九龙江流域降雨径流污染特征研究

Characteristics of Agricultural Non-point Source Pollution Caused by Rainfall Runoff in Jiulong River Watershed

选取福建省九龙江流域内5个典型小流域作为研究区,在GIS技术支持下,采用现场调查与资料收集,野外监测与室内分析相结合的方法,利用2003年5～6月两场降雨事件全过程实测的水文数据、营养盐氮、磷负荷进行对比分析,得到不同土地利用类型小流域降雨径流污染特征与规律:降雨径流中污染物浓度高于非降雨期,且总氮、总磷的流失负荷主要受降雨强度、径流量大小影响,浓度变化过程与流量变化呈大致相同的趋势.溶解性污染物如氨氮,在降雨径流过程中浓度变化幅度较小,表明其溶解性所受到的水环境条件的限制可能大于流量变化对它的影响.施肥水平对污染负荷也有较大的影响.径流流失的氮素以可溶态氮为主,磷素主要以颗粒态磷为主,但以林地为主的小流域,因植被覆盖好,几乎不发生土壤侵蚀,磷素的径流流失以可溶态磷为主.

Characteristics of agricultural non-point source pollution caused by rainfall must be better understood to establish applicable nutrient guidelines and to discern which areas or landscape positions in the Jiulong river watershed are more responsible for nutrient losses.This work was conducted to determine the relationship between nitrogen and phosphorus concentration in rainfall runoff and meteorology, management practics, and to determine the dominant form of nutrient lost from watershed during rainfall. From May to June of 2003, series of water samples were collected from 5 sub-watershed drainage outlets in each rainfall event, flow rate was also measured. Total nitrogen (TN), total dissolved nitrogen (TDN), total phosphorus (TP), total dissolved phosphorus (TDP) and ammonium (NH_3-N) concentration were analyzed for the samples. The results show that:(1) higher nutrient concentration and load were found only in rainfall runoff, rainfall intensity and fertilizer application rate have a great influence on load, larger nutrients load with higher rainfall intensity and fertilizer application rate.(2) The concentration and load of most pollutants are greatly affected by hydrometeorolgy. The concentration changes in roughly the same trend with the changes of flow rate. TN and TP concentration reach peak value nearly in the same moment and always before flow peak occured, then there is a decrease trend because of dilution.(3) For ammonium, Being one of dissolve pollutants, the concentration changes in a relatively little range. This finding indicates that the dissolving capability of dissolve pollutant was influenced likely by water conditions restriction than by runoff flow .(4) TDN are dominant form of nutrient losses from all study sites during rainfall, PP are also dominant from 4 crop predominant sub-watersheds, but there is a low PP ratio from a wood-landscape sub-watershed because of its low soil erosion.