ESNC 201 - Lecture 12 Mercury

What are the key properties of mercury (Hg)?

Metallic mercury (Hg) is liquid at room temperature (unique among metals).

• It is highly useful, leading to widespread contamination.

• Forms inorganic and organic compounds.

• Bacteria methylate Hg in soils and sediments, creating monomethyl mercury (MeHg).

• MeHg bioaccumulates and biomagnifies in the food chain.

• Mercury has no biological function and is extremely toxic.

Why is mercury exposure linked to the phrase "Mad as a Hatter"?

Hat makers (hatters) were exposed to mercury in the felt-making process, leading to neurological symptoms like trembling fits. Mercury is a neurotoxicant.

What are common occupational exposures to mercury?

Mining, processing, and purification of mercury.

• Felt hat industry (historical exposure).

• Gold and silver extraction (amalgamation processes).

• Artisanal gold mining (ASGM) still uses mercury, exposing miners to toxic vapors.

How is mercury used in artisanal gold mining (ASGM)?

Mercury is mixed with gold ore, forming an amalgam.

• The mixture is heated in an open pan, releasing toxic mercury vapors.

• Mercury contaminates rivers, accumulating in fish and affecting local communities.

What happened during the Minamata mercury poisoning incident in Japan?

From 1932 to 1968, a factory released methylmercury into Minamata Bay.

• Neurological disease appeared in children by 1956.

• Over 1,700 people died, and many suffered permanent damage.

• Mercury bioaccumulated in shellfish, affecting people and cats.

What was the industrial source of Minamata Disease?

The Chisso Corporation used mercury as a catalyst in acetaldehyde production, creating methylmercury as a byproduct.

This methylmercury entered the food chain, poisoning humans and wildlife.

What happened to Professor Karen Wetterhahn?

A Dartmouth College professor and expert in metal toxicity.

• Spilled dimethylmercury on her latex glove, which permeated into her skin.

• Symptoms appeared 5 months later—trouble walking and speaking.

• She died several months later, requesting her story be told to students as a warning about mercury toxicity.

When did First Nations communities in NW Ontario become exposed to mercury?

The exposure occurred starting in the 1960s and continued onwards.

Grassy Narrows (Asubpeeschoseewagong) was one of the affected communities.

What was the source of mercury contamination at Grassy Narrows?

• he mercury contamination originated from a pulp and paper mill in Dryden.

• The Reed International company used mercury in the production of caustic soda for bleaching paper.

What actions were taken regarding the mercury contamination in Grassy Narrows?

• In the 1970s, the company was ordered to stop dumping mercury.

• Fisheries in the region were closed.

What are the main remediation options for reducing mercury in sediments at Clay Lake?

1. Wait for natural recovery.

2. Add unpolluted sediment to dilute mercury concentration.

3. Add a clay cap to cover contaminated sediments.

4. Add activated carbon to bind mercury.

5. Dredge lake bottom.

• All options are expensive and some may be unlikely to succeed.

Why is speciation of mercury important in the environment?

• Organically-bound mercury (like methylmercury and dimethylmercury) are the most toxic forms of mercury.

• These forms are neurotoxic, particularly to young children and pregnant women.

What are the primary sources of mercury pollution?

• Coal burning

• Chlor-alkali plants

• Mercury mining

• Gold mining

How is mercury transported in the environment?

• Mercury's volatility allows it to be transported over long distances.

• It can be found in remote regions (e.g., the Arctic), far from industrial sources.

How do most humans get exposed to mercury?

• Through the consumption of fish.

• All mercury in fish tissue is methylmercury.

• Especially concerning for communities where fish is a dietary staple (e.g., Seychelles, First Nations communities in Canada).

What do mercury consumption advisories recommend?

• They provide guidance on the maximum number of fish meals per month based on the mercury levels and other contaminants (like PCBs and pesticides) in the fish.

• The guide varies by region, species, and size/age/gender of the eater.

What are the potential impacts of mercury consumption advisories?

• Alternative foods may be used, which could be less healthy.

• Advisories may be ignored, leading to unknown effects.

• Traditional lifestyles may be disrupted.

• Business opportunities related to recreational fishing (e.g., guiding) may become unavailable.

How do wildfires contribute to the mercury (Hg) cycle?

Wildfires release mercury (Hg) from the soil into the atmosphere due to mercury being a volatile element.

What role does northern peat play in the mercury cycle?

Northern peat stores mercury which could be either natural or anthropogenic in origin.

How has climate change affected wildfires and mercury cycling?

Wildfires are increasing due to climate change, further influencing the release and transport of mercury.

What was previously believed to be the main source of mercury in Arctic organisms?

The main source was thought to be the long-range transport of industrial emissions, though wildfires are now recognized as an additional source