Spatio-temporal Distribution And Driver Factor Analysis Of Heavy Metal Gray Water Footprint In Industrial Wastewater In China

Discharge of industrial wastewater was the major source of heavy metal pollutions in most watersheds in past decades,with major pollutants of Mercury,Cadmium,Chromium,Lead,and Arsenic.The management department has put forward the management mode of prevention and control of heavy metal pollution combining the watersheds and administrative units.However,the insufficient spatio-temporal resolution of heavy metal emission data and the gap in the methodology of environmental risk analysis have greatly limited the implementation of this management mode.In this study,a higher spatio-temporal resolution heavy metal gray water footprint(HMGWF)model was constructed for above five heavy metal pollutants,and spatio-temporal distribution and driver factor of the HMGWF in industrial wastewater in China were revealed during the three five-year plan period(2000-2015).This study could provide theoretical method,data support,and decision basis for the prevention and control of heavy metal pollution.The innovative results obtained in the dissertation are summed up as follows:The HMGWF and heavy metal environmental impact level(HMEIL)have been proposed to quantify the environmental impacts of heavy metal emissions based on the frameworks of grey water footprint and the USEtox model.Then,the HMGWF environmental impact assessment(HMGWF-EIA)model was constructed with detailed parameters and input data collection.Furthermore,the database of HMGWF-EIA was constructed through data collection,measurement and addressing data gaps.Based on the constructed model and database,the monthly HMGWF of industrial wastewater in 2000-2015 was calculated in the scale of 1km×1km,the highest spatio-temporal resolution covering the whole country in the field of industrial wastewater heavy metal emissions.Meanwhile,the spatio-temporal distribution of industrial wastewater HMGWF in different scales was analyzed to identify the heavily contaminated areas,dominant polluting industries and major heavy metal pollutants,which should be paid much attention in industrial wastewater emissions reduction process.Then,the spatio-temporal distribution of industrial wastewater HMEIL in watershed scales was further analyzed to estimate the pollution degree and risk levels in various watersheds.Then,driving effects of the economic scale factor,wastewater intensity factor and pollution concentration factor on industrial wastewater HMGWF were decomposed and discussed by means of the Logarithmic Mean Divisia Index(LMDI).Results showed that the decrease of HMGWF is dominated by wastewater intensity factor and pollution concentration factor,while the economic scale factor is the major factor leading to an increase of HMGWF.As a typical case,the driving effect of three factors and the best pathway to reduce the risk of heavy metal pollution was further discussed in the Liaohe river basin by constructing the cost-benefit analysis model.In view of interaction mode of watersheds and administrative units to heavy metal emission reduction and prevention and control of pollution,suggestions are put forward from three aspects:(1)HMGWF and HMEIL can be used as a reference index for environmental tax;(2)Optimization of industrial production layout should be combined with the hydrological characteristics of the basin;(3)The administrative units in one basin should develope in coordination and trade-off the economic benefits and environmental protection.