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Environmental fate & pathways

Phototransformation in air

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Octane has the potential to volatilize to air, based on a relatively high vapor pressure, where it is subject to atmospheric oxidation. In air, octane can react with photosensitized oxygen in the form of hydroxyl radicals (OH-).

According to Atkinson (1985) the half-life of octane, normalized to a 12-hour day, is 3.7 days, based on 12-hour light / 12-hour dark periods and an OH- concentration of 5E5. The half-life is normalized to a 12-hour day because atmospheric oxidation reactions only take place in the presence of sunlight.

Estimation with the APOWIN model (HSPA Consortium 2009) resulted in a test substance half-life, as mediated by hydroxyl radical (OH-) attack, of 15.493 hours based on a 12-hour day (the 12-hour day half-life value normalizes degradation to a standard day light period during which hydroxyl radicals needed for degradation are generated). The half-life was calculated based on an OH- reaction rate constant of 8.2844 E-12 cm3/molecule-sec and an OH- concentration of 1.5E6 OH/cm3.

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