Metal/metalloid-contaminated sites

In the past, removing metal and metalloid contaminants from soil has been impossible, and site clean-up has meant excavation and disposal in a secure landfill. An exciting new approach to this problem is phytoextraction, where plants are used to extract contaminants from the soil and harvested. Immobilization and Toxicity-Minimization. 

Pollution of soils and waters by human activities is an important and widespread problem. This pollution by, organic and inorganic substances can affect individual organisms, human populations, and ecosystems, each in its own unique way. In particular former military installations, often used for weapons production and nuclear power plants represent a ongoing and substantial threat to environment and human health because of the specific pollutants that can be released Solvents, explosives, fuels, radionuclides, heavy metals, and metalloids all have been identified in the environment around these installations. Remediation technologies for these contaminated sites have been developed based on conventional systems utilising physical and chemical treatments, such as excavation and incineration, pump-and-treat methods, ultraviolet oxidation, soil washing, etc. 

The mechanism of metal and metalloid sorption in soils was postulated some 30 years ago. The interaction of arsenic in soils and sediments at molecular level has been studied using extended x-ray absorption fine structure (EXFAS) and x-ray absorption near-edge structure (XANES) spectroscopies. Much work remains to be conducted to investigate the nature of metal and metalloid species sorbed at varying pH values and ionic strength in highly contaminated sites (see Chapter 5). 

Development of technology for remediation of mixtures (i.e., site contaminated with metals, metalloids, and organics)... 

Natural attenuation was re-assessed by the US National Research Council (NRC) and is considered as an established remedy with a high likelihood of success (at more than 75% of contaminated sites) for only a few types of organic contaminants such as BTEX, low-molecular-weight alcohols, ketones and esters, and methylene chloride. For inorganics such as metals, metalloids, oxyanions and radionuclides, the likelihood of success is rated as moderate or low (at more than 50% or at less than 25% of contaminated sites, respectively Table 10.4). It is assumed that any given site will have the... 

In summary, shale type rocks have a tendency to add a whole series of metals and metalloids such as Cd, Pb, Zn and As to the ecosystem, which approach concentrations typical for certain industrially contaminated sites. 

Mercury and arsenic are extremely toxic heavy metal and metalloid pollutants that adversely affect file health of millions of people worldwide (/). These toxic pollutants have reached unacceptably high levels in file environment due to industrial, def e, agricultural, and municipal properties. The U.S. Department of Energy (DOE) and other government and industrial sites in the United States are heavily contaminated with mercury, arsenic, and other toxic metals such as cadmium, copper, lead, and zinc. Each of these elemental pollutants has common environmentally relevant electrochemical species that are thiol-reactive and thus relevant to the phytoremediation strategies oufiined in Figure 1. Hundreds of Superfimd sites in the United States are listed on file... 

Biosorption is a process where metal ions (or metalloid species), compoimds and particulate substances are removed from solution by biological material through adsorption of the contaminant on a surface site of the biomass. It can be by physical forces (e.g. van der Waals, electrostatic interaction) and/or involving a chemical reaction. It is believed that biosorption using dead biomass is based on the physical sorption phenomenon, whereas sorption using live biomass occurs through both physical and chemical processes as well as transmembrane transport and accumulation of heavy metals in the algal cell. ... 

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