Arsenic — a Review. Part I: Occurrence, Toxicity, Speciation, Mobility

TLDR: In this paper, the authors measured arsenic concentrations up to a few milligrams per litre in natural waters and found that in aqueous environment the inorganic arsenic species arsenite (As) and arsenate (As(V)) are the most abundant species.

Abstract: In natural waters arsenic concentrations up to a few milligrams per litre were measured. The natural content of arsenic found in soils varies between 0.01 mg/kg and a few hundred milligrams per kilogram. Anthropogenic sources of arsenic in the environment are the smelting of ores, the burning of coal, and the use of arsenic compounds in many products and production processes in the past. A lot of arsenic compounds are toxic and cause acute and chronic poisoning. In aqueous environment the inorganic arsenic species arsenite (As(III)) and arsenate (As(V)) are the most abundant species. The mobility of these species is influenced by the pH value, the redox potential, and the presence of adsorbents such as oxides and hydroxides of Fe(III), Al(III), Mn(III/IV), humic substances, and clay minerals.