Biological Approaches for Remediation of Metal-Contaminated Sites

Environmental pollution by several heavy metals and metalloids is a severe problem worldwide, as soils became increasingly contaminated, posing a threat to ecosystems and ultimately to human health. Contamination derives from large scale urbanization and industrialization, threatening land ecosystems, surface and groundwater, as well as food safety and human health. Remediation strategies for heavy metal-contaminated sites are necessary to protect from their toxic effects and conserve the environment for future generations. Numerous physicochemical techniques have been adopted including excavation and deposition in landfills, thermal treatment, leaching and electro-reclamation. These techniques are fast but inadequate, costly, cause adverse effects on soil physical, chemical and biological properties, and may lead to secondary pollution. In fact, many of these approaches only change the problem from one form or place to another, and do not completely destroy the pollutants. There was an urgent need to develop new technologies which are cost-effective and eco-friendly. In this context, biological remediation has tremendous potential. It uses plants and microorganisms to remove or contain toxic contaminants and is considered as the most effective method because it is a natural process, environmentally-friendly, has a low cost, and wide public acceptance. The present chapter aims to provide a comprehensive review of some of the promising processes mediated by plant and microbes to remediate metal-contaminated environments. Some biological processes used for the decontamination of organic compounds will also be included because of their relevance and potential common use for both purposes.

Geochemical analysis of sediments from a polluted waterway in the vicinity of a metallurgical plant, Minas Gerais, Brazil

Mining and metallurgical industries are the most responsible for heavy metal contamination. These contaminants are often associated to poor management strategies and the lack of suitable containment areas. This is the case of one of the largest metal alloy producers in the São Francisco river basin, in Minas Gerais state, Brazil. During operation, the tailings of this activity have been accumulated in the surrounding area, leading to heavy metal contamination (Mn, Cu, Zn, Ni, Pb, Cd, Cr and As), much above the critical levels, which accumulate in the sediments of the nearby waterways, in the soils of the drainage area, and in the water column. In this work we are going to discuss both the contamination level and its extent in the Consciência river, a small tributary of the São Francisco river, the longest river entirely Brazilian, by analyzing the geochemistry and mineralogy of the accumulated sediments. It will be also discuss the reclamation strategies of this site and the impact on the environment.