PH07 Environmental Chemistry and Toxicology of Chiral Pollutants
Exhibit Hall
8:00 AM - Thursday
(PH066) Spatial and Seasonal Variation in Chiral Signatures of PCBs in Matched Air and Topsoil Samples on an Urban-Rural Transect: Implications for Atmospheric Source Apportionment.
Harrad, S1, Jamshidi, A2, Robson, M3, 1 University of Birmingham, Birmingham, UK2 University of Birmingham, Birmingham, UK3 University of Birmingham, Birmingham, UK
ABSTRACT- This study evaluates spatial variation of enantiomeric fractions (EFs) of PCBs 95, 136, and 149 in air and soil from 11 locations at approximately 3-15 km intervals across a rural:urban:rural transect in the West Midlands conurbation of the U.K. In addition, samples are taken monthly between October 2003 and October 2004 to assess seasonal variation. The first 3 months' data reveals racemic EFs for each target PCB in all air samples, supporting our previous findings that volatilisation from soil appears to make a minimal contribution to atmospheric PCB concentrations at each location; and non-racemic EFs for PCBs 95 and 136 (currently interference is preventing EF determination for PCB 149) in topsoil samples. EFs of PCBs 95 and 136 are essentially racemic in all three soil samples taken at the most urban location, while the greatest enantioselective degradation is observed in soils from the most rural locations. This is not inconsistent with previous observations for soils from the Greater Toronto Area that the extent of enantioselective degradation was inversely related to the concentration of both PAH and PCBs (and by inference the degree of urbanisation), which we tentatively hypothesised impaired microbial activity. Furthermore, although one should not infer too much at this early stage of the study, there are appreciable variations in EF values in soil for a given PCB from month-to-month that far exceed the measured variability of our sampling and analytical methodology, and that we cannot currently explain.
Key words: PCB, chiral, urban-rural, air