ABSTRACT
Trivalent chromium remains immobilized in the form of Cr(OH)3; meanwhile, the 1 and 2 are the most soluble and bioavailable hexavalent chromium found in soil. Cyclic conversion of Cr(III) and Cr(VI) operates by a continuous redox reaction in the soil ecosystem. The binding mechanism of Cr(VI) is dependent on the soil pH and mineralogical phase. Hydroxyl groups present in the mineral surface of montmorillonite, kaolinite, aluminium oxide, iron oxide and chromite can easily initiate the surface complexation process to adsorb Cr(VI). Chromium speciation is the guiding factor for its availability, mobility and translocation in soil and plants. While Cr enters into the plant tissue through carrier ions like sulphate. Chromium-related toxicity includes retarded plant growth, decreased germination potential, reduced enzymatic activities and malfunctioning of important plant processes like photosynthesis and oxidative balance. Although Cr(III) is equally harmful to some species, the simultaneous reduction of Cr(VI) and Cr(III) through the bioremediation process of Cr using certain bacteria, algae, fungi and plant species can prove to be an important tool to address the elevated Cr distribution in the soil-plant system.
