Bioremediation of arsenic in contaminated terrestrial and aquatic environments

The name Arsenic is derived from the Greek word arsenikon, meaning potent. This element occurs in the ecosystem in different oxidation states of which As(III) and As(V) are most common to humans, animals, plant species. As is present in drinking water and soil from natural sources as well as a pollutant from agricultural and industrial processes. Differences in arsenic uptake by different plant species is controlled by many factors such as root surface area, root exudates, and rate of evapotranspiration. Some plant species have high affinity to accumulate arsenic in tissues above ground. Hyperaccumulator plants have a threshold arsenic content above 1,000 μg g^-1 DM. We review bioremediation studies with especial emphasis on biosorption research on different arsenic species, plants and their biomass, agricultural and industry wastes, as well as the biomass of some fungi species. Bioremediation is considered as an alternative technique for the removal of As in groundwater. One of the popular methods among bioremediation techniques, phytoremediation uses living plants to remove arsenic from the environment or to render it less toxic, in bioaccumulation processes. Phytoremediation techniques often do not take into account the biosorption processes of living plants and plant litter. In biosorption techniques, contaminants can be removed by a biological substrate as a sorbent such as bacteria, fungi, algae or vascular plants. Bioremediation assures in situ treatment of polluted soils. Biosorption characteristics, equilibrium and kinetics of different biosorbents have also been addressed here. Evaluation of the current literature suggests that arsenic bioavailability and molecular level phytoremediation processes in bioremediation are crucial for designing phytoremediation technologies with improved, predictable remedial success.