Geochemical Cycle of Arsenic in the Earth's Surface and Mechanisms of Its Pollution of Groundwaters

Abstract

Arsenic behavior in natural water and its surrounding area at the earth's surface is reviewed, and the formation mechanisms of arsenic polluted groundwater are explained. The primary arsenic is derived from deep volcanic fluids such as arsine in volcanic gases and arsenic and/or arsenite ions in hydrothermal fluids. The arsenic is moved into environmental water system by direct input from the hydrothermal fluid and by oxidation/decomposition of arsenite minerals and arsenic-bearing sulfides. The arsenic in the surface waters is deposited on the sediments after adsorbance into suspended matters and/or fixation into the microorganisms. Desorption and decomposition of arsenic-fixing materials play an important roles of desolved arsenic in the groundwater. Biological activities are also one of the roles to control the arsenic release into the groundwater.
The origins of arsenic polluted waters reported in the world are not the same, and usually two or more factors are combined in the each case. Highly arsenic containing waters appear in the naturally controlled system, however, anthropogenic factors contribute to the extention of arsenic pollution. Especially, drainage of arsenic polluted waters and highly arsenic containing materials causes to serious pollution of soils and groundwaters in the areas during long time.