Risk Assessment Of Heavy Metals In Soils And Crops From A Pb/Zn Mine Area In Hunan Province

To study the health risks of heavy metals in the agricultural soils and corps collected from one typical lead-zinc mining area in Hunan province, the single factor index method, integrated pollution index method, potential risk evaluation method and in vitro simulated artificial gastrointestinal method were employed. The study would provide the basic information for diagnosing agricultural soil pollution and health risks resulted from crop pollution in the lead-zinc mining area. The results showed that:(1)The average contents of Pb, Zn, Cu, Cd and As in the agricultural soil were566.82mg·kg-1,285.90mg·kg-1,69.00mg·kg-1,10.29mg·kg-1and670.12mg·kg-1respectively, demonstrating that the agricultural soils around the mining area had been polluted by heavy metals to different degrees. The pollution index of Cd was the highest among the study heavy metals. The ecological harm sequence of the heavy metals (Pb, Zn, Cu, Cd and As) in the agricultural soil was Cd>As>Pb>Cu>Zn. Among the five heavy metals, Cd and As were the major ecological risk contribution factors.(2) The average contents of Pb, Zn, Cu, Cd and As in the rice from the mine area were0.68±0.57mg·kg-1,42.64±7.64mg·kg-1,7.47±4.17mg·kg-1,2.08±1.17mg·kg-1and4.31±5.2mg·kg-1respectively, which meaned the contents of Pb, Cd and As in the rice had exceeded the limits specified in national standard for limitation of contaminants in foods. Meanwhile, the health risk evaluation index (hazard quotient and hazard index) had further indicated that potential hazards of Cd and As were existing in the rice. The HI of heavy metals in the rice from the area was more than10, indicated there were certain chronic toxicity when people eat the rice in this area.(3)The average contents of Pb, Zn, Cu, Cd and As in the vegetables (and fruits) of the area were33.01mg·kg-1,0.56mg·kg-1,14.34mg·kg-1,19.40mg·kg-1and3.53mg·kg-1respectively. Compared with the national standard for limitation of contaminants in foods, the over-limit ratios of the contents of Pb and As in vegetables in the mine area are100%and that of Cd is82.05%. The data indicate that certain health risks are existing when people eat the vegetables and fruits.(4) For an adult, the average ecological providing amounts of Pb, Zn, Cu, Cd and As in the rice in the polluted area in the simulated gastric stage are700.05,10351.74,532.17,186.40and14.62μg·d-1respectively.In the simulated gastrointestinal stage, the amounts of bio-availabilities of Pb, Zn, Cu, Cd and As are254.13,710.47,715.87,45.92and12.14μg·d-1respectively. For a child, the amounts of bio-availabilities of Pb, Zn, Cu, Cd and As in the rice of the polluted area in the simulated gastric stage are498.49,7371.27,378.94,132.73and10.41μg·d-1respectively; in the simulated gastrointestinal stage, the amounts of bio-availabilities of Pb, Zn, Cu, Cd and As are180.96,505.91,509.75,32.69and8.64μg·d-1respectively. To both of the adult and children the average amounts of bio-availabilities of Pb, Zn, Cu, Cd and As in the rice of the polluted area are higher than those in the rice of non-polluted areas. The intakes of Pb, Cd and As of the adult and children in the polluted area through eating rice have exceeded the weekly maximum tolerable amounts in foods. Therefore, the potential health risks would be happened when the adult and child eat the rice which has been polluted by these heavy metals, especiallyfor the children.