A comparison of high volume and diffusion denuder samplers for measuring semivolatile organic compounds in the atmosphere

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 degrees (L)) greater than ca. 0.2 Pa (log[p degrees (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 degreesC, max = 18 degreesC). 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 degrees (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<degrees>(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 he adsorbed on atmospheric particulate matter to a similar degree as PAHs.