Gas/particle partitioning of polychlorinated dibenzo-p-dioxins and dibenzofurans in atmosphere; evaluation of predicting models

The gas/particle partitioning of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) was measured at three sites for a year in order to monitor the variation of PCDD/Fs levels and describe their partitioning. The air concentrations of PCDD/Fs ranged from 71 to 1161 fg I-TEQ/m3 and large changes in these levels did not correlate with seasonal changes during this study. Different homolog patterns were observed in the gas/particle phase. High chlorinated dioxin/furans dominated the particle phase while low chlorinated dioxin/furans dominated the gas phase. The high correlation coefficient between log [(PCDD/Fsvap)(TSP)/(PCDD/Fspat)] and 1/T was observed in lower chlorinated dioxin/furans unlike in OCDD/F. The slope of homolog ranged from −0.410 to −1.025 and that of 2,3,7,8-substituted isomers ranged from −0.379 to −0.772 in plots of the log partition coefficient (Kp) versus the log subcooled vapor pressure (PL°). The octanol/air partition coefficient (Koa)-based model of PCDD/Fs is more compatible with experimental data than those of the Junge–Pankow model that tends to overestimate results, even though both models include some level of uncertainty. However, both models can underestimate the particle phase of PCDD/Fs, especially when the ambient air temperature is extremely low in winter.