Biovolatilisation: a poorly studied pathway of the arsenic biogeochemical cycle

Abstract

It has been known for over a hundred years that microorganisms can produce volatile arsenic (As) species, termed "arsines". However, this topic has received relatively little attention compared to As behaviour in soils and biotransformation through the trophic level in the marine and terrestrial environment. We believe this is due to long-standing misconceptions regarding volatile As stability and transport as well as an absence, until recently, of appropriate sampling methods. First and foremost, an attempt is made to unify arsines' designations, notations and formulas, taking into account all the different terms used in the literature. Then, the stability of As volatile species is discussed and new analytical developments are explored. Further, the special cases of diffuse low-level emissions (e.g. soil and sediment biovolatilisation), and point sources with high-level emissions (geothermal environments, landfills, and natural gas) are comprehensively reviewed. In each case, future possible areas of research and unknown mechanisms are identified and their importance towards the global As biogeochemical cycle is explored. This review gathers new information regarding mechanisms, stability, transport and sampling of the very elusive arsines and shows that more research should be conducted on this important process.

A review on completing arsenic biogeochemical cycle: Microbial volatilization of arsines in environment

“…Biomethylation and bio-volatilization of metals and metalloids, As in particular, is very similar to methane biosynthesis and is possibly an inherent feature of methanoarchaea (McBride and Wolfe, 1971;Meyer et al, 2008;Mestrot et al, 2013). Almost all methanoarchaea studied were capable of volatilizing a broad spectrum of metal(loid)s (As, Se, Sb, Te, and Bi).…”

“…Yellowstone National Park hot spring outgassing (Planer-Friedrich et al, 2006). Based on these reports, TMAs can persist and be transported long distance from its emission source, which is important for understanding the As biogeochemical cycle (Mestrot et al, 2013).…”

“…In vivo, the toxicity of soluble inorganic and organic As species are dimethylarsenite (DMAs(III)), monomethylarsenite (MMAs(III)) > As(III) > As(V) > dimethylarsenate, (DMAs(V)), monomethylarsenate (MMAs(V)) > trimethylarsine (TMAs), trimethylarsine oxide (TMAsO) (Akter et al, 2005). Inorganic arsine and mono-, di-, and trimethylarsine, denoted as AsH 3 , MeAsH 2 ((CH 3 )AsH 2 ), Me 2 AsH ((CH 3 ) 2 AsH) and Me 3 As ((CH 3 ) 3 As), termed collectively arsines, are a volatile class of trivalent arsenic compounds and can partition into the atmosphere from aqueous solution due to their low boiling points (Mestrot et al, 2013), as illustrated in Fig. 1.…”

Identification and Characterization of Arsenite Methyltransferase from an Archaeon,Methanosarcina acetivoransC2A

“…Moreover, volatilized As as the final product of methylation has been suggested to contribute to global As cycling. 1,2 One methylcobalamin-dependent methylation of As, which does not require an enzyme, has been reported in methanoarchaea. 3,4 Whether there exists an enzymatic pathway for As methylation in archaea is still unclear.…”

“…16,17 Generally, arsenic methylation is preferred under anaerobic conditions. 1,18 For example, arsenic volatilization has been observed in many paddy soils or wetlands. 19−23 Methylation and volatilization of metal(loid)s have been regarded as an inherent feature of methanoarchaea, 24,25 though the enzymatic mechanism of As methylation by archaea remains unknown.…”