Use of a minimum environmental Gini Coefficient model on optimizing the allocation plan of total pollutant load in water bodies:a case study at Zhangjiagang river-network plain

A Gini Coefficient model was developed in an attempt to optimize the total pollutants load allocation plan at the study area,Zhangjiagang river-net plain,where the environmental capacity of target pollutants and spatial distribution at six different towns in this region have been well addressed via WASP model.The local social,economic and resource factors were integrated and processed in developing this Gini Coefficient model,by which the best solution to the allocation pollutant plan was successfully figured out.As a consequence,the COD Gini Coefficients were decreased by 15.1% and 8.5% while ammonia Gini Coefficients were decreased by 11.0% and 13.7% in terms of pollutant discharge and capacity allocation respectively.The largest reduction rate of COD,approximately 20%,was achieved at Changjing town by the optimized load reduction strategy with an annual reduction,of 231.74tonnes.As to the ammonia pollutant load reduction,Zhutang Town showed the largest reduction rate of 59.9% with an annual reduction amount of 59.74tonnes.