Evaluation Of Water Environmental Capacity In The Downstream Of The Yitong River

Rivers are the important natural resources for human survival.In recent years,human production activities have an important impact on the river evolution and the health of the water environment.The wanton emission of pollution to rivers and the unreasonable exploitation and utilization of water resources directly threaten the ecological environment of the river.The Yitong River,as the mother river in Changchun,has deteriorated in recent years,especially in the lower reaches of the Yitong River,which accommodates a large amount of domestic sewage in Changchun and the pollution of industry and source,and so on.The water quality can not even reach the standard of local water function zoning.The problem of water environment worsening is becoming more and more prominent,and the water environment capacity is evaluated.There is no delay in the planning of emission reduction.In this paper,the lower reaches of the Yitong River are selected as the research object,and the pollution status of the study area is mastered through the pollution source investigation and the water environment quality assessment.The water environment model of the river is constructed with the typical river section as an example.Then the existing model is used,and the surface water environment quality standard(GB3838-2002)and the surface water in Jilin province are based on the existing models.The function zoning(DB22/388-2004)determines the water quality target,selects the linear programming method to evaluate the water environment capacity of the research area,and on this basis uses the maximum daily load(TMDL)plan proposed by the United States Environmental Protection Agency to evaluate the safety margin of the water environment capacity in the downstream of the Yitong River.Measures for reducing the corresponding pollution sources.The main conclusions are as follows:1.The nitrification temperature coefficient ?12 is the most sensitive parameter for ammonia nitrogen,and the COD comprehensive attenuation temperature coefficient ?(9 is the most sensitive parameter for COD.2.The influence of downstream flow of Yitong River on water environmental capacity is greater than that of water temperature.3.The safety margin of ammonia nitrogen in the lower reaches of Yitong River accounts for 30% of the water environmental capacity,and the COD margin accounts for 10% of the water environmental capacity.4.The overall discharge status of the lower reaches of Yitong River is still in the condition of over standard discharge,and the ammonia nitrogen exceeding standard is more serious than COD.