Arsenic atmospheric chemistry

Most particulate arsenic in the atmosphere is inorganic As(V) and As(III) rather than organoarsenicals (Mandal and Suzuki, 2002), 207. Any arsenic vapors would mostly consist of AS4O6 with trace amounts 

Both gaseous and particulate arsenic are potential inhalation hazards and may also contaminate surface soils, sediments, organisms, and waters near their points of origin ((Leoni and Sartori, 1997 Chein et al., 2006 Hedberg, Gidhagen and Johansson, 2005 Shih and Lin, 2003 Martley, Gulson and Pfeifer, 2004 Klumpp et al., 2003) Chapter 4). In particular, the upper 20 cm of soils within 15 km of a copper smelter and industrial complex at Port Kembla, New South Wales, Australia, contain up to 26 mg kg-1 of arsenic. The soils normally have maximum arsenic concentrations of 5.9 mg kg-1 (Martley, Gulson and Pfeifer, 2004). 

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Farinha, M.M., Slejkovec, Z., van Elteren, J.T. et al. (2004) Arsenic speciation in lichens and in coarse and fine airborne particulate matter by HPLC-UV-HG-AFS. Journal of Atmospheric Chemistry, 49(1-3), 343-53. 

Over the past several years, the area of gas-phase transition metal ion chemistry has been gaining increasing attention from the scientific community [1-16]. Its appeal is manifold first, it has broad implications to a spectrum of other areas such as atmospheric chemistry, corrosion chemistry, solution organometallic chemistry, and surface chemistry secondly, an arsenal of gas phase techniques are available to study the thermochemistry, kinetics, and mechanisms of these "unusual" species in the absence of such complications as solvent and ligand... 

Arsenic exists as grey, yellow and black forms of differing physical properties and susceptibilities towards atmospheric oxygen. The general chemistry is similar to that of phosphorus but whereas phosphorus is non-metallic, the common form of arsenic is metallic. Traces of arsenides may be present in metallic residues and drosses these may yield highly toxic arsine, ASH3, with water. 

All ars operons encode an ArsC arsenate reductase enzyme. However, as mentioned above, there are two sequence-unrelated families of arsenate reductases whose role is to reduce less toxic As(V) to more toxic As(lll) (21,34,36). It is only As(lll) and not As(V) that is pumped out from the cells by the ArsB transport protein. It seems counterintuitive from an environmental biology or metabolic chemistry point of view to convert a less toxic compound to a more toxic form. We have speculated that arsenite pumping activity evolved prior to the existence of oxygen in the atmosphere, and ArsC evolved only after an oxidizing atmosphere developed (8). At that point arsenite would spontaneously oxidize to arsenate, presenting a selective pressure for evolution of a reductase. The two types of arsC genes are positioned last in all ars operons shown in Fig. 2. The... 

Burrows continued research on coordination chemistry and between 1928 and 1938 published 15 papers, mostly on metal-arsine complexes(4). His Liversidge Lecture to the Royal Society of New South Wales, titled "Organic arsenicals in peace and war"(6), was an excellent review of arsines and metal-arsine complexes. Burrows was to have a marked effect on subsequent research on coordination chemistry in Australia. Mellor has stated(7) "Burrows lectured on coordination compounds to advanced classes, instituted laboratory courses on the subject, and before long began to attract staff and students to his chosen field. I think that it is fair to say that to Burrows, more than any other man, we owe the formation, at the University of Sydney, of the first school of coordination chemistry in this country [Australia]." It was in s atmosphere that Mellor, Dwyer, and Nyholm began their research careers and it was one of die points from which metal-arsine chemistry emanated. 

The importance of toxic elements in environmental chemistry is rarely questioned, but a relatively small number of elements (mercury, lead, and cadmium) have received a large share of researchers attention. The environmental chemistry of the transition metals, e.g., chromium, nickel, manganese, cobalt, copper, etc., has also been investigated principally because of their roles in metabolism, especially enzymatic processes. However, two non-metals, arsenic and selenium, and two metals, beryllium and vanadium, are elements which will become more significant in the future from environmental and toxicological points of view. Arsenic and selenium have been investigated, but much more work is needed because of the importance of these two elements in the environment. The author considers beryllium and vanadium to be problem metals of the future . The primary exposure route for both beryllium and vanadium is via the atmosphere and as lower environmental standards are imposed, more uses are found for each element, and more fossil fuels (source of V) are burned, the amounts added to the atmosphere will have more significance. 

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