Biogenic sources known

Volatile methanethiol from biogenic sources is released to the atmosphere in coastal and ocean upwelling areas.1 Methanethiol and volatile liquid ethanethiol (bp, 35°C) are intermediates in pesticide synthesis and odorants placed in lines and tanks containing natural gas, propane, and butane to warn of leaks. Information about their toxicities to humans is lacking, although these compounds and 1-propanethiol should be considered dangerously toxic, especially by inhalation. Also known as amyl mercaptan, 1-pentanethiol (bp, 124°C) is an allergen and weak sensitizer that causes contact dermatitis. 

There are many reasons why it is important to know the identities and the quantities of VOCs in the Earth s atmosphere. One of the major motivations is the desire to understand the impact of human activities on the natural atmosphere. Broadly speaking, the sources of VOCs in air can be divided into two groups natural sources, also known as biogenic emissions, and man-made sources, known as anthropogenic emissions [2-4]. 

Subsequent studies show that iodoalkanes of 1-4 carbons (2388) and chloroacetic acids form abiotically in soil (413), in addition to their well-known biogenic enzymatic formation. An abiotic source of CH3Br is suggested for the emission of this gas from ash (Fraxinus excelsior) and saltwort (Batis maritima), plants having known bromine content (2389). The emissions are a function of both temperature increase and bromine concentration. The natural formation of chloroethyne (58) in soil is also proposed to involve a Fenton reaction (382), as is the production of dichloroacetic and trichloroacetic acids from phenols and soil humic acid (413). 

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