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Temperature dependence of PCBs in the UK atmosphere.

Halsall, Crispin J. and Gevao, Bondi and Howsam, M. and Lee, R. G. M. and Ockenden, W. and Jones, Kevin C. (1999) Temperature dependence of PCBs in the UK atmosphere. Atmospheric Environment, 33 (4). pp. 541-552. ISSN 1352-2310

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Abstract

A thermodynamic approach was taken to assess the state of equilibrium between air and the Earth’s surface for PCBs at a variety of sites located in urban and rural areas. The Clausius–Clapeyron equation was applied to atmospheric PCB data, relating PCB partial vapour pressure (ln P) to inverse temperature (1/K); essentially representing the temperature controlled transition between condensed phases and the atmospheric gas phase. The slopes of the resulting plots ranged from −3100 to −8272 for a range of congeners at two city sites, significantly steeper than those generated at two rural locations, where there was little or no correlation between ln P and temperature. It was inferred that advection and variable meteorological conditions mask any localised, temperature dependent, air–surface exchange at these rural locations when weekly or two weekly integrated samples were taken. At a third rural site, close to Lancaster University, an intensive highly time-resolved sampling regime, carried out during very stable meteorological conditions resulted in highly correlated plots (r2>0.6), with slopes ranging from −7151 to −14 148 for different congeners. By reducing meteorological variables in this manner localised temperature controlled air–surface exchange became evident. Enthalpies of phase change generated from the temperature coefficients were similar to literature values for the enthalpy of vapourisation and the enthalpy of phase change from octanol to air. This suggests that, under these stable conditions, equilibrium was achieved as a function of either vapour pressure (P°L) or the octanol–air partition coefficient (KOA).

Item Type: Article
Journal or Publication Title: Atmospheric Environment
Uncontrolled Keywords: Semi-volatile organic compounds ; Partial pressure ; Phase equilibrium ; Clausius–Clapeyron equation
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Departments: Faculty of Science and Technology > Lancaster Environment Centre
Faculty of Arts & Social Sciences > Politics & International Relations (Merged into PPR 2010-08-01)
ID Code: 21710
Deposited By: ep_ss_importer
Deposited On: 04 Feb 2009 15:56
Refereed?: Yes
Published?: Published
Last Modified: 26 Jul 2012 15:50
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/21710

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