Characteristics of Output of Non-Point Source Pollution With Rainfall Runoff in Typical Agricultural Watershed of Liuxi River Valley

The main processes of non-point source pollution(NPS) are rainfall,runoff,and pollution.A typical agricultural watershed in the Liuxi River Valley,Xintian Watershed,was selected as an object in the research.Stationary monitoring of rainfall-induced runoff was carried out to explore dynamics of agricultural non-point source pollutants in the rainfall-runoff condition and contribution of different land use landscapes to NPS.Results show that 1)generally concentrations of non-point source pollutants in output in the event of rainfall were higher than in no rain days.The average concentration of total nitrogen(T-N)in the former is 3.8 times,of total phosphorus(T-P)7.8 times,and of COD_Cr 32.1 times as much as that,respectively,in the latter;2)Throughout the rainfall event,output of NPS peaked in the early period. Variation of the concentration of pollutants lagged behind that of the intensity of rainfall,but followed closely that of runoff;and 3)Pollutant output varied with surface landscape.Runoffs flowing through residential areas were higher in COD_Cr concentration,while the one through paddy fields was the major contributor of N and P pollutions in the water body environment.