In order to clarify output characteristics of different forms of pollutant discharge from upland under rainfall event,the long-term monitoring of runoff and water quality in farmland under natural rainfall was carried out by means of automatic sampling on Chongming Island in Shanghai,China.High-resolution electrical conductivity(EC)and turbidity measurements were used to indicate the concentrations of dissolved and particulate nutrients respective-ly.The runoff curve number(CN)was used to represent the runoff production capacity.The output characteristics of nutrients from upland was studied by the hysteresis loop analysis,which was indicated by concentration-discharge(C-Q)relationship.The results showed that there was a good correlation between runoff coefficient and rainfall,and the CN was well related to soil moisture content(AMC).EC and turbidity could be used as surrogates of soluble salt content(represented by the total salt content),and suspended sediment concentration(SSC)and total phosphorus(TP)concentration,respectively.Turbidity-discharge generally showed clockwise hysteresis and obvious flush effect.Generally,the EC-discharge showed anticlockwise hysteresis,and dilution effect.The output of TP was main-ly due to flush effect.The output characteristics of total nitrogen(TN),nitrate nitrogen(NO-3-N),ammonium ni-trogen(NH+4-N)and soluble total phosphorus(DTP)were highly variable,which had both dilution and flush effects.It was included that the dissolved form of nutrients such as N-related pollutants was probably transported through both soil surface and cultivated layer.Nevertheless,as particulate pollutants,TP mainly transported on soil surface,and that was the reason why the output of particulate pollutants mostly showed a clockwise hysteresis pat-tern.The output process and characteristics of dissolved and particulate pollutants provided scientific basis for the control of non-point source pollution and soil and water conservation.
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