Mercury in the Atmosphere Not Solely Responsible For Pollution in the Arctic

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Arctic region is heavily affected by Mercury pollution. Photo by Troyer, William A, U.S. Fish and Wildlife Service

Mercury Pollution in the Arctic Region

Due to the toxicity of methyl mercury, several studies were performed on its presence in the environment. Particular attention was given to its concentration in remote areas, such as the Arctic region, as mercury-based compounds are carried there by atmospheric currents and deposited/accumulated. High concentration in this area causes concern, not just for the environment itself, but also because the local population has a diet based mainly on fish and other marine animals.

Study on the Sources of Mercury in the Arctic Environment

An interesting study on this topic was published in Nature Geoscience on the 20th of May 2012. The work was developed by the Harvard Atmospheric Chemistry Modeling Group, part of the Department of Earth and Planetary Sciences and the Harvard School of Engineering and Applied Sciences. The work was done in cooperation with the Harvard Department of Environmental Health and Air Quality Processes Research of Environment Canada.

This aim of this study was to understand the main source(s) of the mercury reaching the Arctic coastal regions.

Mercury Concentration: Seasonal Variations

Atmospheric concentration of mercury in several Arctic areas (i.e. Canada, Russia, Norway) always showed variations with the seasons; in particular, an increase was observed in the summer months. This increase is due to a higher mercury concentration in the oceans; consequently, more Hg evaporation takes place, causing an increase in the atmospheric level of mercury. The reason for the higher concentration in the ocean, however, was not previously understood.

The researchers in this study modeled the Hg concentration in these areas, and their variation with the years; they considered several factors, such as ice/snow melting, reaction with sunlight, the presence of microbes resistant to mercury, and waters coming from circumpolar rivers.

Large quantities of mercury come from rivers during summer months. Photo by Jenny Fisher.

The Importance of the Rivers

This last factor was crucial in explaining the summer increase. It was observed that the modeling performed without the contribution from the rivers did not give any Hg increase in the summer. On the other hand, when modeling included the rivers, a higher mercury concentration corresponded to the summer months. The figure to the left shows the amount of mercury detected each month, and its source; it can clearly seen how the rivers are the main contributors during summer months.

Dr. Jenny Fisher, leading researcher in this study, told Decoded Science,

These findings were unexpected, as it was previously thought that the atmosphere was the main source of mercury to the Arctic system, but we’re finding the river source to be a key player. As a consequence, mercury concentrations in the Arctic may be more sensitive to climate than we previously thought. As permafrost melts, mercury currently locked up in frozen soils may be able to enter the Arctic Ocean through these river inputs. Reduced mercury emissions in the atmosphere, on the other hand, may have a more limited impact.

Toxic Mercury in the Atmosphere

If the mercury that finds itself in the atmosphere due to pollution isn’t the main source of Arctic mercury, does this mean that atmospheric mercury isn’t a major concern? Not at all. According to Dr. Fisher, “From a global perspective, it is still crucial to control atmospheric emissions, but this may play less of a role in reducing the high concentrations in Arctic biota than we had previously hoped.”

Sources

Fisher, J.A., et al. Riverine source of Atlantic Ocean mercury inferred from atmospheric observations. (2012). Nature Geoscience. doi:10.1038/ngeo1478. Accessed May 30, 2012.

Environmental Protection Agency (EPA). Methyl mercury health effectsAccessed May 30, 2012.

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