| Nandan County is an important non-ferrous metal base in China.The development of mining activities led to the development of the local economy,but also brought serious environmental pollution,endangering the health of local residents.In order to investigate pollution status of Pb?As and Cd in the surface dust in the mining area,this paper selects Dachang Town and Chehe Town of Nandan county as the research object.Road dust?34 in total?and household dust?41 in total?were collected in march 2016,measured the concentrations of Pb ? As ? Cd and physicochemical properties,used an in vitro test of PBET?Physiologically Based Extraction Test?to assess bioaccessibility in gastric and small intestine phase of Pb?As and Cd.The US EPA Health Risk Assessment Model was employed to evaluate the potential health risk of those heavy metals in surface dust.The results were as follow:?1?The concentrations of Pb?As and Cd in all samples were higher than the surface soil background values of Guangxi province and the third level standard of soil environmental quality.The average content of three kinds of heavy metals in Dachang town road dust are respectively 1224.22 mg/kg,4466.91 mg/kg,55.18mg/kg;the Chehe town are respectively 761.54mg/kg,2997.45mg/kg and 82.81mg/kg.In Dachang town household dust are respectively 1185.88,2864.14,39.25 mg/kg,Chehe town are respectively 826.19,2115.31,86.78 mg/kg.?2?The concentrations of Pb?As in road dust,Dachang town higher than Chehe town,The concentrations of Cd,Dachang town lower than Chehe town;Household dusts were exactly the same.The content of three heavy metals in road dust in Dachang town was higher than household dust.The content of As in road dust in Chehe town was higher than household dust,Pb and Cd were lower than household dust.?3?Surface dust is mainly fine grain size?<75?m?.The contents of three heavy metals were mainly accumulated in fine dust particle size,and the content of heavy metals increased with the decrease of particle sizes.?4?The bioaccessibility of three heavy metals in road dust in gastric were in range of 1.57%-10%,0.63%-14.90%,0.22%-4.33%,while in small instestine phase they raged in 0.11%-1.46%,0.14%-8.37%,0.29%-7.22%;Three heavy metals in household dust in gastric were in range of 0.25%-19.46%,0.46%-27.22%,0.28%-7.33%,in small instestine phase they raged in 0.01%-4.36%,0.31%-8.66%,0.94%-19.91%.Bioaccessibility of Cd and Pb in gastric phase significantly higer than those in small instestine phase.?5?The correlation analysis showed that physicochemical properties of dust?pH,SOM,and particle size?are important factors affecting the bioavailability of heavy metals in dust.The bioavailability of heavy metals decreased with the increase of pH value,and increased with the increase of SOM,and the smaller the particle size,the higher the bioavailability.?6?Health risk assessment indicate that the total non-cancerrisk?HI?of heavy metals in road dust was 243.42 for children,and for adults was 32.87;In household dust was 160.70 for children,and for adult was about 21.62.The non-cancerhazard indexes higher than their threshold values,and the route of ingestion brought the highest levels of risk.Non-cancer risk is higher for children than for adults.The carcinogen risks of As in road dust was 9.28×10-6,5.99×10-6 in household dust,it meant element has a certain carcinogenic risk.Cd carcinogenic risk is lower than the average risk thresholds,therefore not cause carcinogenic health hazard to human body. |
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