Heavy Metals Pollution and Role of Soil PGPR: A Mitigation Approach

Abstract

Heavy metal pollution is a serious threat to human health and the environment. It is severely augmented by several industrial activities. The main causes of metal pollution include several industrial processes such as metal forging, smelting, mining, fossil fuel burning, and the use of sewage sludge on agricultural sites. Toxic heavy metals discharged from these sources adversely affect the population of soil microorganisms and the physicochemical properties of the soil, reducing soil fertility and crop productivity. These heavy metals are not biodegradable and remain in the environment. Several conventional methods are used for removal or detoxification of heavy metals that have several drawbacks such as high cost, difficult to operate and toxic in nature. Therefore, bioremediation techniques have emerged as an alternative technique for remediation of heavy metals that have polluted soils. In metal-contaminated soil, the natural role of metal-tolerant plant growth-promoting rhizobacteria (PGPR) in maintaining soil fertility is fading with increasing use of pesticides. In addition to its role in detoxifying or removing toxic metals, rhizobacteria also promote plant growth via other mechanisms such as the production of growth promoting substances and siderophores. Phytoremediation is another new, low-cost in situ technology used to remove toxic pollutants from contaminated soil. The efficiency of phytoremediation can be enhanced by heavy-metal tolerant PGPR. In this book chapter, the significance of the PGPR for direct application to metal contaminated soil under a wide range of agro-ecological conditions has been discussed. The chapter also gives insight on re-establishment of metal contaminated soils and consequently, promotes crop productivity and their significance in phytoremediation. Thus, in the future bioremediation can be an effective technology for treatment of metal polluted environments.KeywordsBioremediationMetal pollutionPGPRPhytoremediationSoil