Central Valley. Enantiomeric composition of chiral OCPs in air and soil was close to
racemic, with slight depletion of (À)-α-HCH, (À)-cis-chlordane and (+)-transchlordane. A follow-up study on residential and agricultural soil from Mexico was
conducted in 2008–2009 for the level determination and enantiomeric distribution of
o,p
0 -DDT, DDE, DDD and other organochlorine pesticides (Sanchez-Osorio et al.
2017). The agricultural Mexicali and Yaqui valleys (MV, YV) in northwest Mexico
were chosen as sample locations. The o,p'- and p,p'- isomers of DDE, DDD and
DDT, hexachlorocyclohexanes (α-, β-, γ- and δ-HCH) and chlordanes (trans-chlordane, cis-chlordane, heptachlor and heptachlor exoepoxide). Geometric means
(GMs) (ng/g dry weight) were determined as MV soils (n ¼ 27) Σ-DDT
22, Σ-HCH 0.80, Σ-CHL 0.88; YV soils (n ¼ 25) Σ-DDT 5.0, Σ-HCH 0.23,
Σ-CHL 0.67; MV sediments (n ¼ 3) Σ-DDT 5.0, Σ-HCH 0.23, Σ-CHL 0.53; YV
sediments (n ¼ 8) Σ-DDT 2.6, Σ-HCH 0.12, Σ-CHL 0.090. GMs were significantly
higher ( p < 0.05) in MV than YV soils for Σ-DDT and Σ-HCH, but not for Σ-CHL.
Comparison with worldwide regulatory guideline values (RGVs) for residential soils
showed all compounds below mean or GM RGVs, but above the lowest RGV in
some cases. Low p,p'-DDT/(p,p'-DDT + p,p'-DDE) in most soils indicated aged
residues. The enantiomer distribution was found non-racemic in soils and sediments
and indicated enantioselective microbial degradation of (+)-α-HCH, (À)-transchlordane, (À)-cis-chlordane and (+)-o,p'-DDT.
The chiral signature of chiral organochlorines (mainly pesticides) has also been
successfully applied to source elucidation of atmospheric long-range transport over
North America (Shen et al. 2005). Annually averaged concentrations and enantiomeric compositions of organochlorine pesticides (OCPs) in the air were determined
in a measurement campaign in 2000/2001 at 40 stations across North America using
XAD2-based passive samplers. The enantiomer signatures were applied to identifying regional sources of OCP to the atmosphere. Specifically, air samples collected in
the south-eastern United States had elevated concentrations of chlordane-related
compounds (as above mentioned), high ratios of trans- to cis-chlordane and heptachlor to heptachlor epoxide, as well as higher enantiomeric fractions of transchlordane compared to other regions. Similarly, greatly elevated concentrations of
p,p'-DDT, low relative abundance of the metabolite p,p
0 -DDE and a racemic composition of o,p'-DDT in samples from southern Mexico and Belize indicate recent
use of DDT in these regions.
Along this line, a US research group elucidated the atmospheric transport from
pacific source regions for the presence of chiral organic pollutants (Genualdi et al.
2009). Genualdi et al. measured the enantiomeric signatures of organochlorine
pesticides in atmospheric samples from Okinawa, Japan and three remote locations
in the Pacific Northwestern United States: Cheeka Peak Observatory (CPO), Mary’s
Peak Observatory (MPO) and Mt. Bachelor Observatory (MBO). The enantiomeric
signatures of composite soil samples, collected from China, South Korea and the
western U.S. were also measured for comparison. EFs ((+) enantiomer/(sum of the
(+) and (À) enantiomers), for α-HCH was measured in Asian air masses at Okinawa
and in Chinese and South Korean soils. Non-racemic α-HCH (EF ¼ 0.528 Æ 0.0048)
was measured in regional air masses at CPO and may reflect volatilisation from the
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8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants
racemic, with slight depletion of (À)-α-HCH, (À)-cis-chlordane and (+)-transchlordane. A follow-up study on residential and agricultural soil from Mexico was
conducted in 2008–2009 for the level determination and enantiomeric distribution of
o,p
0 -DDT, DDE, DDD and other organochlorine pesticides (Sanchez-Osorio et al.
2017). The agricultural Mexicali and Yaqui valleys (MV, YV) in northwest Mexico
were chosen as sample locations. The o,p'- and p,p'- isomers of DDE, DDD and
DDT, hexachlorocyclohexanes (α-, β-, γ- and δ-HCH) and chlordanes (trans-chlordane, cis-chlordane, heptachlor and heptachlor exoepoxide). Geometric means
(GMs) (ng/g dry weight) were determined as MV soils (n ¼ 27) Σ-DDT
22, Σ-HCH 0.80, Σ-CHL 0.88; YV soils (n ¼ 25) Σ-DDT 5.0, Σ-HCH 0.23,
Σ-CHL 0.67; MV sediments (n ¼ 3) Σ-DDT 5.0, Σ-HCH 0.23, Σ-CHL 0.53; YV
sediments (n ¼ 8) Σ-DDT 2.6, Σ-HCH 0.12, Σ-CHL 0.090. GMs were significantly
higher ( p < 0.05) in MV than YV soils for Σ-DDT and Σ-HCH, but not for Σ-CHL.
Comparison with worldwide regulatory guideline values (RGVs) for residential soils
showed all compounds below mean or GM RGVs, but above the lowest RGV in
some cases. Low p,p'-DDT/(p,p'-DDT + p,p'-DDE) in most soils indicated aged
residues. The enantiomer distribution was found non-racemic in soils and sediments
and indicated enantioselective microbial degradation of (+)-α-HCH, (À)-transchlordane, (À)-cis-chlordane and (+)-o,p'-DDT.
The chiral signature of chiral organochlorines (mainly pesticides) has also been
successfully applied to source elucidation of atmospheric long-range transport over
North America (Shen et al. 2005). Annually averaged concentrations and enantiomeric compositions of organochlorine pesticides (OCPs) in the air were determined
in a measurement campaign in 2000/2001 at 40 stations across North America using
XAD2-based passive samplers. The enantiomer signatures were applied to identifying regional sources of OCP to the atmosphere. Specifically, air samples collected in
the south-eastern United States had elevated concentrations of chlordane-related
compounds (as above mentioned), high ratios of trans- to cis-chlordane and heptachlor to heptachlor epoxide, as well as higher enantiomeric fractions of transchlordane compared to other regions. Similarly, greatly elevated concentrations of
p,p'-DDT, low relative abundance of the metabolite p,p
0 -DDE and a racemic composition of o,p'-DDT in samples from southern Mexico and Belize indicate recent
use of DDT in these regions.
Along this line, a US research group elucidated the atmospheric transport from
pacific source regions for the presence of chiral organic pollutants (Genualdi et al.
2009). Genualdi et al. measured the enantiomeric signatures of organochlorine
pesticides in atmospheric samples from Okinawa, Japan and three remote locations
in the Pacific Northwestern United States: Cheeka Peak Observatory (CPO), Mary’s
Peak Observatory (MPO) and Mt. Bachelor Observatory (MBO). The enantiomeric
signatures of composite soil samples, collected from China, South Korea and the
western U.S. were also measured for comparison. EFs ((+) enantiomer/(sum of the
(+) and (À) enantiomers), for α-HCH was measured in Asian air masses at Okinawa
and in Chinese and South Korean soils. Non-racemic α-HCH (EF ¼ 0.528 Æ 0.0048)
was measured in regional air masses at CPO and may reflect volatilisation from the
198
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants