Arsenic Occurrence and Fate in the Environment; A Geochemical Perspective

Abstract

The arsenic minerals in the environment constitute the primary source of the environmentally occurring arsenic. The As minerals interact with the environment and this renders either their dissolution or the formation of secondary minerals, or both. The distribution of the environmental arsenic is determined by the biogeochemical transformations with respect to the redox conditions, the pH, the availability of ions, the adsorption-desorption, dissolution and the biological activity. The arsenic in the environment is sorbed primarily by metal oxides, especially the ones of iron (Fe), aluminum (Al) and manganese (Mn). These are thought to bind As (+5) readily than As (+3). The overall adsorption depends greatly on pH. Metal oxides such as the ones of hydrous ferric, manganese and aluminum are additional important sinks of arsenic that is adsorbed or co-precipitated. Their dissolution depends also on pH. The redox potential and the microbial activity. Final result is the release of arsenic chemical species into the environment. This review presents a systematic compilation of the major geochemical processes that govern arsenic fate in the environment. The paper attempts to compile the removal capacity of constituents which could be useful for the purpose of As remediation.