Approaching gas-particle partitioning equilibrium of atmospheric PCDD/Fs with increasing distance from an incinerator: measurements and observations on modeling

A comprehensive sampling campaign was carried out around a municipal solid waste incinerator (MSWI) in central Taiwan in order to evaluate the impact of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) emissions on the ambient air and describe their spatial variation of gas-particle partitioning. Stack flue gas samples from the MSWI were also analyzed to investigate the relationship between the source and the impacted sites. Results showed that the PCDD/F emissions from the MSWI were a major source for PCDD/Fs in the ambient air. Moreover, PCDD/Fs in the ambient air tended to be distributed between the gaseous and particulate phases based on molecular weight; the higher chlorinated congener occupied a higher particulate fraction. There was an increase in the proportion of particle-bound PCDD/Fs with increasing distance from the MSWI. This observation supports the assumption that PCDD/Fs emitted were initially more associated with gaseous phase and the gaseous PCDD/Fs would gradually migrate to particles via either adsorption or absorption process. The results obtained were also applied and compared with the subcooled liquid vapor pressure (P-L(0))-based model and with the octanol-air partition coefficients (K-oa)-based model. These two models were found to be excellent descriptors for the gas-particle partitioning of PCDD/Fs. Regressions for log partition coefficient (K-p) versus log P-L(0) and log K-p versus log K-oa both demonstrated that PCDD/Fs were approaching equilibrium partitioning with increasing distance from the MSWI in the current study. (C) 2003 Elsevier Ltd. All rights reserved.