Theoretical predictions of arsenic and selenium species under atmospheric conditions

Thermochemical properties of arsenic and selenium species thought to be released into the atmosphere during the coal combustion were examined using ab initio methods. At various levels of theory, calculated geometries and vibrational frequencies of the species were compared with experimental data, where available. Through a comparison of equilibrium constants for a series of gaseous arsenic and selenium oxidation reactions involving OH and HO2, five thermodynamically favored reactions were found. In addition, it was determined that all favored reactions were more likely to go to completion under tropospheric, rather than stratospheric, conditions.