Improved grey water footprint model of noncarcinogenic heavy metals in mine wastewater

This study focuses on developing an improved grey water footprint (GWF) to evaluate the pollution of noncarcinogenic heavy metals (NHMs) in mine wastewater. The conventional GWF only considers independent dilution, and the health hazards of NHMs are accumulative. The improved GWF is designed on the basis of health risk theory to solve this problem. The improved GWF involves three procedures: (i) deducing the virtual water volume to dilute the accumulative health risk within the allowable limit, (ii) calculating the water pollution level (WPL) to make comprehensive evaluation, and (iii) distinguishing the contribution rates of exposure pathways. The evaluation of NHM pollution in Dexing City shows the following conclusions. (i) The comprehensive GWF of NHMs in Dexing City is 2.31 billion m3, and the WPL is 0.979, which belongs to the “high” grade. Cu, Pb, and Zn account for 98.09%, 1.10%, and 0.89% of GWF, respectively. The contribution rates of drinking and contact are 99.02% and 0.98%, respectively. The risk is majorly introduced by the load of Cu in Dexing copper mine. (ii) Compared with the conventional GWF, the improved GWF has better capacities in representing the accumulative effect of NHMs and distinguishing the effects of different exposure routes on human health.