Pacific Ocean and regional soils. However, during trans-Pacific transport events at
CPO, the α-HCH EFs were significantly more racemic (EF ¼ 0.513 Æ 0.0003, p <
0.001). Racemic α-HCH was consistently measured at MPO and MBO in transPacific air masses that had spent considerable time in the free troposphere. The
α-HCH EFs in CPO, MPO and MBO air masses were negatively correlated ( p ¼
0.0017) with the amount of time the air mass spent above the boundary layer, along
the 10-day back air mass trajectory, prior to being sampled. This suggests that, on the
West coast of the U.S., the α-HCH in the free troposphere is racemic. Racemic
signatures of cis- and trans-chlordane were measured in air masses at all four air
sampling sites, suggesting that Asian and U.S. urban areas continue to be sources of
chlordane that has not yet been biotransformed.
In order to elucidate potential diffusive pollutant sources in US national parks, a
comprehensive survey was launched on the enantiomeric signatures of chiral organochlorine pesticides in surface snow samples, as well as snow and freshwater fish
from high-altitude national parks (Genualdi et al. 2011). The enantiomer fractions
(EFs) of α-HCH, cis-, trans- and oxychlordane, and heptachlor epoxide were
measured in 73 snow, fish and sediment samples collected in seven western
U.S. National Parks/Preserves. The present study is novel because the selected
lakes had no inflow or outflow, and the determination of EFs for chiral organochlorine pesticides (OCPs) in snowpack from these lake catchments provided a better
understanding of the OCP sources in the western United States, whereas their
measurement in fish and sediment provided a better understanding of their biotic
transformations within the lake catchments. Non-racemic α-HCH was measured in
seasonal snowpack collected from continental U.S. National Parks, and racemic
α-HCH was measured in seasonal snowpack collected from the Alaskan parks,
suggesting the influence of regional sources to the continental U.S. parks and
long-range sources to the Alaskan parks. The α-HCH EFs measured in trout collected from the lake catchments were similar to the α-HCH EFs measured in seasonal
snowpack collected from the same lake catchments, suggesting that these fish did not
biotransform α-HCH enantioselectively. Racemic cis-chlordane was measured in
seasonal snowpack and sediment collected from Sequoia, indicating that it had not
undergone significant enantioselective biotransformation in urban soils since its use
as a termiticide in the surrounding urban areas. However, non-racemic cis-chlordane
was measured in seasonal snowpack and sediments from the Rocky Mountains,
suggesting that cis-chlordane does undergo enantioselective biotransformation in
agricultural soils. The trout from these lakes showed preferential biotransformation
of the (+)-enantiomer of cis-chlordane and the (À)-enantiomer of trans-chlordane.
Tao et al. applied a gastrointestinal model for the evaluation of oral
bioaccessibility of chiral organochlorines (Tao et al. 2009). Soil as surrogate of
uptake with solid materials was chosen and α-HCH and DDT derivatives were used
as model substances. The authors assumed that a fraction of the mobilised contaminants is still sorbed on a solid material after digestion, and this fraction could be
desorbed and become bioaccessible in the intestinal tract due to the absorption of the
dissolved fraction by the small intestine. The bioaccessibility would be
underestimated if the sorbed fraction was separated from the fluid by centrifugation
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
199
CPO, the α-HCH EFs were significantly more racemic (EF ¼ 0.513 Æ 0.0003, p <
0.001). Racemic α-HCH was consistently measured at MPO and MBO in transPacific air masses that had spent considerable time in the free troposphere. The
α-HCH EFs in CPO, MPO and MBO air masses were negatively correlated ( p ¼
0.0017) with the amount of time the air mass spent above the boundary layer, along
the 10-day back air mass trajectory, prior to being sampled. This suggests that, on the
West coast of the U.S., the α-HCH in the free troposphere is racemic. Racemic
signatures of cis- and trans-chlordane were measured in air masses at all four air
sampling sites, suggesting that Asian and U.S. urban areas continue to be sources of
chlordane that has not yet been biotransformed.
In order to elucidate potential diffusive pollutant sources in US national parks, a
comprehensive survey was launched on the enantiomeric signatures of chiral organochlorine pesticides in surface snow samples, as well as snow and freshwater fish
from high-altitude national parks (Genualdi et al. 2011). The enantiomer fractions
(EFs) of α-HCH, cis-, trans- and oxychlordane, and heptachlor epoxide were
measured in 73 snow, fish and sediment samples collected in seven western
U.S. National Parks/Preserves. The present study is novel because the selected
lakes had no inflow or outflow, and the determination of EFs for chiral organochlorine pesticides (OCPs) in snowpack from these lake catchments provided a better
understanding of the OCP sources in the western United States, whereas their
measurement in fish and sediment provided a better understanding of their biotic
transformations within the lake catchments. Non-racemic α-HCH was measured in
seasonal snowpack collected from continental U.S. National Parks, and racemic
α-HCH was measured in seasonal snowpack collected from the Alaskan parks,
suggesting the influence of regional sources to the continental U.S. parks and
long-range sources to the Alaskan parks. The α-HCH EFs measured in trout collected from the lake catchments were similar to the α-HCH EFs measured in seasonal
snowpack collected from the same lake catchments, suggesting that these fish did not
biotransform α-HCH enantioselectively. Racemic cis-chlordane was measured in
seasonal snowpack and sediment collected from Sequoia, indicating that it had not
undergone significant enantioselective biotransformation in urban soils since its use
as a termiticide in the surrounding urban areas. However, non-racemic cis-chlordane
was measured in seasonal snowpack and sediments from the Rocky Mountains,
suggesting that cis-chlordane does undergo enantioselective biotransformation in
agricultural soils. The trout from these lakes showed preferential biotransformation
of the (+)-enantiomer of cis-chlordane and the (À)-enantiomer of trans-chlordane.
Tao et al. applied a gastrointestinal model for the evaluation of oral
bioaccessibility of chiral organochlorines (Tao et al. 2009). Soil as surrogate of
uptake with solid materials was chosen and α-HCH and DDT derivatives were used
as model substances. The authors assumed that a fraction of the mobilised contaminants is still sorbed on a solid material after digestion, and this fraction could be
desorbed and become bioaccessible in the intestinal tract due to the absorption of the
dissolved fraction by the small intestine. The bioaccessibility would be
underestimated if the sorbed fraction was separated from the fluid by centrifugation
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
199