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 fura ns (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 conce ntrations of PCDD/Fs ranged from 71 to 1161 fg I-TEQ/m(3) 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 c hlorinated dioxin/furans dominated the particle phase while low chlorinated dioxin/furans dominated the gas phase. The high correlation coefficient be tween log [(PCDD/Fs(vap))(TSP)/(PCDD/Fs(pat))] and 1/T was observed in lowe r chlorinated dioxin/furans unlike in OCDD/F. The slope of homolog ranged f rom - 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 (K-p) versus the log subcooled vapor pressure (P-L(o)). The octanol/air partition coefficient (K-oa)-based model of PCDD/Fs is more compatible with experimental data than those of the Junge-Pankow model tha t 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. (C) 2001 Elsevier Science Ltd. All rights reserved.