Organic Matter and Heavy Metals Sorption

Abstract

Organic matter content in soils is highly variable and includes dead and living organisms and their decomposition products. plant residue and humic substances. Thermodynamically, organic matter is unstable in soils and later will oxidize to Co2, and H2O. The effective substances of organic matter decomposition are fulvic and humic acids (FA+Hu) which contain Several functional groups that release electrons or protons during their decomposition leaving behind several radical groups that act as electron donner to ward heavy metal ions forming FA and Hu-metal soluble and insoluble complexes. Those metallic-organic Complexes are variable by their Stability constant (SC) which is absolutely pH-dependent. The less stable the metal complex, the higher mobility in soil, In contrast, a highly stable metal complex is less soluble and mobility. So, organic matter plays an important role in the accumulation, leaching, and transportation of heavy metal Cations present in water and soils as chelates of different Stability and supplying plant roots by these ions and behavior as a buffering substance to heavy metal mobility.