HIGH-VOLUME AIR SAMPLER FOR PARTICLE AND GAS SAMPLING .2. USE OF BACKUP FILTERS TO CORRECT FOR THE ADSORPTION OF GAS-PHASE POLYCYCLIC AROMATIC-HYDROCARBONS TO THE FRONT FILTER

Atmospheric polycyclic aromatic hydrocarbon (PAH) levels were measured to determine the degree to which the-adsorption of gaseous PAHs to fi lters can cause artifacts in the differentiation of the gaseous and pa rticulate fractions. Two filter/sorbent samplers were used. In the fir st sampler, a quartz fiber filter (QFF) and a second backup QFF were u sed. In the second sampler, a Teflon membrane filter (TMF) and a backu p QFF were used. The amounts of material on the backup QFFs in the two samplers provided two estimates of the amounts of gasphase adsorption to-the front QFF in the first sampler and allowed corrections for gas adsorption to that QFF. The corrections indicated that gas adsorption to a front QFF in a conventional high-volume sampler would have cause d overestimation of the partitioning parameter (F/TSP)/A by a factor o f as much as 1.2-1.6, where F/A is the particle/gas ratio for a given compound and TSP is the total suspended particulate matter concentrati on (mu g/m(3)). The sampler with the TMF gave values for (F/TSP)/A tha t were similar to the corrected QFF values.