Natural Arsenic in Global Groundwaters: Distribution and Geochemical Triggers for Mobilization

Abstract

The elevated concentration of arsenic (As) in the groundwaters of many countries worldwide has received much attention during recent decades. This article presents an overview of the natural geochemical processes that mobilize As from aquifer sediments into groundwater and provides a concise description of the distribution of As in different global groundwater systems, with an emphasis on the highly vulnerable regions of Southeast Asia, the USA, Latin America, and Europe. Natural biogeochemical processes and anthropogenic activities may lead to the contamination of groundwaters by increased As concentrations. The primary source of As in groundwater is predominantly natural (geogenic) and mobilized through complex biogeochemical interactions within various aquifer solids and water. Sulfide minerals such as arsenopyrite and As-substituted pyrite, as well as other sulfide minerals, are susceptible to oxidation in the near-surface environment and quantitatively release significant quantities of As in the sediments. The geochemistry of As generally is a function of its multiple oxidation states, speciation, and redox transformation. The 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. The mobilization of As in groundwater is controlled by adsorption onto metal oxyhydroxides and clay minerals. According to recent estimates, more than 130 million people worldwide potentially are exposed to As in drinking water at levels above the World Health Organization's (WHO's) guideline value of 10 μg/L. Hence, community education to strengthen public awareness, the involvement and capacity building of local stakeholders in targeting As-safe aquifers, and direct action and implementation of best practices in identifying safe groundwater sources for the installation of safe drinking water wells through action and enforcement by local governments and international water sector professionals are urgent necessities for sustainable As mitigation on a global scale.

Estimating Soil Arsenic Content with Visible and Near-Infrared Hyperspectral Reflectance

“…Arsenic (AS) is a kind of metalloid that is widely found in nature [1]. Atmospheric deposition, industrial production, sewage irrigation, and soil arsenic -containing pesticides cause soil AS pollution [2,3].…”

Arsenic accumulation in rice (Oryza sativa L.) is influenced by environment and genetic factors

“…Natural processes such as rock weathering, alluvial deposits may contribute As release into the paddy environment (Bundschuh and Maity, 2015;Herath et al, 2016). Anthropogenic activities (i.e., mining and use of As-contaminated groundwater in the form of irrigation water) promote the accumulation of natural As in paddy ecosystems.…”

Elementary Iodine-Doped Activated Carbon as an Oxidizing Agent for the Treatment of Arsenic-Enriched Drinking Water

“…As an example, the data concerning the groundwater of central Italy shows a mean arsenic concentration of 23 µg/L [5]; therefore, assuming a hypothetical water with a similar arsenic concentration (20 µg/L) and a 100% presence of As(III), 1 cc of IodAC(30) could theoretically oxidize about 1250 liters of such water. According to the available world data [24], even in the countries most vulnerable to arsenic occurrence in groundwater, including the regions where the incidence of reducing conditions boost the portion of As(III), the concentration of the element is still much lower than the amount used in our experiments. No significant differences were observed when the experiment was repeated using the arsenite solution prepared with real groundwater, resulting in a very similar progress of the oxidation efficiency.…”