Arsenic Speciation in Natural Waters

Abstract

Speciation studies are necessary to understand the biogeochemical cycling of arsenic in aquatic systems. The species of arsenic present, their behaviour and toxicity will change depending on the biotic and abiotic conditions in the water. In groundwater, arsenic is predominantly present as arsenite (As III ) and arsenate (As V ). The major arsenic species in freshwater are As III and As V and minor amounts of MMA , DMA and methylated As III have also be detected. In seawater, the arsenic speciation differs in the surface and deep zone. In addition to the above species, uncharacterized arsenic species may constitute a significant portion of the total arsenic present in some water and the identification of these compounds is necessary to fully understand the arsenic biogeochemistry in water.A knowledge of the speciation of As in natural water is important because the bioavailability and the physiological and toxicologial effects of As depend on its chemical forms. Arsenic occurs in a variety of chemical forms in water, and this is a result of many chemical and biological transformations in the aquatic environment. The mechanism of transport and biological availability of arsenic depends on the chemical species present.The main arsenic compounds detected in natural waters are arsenite [As 111 ],

Reassessing the role of sulfur geochemistry on arsenic speciation in reducing environments

“…Both diagrams shown in Fig. 3 imply that the inclusion of (oxy)thioarsenic species reduces the stability fields of the orpiment (As 2 S 3 ) and realgar (AsS) mineral phases appreciably, which suggest that these minerals are less likely to form than expected from previously published E h -pH diagrams for the As-O-H-S system using similar S(−II) concentrations [20,21,36,47,48].…”

Arsenic Speciation Analysis in Human Saliva

“…Furthermore, correlation coefficients between arsenic species in saliva and total arsenic in drinking water were As III 0.470, As V 0.589, MMA V 0.663, and DMA V 0.485 (P Ͻ0.001 for all). Arsenic in drinking water is mostly in inorganic forms, As V and As III (31)(32)(33)(34)(35). Various organic arsenic species are present in food (34 -35 ).…”

Extraction of arsenate and arsenite species from soils and sediments

“…Arsenic is also a redox sensitive element which can exist in multiple oxidation states (5, 3, 0, and −3). Conversion between different oxidation states occurs readily in environmental and biological systems (Frankenberger Jr., 2002;Meng et al, 2003;Watt and Le, 2003). The environmental fate, bioavailability and toxicity of arsenic vary dramatically with its chemical forms.…”