Influence of selected mineral material on the water solubility and leachability of heavy metals from contaminated soil

Heavy metal pollution in soils is currently a critical environmental issue. Soil amendments can reduce the availability of contaminants and retard their offsite movement by water. A study was conducted to reduce the water solubility and leachability of heavy metals (HM) (cadmium (Cd), lead (Pb), nickel (Ni), chromium (Cr), and copper (Cu)) from polluted soil using various ground natural materials, namely slate, gypsum, lime, shale, and clay. Polluted soil samples were collected from Hattar Industrial areas of Haripur, Pakistan, noted for metal contamination. Mineral amendments were applied to those soil samples at the rate of 2.5 and 5% along with the control (no amendment). Results showed that the amendment material apparently reduced the solubilization of heavy metals (p < 0.05). The heavy metal concentrations in the soil were in the order Pb > Cr > Ni > Cd > Cu. After 10 days of incubation, the Cd concentration was reduced on average by the mineral amendment, but the reduction varied in the order slate > clay > lime > shale > gypsum. These materials were also differed for Pb (at p < 0.05), the reduction was in the order shale > lime > clay > slate > gypsum, and for Ni as the order was slate > clay > gypsum > shale > lime. Chromium and Cu were reduced similarly. Reduction in the metal solubility was highly related to the application rate of material. The leachability of trace elements from soil was also a function of amendment and the material differed for heavy metals during the leaching process. This research indicates that mineral material may act as an adsorbent for the metal contaminant and thus reduces their leachability from soils. Moreover, the availability of heavy metals in contaminated soils can be reduced by using mineral amendment.