or filtration in an in vitro test. In this experiment, a procedure using multiple fluid-tosolid ratios was developed to characterise the sorption. It was found that 8–38% of
the mobilised OCPs were sorbed on the residue and remained in the solid phase after
the separation. Taking into consideration the sorbed fraction, the measured
bioaccessibilities of the OCPs varied from 4 to 97% depending on the properties
of the soils and the compounds. The enantiomeric ratios of chiral compounds studied
were also determined to distinguish biotic (enzymatic) and abiotic (chemical extraction) processes in the in vitro digestion model. It was found that although α-HCH in
the raw soils was racemic, (+)-α-HCH was enriched in the gastric digestive fluid but
finally depleted in the intestinal digestive fluid.
The enantioselective distribution and enantiomer profiling has been recently
proposed as a suitable scientific tool for the assessment of climate change influence
on fate and distribution of anthropogenic pollutants (Bidleman et al. 2012). The
authors acknowledge that elimination of persistent organic pollutants (POPs) under
national and international controls reduces effectively “primary” emissions, but
“secondary” emissions continue from residues deposited in soil, water, ice and
vegetation during former years of high usage. Secondary sources are expected to
dominate in the future, when POPs transport and accumulation will be controlled by
air-surface exchange and the biogeochemical cycle of organic carbon. Climate
change is likely to affect the mobilisation of POPs through, for example, increased
temperature, loss of ice cover in polar regions, melting glaciers and changes in soil
and water microbiology, which affect degradation and transformation. Chiral compounds offer advantages for following transport and fate pathways because of their
ability to distinguish racemic (newly released or protected from microbial attack)
and non-racemic (microbially altered) sources. Here, we explain the rationale for this
approach and suggest applications where chiral POPs could aid the investigation on
climate-mediated exchange and transformation processes. Examples include
distinguishing agricultural vs. non-agricultural and recently used vs. residual pesticides, transformation and sequestration processes in soil, historical vs. recent atmospheric deposition, sources in Arctic air and influence of ice cover on volatilisation.
Recently, the occurrence of new brominated flame retardants and organochlorine
pesticides were examined in urban soil. Many of these contaminants of emerging
concern (CEC) are chiral compounds. In this context, Wong et al. developed a new
enantiomer-selective method for the determination of enantiomer profiles (Wong
et al. 2012). New generations of flame retardants are entering the global market as
the use of polybrominated diphenyl ethers (BDEs) are being phased out in many
countries. Therefore, it is expected that soils could become a secondary emission
source to the atmosphere for brominated flame retardants (BFRs). So far little is
known about the environmental fate of novel BFRs in soils. In this study, the
volatility and transformation of BFRs and organochlorine pesticides (OCPs) in soil
were reported. A low organic carbon (5.6%) urban soil was spiked with a suite of
BFRs and OCPs, followed by incubation under laboratory conditions for 360 days.
These included BDE-17, -28, -47, -99; α- and β-1,2-dibromo-4-(1,2-dibromoethyl)
cyclohexane
(TBECH),
β-1,2,5,6-tetrabromocyclooctane
(TBCO)
and
2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE), OCPs: α-HCH and transchlordane. The volatility of spiked chemicals was investigated using a fugacity meter
200
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants
the mobilised OCPs were sorbed on the residue and remained in the solid phase after
the separation. Taking into consideration the sorbed fraction, the measured
bioaccessibilities of the OCPs varied from 4 to 97% depending on the properties
of the soils and the compounds. The enantiomeric ratios of chiral compounds studied
were also determined to distinguish biotic (enzymatic) and abiotic (chemical extraction) processes in the in vitro digestion model. It was found that although α-HCH in
the raw soils was racemic, (+)-α-HCH was enriched in the gastric digestive fluid but
finally depleted in the intestinal digestive fluid.
The enantioselective distribution and enantiomer profiling has been recently
proposed as a suitable scientific tool for the assessment of climate change influence
on fate and distribution of anthropogenic pollutants (Bidleman et al. 2012). The
authors acknowledge that elimination of persistent organic pollutants (POPs) under
national and international controls reduces effectively “primary” emissions, but
“secondary” emissions continue from residues deposited in soil, water, ice and
vegetation during former years of high usage. Secondary sources are expected to
dominate in the future, when POPs transport and accumulation will be controlled by
air-surface exchange and the biogeochemical cycle of organic carbon. Climate
change is likely to affect the mobilisation of POPs through, for example, increased
temperature, loss of ice cover in polar regions, melting glaciers and changes in soil
and water microbiology, which affect degradation and transformation. Chiral compounds offer advantages for following transport and fate pathways because of their
ability to distinguish racemic (newly released or protected from microbial attack)
and non-racemic (microbially altered) sources. Here, we explain the rationale for this
approach and suggest applications where chiral POPs could aid the investigation on
climate-mediated exchange and transformation processes. Examples include
distinguishing agricultural vs. non-agricultural and recently used vs. residual pesticides, transformation and sequestration processes in soil, historical vs. recent atmospheric deposition, sources in Arctic air and influence of ice cover on volatilisation.
Recently, the occurrence of new brominated flame retardants and organochlorine
pesticides were examined in urban soil. Many of these contaminants of emerging
concern (CEC) are chiral compounds. In this context, Wong et al. developed a new
enantiomer-selective method for the determination of enantiomer profiles (Wong
et al. 2012). New generations of flame retardants are entering the global market as
the use of polybrominated diphenyl ethers (BDEs) are being phased out in many
countries. Therefore, it is expected that soils could become a secondary emission
source to the atmosphere for brominated flame retardants (BFRs). So far little is
known about the environmental fate of novel BFRs in soils. In this study, the
volatility and transformation of BFRs and organochlorine pesticides (OCPs) in soil
were reported. A low organic carbon (5.6%) urban soil was spiked with a suite of
BFRs and OCPs, followed by incubation under laboratory conditions for 360 days.
These included BDE-17, -28, -47, -99; α- and β-1,2-dibromo-4-(1,2-dibromoethyl)
cyclohexane
(TBECH),
β-1,2,5,6-tetrabromocyclooctane
(TBCO)
and
2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE), OCPs: α-HCH and transchlordane. The volatility of spiked chemicals was investigated using a fugacity meter
200
8 Enantiomer-Specific Fate and Behaviour of Chiral Contaminants