As mentioned above, chlorinated pesticides were identified and investigated
thoroughly as major contaminants in Alabama soils (Wiberg et al. 2001a, b). In
order to elucidate the microbial fate of these chiral organochlorine pesticides, the
authors conducted enantiomer-selective analysis. The enantiomeric signature for
selected organochlorine (OC) pesticide residues was investigated in 32 agricultural
and 3 cemetery soil samples. The enantiomeric profiles found were similar to those
from other soils in US and Canada previously discussed. The enantiomer fractions
(EFs) of o,p'-DDT showed great variability, ranging from 0.41 to 0.57 while the EFs
of chlordanes and chlordane metabolites were less variable and differed in general
significantly from racemic. Enantioselective depletion of (+)-trans-chlordane, (À)cis-chlordane, the first eluting enantiomer of MC5 and enrichment of (+)-heptachlorexo-epoxide and (+)-oxychlordane was found in a large majority of the samples. The
enantiomeric composition of α-HCH was racemic or close to racemic in most of the
soil samples.
Previously, elevated levels of organochlorine pesticides were found in urban soil.
The associated enantiomeric signature may help to understand and improve microbial transformation processes. Thus, a comprehensive study on distribution and
levels of chiral organochlorine pesticides was recently conducted in urban soil
(Wang et al. 2009). The here-reported investigations were performed in urban
soils of Yinchuan, RP China. The median levels of Σ-HCHs and Σ-DDTs were
0.852 and 2.24 ng/g, respectively, which suggested little risk for the ecological
environment and human health in the study area. The chiral α-HCH and o,p'-DDT
expressed non-racemic signatures in all samples. The isomer ratios of Σ-HCHs and
Σ-DDTs combined with enantiomer fractions (EFs) of α-HCH and o,p'-DDT indicated that a contamination source of HCHs derived from historical HCHs for DDTs,
the identified levels stem from an old source characterised by a mixture of technical
DDTs and dicofol.
The fate of chiral organochlorines in remote, high-altitude regions is only
sparsely investigated. Therefore, a Chinese research group further examined the
enantiomeric profile of organochlorine pesticides in soil samples from the Central
Tibetan plateau (Yuan et al. 2014). Enantiomer-selective analysis was conducted for
α-HCH and o,p'-DDT in paired soil and grass samples from the Central Tibetan
Plateau (CTP). For α-HCH, excess of (À)-α--HCH was predominant in 83.3% of all
soil samples, and 80% of the grass samples showed an excess of the (+)-enantiomer.
For o,p'-DDT, 90.9% of the grass samples showed an excess of (À)-o,p'-DDT while
50% of the soil samples showed an excess of the (À)-enantiomer. A correlation
between EFs of soil and grass was not observed. The EFs of both compounds were
correlated with soil concentration and with the change of sampling altitude, within
EFs being lower than racemic. However, these trends were not found for grass.
In order to understand the degradation pathways of organochlorine pesticides in
soil, a compound field and laboratory study was conducted in Canada using
enantiomer-selective analytical methods (Kurt-Karakus et al. 2007). In this investigation, the enantioselective degradation of chiral organochlorine pesticides (α-HCH,
cis- and trans-chlordane and o,p'-DDT) were examined. The authors assume that
background soils presumably receive the same EF signature of a compound via
atmospheric deposition. The substance is then subsequently transformed in a way
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8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants
thoroughly as major contaminants in Alabama soils (Wiberg et al. 2001a, b). In
order to elucidate the microbial fate of these chiral organochlorine pesticides, the
authors conducted enantiomer-selective analysis. The enantiomeric signature for
selected organochlorine (OC) pesticide residues was investigated in 32 agricultural
and 3 cemetery soil samples. The enantiomeric profiles found were similar to those
from other soils in US and Canada previously discussed. The enantiomer fractions
(EFs) of o,p'-DDT showed great variability, ranging from 0.41 to 0.57 while the EFs
of chlordanes and chlordane metabolites were less variable and differed in general
significantly from racemic. Enantioselective depletion of (+)-trans-chlordane, (À)cis-chlordane, the first eluting enantiomer of MC5 and enrichment of (+)-heptachlorexo-epoxide and (+)-oxychlordane was found in a large majority of the samples. The
enantiomeric composition of α-HCH was racemic or close to racemic in most of the
soil samples.
Previously, elevated levels of organochlorine pesticides were found in urban soil.
The associated enantiomeric signature may help to understand and improve microbial transformation processes. Thus, a comprehensive study on distribution and
levels of chiral organochlorine pesticides was recently conducted in urban soil
(Wang et al. 2009). The here-reported investigations were performed in urban
soils of Yinchuan, RP China. The median levels of Σ-HCHs and Σ-DDTs were
0.852 and 2.24 ng/g, respectively, which suggested little risk for the ecological
environment and human health in the study area. The chiral α-HCH and o,p'-DDT
expressed non-racemic signatures in all samples. The isomer ratios of Σ-HCHs and
Σ-DDTs combined with enantiomer fractions (EFs) of α-HCH and o,p'-DDT indicated that a contamination source of HCHs derived from historical HCHs for DDTs,
the identified levels stem from an old source characterised by a mixture of technical
DDTs and dicofol.
The fate of chiral organochlorines in remote, high-altitude regions is only
sparsely investigated. Therefore, a Chinese research group further examined the
enantiomeric profile of organochlorine pesticides in soil samples from the Central
Tibetan plateau (Yuan et al. 2014). Enantiomer-selective analysis was conducted for
α-HCH and o,p'-DDT in paired soil and grass samples from the Central Tibetan
Plateau (CTP). For α-HCH, excess of (À)-α--HCH was predominant in 83.3% of all
soil samples, and 80% of the grass samples showed an excess of the (+)-enantiomer.
For o,p'-DDT, 90.9% of the grass samples showed an excess of (À)-o,p'-DDT while
50% of the soil samples showed an excess of the (À)-enantiomer. A correlation
between EFs of soil and grass was not observed. The EFs of both compounds were
correlated with soil concentration and with the change of sampling altitude, within
EFs being lower than racemic. However, these trends were not found for grass.
In order to understand the degradation pathways of organochlorine pesticides in
soil, a compound field and laboratory study was conducted in Canada using
enantiomer-selective analytical methods (Kurt-Karakus et al. 2007). In this investigation, the enantioselective degradation of chiral organochlorine pesticides (α-HCH,
cis- and trans-chlordane and o,p'-DDT) were examined. The authors assume that
background soils presumably receive the same EF signature of a compound via
atmospheric deposition. The substance is then subsequently transformed in a way
196
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants