Persistent organic pollutants in large concentrations in Arctic areas: Fires spread environmental toxins over the Arctic

For the last decades, persistent organic pollutants (POPs) have been found in large concentrations in Arctic areas. These substances accumulate in living organisms and are enriched throughout the food chain. Polychlorinated biphenyl (PCB) is one of the most important environmental toxins of this type. 'We wanted to draw attention to the causes of the environmental impact in the Arctic and trace the sources of the problem,' says Sabine Eckhardt, postdoctoral researcher in the FLEXPOP project, which has been carried out at the Norwegian Institute for Air Research (NILU).

Record-high emissions of PCB

The PCB content in the soil is high in North America and Eastern Europe. This is the result of pollution during earlier periods. When biomass from trees and dead grass and leaves catches fire, it releases both PCB and other environmental toxins and creates yet another source of PCB emissions.

In 2004 and 2006, big fires ravaged these areas. About 5.8 million hectares of coniferous forest burned down in North America. Eastern Europe experienced extensive emissions from agriculture due to straw and stubble burning. Several weeks later, the researchers found record-high values of PCB in the atmosphere above Svalbard.

'As far as we know, this is the first study that shows a connection between the burning of biomass and PCB concentrations in the atmosphere far away,' says Sabine Eckhardt. 'With a climate that is constantly changing, we expect the extent of such fires to increase.

In such case, it also means that the fires may represent an increasing environmental problem in the Arctic. That in turn will reduce the effect of the international agreements that aim to reduce emissions of these environmental toxins,' says Ms Eckhardt.

New methods locate the source

Using completely new methods, researchers can now 'backdate' emissions in the atmosphere. In this way, they can find out where the pollution originated and its cause. In addition to PCB, substances such as gamma-HCH (gamma-hexachlorocyclohexane, also known as the insecticide Lindan) and DDT (dichlorodiphenyltrichloroethane) are registered using these methods.

The air measurements in this project were performed by the Zeppelin measuring station near Ny Ålesund on Svalbard. Similar measurements were carried out near Birkenes in Southern Norway. Here, both PCB and gamma-HCH were registered during a period of four years.

While the PCB emissions primarily come from Eastern Europe, gamma-HCH could be traced back to south-western areas of Europe.

Accumulates in the food chain

PCB is a group of synthetically-produced persistent toxic chlororganic compounds. PCB is stored in the fatty parts of the organism and accumulates in the food chain. Humans, fatty fish and carnivores (such as polar bears) can therefore accumulate concentrations in their bodies that are so high that they are poisoned.

Lindan is a chlororganic compound that has been used both as an insecticide in agriculture and as pharmaceutical treatment for head lice and scabies. Lindan is a neurotoxin that primarily affects the nervous system, liver and kidneys in humans. It can also have a carcinogenic effect.

Successful new model

The project has succeeded in developing a new atmospheric dispersion model (FLEXPART). It includes processes that can simulate how POPs are transported via the atmosphere. It also takes account of new knowledge about global emissions of PCB and new data about the chemical composition of different technical blends that were produced previously.

The model was tested by using data from Birkenes metering station. Clear concordance was found between registered findings and the model's identification of PCB and gamma-HCH. The model was then used to identify where the PCB emissions near Birkenes come from.

The study shows that emissions from straw and stubble burning in Russia were the cause of the very high PCB concentrations measured at the Zeppelin station on Svalbard between 1 and 3 May 2006.

Fires -- a new challenge

As the primary emissions of organic environmental toxins are reduced, the researchers believe that fires caused by climate change will become more important. They point to the fact that there has been little focus on the significance of burning biomass, and the potential consequences of this for the Arctic environment.

'For the first time, we have proved that burning biomass is also an important source of persistent organic pollutants in polar areas. This can be of great importance to international agreements that aim to protect the environment in Arctic areas,' says Sabine Eckhardt and underlines the need for further research in this area.