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Abstract

Selenium (Se) is trace element of global importance with a substantial atmospheric compo- nent to its biogeochemical cycling. Marine and terrestrial biogenic systems contribute up to 59% of the total atmospheric cycling of Se by metabolizing oxidized Se species and sub- sequently forming the volatile organic Se species dimethyl selenide (CH₃SeCH₃), dimethyl selenyl sulfide (CH₃SeSCH₃) and dimethyl diselenide (CH₃SeSeCH₃). Upon emission to the atmosphere, those volatile organic Se species are subjected to oxidation which results in for- mation of lower volatility species and potentially aerosols. Ultimately, Se is removed from the atmosphere by wet deposition which has been identified as a key input mechanism of Se to soils. Identifying the atmospheric fate in respect to products and lifetimes can serve to better constrain and predict the global atmospheric Se flux. Moreover, real-time mea- surements of atmospheric CH₃SeCH₃, CH₃SeSCH₃ and CH₃SeSeCH₃ are needed but remain challenging due to their low mixing ratios (