Mercury: Headlining the Arctic

Ladies and gentlemen please welcome to the stage a new form of long range pollution… Mercury! *APPLAUSE*. This post aims to explain what mercury is, where it is from and its presence in the Arctic region. Despite being a remote region, the Arctic has accumulated high levels of Mercury. The element is having many negative implications for the biota in this region thus creating a topic of both interest and concern.

Mercury is headlining the Arctic.

What is mg?

Mercury (Hg) is a naturally occurring element. With a very low melting point of -38.87 degrees Celsius, mercury is most often found as a silver liquid. Before the industrial revolution the total amount of mercury in the environment was in equilibrium. The anthropogenic creation of mercury has upset this balance causing excess mercury to be found in the soils, surface water and oceans (all of which are large global stores of the element).

Map showing Mercury released into the atmosphere
tonnes per year

Sources of Mercury.

The natural abundance of mercury, in the environment is doubled, by that produced from human innovation (about 4000 tonnes). Burning coal is by far the largest production of man-made mercury, followed by the smelting and metal production industries (as Hg is used in the creation ferrous and non-ferrous metals). A larger proportion is generated through the mining industry, which uses mercury to extract from gold natural ores. “Hot Spots” for release of atmospheric mercury include China, Sudan and the North West Coast of South America, demonstrated by the map (right).

Chart showing the sources of anthropogenic
Mercury.

Mercury’s presence in the Arctic.

It has been estimated that the net amount of mercury added to the Arctic environment each year is between 80 to 140 tonnes (NB: mercury is also leaving the Arctic system). Most of the Mercury present in the Arctic is transported by prevailing winds, ocean currents and rivers. Atmospheric pollution, from mid latitude power stations, can take as little as a few days to be transported from source to the Arctic. Transportation through the atmosphere can have detrimental impacts as gaseous Hg can have a lifespan of up to a few months (within this time a mercury atom has the potential to circulate the majority of the northern hemisphere).

The oceans are also a great transporter of Hg, yet a much slower method of distribution. However, it is important to remember the amount of mercury reported in the atmosphere is smaller in comparison to the volume stored in the oceans.

Mercury budget in the Arctic Ocean.

The Mercury budget, for the Arctic Ocean, suggests the Atlantic and Pacific oceans, coastal erosion and the atmospheric (through mercury depletion events during spring) are all large inputs of mercury to the Arctic system. The proportion of mercury sourced from atmospheric deposition demonstrates the large surface area of the Arctic Ocean. The outflows of mercury are less apparent including sedimentation, the removal through ocean systems and to a very small extent the remission of gases. The disproportionate ratio of inflows to outflows demonstrate why the Arctic is a site of mercury accumulation.

Modelling the Arctic mercury budget must be completed on a global scale to incorporate the influence of long range transport. A large scale results in a greater level of uncertainty associated with the models as resolution of results are low. This can be overcome by using a multi-scale approach (using models which integrate global and regional scales) which is adopted within a study published in the Atmospheric Environment Journal. Within the paper Dastoor and Larocque use a global/regional atmospheric heavy metals model to simulate the movement of mercury within the atmosphere, allowing a higher resolution to be obtained.

Stay tuned for my next post which will delve deeper into the impacts of mercury on ecosystems in the Arctic. Until then please comment any questions or thoughts you have in response to this post.

P.S. For those of you who found the topic of mercury particularly thrilling this website http://www.mercurywatch.org/ is well worth a read. The site monitors the use of mercury across the world in small scale gold mines. Sponsors aid projects which aim to reduce mercury production by training workers to use mercury free extraction methods in Ghana, Senegal and Burkina Faso. Benefiting both the environment and the health of works.