A global atmospheric selenium budget

Abstract

An examination of the major anthropogenic and natural sources of atmospheric selenium indicates that approximately 13-19 x 109 g Se are cycled through the troposphere annually. Perhaps 60% of this flux is natural in origin, and both man-made and biological emissions appear to be predominantly gaseous in nature. Emissions from the marine biosphere and the combustion of coal account for 50 -65% of the total atmospheric selenium emissions, and the natural marine flux appears to be roughly twice as large as that due to coal combustion.Research Council (NRC), 1976]. A realistic assessment of the actual and potential impact of human activity on the biogeochemical cycling of selenium requires that both natural and anthropogenic source functions be quantified. The atmosphere plays and important role in the transformation and transport of both natural and anthropogenically derived selenium, but, as is the case with many substances, anthropogenic fluxes generally are much more thoroughly studied and thus easier to quantify than natural sources and sinks. This is in part because it has only recently become evident that selenium is present in the atmosphere as a gas as well as in the aerosol phase [Mosher and Duce, 1983]. The very few vapor phase measurements available have made it necessary to use indirect methods to estimate important natural fluxes such as volatile terrestrial and marine

Comparison of Selenium and Sulfur at Remote Sites

“…Continental biological activity contributes more selenium than soil does. 2 However, since the selenium is primarily emitted as vapor, it is not clear how it effects the particulate concentration.…”

“…[2][3][4] However, because the selenium vapor condenses to a particle more rapidly than the SO 2 is converted to sulfate, the S/Se ratio for particles should increase as the plume ages. 5 Tuncel et al measured ratios of 1000 ± 500 at urban sites with high coal combustion, 1700 ± 1200 at three remote sites in the Ohio Valley, and 3400 ± 1400 in the Shenandoah Valley.…”

“…Mosher and Duce estimate that 50% of the worldwide anthropogenic selenium emissions come from coal combustion, 20% from copper production, and 9% from oil combustion. 2 Other sources include biomass combustion, such as field and slash burning (5%), incinerators (4%), zinc and lead production (4%), selenium production (4%), and glass and ceramic manufacturing (3%). Natural sources include soil, sea salt, volcanoes, and biogenically emitted selenium vapors.…”

Natural wetland emissions of methylated trace elements

“…However, previous studies suggested that DMDSe in terrestrial environments is strongly retained on soil particles and thus not efficiently volatilized 28 . It is currently believed that DMSe and DMS volatilization is more significant than DMDSe and DMDS volatilization 8,11,29 . In addition to trapping products of DMDSe and DMDS, the dominating presence of MSeA and MSA in the trapping liquids could also be explained by other processes, such as atmospheric oxidation of DMSe inside the flow-through box before trapping in the acid traps (which potentially leads to the formation of MSeA in analogy to atmospheric gas-phase reactions of S 30 ) or the trapping of other species that are naturally produced (for example, dimethyl selenenyl sulphide (CH 3 -Se-S-CH 3, DMSeS) 31 , methane selenol (CH 3 -Se-H) 24 and methane thiol (CH 3 -S-H) 27,32 .…”

“…Our field experiments provide the first quantification of fluxes of volatilized Se, As and S measured in a pristine terrestrial 29 . We found that Se and S volatilization are positively correlated ( Supplementary Fig.…”