Health Risk Evaluation And Management Of Heavy Metals In Surface Water From Honghu Lake Based On Fuzzy Theory

The current water pollution situation in China is relatively severe.According to the "Chinese Water Resources Bulletin in 2016",the lakes with water qualities below IV standard accounted for 76.3%of the 118 major lakes.Water pollution not only leads to the deterioration of water quality,the decline of water function,the decrease of biological quantity and diversity,but also threatens the human health.Honghu Lake is the seventh largest lake in China,and was listed in the Ramsar Convention in 2008.It plays a key role in flood regulation,water storage,production and living water supply,eco-tourism,agricultural irrigation and species protection.Since 2000,the water quality in Honghu Lake has basically wandered between III and IV standard of surface water,and has not steadily achieved the goal of water quality management(III standard).Previous studies revealed that water and sediment in Honghu Lake was polluted by heavy metals due to anthropogenic activities.Heavy metals are a class of pollutants with high toxicity and persistence.In recent years,with the frequent occurrence of public hazards related to water heavy metal pollution,people have paid close attention to the relationship between water pollution and human health.Environmental health risk evaluation and management aims to carry out targeted pollution prevention and risk management measures by investigating and evaluating the health risk level of environmental pollutants to human health.Environmental health risk assessment is an effective way to evaluate the hazard degree of environmental pollutants to human health,which can provide an important reference for environmental risk control and management.However,due to the complexity of environmental system and the limitations of human cognition,there are always certain uncertainties in the process of health risk assessment and management.Therefore,it is necessary to investigate heavy metals contents in water and evaluate health risk of heavy metals to human based on effective uncertainty control,which can provide comprehensive informations for environmental health risk management.This study investigated the total concentrations and spatial distribution of heavy metals in surface water from Honghu Lake.According to the comprehensive analysis of research progress about environmental health risk assessment and uncertainties reduction,an improved health risk assessment method based on the triangular fuzzy number was proposed.The improved evaluation method selected parameters on the basis of behavior patterns and exposure characteristics of receptors,and then evaluated the health risk level of heavy metals by means of fuzzy mathematics,health risk assessment model and geographic information system(GIS)technology.The fuzzy evaluation results presented the subordinate grade and corresponding reliability of risk,identified the major risk pollutant and risk priority control areas,and provided more full-scale results for decision-makers.In addition,multivariate statistical analysis was conducted for source identification of heavy metals.Finally,the countermeasures and suggestions for the risk management of heavy metals in Honghu Lake were pertinently put forward.The research results were as follow:(1)The mean total contents of heavy metals(Cu,Zn,Cr,Cd,Pb and As)in surface water from Honghu Lake were within the limits of the surface water quality standards and drinking water health standards.(2)The integrated non-carcinogeinic risk of the six heavy metals was within the highest acceptable risk level,which indicated that residents around Honghu Lake were not in danger of non-carcinogenic hazard.(3)The integrated carcinogenic risk of heavy metals through ingestion and dermal contact was[2.74E-05,8.16E-05],which was closed to the target risk(1.00E-04)proposed by United States Environmental Protection Agency(USEPA).In general,the integrated carcinogenic risk level of heavy metals was between Grade III(low-medium risk),Grade Ⅳ(medium risk).As was regarded to have the highest carcinogenic risk among the six selected trace elements because it generally accounted for 64%of integrated carcinogenic risk.And the areas around Chantan Peninsula and in the northeast of Honghu Lake were recommended as the priority risk control areas.(4)The fuzzy risk evaluation results indicated that there was fuzziness in major risk pollutants and control areas identification,which may mislead the decision-makers.Fortunately,health risk assessment based on triangular fuzzy numbers could obtain the health risk level and corresponding reliability,present the spatial distribution of risk level and reliability,and provide more comprehensive and intuitive information.(5)The suggeations for environmental health risk control and management were offered based on the source identification and health risk assessment.On one hand,the environmental health risk management system should be improved to guide the practical work.On the other hand,heavy metals pollution and risk management measures should be conducted based on the actual situation in Honghu Lake,in order to control water pollution and protect human health.