GIS Based Transport Routes Identification And Health Risk Assessment Of Heavy Metal(Loid)s In Soil With Different Land Uses Around A Smelting Site

Heavy metal（loid）s in soils around smelting sites have received widespread attention due to their toxicity,persistence,and substantial difficulty in removal by natural degradation.The bioaccumulation of heavy metal（loid）s may increase human health risks through several pathways,including food consumption,particle ingestion,particle inhalation,and skin absorption.Therefore,identifying potential sources,transport routes,and assessing the health risks（non-carcinogenic（NCR）and carcinogenic（CR））of soil heavy metal（loid）s are critical for protecting the natural environment and human health.In this work,soil samples were collected from around a smelting site,and multivariate statistics,geostatistics,receptor models,mineralogical characterization techniques,and health risk assessment models were used to investigate sources,transport routes,human health risks,and distances of risk affected areas.（1）The results showed that the mean concentrations of As,Hg,Cd,Pb,Zn,and Cu in the soil exceeded their background values except for Cr,Mn,and Fe.According to the I_geo values,As,Hg,Cd,Pb,Cu,and Zn accumulation among the different land uses decreased in the order of grassland>agricultural land>forestland.The GIS based PCA and PMF analyses established that the smelter and parent materials were the sources of heavy metal（loid）s among the different land uses.The PMF results revealed that 70.7%of heavy metal（loid）s in agricultural land,48.3%in forestland,and 67.5%in grassland were attributed to the emissions from the smelter.The PCA and PMF factor hotspots were largely concentrated within the smelting site,the slag and wastewater runoff areas,and the main wind direction.The PMF and GIS mapping confirmed that As,Cd,Pb,Cu,and Zn were mostly transported by surface runoff and atmospheric deposition from the smelting site,Hg pollution was caused by atmospheric deposition from the smelter,and Cr,Mn,and Fe were mainly from the soil parent materials.Furthermore,soils in agricultural land and grassland received heavy metal（loid）s from surface runoff and atmospheric deposition,while soils in forestland only received from atmospheric deposition,which makes the concentration lower than in agricultural land and grassland.The results indicate that heavy metal（loid）s transported from the smelter to the surrounding soils were strongly influenced by surface runoff and atmospheric deposition in the dominant wind direction.（2）Pb isotope fingerprinting results using the Iso Source mixing model revealed that Pb and the other heavy metal（loid）s in the soil were mostly derived from smelter emissions,with a minor contribution from the natural source.The spatial distribution of the Pb ratios showed a noticeable pattern of atmospheric deposition and surface runoff around the smelter.In addition,agricultural land and forestland received Pb and other metal（loid）s contributions mainly from smelting dust via atmospheric deposition,while grassland was mostly from slag via surface runoff.Moreover,the mineralogical characterization findings revealed that the soil’s dominant mineral phases were quartz,calcite,hematite,volkonskoite,and graphite,with comparable results in smelting dust and slag collected from the smelter in the study area.Soil,smelting dust,and slag samples were mainly composed of Si and metal（loids）such as O,Al,C,Fe,Cu,Ca,Pb,and As.The results further revealed that heavy metal（loid）s migration and existence from the smelter to the soil were mostly controlled by oxide compounds.（3）The health risk assessment based on heavy metal（loid）concentration results revealed that ingestion was the main NCR and CR exposure pathway for adults,followed by dermal contact and inhalation for all the land uses,signifying an increased likelihood of hand and dermal exposure may enhance human health risks.In addition,the mean total hazard index（THI）and total cancer risk（TCR）values for all the land uses were above the safety limits,except for forestland.The hotspots of NCR for the land uses were mostly around the smelting site and the wastewater and slag runoff areas,while TCR values were in the entire area.Moreover,smelting dust（factor 2）and slag（factor 3）particles were the main soil heavy metal（loid）s contributing sources of health risks in the study area.Factors2 and 3 had NCR and CR mean values above the safety threshold,suggesting severe risk contribution.Visualized by GIS mapping,high values of NCR and CR for factors 2 and 3 were relatively similar,concentrated close to the smelter.The risk affected areas decreased exponentially as distances from the smelting site increased（1.6 km for factor 2 and 0.4 km for factor 3）.The identification of the sources of heavily polluted areas,transport routes,and health risk assessment serves as the foundation for policymakers to adopt actions to restore soil quality.In addition,the findings provide a useful approach for quantifying risk apportionment and predicting the distance of risk affected areas from different sources,which is critical in providing policymakers with vital information on health risks and pollution control measures in dense industrial areas.Furthermore,controlling heavy metal emissions from these industries should be prioritized to help reduce heavy metal accumulation in soils.