Circumpolar rivers are a source of Hg during summer. Photo from Nasa.
Is all that toxic mercury in the Arctic coming from pollution in the atmosphere? Apparently not, according to a recently-published study, which showed that the main source of mercury pollution in the Arctic area is circumpolar rivers, not atmospheric emissions, as previously thought. (Circumpolar rivers are simply rivers found in the polar region) These findings may affect future methods to combat mercury pollution.
Mercury and Its Compounds
Mercury (Hg) is a natural element which is used in many different applications. Its use is due mainly to its interesting properties; Hg, for instance, is the only metal which is liquid at room temperature.
Furthermore, it can form alloys with the majority of metals (i.e. gold, copper, silver, etc.); these alloys are called amalgams.
Mercury can be oxidized, the most common oxidation state is +2; in this state it can form several compounds, the most common one is methyl mercury CH3 – Hg – X. As the formula shows, Hg is bonded to a methyl group CH3 and another atom X, which is normally a halogen (i.e. chlorine or bromine).
Mercury Toxicity
Mercury and its compounds are very toxic for humans. The ingestion of mercury itself is very dangerous, as Hg is highly poisonous. Hg is a very volatile element; mercury vapors can form at room temperature, and inhaling them is very dangerous.
Methyl mercury is very hazardous too – it’s a neurotoxin, so it can cause impaired neurological development. Furthermore, exposure and/or ingestion of methyl mercury by pregnant women can also have effects on the development of fetuses, and cause damage to unborn babies.
Other problems caused by mercury Hg-based compounds are damage to the gastrointestinal tract and to the kidneys.
The Mercury Cycle and the Environment
In recent years, Hg release into the environment has increased due to human activities. Burning industrial or domestic wastes containing mercury, for instance, causes mercury emissions in the atmosphere. Another possible source is the mining industry, which can contaminate rivers and soils.
Once released into the environment, mercury is accumulated in some marine species, such as fish and other marine invertibrates, in the form of methyl mercury. Further to the damage caused to these species, from there mercury is then introduced into the food chain, causing problems for other animals and/or humans.
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