differences between these geographical regions. ARDRA patterns that indicated
taxonomic identity turned out to exhibit gene-sequence identity (except for two
isolates from Norway). A comprehensive interpretation of the results obtained
from enantioselective analysis and from the ARDRA patterns supplied the notable
result that isolates with identical ARDRA pattern exhibited the same
enantioselectivity phenotype regardless of their geographical origins, except for
the two isolates from Norway mentioned above. In conclusion, Lewis et al. suggest
that microbial enantioselectivity with environmental pollutants is controlled by the
activation of metabolically quiescent microbial populations or the induction of
enantiomer-specific enzymes, as was the case with amino acids, and that this
selectivity follows lines of genetic similarity where different groups of related
microbes are activated by different kinds of environmental changes.
Desborough and Harrad (2011) presented evidence that chiral PCB signatures
show volatilisation from soil, contributing to polychlorinated biphenyls in the grass.
Enantiomer fractions (EFs) of PCB 95 and concentrations of PCBs 28/31, 52, 101,
118, 138, 153 and 180 were determined in air. Samples were taken at $14 day
intervals on a vertical gradient at an urban background site in Birmingham U.K. in
summer 2009 (114 days) and spring 2010 (84 days). EFs in the air at 3 cm height
were non-racemic (average 0.453 (2009) and 0.468 (2010)) and differed significantly ( p < 0.05) from the racemic EFs in air at 10, 40, 90 and 130 cm. EFs in soil
(average 0.452 (2009) and 0.447 (2010)) closely matched those in the air at 3 cm,
while those in the grass (average 0.468 (2009) and 0.484 (2010)) were intermediate
between those in soil and the racemic EFs in air at !10 cm. The authors concluded
that this implies that at the study site, PCBs volatilise from soil to an extent
discernible only at the soil-air interface, and that PCBs in grass arise due to foliar
uptake of volatile emissions from soil. Atmospheric concentrations of ΣPCBs
increased significantly ( p < 0.05) with increasing height. Combined with the chiral
signature data, this suggests the influence of PCB emissions from soil on airborne
concentrations decreases with altitude, while that of emissions from the built environment increases.
As reported above enantiomeric profile determinations of chiral POPs like
chlorobornanes and other organochlorine pesticides have been utilised for source
elucidation and the investigation of inter-compartmental distribution processes
(Bidleman et al. 2002). Bidleman et al. continued their investigations on soil–air
exchange processes by enantiomer-selective gas chromatography aiming at fugacity
fraction determinations (Bidleman and Leone 2004). The research group collected
samples from 30 farms in Alabama, Louisiana and Texas from 1999 to 2000 for the
quantitative determination of major organochlorine pesticides (OCPs). In this study,
the fugacity fractions were determined for all target compounds. Mean fugacity
fractions indicated near-equilibrium for some OCPs (p,p'-DDE, chlordanes, transnonachlor and dieldrin) and net volatilisation for others (p,p'-DDT, o,p'-DDT,
toxaphene, γ-HCH). Enantiomer-selective analyses of all chiral pollutants showed
that enantioselective degradation of (+) or (À) o,p'-DDT in soil was accompanied by
enrichment or depletion of the corresponding enantiomers in the overlying air,
although there appeared to be some dilution by racemic o,p'-DDT from regional
air transport.
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
195
taxonomic identity turned out to exhibit gene-sequence identity (except for two
isolates from Norway). A comprehensive interpretation of the results obtained
from enantioselective analysis and from the ARDRA patterns supplied the notable
result that isolates with identical ARDRA pattern exhibited the same
enantioselectivity phenotype regardless of their geographical origins, except for
the two isolates from Norway mentioned above. In conclusion, Lewis et al. suggest
that microbial enantioselectivity with environmental pollutants is controlled by the
activation of metabolically quiescent microbial populations or the induction of
enantiomer-specific enzymes, as was the case with amino acids, and that this
selectivity follows lines of genetic similarity where different groups of related
microbes are activated by different kinds of environmental changes.
Desborough and Harrad (2011) presented evidence that chiral PCB signatures
show volatilisation from soil, contributing to polychlorinated biphenyls in the grass.
Enantiomer fractions (EFs) of PCB 95 and concentrations of PCBs 28/31, 52, 101,
118, 138, 153 and 180 were determined in air. Samples were taken at $14 day
intervals on a vertical gradient at an urban background site in Birmingham U.K. in
summer 2009 (114 days) and spring 2010 (84 days). EFs in the air at 3 cm height
were non-racemic (average 0.453 (2009) and 0.468 (2010)) and differed significantly ( p < 0.05) from the racemic EFs in air at 10, 40, 90 and 130 cm. EFs in soil
(average 0.452 (2009) and 0.447 (2010)) closely matched those in the air at 3 cm,
while those in the grass (average 0.468 (2009) and 0.484 (2010)) were intermediate
between those in soil and the racemic EFs in air at !10 cm. The authors concluded
that this implies that at the study site, PCBs volatilise from soil to an extent
discernible only at the soil-air interface, and that PCBs in grass arise due to foliar
uptake of volatile emissions from soil. Atmospheric concentrations of ΣPCBs
increased significantly ( p < 0.05) with increasing height. Combined with the chiral
signature data, this suggests the influence of PCB emissions from soil on airborne
concentrations decreases with altitude, while that of emissions from the built environment increases.
As reported above enantiomeric profile determinations of chiral POPs like
chlorobornanes and other organochlorine pesticides have been utilised for source
elucidation and the investigation of inter-compartmental distribution processes
(Bidleman et al. 2002). Bidleman et al. continued their investigations on soil–air
exchange processes by enantiomer-selective gas chromatography aiming at fugacity
fraction determinations (Bidleman and Leone 2004). The research group collected
samples from 30 farms in Alabama, Louisiana and Texas from 1999 to 2000 for the
quantitative determination of major organochlorine pesticides (OCPs). In this study,
the fugacity fractions were determined for all target compounds. Mean fugacity
fractions indicated near-equilibrium for some OCPs (p,p'-DDE, chlordanes, transnonachlor and dieldrin) and net volatilisation for others (p,p'-DDT, o,p'-DDT,
toxaphene, γ-HCH). Enantiomer-selective analyses of all chiral pollutants showed
that enantioselective degradation of (+) or (À) o,p'-DDT in soil was accompanied by
enrichment or depletion of the corresponding enantiomers in the overlying air,
although there appeared to be some dilution by racemic o,p'-DDT from regional
air transport.
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
195