Gas/particle distributions of coplanar PCBs in urban air
- Youngstown State Univ., OH (United States)
- Atmospheric Environment Service, Downsview, Ontario (Canada)
This investigation tested the hypothesis that the distribution of PCBs between the particle and gas phases is influenced by the number of ortho-chlorines on the biphenyl molecule. The extent of association with particulate matter is dependent on the compound`s vapor pressure. Because mono- and non-ortho PCBs have lower vapor pressures than other congeners of the same homolog, they may preferentially absorb to atmospheric particles. Liquid-phase vapor pressure data used to predict the adsorption of PCBs to aerosols using the Junge-Pankow equation. Particulate percentages increased with homolog number and within a homolog, PCBs having fewer ortho-chlorines were associated to A greater extent with particles. Air samples taken in Chicago in February 1988 and June 1989 were fractionated into ortho-chlorine groups using ``mini`` activated carbon columns. Partitioning of coplanar congeners to filter-retained particles was enhanced when compared to multi-ortho congeners in the same homolog. Particulate percentages for the mono-orthos were 2-3 times higher than for the multi-orthos. A laboratory system was designed to equilibrate particle-loaded glass fiber filters at a constant PCB vapor concentration and temperature. Using filters coated with Chicago aerosols, the system was used to gauge relative strengths of adsorption for several PCBs with differing ortho-chlorine numbers. Results showed the same trend of increased particulate percentages for PCBs with fewer ortho-chlorines. The combination of theoretical calculations, field results and laboratory investigations indicates that the ``ortho-effect`` significantly influences the atmospheric behavior of PCBs.
- OSTI ID:
- 33551
- Report Number(s):
- CONF-9410273--
- Country of Publication:
- United States
- Language:
- English
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