Natural arsenic in global groundwaters: distribution and geochemical triggers for mobilization

Natural arsenic in global groundwaters: distribution and geochemical triggers for mobilization

The occurrence of elevated concentrations of arsenic (As) in
groundwaters of many countries worldwide has received much
attention during the recent decades. T his review presents an overview of natural geochemical processes that mobilize As from aquifer sediments into groundwater and, subsequently, provides a concise description of the distribution of As over global groundwater
systems disseminated in highly vulnerable regions with an emphasis on Southeast Asia, the USA, Latin America, and Europe. Natural biogeochemical processes and anthropogenic activities may lead the contamination of groundwaters at increased As concentrations. The primary source of As is mainly natural which can be derived as of the interactions between groundwater and aquifer sediments of
minerals such as pyrite and arsenopyrite. The geochemistry of As is generally a function of its multiple oxidation states, speciation, and redox transformation. T he reductive dissolution of As-bearing Fe(III)oxides and sulfide oxidation are the most common and significant
geochemical triggers that release As from aquifer sediments into groundwaters. T he mobilization of As in groundwater is controlled by adsorption onto metal oxyhydroxides and clay minerals. With regard to the recent estimations, globally, over 130 million people are potentially exposed to As in drinking water at levels above the World Health Organization (WHO) guideline value of 10 μg/L. Hence, strengthening awareness via public education as well as
direct action and enforcement by local governments is an urgent necessity for a sustainable As mitigation whole over the world.

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