Trends and variability in transport of persistent organic pollutants (POPs) to the Arctic and possible relation to climate change

Abstract

In this thesis, transport pathways, temporal trends and seasonality of persistent organic pollutants (POPs) in the Arctic are examined. These pollutants, which can be transported over long distances, constitute a great threat to humans and wildlife because they can accumulate in fatty tissue and lead to e.g. hormon production failure and even death.

Atmospheric POP measurements from the Zeppelin monitoring station in Ny-Ålesund, Svalbard, from 1993 to 2007 and an ice core collected from Kongsvegen glacier near Ny-Ålesund covering the years from 1994 to 2005 were analyzed for temporal variations in different POP concentrations. These data were then correlated to large scale atmospheric patterns (North Atlantic Oscillation and Arctic Oscillation) and transport pathways. The latter were estimated from the transport model FLEXPART, empolying CO as an emission tracer.

Results show that seasonal variations of POPs are influenced by temperature, photochemistry, meteorology, application patterns and snow melt. It is also found that POP concentrations are generally declining, in accordance with the downward trends in POP emissions. Levels of HCB and high-chlorinated PCBs have increased since approximately 2005, probably because of the increasing number of boreal forest fires and because of temperature increase, leading to re-emissions from oceans and soil.

Continent analysis of POPs shows that in general, Europe is the continent associated with PCB events detected at Zeppelin. Pesticides, especially gamma-HCH and chlordanes, are mainly transported to Svalbard from Asia because they are most heavily used there. North American events seldom lead to enhanced POP levels at Zeppelin because compounds are often washed out on the way. Correlations between NAO and PCBs and between AO and pesticides were found, though not very strong.

The data from the ice core were compared with the air measurements to examine the relationship between the two data sets. This has never before been done for ice cores collected in Svalbard. The analysis shows three "zones" in the ice core; a surface layer, containing low concentrations of POPs, an accumulation zone, showing significantly higher concentrations, and a background level, showing lower and more stable concentrations compared to the accumulation zone. Correlations between the data series in air and ice for gamma-HCH and HCB were calculated, but no correlations were found.