Environmental Engineering Reference
In-Depth Information
1. Are POPs being moved far from their sources in the atmosphere?
Evidence sup-
porting the long-range transport hypothesis to explain distribution of POPs was looking
more and more convincing. It included a string of measurements of air concentrations of
dioxinsandpesticidesmadebyMichaelOehmefromBirkenesinsouthernNorwaytoSval-
bard. The sampling frequency conducted over two years enabled episodes of contaminated
air to be detected and for the prior history of those “contaminated” air parcels to be tracked
backwards for about four days. This technique is known as
back trajectory analysis
. It in-
dicated that most of the POP pulses or transport episodes to the Nordic Arctic came from
Eastern Europe and the (then) Soviet Union. Mats Tysklind and his colleagues were able
to use this technique to also follow the transport to southern Sweden of dioxins and fur-
ans in air from sources in Central and Western Europe. Meanwhile, studies in southern
Ontario, Canada, were showing that concentrations of toxaphene, DDT, HCH, chlordane,
endosulfan and dieldrin could be linked to their use in the southern United States, Mexico
and the Caribbean.
At the same time, Frank Wania and Don Mackay had just about tied up the funda-
mental physics of the grasshopper/cold trapping hypothesis, which now carried the more
impressivenamesof“globalfractionation”and“coldcondensation”.Therewasnodenying
that it explained the patterns of concentrations of different POPs across Canada in Arctic
air and snow. These included measurements made on an ice island drifting westwards off
the northern coast of Axel Heiberg Island, on the Agassiz Ice Cap and at Alert on the north-
ern tip of Ellesmere Island. It would be difficult to find three more remote locations, but
all our (then-known) POPs were found there. Terry Bidleman and colleagues reported the
ice island results and Dennis Gregor was responsible for the Agassiz measurements. Over
several years, Dennis dug from the surface down to the fully consolidated ice. This enabled
the volatilization dynamics of different pollutants to be measured as the snow was gradu-
ally compacted into ice. That information was vital to enable us to interpret the pollutant
concentration history recorded in ice cores. One member of the team was from India and
he had a reputation across the Arctic for his curries. I landed there once in a ski-equipped
TwinOtter enroute fromthe meteorological station at Eureka toAlert. Itwasastrange sen-
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