| Abstract
| - Recently, experimental data on the scavenging ofpolychlorinated biphenyls (PCBs) and polycyclic aromatichydrocarbons (PAHs) from the atmosphere by snowwere interpreted assuming that the distribution of chemicalbetween particles and dissolved phase measured in themeltwater reflects the state of the chemical duringthe scavenging process (Franz, T. P.; Eisenreich, S. J.Environ. Sci. Technol.1998, 32, 1771−1778). A consequenceof this assumption is that vapor scavenging is found tobe unimportant relative to particle scavenging. An alternativeinterpretation is presented that during melting repartitioningoccurs from the dissolved phase to the particle-sorbedphase. Further, it is argued that a constant particle scavengingratio may apply to all chemicals of the same class in thesame precipitation event, and its value can be estimatedfrom the scavenging characteristics of predominantlyparticle-sorbed, high molecular mass chemicals. Thisanalysis suggests that for more volatile PCBs and PAHsvapor scavenging is an important, if not the dominating, snowscavenging process. Gas scavenging ratios obtainedwith this method are, as expected, negatively correlatedwith the vapor pressure of a substance, indicating thatadsorption to the air-ice interface is the process responsiblefor vapor scavenging.
|
