Indicators And Methods Of Water Environment Pollution Ecological Risk Assessment In Daliao River Estuary

Estuaries are major corridors between drainage basins and the sea where landand sea interact intensively, with remarkable environmental characteristics andimportant ecological service function. Daliao River is a multifunctional river withshipping, farming, irrigation, etc. Due to intense human activity, Daliao River estuaryis sufferring significant water pollution and ecological degradation, and arouse theattention of research scholar at home and abroad. Previous studies was mainly aimedat a single contaminants or one kind of pollutant, and it cannot reflect thecomprehensive pollution situation in this area, so conducting the water environmentpollution ecological risk assessment in Daliao River estuary is necessary with veryimportant reality meaning for identifying the main sources of pollution and protectingthe ecological environment.Water quality parameters were determined and their distribution characteristicswere analyzed for the samples collected from the Daliao River estuary in May andAugust2010. Accordingly, main water environment pollution status of the DaliaoRiver estuary was estimated, ecological risk evaluation index system of waterenvironment pollution was established, and ecological risk assessment model basedon the fuzzy comprehensive evaluation was established. The main conclusions are asfollows:(1) Distribution characteristics of water quality parametersThe concentration of DO in Daliao River estuary was4.36-10.23mg/L and4.42-7.82mg/L in May and August respectively, with mean values of7.01mg/L and5.99mg/L. Compared with the sea water quality standard, almost all the survey resultsbelong to sea water quality category I or II without hypoxia phenomena.The concentration of NH4+-N in about half of the survey stations beyond the seawater quality category â…¢, which was overweight with the value of0.005-0.870mg/Land0.411-1.502mg/L in May and August respectively. Inorganic nitrogen (IN) in all the survey stations was beyond the sea water quality category â…£, with the value of0.615-5.395mg/L and1.435-2.860mg/L in May and August respectively. Theconcentration of TN in Daliao River estuary was3.891-11.663mg/L and2.564-5.411mg/L in May and August respectively. All the sample stations was beyondthe sea water quality category â…¤, so the TN pollution is serious especially in May,which was2-6times than the â…¤ class limit of surface water environment qualitystandard, and it was related with the discharge of waste water from the chemicalplants, paper mills, and sewage treatment plants along the coast.The concentration of PO43-in Daliao River estuary was0.003-0.074mg/L and0.016-0.075mg/L in May and August respectively, with mean values of0.037mg/Land0.071mg/L. The survey results are beyond the sea water quality category â…¡except for one or two, and nearly40%of the sample stations was even more than â…£class standard.(2) The risk evaluation of water environment pollution in Daliao River estuaryThe risk assessment of heavy metals was index method of potential ecologicalharm, and the results showed that the potential ecological risk index was less than150,in other words, the level of ecological risk of heavy metals was slight damage.The risk assessment of Nonylphenol (NP) was Risk Quotient (RQ). The value ofRQ in the river section were calculated as0.176-0.705and1.096-1.636in May andAugust respectively. Further observation is needed when RQ was more than0.1aswell as less1, and risk reduction measures such as reducing production wastewatershould be taken when RQ was more than1. Due to the dilution effect of seawater, theRQ was decreasing from the entrance to the outlets in offshore section.The risk assessment of nutrient was nutrition state quality. The nutrition stateindex was9.27-28.73and7.18-12.13in May and August respectively. The seawater isconsidered as eutrophication when the nutrition state index is more than4, so thewater was in serious status of eutrophication in Daliao River estuary.(3) Built ecological risk evaluation index system, established ecological riskassessment model based on fuzzy comprehensive evaluation, and evaluated the waterenvironmental pollution status in Daliao River estuary This paper built ecological risk evaluation index system from water environmentconditions, sediment environment conditions and ecological environment conditionson the basis of investigation of water environment quality and ecologicalcharacteristics, and established ecological risk assessment model based on fuzzycomprehensive evaluation through determining the evaluation level and index weight.The comprehensive evaluation results of water environmental pollution conditions inDaliao River estuary showed that the overall ecological risk degree in Daliao Riverestuary is in higher levels, so it is urgent to strengthen environmental pollutioncontrol.