Heavy Metal Contamination And Copper Tolerant Plants In The Vicinity Of Jiuhua Copper Mine

Copper is an essential micronutrient for plants that is a component of severalelectron transport enzymes. However, Cu also induces toxicity to plant when thetissue concentration is slightly above its optimal levels. Mining and milling result inenvironmental pollution in mine. Eventually, they may pose a potential health risk toresidents in the vicinity of mining areas. So the heavy metal contamination of soilsand crops by metalliferous mining activities in Jiuhua copper mine, located in easternNanjing city, jiangsu province was surveyed. The result shows that elevated Cuconcentrations of soils and crops were found in the study area. About halves of all soilsamples contained Cu concentration exceed the third class of environment qualitystandards for Chinese soils, and the average of DTPA extracted soil Cu is 117 mg/kg.The pollution index (PI) result also shows the percentage of PI>1.0 is 57.3%, whichcan illuminate most of soils were contaminated by multiple elements. In edible partsof crops, the concentration of Cu in 67.46% samples exceed 10 mg/kg as thepermissible concentration by the national criterion for food environmental quality. The correlation analysis among heavy metals in soils shows there is a positivecorrelation between concentrations of Cu and Zn, Pb or Cd (p < 0.01). And there isnot any correlation between concentrations of Cu and Cr, Ni or Co. The investigationalso shows that some soils are contaminated by Zn. And the concentrations of Pb, Cdare not above the third class of standards. However, the percentages of Zn, Pb, Cd orCr in the edible parts of crops exceeding the criterion respectively are 90.03%, 62.5%,47.06% or 91.76%. Copper tolerant plants were surveyed in several copper mines of southern Chinaalong Yangtse river, and a series of pot experiments of Commelina communis L. andPolygonum perfoliatum in greenhouse were performed to evaluate their possibilitiesin repairing Cu contaminated soils. The survey results showed that no plant was yetfound in these areas to strictly meet the definition of Cu hyperaccumulator.Commelina communis L. is very tolerant to Cu toxicity in a culturing solution with Cuconcentration up to 400μmol/L, and can take up high Cu contents in shoot. Thepresence of EDTA enhanced Cu uptake of Commelina communis L., but wasdisadvantageous for its growth to some degree. Hydroponic cultures were conducted to investigate the copper tolerance andtoxicity mechanisms on the growth of Commelina communis L., which as a coppertolerant plant was sampled from Jiuhua copper mine. The experimental result showsCommelina communis L. has higher Cu concentration in the roots, but lower in itsshoots. And Cu concentration in shoots and roots increases with the increasing Cuconcentration in solution and lengthening treatment time. The uptake of Ca, Mn or Fein Commelina communis L. is influenced by different Cu concentration in solution. Inits roots high Cu hydroponic culture can restrain the uptake of Mn and Fe, however,increase the uptake of Ca. The presence of Cu can enhance the production of Chlcontents, shoot sugar contents on fresh weight, root livingness or SOD activity inshort times, which can increase the endurances of Commelina communis L.to Cu. Butwith lengthening treatment time this effect will decrease gradually. Lower Cutreatment can induce the synthesis of GSH of Commelina communis L.in initial stages.It can detoxify the toxicity of Cu because GSH can induce the synthesis of PCs.