Spatiotemporal Distribution Characteristics And Source Analysis Of Pollution Load In Liaohe Main Stream

The transport of pollutants into the sea has become the main influencing factor of water pollution in the coastal waters.The key to improve the quality of the offshore water is to carry out the land source pollution control.Liaohe River is one of the main rivers in Liaodong Bay of Bohai Sea.After years of water environment control measures,the pollution from urban domestic sewage and industrial wastewater in Liaohe River Basin has been effectively treated.However,the non-point pollution from mountains,forests,farmland and cities will be the key factor to affect the environmental quality of water receiving.This paper takes Liaohe River Basin(below Fudian)as the research object,through SWAT model to simulate the hydrology and water quality of Liaohe River Basin,and collect the data of point source pollution,and study the spatial and temporal distribution characteristics of nitrogen and phosphorus pollution load in the region,define the source of pollution load in each sub basin,and carry out problem identification and cause analysis for pollution characteristics,The corresponding countermeasures are put forward.The main conclusions are as follows.(1)Spatial and temporal distribution characteristics of pollution load: in terms of time distribution,the annual variation of pollution load is affected by rainfall.In 2016,the water volume was sufficient,and the proportion of pollution load into the sea increased,and more nitrogen and phosphorus loads entered Bohai sea every year.In dry year,the total nitrogen pollution load would be reduced from the river basin.The non-point source pollution load of total nitrogen was concentrated in May and July,accounting for 78% of the total pollution load.The total phosphorus non-point source pollution load was concentrated in July,accounting for68% of the total pollution load.In terms of spatial distribution characteristics,the total nitrogen pollution load of the two regions,the upstream intersection(near Fudian)and the transition area of the middle and lower reaches,is mostly lower than 100 tons,while the total nitrogen pollution load of Tieling Section and Panjin section in the middle and upper reaches is mostly higher than 100 tons.(2)Analysis of pollution load source: the pollution source of total nitrogen in the study area accounts for a relatively high proportion of the pollution load sources.Non point source pollution accounts for a high proportion of the total phosphorus pollution load sources.In 2016,the total nitrogen content of the pollution load of the point source in the research area was2904.6 tons and the total phosphorus was 109.1 tons.The proportion of non-point source total nitrogen pollution load to total pollution load is 41.0%,and non-point source total phosphorus pollution load accounts for 80.7%.The sub basins with the pollution load of point source account for more than 70% are Tieling,Shenyang(Shenbei New District)and Panjin.The non-point pollution load accounts for more than 70% of the sub basins,and the non-point pollution load is concentrated in the middle and upper reaches of the study area.(3)The point source pollution in the research area is mainly the tail water discharge of sewage plant.It is necessary to further treat and purify the tail water of the sewage treatment plant and construct ecological treatment facilities to avoid the burden on the river water environment.Non point source pollution mainly includes agricultural planting,a large number of fertilization irrigation and pesticide use,which brings the increase of the total pollution load in the basin.And this kind of agricultural non-point source pollution has not been treated subsequently,which is the main source of pollution load in rural areas with area accounting for more than 70%.The suggestions for the management are that the amount of fertilizer should be strictly controlled in agricultural activities,the efficiency of fertilizer use should be improved,the livestock manure should be recycled,the waste should be used for resource,and the dependence on fertilizer should be reduced.