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1K - Tropospheric Fate (MO13/9) Effects of coarse particles on gas-particle partitioning of PAHs. Shin, Yong Seung1, Park, Jin Su2, Lee, Dong Soo1, Kim, Jong Guk2, 1 GSES, Seoul National University, Seoul, Korea2 Dept. Environ. Eng., Chunbuk National University, Chonju, Korea ABSTRACT- As extent of partitioning to particulate matters (PM) impacts on the transport and fate of PAHs in air, precise estimation of gas-particle partition constant (Kp) in the field conditions is critical. Concentrations of PM, gas-phase and particle-phase PAHs were measured at urban and industrial sites. Size-segregated Kp and geometric mean diameter (GMD) of PAHs were calculated to address the the effect of coarse particles (Dp>2.5 Key words: particle size distribution, PAHs, gas-particle partition, non-equilibrium |
m) on Kp. GMDs of PAHs were positively correlated with the vapor pressure (PL0). Steeper slope (mg) and larger y-intercept (bg) of the logPL0-GMD plot were obtained with increasing coarse particle fraction, indicating more rapid redistribution of light PAHs (LPAHs) onto relatively clean coarse particles from soil origin. Throughout all particle sizes the slopes (mr) of the logPL0-logKp plots consistently deviated from equilibrium conditions (slope of -1). Distinctively smaller Kp for heavier PAHs (HPAHs) over the coarse particle ranges was a major cause of the shallower slopes of the plots. This condition suggests that the extent of deviation from the partitioning equilibrium increases with the molecular size of PAHs possibly due to sorption-desorption kinetics. The particle size dependence of Kp observed in the field conditions would significantly be affected not only by the sorbing properties of PM but by the prevailing non-equilibrium states occurred upon introduction of fresh coarse particles in contaminated air. The coarse particle effect will become more noticeable with HPAHs. The observed Kp values for some HPAHs showed a variation of greater than two orders of magnitude across the particle size in this study. Therefore, the validity of equilibrium assumption frequently used in various flux or fate models should be re-examined.