the hilly area of the central Sichuan Basin, China, a catchment (area of 2.32 ha) in Linshan Township was selected to examine runoff and quality parameters such as total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD) and suspended solid (SS) in stormwater runoff of 12 rainfall events over a period from June 2006 to July 2007. The average values of EMCs (Event Mean Concentrations) were 21.31 mg/L for TN, 3.00 mg/L for TP, 526 mg/L for COD, and 1941 mg/L for SS. The EMCs values for both TN and TP were negatively correlated with the maximum rainfall intensity, precipitation, total flow volume, and runoff duration, while EMCs values for both COD and SS were not related to any of those rainfall characteristics. The significant correlations of TN to TP, and COD to SS indicated the similar pollutant sources for nitrogen and phosphorus, and COD and SS respectively. The FF30 (FF, First Flush) for TN, TP, COD and SS were positively correlated to the maximum rainfall intensity, and TP was also positively correlated to the average rainfall intensity, indicating that the magnitude of first flush increased with the rainfall intensity in Linshan Township. There were significant negative correlations between the EMCs and the FF30 for TN, TP, COD and SS, indicating that the transport load by first flush runoffwas pertinent greater. In fact, about 40% of the masses ofTN, TP, COD and SS were transported by the first 30% of the total flow volume, supporting that medium first flush effects were common for the stormwater runoff pollutants in Linshan Township.