Typical Pollutants Detection And Analysis And Health Evaluation Of Rivers In Liao River Conservation Area

With the acceleration of urbanization and the continuous development and industrialization of the Liao river conservation area,the Liao river ecosystem has been seriously damaged.In order to protect and restore the ecological environment of the Liao River,Liaoning Province delineated the Liao river conservation area in 2010.Therefore,in order to comprehensively control the pollution situation of the Liao river conservation area and achieve its benign operation,the premise is to understand the health status of the rivers in Liao river conservation area.The river is based on water.The physical and chemical indicators of water quality can quantitatively reflect the nutritional status of river water.The quality of water directly affects the survival and reproduction of aquatic organisms,and affects the health problems of people around.Therefore,this paper firstly analyzed the changes of typical pollutants in the rivers of the Liao river conservation area,and then established the river health assessment technical system of the Liao river conservation area,and selected appropriate methods to evaluate the health status of rivers in Liaohe Nature Reserve,then proposed governance and repair recommendations.The details are as follows:A total of 32 detection sites were selected from the main stream and tributaries of the Liao river conservation area.The spatial variation of temperature,pH,Dissolved oxygen（DO）,turbidity and conductivity of river water was analyzed by portable dissolved oxygen meter and turbidimeter.The river water temperature and pH space of the Liao river conservation area are less different,and the river water was slightly alkaline.The river water was turbid,the turbidity of the midstream water was greater than the upstream and downstream.The downstream was close to the estuary,and the water conductivity was higher.The overall oxygen content of the Liao river conservation area was sufficient,but the DO content in the midstream water was relatively low.Sampling at 22 detection sites in the main stream of Liao River,the Total phosphorus（TP）content in water was detected by ammonium molybdate spectrophotometry,the Total nitrogen（TN）content of water was detected by alkaline potassium persulfate digestion ultraviolet spectrophotometry,and the water quality Ammonia nitrogen（NH₄-N）was monitored by salicylic acid spectrophotometry.The results showed that the water quality TP content belonged to Class IV water quality standard.The water quality TP content in the middle and upper reaches of the Liao river conservation area was higher than that in the lower reaches of the Liao river conservation area.The overall water quality of NH₄-N was relatively small,and only the water content of NH₄-N in the two detection sites belonged to the Class III water quality standard.The other detection sites of water quality NH₄-N belonged to Class II water quality standards.The TN content of Liaohe water quality was seriously exceeded.Only one sampling point of 22 detection sites had lower water quality TN content than surface water V water quality standard.In terms of space,the water pollution in the middle reaches of the Liao River was more serious.River sediments were collected from 32 detection sites in the main stream and tributaries of the Liao river conservation area,and then digested by tetraacid method（hydrochloric acid,nitric acid,perchloric acid,hydrofluoric acid）.Inductively coupled plasma mass spectrometry（ICP-MS）was used to detect and analyze heavy metals such as Cu,Zn,Ni,Cd,Cr,Pb and As in the sediment.The spatial variation showed that the contents of heavy metals such as Cu,Ni and Pb in Liao River water sediments were relatively low,and only two detection sites exceed the soil background value of Liaoning Province.The content of heavy metal Zn in the water sediments of 4 of the 32 detection sites is 1.0-1.7 times that of the soil in the region.The content of heavy metal As in the sediments of 6 of the 32 detection sites was 1.1-3.3 times of the background value of the soil.The content of heavy metal Cr in the sediments of 6 of the 32detection sites was 1.0-5.5 times of the background value of Liaoning soil.The content of heavy metal Cd in the sediments of 11 of the 32 detection sites exceeded the background value of Liaoning soil.From the perspective of spatial distribution,the contents of heavy metals Cu,Zn,Ni,Pb,As and Cd in the sediments of the middle and lower reaches of the Liaohe River were relatively high.The content of heavy metal Cr in the sediments of the Liaohe River was higher than that in the middle and lower reaches of the Liaohe River.In general,the local sediments of the Liaohe River were most polluted by Cd and Cr,contaminated by Zn and As,and slightly polluted by Cu,Ni and Pb.Based on the river’s health connotation,combined with the regional characteristics of the Liao river conservation area,an evaluation system consisting of 5 criterion layers and 24indicator layers was established.The criterion layer includes the natural form,water quality and sediment status.Five aspects of aquatic life,ecological environment and social service status.According to the evaluation criteria of related fields at home and abroad,combined with the actual situation of rivers in the Liao river conservation area,the evaluation criteria of various indicators for river health assessment were established,and five healthy levels of“excellent,good,medium,unhealthy and morbid”rivers in the Liao river conservation area were determined..Obtain relevant data for evaluating the health status of rivers in the Liao river conservation area by collecting data,collecting samples on site and analyzing samples from the laboratory.The analytic hierarchy process was used to determine the weight value of each evaluation index,and then the fuzzy comprehensive evaluation method and the grey correlation analysis method were used to comprehensively evaluate the overall river health status of the Liao river conservation area.The results showed that the rivers in the Liao river conservation area had a moderate health level,and the rivers were facing low river bed stability and erosion and siltation.The content of TN in water quality was seriously exceeded,and the content of chemical oxygen demand（COD）and TP in water quality belonged to Class IV water quality standard.There were a series of health problems such as less aquatic species and excessive water resources development（the utilization rate of water resources was69.20%,which exceeded 40%of the national water resources development warning line）.Then,according to the health problems existing in the rivers of the Liao river conservation area,four corresponding restoration strategies were proposed.