Review on the research advances of the pollution and bioremediation of heavy metals in the soil

The present paper intends to review the research advances in the pollution of heavy metals in the soil and their bioremediation to the soil. For its purpose, we have, first of all, pointed out the ever more great significance of such research in helping to restore the fertility of the land soil and then illustrated some more effective and efficient new pollution-reducing and removing techniques. In addition, methods on finding the pollution sources, the classification of such pollution sources and removal measures of such heavy metal pollutions from the soil are generalized and summarized. It has thus been found that the main sources of heavy metal pollution in soil come from industrial and agricultural production, traffic and transportation, as well as that of energy consumption. As to the kinds of heavy metal pollution in the soil, it is usually divided into six categories, i.e. water soluble fraction, exchangeable fraction, acid soluble fraction, oxidizable fraction, reducible fraction, and the residual fraction. Removal rules of heavy metal pollution in the soil have so far been generalized. It has been classified that the remove and transform of heavy metals are effected by sorption of soil colloid, reaction between heavy metals and humus and Eh, pH of soil. And, remediation techniques of heavy metal pollution in the soil have thus also been discussed. The bioremediation to be paid more attention to at present is the keystone. The main problems and the further research trends of heavy metal pollutions of soil are also mentioned with the bioremediation being the keystone.