Evaluation of a Denuder-MOUDI-PUF Sampling System to Measure the Size Distribution of Semi-Volatile Polycyclic Aromatic Hydrocarbons in the Atmosphere

Abstract

We dedicate this paper to the late professor Glen Cass for his pioneering contributions to the field of air pollution science and engineering and his suggestions in the design of the field experiments reported in this paper. We all will sorely miss him. The authors thank William C. Hinds, Rong C. Yu, Douglas A. Lane, and Peter H. McMurry for helpful discussions; Bill Grant for the fieldwork; and the referees for their valuable recommendations for the final manuscript. This research was supported by the Southern California Particle Center and Supersite. Although the research described in this article has been funded wholly or in part by the United States Environmental Protection Agency through grants #R827352-01-0 and CR-82805901 to UCLA, it has not been subjected to the Agency's required peer and policy review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred.Address correspondence to Antonio H. Miguel, SCPCS, CHS 51.297, 650 Charles E. Young Dr. South, University of California, Los Angeles, CA 90095-1772. E-mail: ahmiguel@ucla.edu that for both sites, using either sampling system, the size distributions obtained are similar for the less volatile PAHs (log [p• L] ≤ −3.2), but different for the more volatile PAHs (log [p• L] ≥ −2.06). In the central Los Angeles site, the largest PAH fraction was found in the 0-0.18 µm (mode I) size range, typical of primary emissions. At the downwind location, the largest fraction was in the 0.18-2.5 µm (mode II) size range, consistent with an "aged" aerosol. At both sites, albeit not statistically significant, the mean regular to denuded MOUDI mass ratios were 33-36% and 11-19% higher, respectively, for the more volatile and the less volatile PAH groups. Sampling with the regular MOUDI configuration is simpler and thus recommended for measurement of the size distribution of PAHs in either group.

Measurements of semivolatile and particulate polycyclic aromatic hydrocarbons in a bus station and an urban tunnel in Salvador, Brazil

“…In addition, because the concentrations of FLT and PYR in the bus station correlated well (R 2~0 .996), the differences found in the measured FLT and PYR concentrations in the tunnel and the bus station samples do not necessarily indicate that sources other than heavy-duty diesel vehicles are responsible for the PAHs measured at the Lapa bus station. One possible explanation for the differences in the observed FLT and PYR profiles is that, in ambient air, PAHs with log p G L values in the range from 1.57 to 22.0 are found mostly in the vapor phase, 22 and may partition out of the particle phase after being emitted from diesel engines, while idling, at the bus station. Another possibility that may also account for the different emission profiles of these low MW PAHs would be differences in the composition of the diesel fuel used in Salvador.…”

Analysis of the Dynamic Interaction Between SVOCs and Airborne Particles

“…However, by design, the denuder removes gas-phase SVOCs from the airstream, and therefore perturbs the equilibrium between gas-and particle-phase SVOCs. Hence, there is the opportunity for particulate SVOC to desorb from particles while they are in the air upstream of the filter (Eiguren-Fernandez et al 2003;Subramanian et al 2004). The model presented in this article allows one to calculate, for a given SVOC and particle, whether there is sufficient time for such desorption to meaningfully affect diffusion-denuder measurements.…”

Positive sampling artifact of carbonaceous aerosols and its influence on the thermal-optical split of OC/EC

“…1, SVOC could account for a substantial fraction (10∼70%) of the organic particulate matter. For the determination of gas-particle partitioning of individual organics (such as PAHs), PUF Peters et al, 2000;Eiguren-Fernandez et al, 2004) and XAD resin (Gundel et al, 1995a, b;Temime-Roussel et al, 2004a, b;Goriaux et al, 2006) could also be used as backup adsorbent. A critical review of the organic denuder approach has been performed by Cheng et al (2009).…”