| The Xiangjiang River is the lifeblood of Hunan economy development.Due to the discharge of wastewater from smelting and chemical industries along the Xiangjiang River,environmental problems such as heavy metal pollution have been caused in the Xiangjiang River.Although the treatment of heavy metal pollution in the Xiangjiang River has achieved some success in recent years,there are still health risks.Therefore,it is very important to evaluate the water quality and health risk of heavy metal pollution in the Xiangjiang River to ensure the health of residents along the river.This study systematically analysed the monitoring data of the Xiangjiang River from 2005 to 2016 and revealed the time and space distribution characteristics of heavy metal pollution evolution law.Sub basin scale spatial variation characteristics of water quality and pollutant accurate traceability method was raised.Health risk assessment method based on rural and urban spatial heterogeneity analysis of heavy metals in Xiangjiang River was carried out.The prediction model of heavy metal pollution and health risk in the Xiangjiang River based on artificial intelligence was constructed,and a management platform for pollution evolution and risk prediction in the Xiangjiang River was developed..(1)Based on large spatial scale and long time series(2005-2016),the spatial and temporal distribution characteristics and evolution rules of heavy metal pollution in the Xiangjiang River Basin were revealed.The results showed that the monthly average concentrations of eight heavy metals(As,Cd,Hg,Cr,Cu,Pb,Zn and Se)fluctuated during the past 12 years but were adjusted by industrial policies and scale.After a series of regulation measures,the monthly mean concentrations generally showed a downward trend.In spatial scale,heavy metal pollution in Yongzhou and Hengyang sections has more serious problems.The analysis of the evolution trend of heavy metal pollution in the Xiangjiang River Basin showed that Se has a significant growth trend in most areas of the study area from 2005 to 2016,while Hg has a high and significant growth trend in Yongzhou and Changsha sections.The study aims to identify growth poles and provide key data for industry optimization.The results of correlation analysis,cluster analysis and principal component analysis showed that smelting industry,industrial and agricultural production activities,and natural evolution are three main sources of water pollution.The research aims to find out the sources of pollution and guide the adjustment of industrial structure.Cluster analysis results showed that: the first group is Guiyangzhen,Songbai and Aozhou;The second group is Lvputou and Gangzikou;The third group is Zhuting,Baishi,Fengxi,Xiawan,Majiahe,Yijiawan,Yishuichang,Zhaoshan,Houzishi,Sanchaji,Qiaokou and Zhangshugang.The sampling sites of these groups have similar evolution rules in the variation of some elements concentration and have significant geographical characteristics.The first group is mainly from Hengyang;The second group mainly came from Yongzhou;The third group is mainly from Changzhutan and Yueyang.This study aims to provide theoretical basis for the regional layout and industrial location adjustment of the Xiangjiang River.(2)Based on statistical analysis and spatial analysis,combined with socio-economic status and industrial structure characteristics,spatial variation characteristics of water quality at sub-watershed scale and accurate pollutant traceability method were proposed.In Yongzhou section,most of the indicators are in line with the class Ⅲ standard of Environmental Quality standard for Surface Water(GB3838-2002).Principal component analysis showed that there were 5 principal components,accounting for 72.63% of the total variance,which privides a new method for water quality assessment in the Xiangjiang River.The results of cluster analysis showed that the water quality indexes can be divided into two groups: heavy metals and other indexes,which provides a new method for water quality evaluation of the Xiangjiang River.The sampling sites were divided into two groups.In hengyang section,the concentration of pollution indexes in dry season was higher than that in wet season,and the average concentration of heavy metals was in the order of Zn > Cu > As > Pb > Cd > Se > Hg.The highest concentration of As was close to the class Ⅲ standard of Environmental Quality Standard for Surface Water(GB3838-2002).Multivariate analysis showed that the main components affecting the water quality in Hengyang section of the Xiangjiang River basin were different in wet season and dry season.Cluster analysis further divided the sampling points and water quality indicators into three categories.In the Changsha-Zhuzhou-Xiangtan section,most of the water quality indicators meet the class Ⅲ standards of The Environmental Quality Standard for Surface Water(GB3838-2002).Principal component analysis showed that there were three categories,including human activities,nutrient input and natural erosion,accounting for 90.46% of the total variance.The sampling sites were divided into three groups by cluster analysis.Compared with the three cities of Changsha,Zhuzhou and Xiangtan,heavy metal pollution is the main pollution source of Changsha and Zhuzhou,urban sewage pollution is the main pollution source.