Polychlorinated
Biphenyls in Glaciers. 2. Model Results
of Deposition and Incorporation Processes
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Abstract
In
previous work, Alpine glaciers have been identified as a secondary
source of persistent organic pollutants (POPs). However, detailed
understanding of the processes organic chemicals undergo in a glacial
system was missing. Here, we present results from a chemical fate
model describing deposition and incorporation of polychlorinated biphenyls
(PCBs) into an Alpine glacier (Fiescherhorn, Switzerland) and an Arctic
glacier (Lomonosovfonna, Norway). To understand PCB fate and dynamics,
we investigate the interaction of deposition, sorption to ice and
particles in the atmosphere and within the glacier, revolatilization,
diffusion and degradation, and discuss the effects of these processes
on the fate of individual PCB congeners. The model is able to reproduce
measured absolute concentrations in the two glaciers for most PCB
congeners. While the model generally predicts concentration profiles
peaking in the 1970s, in the measurements, this behavior can only
be seen for higher-chlorinated PCB congeners on Fiescherhorn glacier.
We suspect seasonal melt processes are disturbing the concentration
profiles of the lower-chlorinated PCB congeners. While a lower-chlorinated
PCB congener is mainly deposited by dry deposition and almost completely
revolatilized after deposition, a higher-chlorinated PCB congener
is predominantly transferred to the glacier surface by wet deposition
and then is incorporated into the glacier ice. The incorporated amounts
of PCBs are higher on the Alpine glacier than on the Arctic glacier
due to the higher precipitation rate and aerosol particle concentration
on the former. Future studies should include the effects of seasonal
melt processes, calculate the quantities of PCBs incorporated into
the entire glacier surface, and estimate the quantity of chemicals
released from glaciers to determine the importance of glaciers as
a secondary source of organic chemicals to remote aquatic ecosystems