Abstract:

Based on the current condition of environmental data in China,this study developed a practical model for calculating watershed nonpoint sources load of heavy metals.The model integrates complex hydrology and sediment simulations (using the SWAT model) with simple export coefficient approaches.The model was applied to the cadmium pollution at the drainage area of the Xiangjian River in the Zhuzhou City,China.The uncertainty of the model simulations was also analyzed.The results showed that the total nonpoint sources load of cadmium at this area was about 2 435 kg/a,and the polluted soil was the major source which accounted for 657% of the total load.The nonpoint sources pollution was mainly controlled by the soil erosion process,and thus soil pollution prevention and conservation should be the key measures for controlling the nonpoint source pollution.The locations with highly polluted soil and/or those vulnerable to soil erosion (such as the Qingshuitang Industrial Park and its surrounding areas) were the critical zones for the pollution control,and April and May were the critical periods.The uncertainty analysis revealed that,with a probability of over 50%,the total nonpoint sources load was within the range of 2 000~3 000 kg/a,but there was still a possibility that the load was below 1 500 kg/a or over 4 000 kg/a