Gas-phase perfluoroalkyl carboxylic acids (PFCAs) sorb strongly on filter material (i.e., GFF, QFF) used in conventional high volume air samplers, which results in an overestimation of the particle-phase concentration. In this study, we investigated an improved technique for measuring the gas-particle partitioning of per- and polyfluoroalkyl substances (PFASs) using an annular diffusion denuder sampler. Samples were analyzed for 7 PFAS classes [i.e., PFCAs, perfluoroalkane sulfonic acids (PFSAs), fluorotelomer alcohols (FTOHs), fluorotelomer methacrylates (FTMACs), fluorotelomer acrylates (FTACs), perfluorooctane sulfonamides (FOSAs), and perfluorooctane sulfonamidoethanols (FOSEs)]. The measured particulate associated fraction (Φ') using the diffusion denuder sampler generally followed the trend FTACs (0%) < FTOHs (~8%) < FOSAs (~21%) < PFSAs (~29%) < FOSEs (~66%), whereas the Φ' of the C(8)-C(18) PFCAs increased with carbon chain length, and ranged from 6% to 100%. The ionizability of some PFASs, when associated with particles, is an important consideration when calculating the gas-particle partitioning coefficient as both ionic and neutral forms can be present in the particles. Here we differentiate between a gas-particle partitioning coefficient for neutral species, K(p), and one that accounts for both ionic and neutral species of a compound, K(p)'. The measured K(p)' for PFSAs and PFCAs was 4-5 log units higher compared to the interpolated K(p) for the neutral form only. The measured K(p)' can be corrected (to apply to the neutral form only) with knowledge of the pK(a) of the chemical and the pH of the condensed medium ("wet" particle or aqueous aerosol). The denuder-based sampling of PFASs has yielded a robust data set that demonstrates the importance of atmospheric pH and chemical pK(a) values in determining gas-particle partitioning of PFASs.

A passive air sampler comprising a polyurethane foam (PUF) disk impregnated with XAD-4 powder has been developed. This sorbent-impregnated PUF (SIP) disk builds on previous work using PUF disk passive air samplers that have been effective in spatial air mapping studies of nonpolar hydrophobic chemicals, without the need of electricity or expensive air sampling equipment. In this study, PUF disks and SIP disks are calibrated for sampling volatile polyfluorinated chemicals--specifically, the fluorotelomer alcohols (FTOHs) and perfluoroalkyl sulfonamides (PFASs). Results demonstrate the low sorptive capacity of the PUF disk samplers, particularly for the FTOHs, with PUF disks reaching equilibrium within 1 day, after collecting approximately 0.4 and 1.2 m3 of air for 8:2 FTOH and 10:2 FTOH, respectively. This limits their use for these target compounds when time-weighted, linear-phase sampling is desired. The presence of just 0.4 g of XAD powder in the SIP disks greatly increases the sorptive capacity (by approximately 2 orders of magnitude for the FTOHs) and provides linear-phase sampling for a period of several weeks. PUF-air partition coefficients, KPUF-A, calculated for the FTOHs and PFASs are considerably lower than values predicted using previously established correlations against the octanol-air partition coefficient, KOA, demonstrating the unique partitioning behavior of the polyfluorinated chemicals. Using results from these calibration tests, air concentrations of FTOHs were derived from PUF disk samples that were deployed in 52 homes in Ottawa, Canada, during 2002/2003. These represent the first comprehensive measurements of FTOHs in indoor air in North America. Range and (geometric mean) air concentrations (pg m-3) were 261-28 900 (2070) for 8:2 FTOH and 104-9210 (890) for 10:2 FTOH. These air concentrations are orders of magnitude higher than observed for outdoor air, establishing indoor environments as important for human exposure and also as potential sources to the larger environment.

Naphthalene is the most abundant polycyclic aromatic hydrocarbon (PAH) found in urban air. It is reactive in the atmosphere under ambient conditions, its chief reaction partner being the hydroxyl radical, OH • . In this work, the reactions of OH • with naphthalene, 1-and 2-naphthol, and 1-and 2-nitronaphthalene were studied in a 9.4 m 3 smog chamber. Relative rates of reaction accorded well with previous studies and allowed estimates to be made of the atmospheric lifetimes of these compounds. Numerous oxidation products were identified, and mechanisms proposed for their formation were based on the further transformation of benzocyclohexadienyl radicals formed by addition of OH • to naphthalene. The naphthols and nitronaphthalenes were deduced not to be on the major reaction pathway to the more oxidized products. Because of the high reactivity of PAH in air, we suggest that priority be given to identifying and quantitating their reaction products, some of which may be relatively persistent air toxics.

A detailed comparison of two inherently different ambient air samplers has been conducted to fully characterize and compare their performance in sampling and measuring the partitioning of a suite of 29 semivolatile organic compounds (SVOCs). A high volume air sampler (hi-vol) utilizing polyurethane foam (PUF) adsorbent for vapor-phase trapping and an annular diffusion denuder sampler were operated concurrently. Sampling artifacts were observed and can be related to the physicochemical properties of the analytes and the designs of the samplers. The results suggest that high volume air samplers equipped with PUF are unsuitable for measuring those organochlorine compounds and 2-and 3-ring PAHs which have subcooled liquid vapor pressures (p°L) greater than ca. 0.2 Pa (log-[p°L] ) -0.7), owing to their breakthrough on PUF sampling media at relatively low sample volumes (170 m 3 ) and ambient temperatures typical of temperate regions (mean ) 11 °C, max ) 18 °C). Theoretical calculations of breakthrough volumes for SVOCs on PUF are presented and in most cases these successfully predict observed behavior. The denuder sampler is more efficient at measuring the relatively volatile SVOCs. For total SVOC measurements the hi-vol and denuder were in good agreement for those compounds which were efficiently sampled, and the denuder yielded total SVOC concentrations which differed by a mean factor of 1.2 relative to those obtained with the hi-vol sampler. The hi-vol sampler provides good agreement with the Junge-Pankow model for partitioning of the relatively less volatile PAHs (log[p°L] < -3), though the fraction of the PCBs in the particle-phase is underestimated. The results from the diffusion denuder indicate that for the more volatile SVOCs (log[p°L] > -3), particulate loadings are overestimated with respect to the Junge-Pankow model, and for less volatile SVOCs, particulate loadings tend to be underestimated. An important observation is that the results from the denuder indicate that PCBs may be adsorbed on atmospheric particulate matter to a similar degree as PAHs.