An atmospheric selenium budget for the region 30° N to 90° N

Abstract

Using a mass balance approach, an atmospheric selenium budget for the region 30° N−90° N has been constructed. The atmosphere was assigned four different aerosol burdens corresponding to mean selenium aerosol concentrations in urban, intermediate (rural), remote/continental, and oceanic air. The budget calculations indicate that nearly all atmospheric selenium originates from anthropogenic emissions and biological activity in terrestrial and marine ecosystems. After comparing the sources of selenium to those of sulphur it is concluded that there are many similarities in their atmospheric cycling, but that there are also important differences.

Selenium

“…Additional less significant sources of atmospheric selenium may be of natural origin such as volcanic emissions and volatile releases from plants, soils, and animals. The total (volatile and particulate) anthropogenic emission of selenium, reported by Ross (1985) to be 6700 to 8300 tons per year, is in good agreement with the estimate of 3020 to 9625 tons per year made by Nriagu and Pacyna (1988), who estimated that volatile selenium accounts for about 40% of the selenium released. These figures were calculated from statistics on global production or consumption of industrial goods (including combustion) and from emission factors.…”

Selenium in Seleniferous Environments

“…That amount is equivalent to 1.5 g Se/ha annually, which is about one-tenth the amount of fertilizer Se that is applied annually in Se-deficient areas such as Finland and New Zealand. The wet depositional flux calculated by Cutter and Church (1986) falls between the values estimated by Ross (1985) for remote continental (75 pmol/cm 2 per year) and urban (840 pmol/cm 2 per year) wet deposition.…”

Terrestrial selenium distribution in China is potentially linked to monsoonal climate

“…However, this factor alone cannot explain the large-scale distribution of Se but rather explains localized areas with high soil-Se concentrations, for example, at Enshi, Hubei Province, China, where weathering of carbonaceous black shales has led to very high (up to 60 mg kg À 1 ) soil-Se concentrations 8,9 . Another source of Se in the terrestrial environment could be the atmosphere, which is an important reservoir in the Se cycle [10][11][12][13][14] . The marine environment has been identified as the largest natural source of Se to the atmosphere [12][13][14] .…”

“…Atmospheric Se mass-balance calculations indicate that wet deposition is the dominant mechanism of atmospheric Se deposition and selenite (Se(IV), SeO 2 À 3 ) and selenate (Se(VI), SeO 2 À 4 ) have been found as the dominant Se species [18][19][20] . Global Se deposition by precipitation has been estimated to be 35-100 Â 10 8 g Se per year compared with 17-24 Â 10 8 g Se per year via dry deposition 11 , although these processes are presumably highly dependent on local and regional conditions. Whereas Se has been shown to be enriched in sea spray and precipitation in coastal areas 18 , there has been little evidence indicating longrange transport of Se to inland terrestrial environments.…”