Photolysis Kinetics of Toluene, Ethylbenzene and Xylenes at Ice Surfaces

Benzene, toluene, ethylbenzene, and xylenes (BTEX) are important organic pollutants. Due to increasing anthropogenic activity in the artic, understanding the fate of these compounds in snow covered regions is essential. BTEX do not undergo direct photolysis in natural waters because their absorbance spectra do not overlap with solar radiation at the Earth's surface. Recent research has suggested that benzene is able to undergo direct photolysis when present at ice surfaces. However, the photolysis of toluene, ethylbenzene, and xylenes (TEX) at ice surfaces has not been reported. We have investigated the photolysis kinetics of TEX in water, ice cubes, and in ice granules which reflect reactivity at ice surfaces. Rates measured in ice granules ranged from 3.8-5.4 ×10-4 s-1 which was greater than those measured in water and ice cubes for all compounds studied. Our results suggest that TEX is able to undergo direct photolysis on ice surfaces. Photolysis of TEX molecules appears to be enabled by a red shift in the absorbance spectra at ice surfaces, although photosensitization may also occur. Therefore, photolysis could be an important removal pathway for TEX in snow covered environments.