Gas/solid partitioning of semivolatile organic compounds (SOCs) to air filters. 2. Partitioning of polychlorinated dibenzodioxins, polychlorinated dibenzofurans, and polycyclic aromatic hydrocarbons to quartz fiber filters

Gas/particle distributions of atmospheric semi-volatile organic compounds ( SOCs) are often measured using filter/sorbent samplers. Unfortunately, the adsorption of gaseous SOCs onto a filter can cause positive biases in the m easured particle-phase concentrations, and negative biases in the measured gas-phase concentrations. When quartz fiber filters (QFFs) are used, surfac e-area-normalized gas/quartz partition coefficient (K-p,K-s, m(3) m(-2)) va lues will be useful when estimating the magnitudes of these errors. Gas/QFF K-p,K-s values have been reported in the literature only for polycyclic ar omatic hydrocarbons (PAHs) and n-alkanes. Gas/QFF K-p,K-s values were measu red here for a series of polychlorinated dibenzodioxins (PCDDs) and polychl orinated dibenzofurans (PCDFs), and also for a range of PAKs. Within each o f the three individual compound classes, plots of log K-p,K-s vs. log P-L(o ) (sub-cooled liquid vapor pressure) were found to be linear with slopes of approximately - 1. At relative humidity (RH) = 25%, the pooled log K-p,K-s data at 25 degreesC for the three compound classes were correlated with lo g p(L)(o) nearly as well (r(2) = 0.95) as were the data for the individual compound classes (r(2) approximate to 0.97). In general, the K-p,K-s values for the PAHs and PCDD/PCDFs studied were found to be about a factor of 2 l arger for partitioning to clean QFFs at RH = 25% than for TMFs at RH = 21-5 2%. Backup QFFs used in filter/sorbent sampling in a suburban area yielded K-p,K-s values for PAHs at RH = 37% that were significantly lower than for clean QFFs at the same RH. (This may have been the result of the adsorption of ambient organic compounds that at least partially blocked the direct ad sorption of the SOCs to the QFF surface). Therefore, when QFFs are used to separate atmospheric gas- and particle-phase SOCs, corrections for compound -dependent gas adsorption artifacts for QFFs may need to be carried out usi ng K-p,K-s values that were obtained with ambient backup QFFs. (C) 2001 Els evier Science Ltd. All rights reserved.