Effects Of Organic Acid On Heavy Metal Fraction In Soil In Mining Area

Tongling Mining area is the one of the seven largest mining areas in China. It is rich in deposits resources, yet heavy metals greatly accumulated in soil of the area with the activities like mine exploitation, smelting, transportation, and tailing disposal. After heavy metals entered into soil, it would also transfer to water and air through food cycle, accordingly threatened the public health and ecology. Since the heavy metal pollution has the feature of concealment, irreversibility, and chronicity, it is widely concerned domestically and abroad as a difficult issue.Selecting Xinqiao Area in Tongling as study area.we measured the physico- chemical properties and the XRD of the soil, subsequently analyzed the CK of Cu in soil, and the transformation of the heavy metal status after added external heavy metals. Besides, Comparison study was conducted between the status of heavy metals in polluted soil with organism acid added and that without organism acid. We draw the conclusions as following.The soil in Xinqiao Area is weak acidic with low content of organism. It is composed with largest percentages of quartz, followed by illite and kaolinite. The Cu and Cd concentration is high, significantly exceeding background values.Adsorption and desorption of soil to heavy metal increases as more heavy metals added. The adsorption rate to Cu decreased at first, and then increased. In a whole, adsorbed Cd increases with the concentration of Cu added, so does the absorbed rate.Residual fraction is the most component of Cu in original soil (about 55.37%). The content order of the other fraction are following Fe-Mn oxide-bound fraction, humic -bound fraction, organic-bound fraction, carbonate-bound fraction,and dissoluble fraction is the lowest.After external Cu entered soil, The percentage of residual fraction declines, and that of dissoluble Cu increases. The percentages of other four components do not change in sequent. After external Cd entered soil, dissoluble Cd became the majority. Carbonate-bound fraction, humic-bound fraction, Fe-Mn oxide-bound fraction, organic-bound fraction changes with the concentration of Cd added. While the residual fraction is the lowest with a decreasing trend.After organic acid added into soil, different types of organic acid with different concentrations influent heavy metals distinctly. DTPA behaves effectively in activation of soil Cu. With higher external Cu added, soil Cu becomes more active requiring less organic acids. Organic acid can activate soil Cd in some extent, but the function is weaker than Cu.and when the concentration of added Cd reach 100mg/kg and 130mg/kg, the activation of 1mmol/kg organic acids is much more obvious.