Contamination Of Heavy Metals In Soils And Plants In The Vicinity Of Two Copper Mines In The East Of Nanjing

Heavy metals(Cu,Zn,Pb and Cd)contamination in soils and plants(mainly vegetables)in the vicinity of two copper mines(Jiuhuashan copper mine and Anjishan copper mine)in China were investigated.1.Around Jiuhuashan copper mine,Cu concentrations of all 93 soil samples ranged from 30.4-3191 mg kg-1 for a mean of 816.8 mg kg-1.Cu concentrations of over 96%soil samples were above China National Standard(100 mg kg-1).Among 15 samples from a 0-20-cm soil layer used for the toxicity characteristic leaching procedure(TCLP)test,the highest value of Cu-TCLP was 133.8 mg kg-1 and the TCLP values were positively correlated with the total Cu content of the soils.The sequential extraction of soils in the 0-20-,20-40-,and 40-60-cm soil layers showed that Cu existed mainly in the Fe-Mn oxide fraction and residual fraction in the 0-20-cm soil layer,and the residual fraction in deeper soil layers.The copper contamination of 21 species of vegetables from in situ sampling was also examined.Cu concentrations in the edible portions of Brassica chinensis and Solanum melongena were higher than the FAO/WHO standard(40 mg kg-1 DW).The health risk of copper for local inhabitants from consuming these vegetables was assessed on the basis of the target hazard quotient(THQ).Enriched concentrations of copper were also found in situ in eight cultivars of Brassica chinensis planted in the fields,with two levels of Cu concentration.The results showed that there is severe copper contamination in this mine area,and the pollutant in soils show a high risk of leaching into the groundwater and diffusing through the food chain.2.The area of Anjishan copper mine was divided into six sampling districts.One hundred and fourteen soil samples were collected.Cu concentrations ranged from 20.1-5435.2 mg·kg-1 for a mean of 474.1 mg·kg-1 showed that there was a severe copper contamination in paddy soils.Only a few soil samples had slight Zn contamination and no Pb and Cd contamination were detected.Cu-TCLP values for 15 soil samples still showed the positive correlation between Cu-TCLP content and the total Cu content.The highest value of Cu-TCLP was 148 mg kg-1 and Cu-TCLP value of whose total Cu value exceeded 500 mg kg-1 was above the International Standard 15 mg kg-1(Federal Register,1986).The result of sequential extraction experiment of six soil samples from six sampling areas was similar to that from Jiuhuashan copper mine.Shoots of rapes and garden vegetables were collected from three sampling areas.Cu concentrations of the plants were less than the FAO/WHO standard while the corresponding soils had a copper contamination.Nevertheless,Zn and Pb concentrations of plants were higher than or very close to the FAO/WHO standard while soils were not contaminated by Zn and Pb.