including enantioselective gas chromatographic analyses of α-HCH (Bidleman et al.
2002; Bidleman and Leone 2004; Law et al. 2004; Shen et al. 2004; Kurt-Karakus
et al. 2005; Bidleman et al. 2007; Gouin et al. 2007; Kurt-Karakus et al. 2007;
Jantunen et al. 2008; Wong et al. 2011; Zhang et al. 2012a, b, c; Bidleman et al.
2013a, b; T, L et al. 2013; Sanchez-Osorio et al. 2017). For example, air–water
interaction studies in Lake Ontario water, rain and air samples supplied a comprehensive survey (Ridal et al. 1997; Bidleman et al. 1998a, b, c, d). The α-HCH rain
samples collected at Point Petre were racemic, the ER values ranged from 0.98 to
1.02 (n ¼ 7), while concentration data ranged from 870 to 3030 pg/L. Water samples
taken from Western, Central and Eastern Basins of Lake Ontario were similar and
did not differ between April and October 1993. An average ER of 0.86 Æ 0.02
(n ¼ 16) was obtained for surface samples. ERs of α-HCH in water taken from the
hypolimnion averaged 0.85 Æ 0.02 (n ¼ 29) and were not significantly different
from surface water ERs. Higher enantiomeric ratios were observed in water samples
from the Niagra River (0.91 Æ 0.02). The enantiomeric compositions of α-HCH in
air samples taken on shipboard during cruises across Lake Ontario at 10 m above the
lake vary seasonally with near racemic values in the spring and fall and values as low
as 0.91 in mid-summer. A simple air–water gas transfer model demonstrated that
enantiomeric ratios <1 in air were derived from equilibration of the air with the
water during transport of the air mass over the lake. Based on the experimental ERs,
Ridal et al. calculated that as much as 60% of the α-HCH in air above Lake Ontario
was derived from the lake itself. These results strongly support the need for overwater air measurements to provide better estimates of air–water gas transfer fluxes of
persistent organic pollutants, but they also suggest the application of
enantioselective gas chromatography as a valuable tool, if chiral pollutants are
being included in the course of air-water interaction studies.
As an extension of the Integrated Atmospheric Deposition Network (IADN)
project, which has been monitoring the deposition of organochlorine compounds
to the Great Lakes, Ulrich and Hites determined the spatial trends of chlordanerelated compounds in the air near the Great Lakes (Ulrich and Hites 1998). From
August 1994 through September 1995, 48 air samples were taken near Lake Erie,
five air samples were taken near Lake Michigan and six air samples were taken near
Lake Superior. While there were only slight differences in the enantiomeric ratios
between the various sites, there were considerable differences between the compounds (ER defined as the amount of the (+)-enantiomer divided by the amount of
the (À)-enantiomer). The overall ER for cis-chlordane was 1.05 Æ 0.02, which is
close to racemic. The overall ER for trans-chlordane was 0.88 Æ 0.02, which is
significantly different from racemic and from the respective cis-chlordane value.
This discrepancy suggests that trans- and cis-chlordane are metabolised differently
in the environment. The overall ER of heptachlor exoepoxide was 1.99 Æ 0.04; this
large deviation from racemic indicates that this compound largely is an enzymatic
transformation product of heptachlor. Wiberg et al. (1997a, b) found non-racemic
values for the same three compounds in Great Lake air and non-racemic values for
heptachlor exoepoxide in southern U.S. air, while Buser and Müller (1993) and
Wiberg et al. (Falconer et al. 1998) reported ER values near 1.0 for heptachlor, cisand trans-chlordane in Norwegian air and in southern U.S. air, respectively.
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8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants
2002; Bidleman and Leone 2004; Law et al. 2004; Shen et al. 2004; Kurt-Karakus
et al. 2005; Bidleman et al. 2007; Gouin et al. 2007; Kurt-Karakus et al. 2007;
Jantunen et al. 2008; Wong et al. 2011; Zhang et al. 2012a, b, c; Bidleman et al.
2013a, b; T, L et al. 2013; Sanchez-Osorio et al. 2017). For example, air–water
interaction studies in Lake Ontario water, rain and air samples supplied a comprehensive survey (Ridal et al. 1997; Bidleman et al. 1998a, b, c, d). The α-HCH rain
samples collected at Point Petre were racemic, the ER values ranged from 0.98 to
1.02 (n ¼ 7), while concentration data ranged from 870 to 3030 pg/L. Water samples
taken from Western, Central and Eastern Basins of Lake Ontario were similar and
did not differ between April and October 1993. An average ER of 0.86 Æ 0.02
(n ¼ 16) was obtained for surface samples. ERs of α-HCH in water taken from the
hypolimnion averaged 0.85 Æ 0.02 (n ¼ 29) and were not significantly different
from surface water ERs. Higher enantiomeric ratios were observed in water samples
from the Niagra River (0.91 Æ 0.02). The enantiomeric compositions of α-HCH in
air samples taken on shipboard during cruises across Lake Ontario at 10 m above the
lake vary seasonally with near racemic values in the spring and fall and values as low
as 0.91 in mid-summer. A simple air–water gas transfer model demonstrated that
enantiomeric ratios <1 in air were derived from equilibration of the air with the
water during transport of the air mass over the lake. Based on the experimental ERs,
Ridal et al. calculated that as much as 60% of the α-HCH in air above Lake Ontario
was derived from the lake itself. These results strongly support the need for overwater air measurements to provide better estimates of air–water gas transfer fluxes of
persistent organic pollutants, but they also suggest the application of
enantioselective gas chromatography as a valuable tool, if chiral pollutants are
being included in the course of air-water interaction studies.
As an extension of the Integrated Atmospheric Deposition Network (IADN)
project, which has been monitoring the deposition of organochlorine compounds
to the Great Lakes, Ulrich and Hites determined the spatial trends of chlordanerelated compounds in the air near the Great Lakes (Ulrich and Hites 1998). From
August 1994 through September 1995, 48 air samples were taken near Lake Erie,
five air samples were taken near Lake Michigan and six air samples were taken near
Lake Superior. While there were only slight differences in the enantiomeric ratios
between the various sites, there were considerable differences between the compounds (ER defined as the amount of the (+)-enantiomer divided by the amount of
the (À)-enantiomer). The overall ER for cis-chlordane was 1.05 Æ 0.02, which is
close to racemic. The overall ER for trans-chlordane was 0.88 Æ 0.02, which is
significantly different from racemic and from the respective cis-chlordane value.
This discrepancy suggests that trans- and cis-chlordane are metabolised differently
in the environment. The overall ER of heptachlor exoepoxide was 1.99 Æ 0.04; this
large deviation from racemic indicates that this compound largely is an enzymatic
transformation product of heptachlor. Wiberg et al. (1997a, b) found non-racemic
values for the same three compounds in Great Lake air and non-racemic values for
heptachlor exoepoxide in southern U.S. air, while Buser and Müller (1993) and
Wiberg et al. (Falconer et al. 1998) reported ER values near 1.0 for heptachlor, cisand trans-chlordane in Norwegian air and in southern U.S. air, respectively.
202
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants