Study On Heavy Metals Pollution Characteristics And Soil Enzyme Activities Around Typical Copper Mine Tailings

Soils, as the center of the natural environment, are responsible for occurance of approximately 90% of pollutants. Soil enzyme is one of the factors in soil metaboly. It plays an important role in the soil substance recycle including biochemical process. Heavy metals may enter the soil by human activity. The influence of heavy metals on soil enzyme activities was found. Thus soil enzymes can be regarded as indicators to direct the impact of pollution on soil environment.In this paper, the soils around Dexing Copper Mine tailings were studied. Contamination in this area evaluated by heavy metal content and speciation analysis, the characteristics and source of heavy metal pollution were revealed. Besides, the relationship between the heavy metals and soil enzyme activities were discussed. Additionally, in laboratory conditions, the quantitative of heavy metal pollution on soil enzyme activities was investigated.The results indicated that the farmland contamination comprehensive indexes were high, and soil environment have been in the specific heavy contamination range. Single-gene contaminated indexes indicated that Cu and Cd contents seriously exceeded the allowed value in heavy pollution; Ni was in slight pollution, while Zn, Pb and Cr contents did not exceed the allowed value. Cu exists mainly in organic matter fraction and Zn exists mainly in residual fraction, which has good stability. While the exchangeable speciation of Cd takes large percent, which would easily polluted the soil.Hakanson potential ecological risk index techniques, correlation analysis, principal component analysis (PCA) were applied to estimate the character of heavy metal combined contamination (Cu, Zn, Ni, Pb, Cr, Cd). The degree of potential ecological risks in soils around copper tailing, the main factors of environment pollution and potential ecological risks were determined. The results showed that soils around copper mine tailing were contaminated at different degrees with heavy metals. The order of pollution extents was Cd>Cu>Pb>Ni>Cr> Zn, Cd was the main factor of potential ecological risks. The average RI (risk index) in this region was above 600.The soil enzyme activities surrounded this area were studied. In the area, soil enzyme activities were inhibited by heavy metals in different degrees. The total enzyme activities were established by main component analysis. This index was consistent to actual division. Therefore, it is feasible to use soil total enzyme activities to indicate the pollution of heavy metals.Under laboratory conditions, Cu, Cd had a remarkable inhibitory effect on soil urease activity, with Cu+Cd being the most in extent and intensity. It is showed that soil urease activity reduced with the concentration of heavy metals increases. Urease activity can be an index of heavy metals pollution of soil.