Study On Total Content And Speciation Of Heavy Metals In Soils Of Zhongkai High-tech Zone, Huizhou City

Recently, heavy metal contamination in the soils has been an environment problemnoticed all over the word. Due to the deep research on the accumulation and migration ofheavy metals, the toxicity was recognized to be not only related to its total contents, butmostly depended on its speciation and distribution. Numbers of agricultural production andindustrial activities occurred in Zhongkai High-tech Zone, Huizhou city of Guangdongprovince. So doing research in total contents and speciation distribution of heavy metals insoil should be very significant.Samples collected from sites of53for soils in industrial and agriculture area wereanalyzed to produce active speciation (exchangeable, carbonate-bound, manganeseoxides-bound, organic-bound) and residual contents with a sequential extraction technique byTessier. Correlational analysis, principal component analysis and concentration gradientanalysis were used to investigate the total content and the speciation distribution of9kinds ofheavy metals.The findings indicated that the average contents of Pb, Zn, Cu, Mn and Cr in industrialarea were respectively35.57,64.56,22.26,240.98,46.14mg/kg, higher than that inagricultural area, which were respectively28.25、45.12、15.19、185.49、33.80mg/kg. Statisticsof most samples were lower than national first-level soil standard.The existence of Fe and Tiwas almost all in residual form, with an average over94.1%, and the other elements in mostsamples mainly were residual. The average percentages of active speciation in industrial andagricultural area were between5.8%to26.9%for Ni, Co and Cr,18.7%to40.4%for Pb,27.6%to47.9%for Cu and Zn, and36.2%to61.5%for Mn respectively.On average, the activespeciation of Cu, Pb, Zn, Mn and Cr in industrial area were respectively9.56、12.70、17.61、136.01、4.04mg/kg, and that in agriculture area were respectively5.44、6.87、14.04、88.62、6.62mg/kg. The farmland pollution from active Cu, Pb and Zn must not be overlooked. Theresults also demonstrate that the exogenous heavy metals were dominated by both industrialand agriculture produce. Among the various exogenous factors, the industrial area sufferedfrom relatively high Pb, Zn and Cu pollution, and the pollution mainly came from theincreasingly busy traffic transportation. The agricultural area suffered from relatively low Pbpollution and relatively high Zn and Cu pollution. This was mainly caused by traffictransportation and the use of pesticides and fertilizers.