Evaluation Of Heavy Metal Grey Water Footprint In Hunan Province Based On Health Risk

The grey water footprint assessment model for heavy metals based on health risks refers to the virtual amount of water required to dilute the total genotoxicity risk and somatic toxicity risk formed by all heavy metal pollution loads to below the allowable limit by calculating.This model can effectively and intuitively represent the local water resources situation by conducting a cumulative assessment of various heavy metals on local water resources and local ecological resources,and finally appearing in the form of a comprehensive gray water footprint.Compared with the traditional grey water footprint theoretical model,it solves the following problems:(ⅰ)Heavy metal pollution emitted from natural sources in industrial production can pose genetic and physical toxicity risks to the human body.However,in traditional grey water footprint theory,the environmental impact of pollutants is considered independent.Today’s toxicological experiments have proven that heavy metals have cumulative effects on human health.Therefore,the traditional gray water footprint model is difficult to directly apply to the gray water footprint calculation of heavy metal pollution loads.(ⅱ)During the establishment of the evaluation model,there is a phenomenon of uncertain background values for special heavy metals during the evaluation process,which makes it impossible to conduct cumulative evaluation.Therefore,a separate study is conducted on them.Hunan Province is an important production base of non-ferrous metals in China,which has caused serious heavy metal water pollution in the development process,so the heavy metal gray water footprint assessment model of health risks is used for evaluation.At the same time,aiming at the uncertainty of antimony background value in the Zijiang River Basin,a model of antimony gray water footprint was developed based on the principle of triangular fuzzy numbers in Shaoyang,Loudi and Yiyang cities in the Zijiang River Basin.The results of the evaluation showed:(ⅰ)From 2011 to 2017,the footprint of heavy metal gray water in Hunan Province was: 143.02 billion m3,114.85 billion m3,67.58 billion m3,66.80 billion m3,58.45 billion m3,29.52 billion m3 and 17.84 billion m3,showing a significant downward trend.The footprint pressure of heavy metal gray water was 1.27,0.58,0.43,0.37,0.30,0.13 and 0.09,and the overall trend was also significantly declining.(ⅱ)In 2011,the heavy metal grey water footprint pressure in Hunan Province was at a "very high" level,indicating that the threat of heavy metals to drinking water safety is extremely high.From 2012 to 2015,the heavy metal grey water footprint pressure in Hunan Province was at the "medium" level,indicating that the gray water footprint did not exceed the total runoff,but the impact of heavy metal pollution load on drinking water safety could not be ignored.Since 2016,the heavy metal grey water footprint pressure in Hunan Province has been at a "low" level,indicating that the impact of heavy metal pollution load on drinking water safety is negligible.(ⅲ)The pollutants that contribute the most to the heavy metal greywater footprint pressure in Hunan Province are arsenic,cadmium and hexavalent chromium,all of which are carcinogenic heavy metals.The main industrial driver of heavy metal greywater footprint pressure in Hunan Province is mining production,and the main agricultural driver is hemp production.(ⅳ)Among the three cities in the Zijiang River Basin,Loudi City has the largest footprint of antimony gray water,with an upper limit of 3.927 billion m3,a lower limit of 2.965 billion m3,and a median value of 3.247 billion m3.Shaoyang has the second largest antimony greywater footprint,with an upper limit of 463 million m3,a lower limit of 350 million m3,and a median value of 383 million m3.Yiyang City has the smallest antimony greywater footprint,with an upper limit of 171 million m3,a lower limit of 129 million m3,and a median value of 141 million m3.Loudi has the largest antimony greywater footprint pressure,with an upper limit of 0.954,a lower limit of0.732,a median of 0.792,a membership of 0.36 for the "medium" level,and a membership degree of 0.64 for the "high" level.This shows that the impact of antimony pollution load on drinking water safety in Loudi City cannot be ignored,and there is a64% probability of causing water quality water shortage.Shaoyang has the second highest antimony greywater footprint pressure,with an upper limit of 0.040,a lower limit of 0.030,and a median value of 0.033.Yiyang City has the smallest antimony grey water footprint pressure,with an upper limit of 0.021,a lower limit of 0.016,and a median value of 0.017.The antimony greywater footprint pressure in Shaoyang and Yiyang was both 1 for the "low" level,indicating that the antimony pollution load in both cities had little impact on local water resources and did not threaten drinking water safety.