(3)In order to assess the health risk of heavy metal pollution more accurately in the Xiangjiang River,we have made innovations in assessment methods,and proposed a population classification method and exposure parameter selection which is more suitable for the Xiangjiang River.Therefore,a health risk assessment method of heavy metal pollution in the Xiangjiang River Basin was established based on spatial heterogeneity analysis of rural,urban,and industrial areas.The health risk assessment showed that the health risk of heavy metals in the Xiangjiang river decreased year by year from 2005 to 2016,and the health risk level was As > Cr > Cd > Hg > Cu > Se > Zn > Pb.As and Cr are the main factors causing potential health risks in the whole Xiangjiang River basin,while other heavy metals are less harmful.The health risk assessment results of heavy metals in Yongzhou section,Hengyang section and ChangshaZhuzhou-Xiangtan section showed that the health risk levels of all elements in Yongzhou section were As > Cd > Zn > Cu > Hg > Se > Pb,and the health risk was within the acceptable range.The health risk levels of elements in hengyang section during wet season were As > Cd > Cu >Se > Pb > Zn > Hg.The health risk levels of elements in dry season were As > Cd > Cu > Pb > Se > Zn >Hg.The health risk of As was highest in dry season,and its hazard index was 1.41.The health risk levels of elements in changsha-Zhuzhou-Xiangtan section are As > Cd > Cu > Pb >Se > Hg > Zn.The health risk index value of As to children was 1.27,which was the main factor causing potential health risk in Changsha-ZhuzhouXiangtan of the Xiangjiang River.(4)The prediction model of heavy metal pollution and human health risk in Xiangjiang River basin based on machine learning was established.Based on the correlation analysis,the feature selection prediction method of multiple monitoring points was proposed.By analyzing the heavy metal elements in different discrete distribution conditions and comparing the single variable method with the feature selection time series method,the method to improve the prediction accuracy of the model was found,to better understand the variation trend of heavy metals in the Xiangjiang River water body.The results show that machine learning can learn the general change rule from the training samples and predict the real samples effectively in the process of predicting the concentration of these heavy metals,which will provide theoretical basis and technical support for the early warning of water quality and health risks in the Xiangjiang River Basin.(5)The management platform for pollution evolution and risk prediction in Xiangjiang River was developed.The Xiangjiang River Basin pollution evolution and risk prediction technology system has been established by integrating 3D Web GIS technology,database technology and model development.The management platform of the Xiangjiang River Basin pollution evolution and risk prediction has been constructed,providing functions such as water situation monitoring,pollution simulation,sediment simulation,risk prediction and damage assessment.To improve the information level of environmental management in the Xiangjiang River basin,it provides intuitive,scientific and accurate event evolution process for decision-makers to assist decision-making.In addition,the water quality and health risk visualization system based on the Xiangjiang River was established.Surface water of the Xiangjiang River was taking as the research object and the characteristics of the basin was taking into consideration.Visual Stdio.Net platform,Arc GIS Engine component,geostatistical interpolation and GDI+ technology were used to read and display the spatial data,realized continuous gradual change of water quality and health risk,and enhanced the visualization effect by inverse distance interpolation method.The platform,which is function complete,user-friendly,efficient operation,can clearly show the water quality and health risk status in the Xiangjiang River.This platform can provide strong technical support for environmental management. |
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