8.2.3.2 Air/Sea Gas Exchange Studies
A bridge between air-water exchange studies performed on a lake and on the open
sea is being formed by an investigation carried out by Falconer et al. both on Amituk
Lake, Cornwallis Island (N.W.T., Canada) and off the coast of Cornwallis Island in
Resolute Bay (Falconer et al. 1995a, b). Air and water samples were taken at
Cornwallis Island (74
N, 95
W) in August–September, 1992. Water samples
were collected from Resolute Bay and Resolute Passage by small boat or helicopter.
Several samples were also taken from Amituk Lake, a small stream-fed lake on the
east side of Cornwallis Island (Falconer et al. 1995a, b). In air samples from Resolute
Bay, where the probability for biotic metabolism was low, an ER of 1.00 Æ 0.04 was
found for α-HCH, which clearly indicates a racemic mixture. In the seawater
samples, the (+)-α-HCH enantiomer was depleted resulting in an average ER of
0.93 Æ 0.06. Enantiomeric ratios of Amituk Lake samples differed greatly
depending on location and date. Water samples from tributaries of the lake, which
are fed by snow melt but also drain water from other small lakes, exhibited ER
values from 0.88–0.99 in late June to 0.65–0.86 in mid-July. The lake water at about
20 m depth showed an average ER ¼ 0.77. On 30 June and 4 July, the outflow from
the well-mixed lake had ERs ¼ 0.74-0.77. On 7 and 9 July, the outflow value rose to
0.85–0.86, corresponding to peak snowmelt and cold, less dense water flowing
across the surface. On 15 and 16 August, the outflow ER returned to 0.74–0.77, as
contributions from tributaries decreased. These results suggest that microbial transformation of α-HCH is taking place in Arctic lakes and near-shore marine waters.
Furthermore, these results encouraged Bidleman and co-workers to expand their
enantioselective analyses of air and seawater samples for deepened studies of
air/seawater gas exchange studies using similar theoretical approaches as earlier
explained.
In the summer of 1993, the Russian ship Okean completed a 50-day cruise
(BERPAC-93) of the Bering and Chukchi Seas, where water and air sampling for
HCHs was included (Jantunen and Bidleman 1996). In July–September 1994,
another series of samples was collected from the Canadian research vessel Louis
S. St. Laurent on a transect of the Arctic Ocean and adjacent waters from Victoria,
British Columbia, to Halifax, Nova Scotia, across the north pole. Water and air
sampling media were processed for analysis by previously described methods.
Extract volumes were brought to 1 mL (quantitative analysis) or 100 μL
(enantiomer-selective analysis) by blowdown with nitrogen into isooctane. Results
of the enantiomeric ratios of α-HCH in the water samples of the latter cruise were
already presented earlier. Samples from the Canada Basin and Greenland Sea were
depleted in the (+)-α-HCH, resulting in ER values of < 1.00. An opposite enantiomer degradation pattern was found in the Bering and Chukchi Seas, where the ERs in
surface water were generally > 1.00, indicating selective breakdown of (À)-α-HCH.
The α-HCH in air samples taken in 1993 and 1994 within 40 m of the sea surface
was non-racemic and followed the same order of degradation as in surface water
(Fig. 8.28). Air over the Bering Sea and the southern Chukchi Sea was depleted in
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
203
A bridge between air-water exchange studies performed on a lake and on the open
sea is being formed by an investigation carried out by Falconer et al. both on Amituk
Lake, Cornwallis Island (N.W.T., Canada) and off the coast of Cornwallis Island in
Resolute Bay (Falconer et al. 1995a, b). Air and water samples were taken at
Cornwallis Island (74
N, 95
W) in August–September, 1992. Water samples
were collected from Resolute Bay and Resolute Passage by small boat or helicopter.
Several samples were also taken from Amituk Lake, a small stream-fed lake on the
east side of Cornwallis Island (Falconer et al. 1995a, b). In air samples from Resolute
Bay, where the probability for biotic metabolism was low, an ER of 1.00 Æ 0.04 was
found for α-HCH, which clearly indicates a racemic mixture. In the seawater
samples, the (+)-α-HCH enantiomer was depleted resulting in an average ER of
0.93 Æ 0.06. Enantiomeric ratios of Amituk Lake samples differed greatly
depending on location and date. Water samples from tributaries of the lake, which
are fed by snow melt but also drain water from other small lakes, exhibited ER
values from 0.88–0.99 in late June to 0.65–0.86 in mid-July. The lake water at about
20 m depth showed an average ER ¼ 0.77. On 30 June and 4 July, the outflow from
the well-mixed lake had ERs ¼ 0.74-0.77. On 7 and 9 July, the outflow value rose to
0.85–0.86, corresponding to peak snowmelt and cold, less dense water flowing
across the surface. On 15 and 16 August, the outflow ER returned to 0.74–0.77, as
contributions from tributaries decreased. These results suggest that microbial transformation of α-HCH is taking place in Arctic lakes and near-shore marine waters.
Furthermore, these results encouraged Bidleman and co-workers to expand their
enantioselective analyses of air and seawater samples for deepened studies of
air/seawater gas exchange studies using similar theoretical approaches as earlier
explained.
In the summer of 1993, the Russian ship Okean completed a 50-day cruise
(BERPAC-93) of the Bering and Chukchi Seas, where water and air sampling for
HCHs was included (Jantunen and Bidleman 1996). In July–September 1994,
another series of samples was collected from the Canadian research vessel Louis
S. St. Laurent on a transect of the Arctic Ocean and adjacent waters from Victoria,
British Columbia, to Halifax, Nova Scotia, across the north pole. Water and air
sampling media were processed for analysis by previously described methods.
Extract volumes were brought to 1 mL (quantitative analysis) or 100 μL
(enantiomer-selective analysis) by blowdown with nitrogen into isooctane. Results
of the enantiomeric ratios of α-HCH in the water samples of the latter cruise were
already presented earlier. Samples from the Canada Basin and Greenland Sea were
depleted in the (+)-α-HCH, resulting in ER values of < 1.00. An opposite enantiomer degradation pattern was found in the Bering and Chukchi Seas, where the ERs in
surface water were generally > 1.00, indicating selective breakdown of (À)-α-HCH.
The α-HCH in air samples taken in 1993 and 1994 within 40 m of the sea surface
was non-racemic and followed the same order of degradation as in surface water
(Fig. 8.28). Air over the Bering Sea and the southern Chukchi Sea was depleted in
8.2 Transformation/Accumulation of Chiral Xenobiotics in Higher Organisms
203