the Arctic Ocean to 4.61 0.45 ng/L and decreased
6
a. Water
in the Greenland Sea to 1.52 0.33 ng/L. The
5
trend of α-HCH in air was opposite to that found
4
in the water. The concentrations were highest over
3
the Bering and Chukchi Seas (123 16 pg/m3)
2
and the Greenland Sea (119 16 pg/m3) but de-
creased dramatically over the Arctic Ocean (57 20
1
pg/m3). The dip over the polar ice cap may be due
0
140
to rain scavenging by fog and drizzle and inhibited
b. Air
120
revolatilization from surface water by the ice cap.
100
The water/air fugacity ratio can be calculated
from the α-HCH concentrations in air and water
80
and the temperature-dependent Henry's Law con-
60
stant. The fugacity ratio expresses the saturation
40
state of surface water relative to the partial pressure
20
of the α-HCH in air. In the 1980s fugacity ratios
0
of α-HCH were less than 1.0 in Arctic and sub-
Arctic waters, indicating that the surface water was
Latitude (N)
Bering Sea
Greenland Sea
undersaturated and the net flux was air to sea. Our
Surface water and air concentrations of α-HCH meas-
measurements in the Bering and Chukchi Seas
ured on BERPAC93 and AOS-94, averaged within
bands of 5 latitude.
(Jantunen and Bidleman 1995) and on the AOS-
94 cruise show that concentrations of α-HCH in
the air have decreased by three-fold since 1990.
1.2
Reducing the partial pressure of α-HCH in air has
c. Water
raised fugacity ratios to above 1.0. Thus the surface
1.1
waters are now oversaturated and volatilizing α-
1.0
HCH.
Release of α-HCH from the ocean can be sensed
0.9
by following the proportion of its two enantiomers
0.8
in water and air. Enantiomers are mirror-image
0.7
molecules that have the same physicochemical
1.2
properties but that often differ in their biochemi-
d. Air
cal characteristics. Right- and left-handed amino
1.1
acids are familiar examples, and α-HCH is simi-
1.0
lar. The enantiomeric ratio (ER) of α-HCH is de-
fined as (+)α-HCH /()α-HCH. The ER in the
0.9
manufactured pesticide is 1.00 (racemic) and is
0.8
not changed by abiotic reactions such as hydroly-
sis and photolysis. However, enzymes can and fre-
0.7
quently do react selectively with one enantiomer,
leading to ERs that differ from 1.00 (Buser and
Latitude (N)
Bering Sea
Greenland Sea
Muller 1995). We have found selective depletion
Enantiomeric ratios of α-HCH in surface water and
of either (+) or () α-HCH in surface water, pre-
air in the same bands of 5 latitude.
65
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