• Jones, Kevin Christopher
• Thomas, Gareth O.
• Harner, Tom
• Lohmann, Rainer

Abstract

Air samples were taken concurrently for four sampling events in the winter of 1998 at three contrasting sites: an urban center and two rural sites. The rural sites were characterized by the extensive usage of coal and wood for space heating. Samples were analyzed for PCDD/Fs, PCBs, and PAHs. Recently measured octanol−air partition coefficients (Koa) for PCDD/Fs enabled a comparison of the Koa-based versus the subcooled liquid vapor pressure (pL)-based partition model for all three compound classes. Both Koa and pL were found to be excellent descriptors of the gas-particle partitioning of PCDD/Fs, PCBs, and PAHs. However, regressions for log Kp-log pL gave higher regression coefficients than for log Kp-log Koa. Both models showed roughly similar relative states of equilibrium for PCDD/Fs, PCBs, and PAHs. PCBs were closest to equilibrium at the urban site. It is argued that newly released particles at the rural sites caused nonequilibrium partitioning at those sites for PCBs. PAHs were released at all sites and were, in line with expectations, approaching equilibrium. The Koa-based and the pL-based model gave contradictory results for PCDD/Fs: according to the pL-model, PCDD/Fs were in equilibrium for event I but not for the other events, whereas the Koa-model showed the PCDD/Fs not being in equilibrium for event I. A simple Koa-model, combining advective transport and locally released PCDD/Fs and PAHs, can explain the observed nonequilibrium partitioning for the first sampling event.

Topics

• impedance spectroscopy
• compound
• wood