Gas/particle partitioning of PCDD/Fs, PCBs, PCNs and PAHs

Abstract

In a study to establish the baseline contamination of the environment prior to the start-up of a new municipal incinerator, air samples were collected continuously over a period of one year at eight locations in southern Bavaria. The air samples were analysed in six week intervals for the particle bound and gaseous concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), biphenyls (PCBs) and naphthalenes (PCNs) as well as polycyclic aromatic hydrocarbons (PAHs). The logarithms of the particle/gas partition coefficients (K p) were closely correlated with the inverse mean ambient temperature (r 2 > 0.9 in most cases). When log K p at 25°C was plotted vs. the logarithm of the compounds' subcooled liquid vapour pressure (P L), the investigated compounds separated out into two groups. Within each of the two groups a linear correlation between K p and P L was observed, but for the PAHs and PCNs the particle bound fractions were always considerably higher than for the PCDD/Fs and PCBs with comparable P L. These differences indicate that P L is not a good parameter for describing the interchemical variability in gas/particle partitioning. Log K p was also plotted against the logarithm of the octanol/air partition coefficient (K OA), and in this case the different chemical groups did not separate out on the plot. This suggests that K OA may be a better descriptor of partitioning behaviour for these substances. However, the r 2 for the log K p vs. log K OA plot was identical to that for the log K p vs. log P L plot (0.77), and hence no conclusions could be drawn about the relative utility of the two properties. Future improvements in the K OA data base may help to resolve this issue.