Sorption of volatile organic compounds to particles from a combustion source at different temperatures and relative humidities

Sorption of polar and non-polar volatile organic compounds to particles from a combustion source has been measured at different temperatures and relative humidities in laboratory experiments. The soot particles collected from oil furnaces contained 60% (w/w) iron sulfate and 9% (w/w) carbon comparable to the chemical composition of aerosol particles. Sorption experiments were conducted with the unmodified original soot as well as with a water-extracted subsample. A decrease in the sorption with increasing relative humidity was observed for all VOCs on both sorbents. Sorption enthalpies calculated from the measured temperature dependence of the sorption coefficients suggested stronger sorption for polar compared to non-polar compounds of comparable volatility. VOC sorption coefficients normalized to the surface area of the soot were greater than have been previously reported for mineral surfaces. A comparison of sorption coefficients with field data for gas-particle partitioning indicated good agreement on the basis of a log Kp,s vs log pL0 relationship.