Characteristics of Non-point Source Pollution Discharge under Different Land Use Conditions in Panyu District of Guangzhou

Four typical runoff plots were constructed in Panyu District of Guangzhou,representing urban,cropland,rural and orchard catchment respectively.Three rainfall events per runoff plot were monitored to investigate characteristics of non-point source pollution discharge under different land use conditions.The results show that the pollutant concentration varies for different land use conditons.For TSS and COD,the sequence of event mean concentration is as orchardcroplandruralurban for TSS and COD;croplandurban orchardrural for NO3--N and TN;urbancroplandrural orchard for NO3--N;croplandorchardurbanrural for TP.For cropland catchment,fertilizer exerts obvious influence on discharge concentration of pollutant such as N and P,but not TSS and COD,which is greatly influenced by rainfall.For urban catchment,pollution load in preliminary runoff depends on rainfall and the amount of pollutant accumulated during dry days.Regression analysis between pollution load and runoff in four catchments result in a high value of pearson correlation coefficients,and particles are an important carrier of pollutants.The analysis of first flush effect demonstrates that first flush effect is occurred more frequently in impervious surfaces than in other catchments and the influence of rainfall intensity on the first flush is significant.