When people think of the Arctic, they often think of polar bears on melting sea ice, not of an area contaminated by pollutants. However, according to an article by Maria Papale et al. in the Marine Pollution Bulletin, findings of polychlorinated biphenyls (PCBs) in the Arctic demonstrate that ice can be a major transporter of pollutants in this remote region. The research team examined the concentration of PCBs in a fjord called Kongfjorden, located in Svalbard in Arctic Norway (79° N, 12° E), in order to understand how the Arctic is affected by pollutants. Given the impact these chemicals can have on human and animal health, the increase in ice melt due to climate change will have serious consequences for the release of these toxins.
PCBs are an important type of persistent organic pollutants (POPs); as such, they have a long lifetime in the environment, although they can be broken down by sunlight or some microorganisms. They are compounds once used heavily in the production of refrigerator coolants, electrical insulators and other items from 1929 until the late 1970s, when they were banned in the United States and elsewhere due to health concerns, particularly their carcinogenic effects. The presence of PCBs in Svalbard in the Arctic Basin indicates some form of long-distance transport because the Arctic is thousands of miles from industrial centers where PCBs are produced. Pollutants like PCBs are transported from regions in the northern mid-latitudes into the Arctic by the prevailing winds and ocean currents.
As Papale et al. explain, the PCBs deposited from the atmosphere accumulate on the snow and ice. This deposition has a drastic effect on the region, because PCBs that get trapped in the ice are ultimately released into the environment once the ice melts. For this reason, decades-old PCBs can enter rivers and oceans now, as glaciers melt; they are also emitted when PCB-containing materials wear out through use or when they are burned. In the Arctic, concentrations of PCBs are on average 0.2 ng/m3. Those concentrations have increased since the 1980s, after the banning of PCBs in the United States.
Once introduced into the food web, the fate of PCBs depends on which bacteria is present in the environment, since bacteria, such as Actinobacteria and Gammaproteobacteria, possess genetic and biochemical capacities for breaking down PCB pollution. Papale et al. gathered data on the occurrence of cold-adapted, PCB-oxidizing bacteria in seawater and sediment along Kongsfjord, a fjord located on the west coast of Spitsbergen, an island in the Svalbard archipelago. The fjord is fed by two glaciers, Kronebreen and Kongsvegen. The outer fjord is influenced by oceanographic conditions, while the inner fjord is influenced by large tidewater glaciers.
Higher concentrations of PCBs were observed in the water right next to the glacier (due to high flows of sediment and sea currents) or next to the open sea (likely due to water circulation inside the fjord). The higher concentrations of PCBs next to the glacier indicate the influence of glacial meltwater containing PCBs. Once the PCBs arrive in Svalbard Archipelago by long-range transport, they build up in the glaciers on Kongfjorden, sometimes by attaching to fine-grained particles, which are then incorporated into the ice. When the ice melts in the summer, the glacier meltwater containing PCBs flows into the fjord and could also freeze into sea ice in the winter. Sea ice transported from other regions also brings POPs to the region. For example, Arctic Ocean sea ice that forms near Siberia can contain pollutant-laden sediments; it is carried to Svalbard by currents, receiving depositions from the atmosphere as it travels. It can also contain heavy metals like lead, iron and copper, as well as organochlorides like PCBs or DDTs.
Once PCBs enter the waters of Kongsfjorden, they can be absorbed by plankton and other organisms at the bottom of food webs. They become concentrated in the tissues of the invertebrates that eat these organisms. As they pass up the food webs to organisms such as fish, and then to birds and mammals, the concentrations increase, through a process known as bioaccumulation. Recent research has found dangerous levels of these compounds in polar bears, a top predator. As advocacy organizations for these iconic animals have argued, these toxins represent an additional threat to the viability of the species, already challenged by the loss of icebergs and sea ice so critical to their survival. In this way, polar bears can provide testimony to the dangers of chemical pollution, as well as to the dangers of global warming, in the remote high Arctic.