Mercury

Climate change slows reduction of methylmercury levels in Arctic: U of T researchers

Christopher.Sorensen — Fri, 19 Feb 2021 18:31:22 +0000

Climate change slows reduction of methylmercury levels in Arctic: U of T researchers

Christopher.Sorensen Fri, 02/19/2021 - 13:31

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Igor Lehnherr, a researcher at U of T Mississauga, assessed the build-up of methylmercury, a dangerous neurotoxin, in Lake Hazen, one of Canada’s northernmost lakes (photo by Igor Lehnherr)

Patchen Barss

Topic

Breaking Research

Arctic

Geography

Mercury

Research & Innovation

Sustainability

U of T Mississauga

Climate change may be slowing the reduction of methylmercury – a dangerous organic neurotoxin created by microbes that metabolize mercury – in Arctic waters despite a global movement to reduce industrial mercury emissions.

That is among the findings of Igor Lehnherr and his research team at the ��Ƶ after assessing the build-up of methylmercury in Lake Hazen, one of Canada’s northernmost lakes.

The study is published in the journal Environmental Science & Technology.

“Mercury pollution has gone down in the atmosphere,” says Lehnherr, an assistant professor of geography at U of T Mississauga. “We’re doing things to tackle it, but climate change is throwing things for a loop [because] it can actually undo some of the benefits from emission reductions.”

Methylmercury levels rise only indirectly from human activity. Burning fossil fuels, mining and other industrial processes release unmethylated mercury into the atmosphere. As the mercury settles into aquatic ecosystems, certain types of microbes metabolize it to form the much more dangerous methylmercury.

A “persistent organic pollutant,” Methylmercury becomes more concentrated as it moves up the food chain – from bacteria to fish, predators and people. It affects the nervous system and can also cause cardiovascular damage. The toxin is especially dangerous for pregnant women and for fetuses, babies and young children whose nervous systems are still developing.

While the area where the U of T team collected samples is not close to any northern communities, Lehnherr says the work is relevant for Indigenous people who hunt and fish for food.

“What we’re learning is not constrained to that location,” he says. “We put a lot of import on understanding mechanisms that affect methylmercury, so we can apply what we learn in one place somewhere else.”

Igor Lehnherr, an assistant professor of geography at U of T Mississauga, says the field work for his latest study spanned several seasons and involved collaboration with other research teams in order to expand sampling (photo by Igor Lehnherr)

Arctic methylmercury levels depend on a complex mix of factors, including industrial emissions, precipitation patterns, microbial numbers and activity, as well as changes in seasonal sea ice. The complexity, along with the remoteness of northern ecosystems, make Lehnherr’s work particularly challenging.

“The field work spanned a few seasons,” he says of his latest study. “Some years we were there in the spring when it’s all snow and ice cover, some years in the summer, some years for both. By combining efforts with other teams, we expanded the sampling. Arctic research by nature is fairly collaborative – we share costs, time and ideas.”

Igor Lehnherr and his research team take water samples through the ice (photo by Igor Lehnherr)

In general, methylmercury-producing microbes are more active in warmer environments, implying a direct correlation between global warming and increased toxicity. But climate change also has many other effects that can exacerbate, mitigate and further complicate the situation.

“Temperature in the Arctic also controls permafrost thaw. It affects the amount of precipitation by controlling cloud cover, sea ice cover, rates of evaporation and these kinds of things,” Lehnherr says.

Changing weather patterns also affect how much methylmercury builds up in specific isolated areas and how efficiently it flows from one lake to the next, creating more widespread problems. In the short term, Lehnherr says it looks as though reduced emissions have not fully translated into cleaner Arctic ecosystems. However, Lehnherr says it should not necessarily be interpreted as a sign that efforts to reduce mercury aren’t worth it.

“I mostly think it validates the ongoing efforts to reduce anthropogenic mercury emissions,” he says. “Countries have shown this is something they’re willing to take on. These results allow us to have reasonable expectations about how long it will take for mercury levels to go down and stabilize.”

Lehnherr also wants to reassure people in northern communities who may be concerned about the safety of their food supply.

“Whenever I talk about the risks of mercury and negative health impacts, I always stress that the benefits of consuming traditional foods vastly outweigh the risks of contaminants. Locally caught Arctic char has better nutritional value than dried goods and flown-in goods,” he says.

Lehnherr plans to continue his study of methylmercury in the Arctic region to get a better sense of the long-term impacts of climate change.

Some like it hot: U of T PhD student’s research takes him to active volcano in New Zealand

ullahnor — Fri, 03 Feb 2017 21:00:46 +0000

Some like it hot: U of T PhD student’s research takes him to active volcano in New Zealand

ullahnor Fri, 02/03/2017 - 16:00

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David McLagan travelled to an active volcano off New Zealand to install passive air samplers (pictured to right of McLagan) to monitor mercury concentrations (photo courtesy of David McLagan)

Don Campbell

Author legacy

Don Campbell

Topic

Environmental Sciences

Chemistry

UTSC

Education

David McLagan’s research has taken him to some interesting places, but going to an active volcano tops the list.

“I’ve never been to a place quite like it,” says McLagan, who needed to deploy a series of passive air samplers on White Island, an active volcano 48 km off the coast of New Zealand’s North Island.

The U of T Scarborough PhD candidate is working on developing passive air samplers that can monitor mercury concentrations in remote locations.

Working under the supervision of U of T Scarborough Chemistry Professor Frank Wania and Associate Professor of Environmental Sciences Carl Mitchell, McLagan is looking at monitoring mercury in the air since it can last in the atmosphere for around a year, can be transported great distances and is linked to a host of brain and nervous system disorders.

New Zealand’s White Island, which spews out huge amounts of gas, is open to tourists but is only accessible by helicopter or boat.

McLagan received funding for the research trip from U of T's Centre for Global Change Science (CGCS). In planning the trip, McLagan connected with GNS Science, a local public-private research organization that monitors volcanic activity on the island and across New Zealand. Along with crucial logistical support, GNS also provided extensive training on how to do research safely.

Masks are necessary to avoid passing out from noxious vapours continuously being vented. In addition to hard hat and boots, walking with a prodder was also important to avoid soft spots in the ground that can burn feet.

There’s also the ever-present risk of eruption, but McLagan felt reassured by the team at GNS who take extra precautions. They aren’t allowed to travel to the island if any unusual seismic activity is recorded, even if it’s deemed safe for tourists. The island was also once home to a sulfur mine where an eruption in 1914 killed all of the miners working there.

While in New Zealand, McLagan also deployed his air samplers at another site called Craters of the Moon, the largest geothermal field in the country. The site gets its name from its unearthly appearance, one that is barren yet bright with constantly shifting ground and endless steam vents dotting the landscape.

Since there’s no electricity in these remote locations – nor is it possible to supply tanks of argon gas that active air samplers rely on – the passive air sampler developed by McLagan uses the natural movements of air and a carbon material to capture mercury in the atmosphere.

As it works its way into unoxygenated sediments, the mercury can be transformed into methylmercury, which is the most toxic and concerning form from a human health perspective. A neurotoxin, it can affect fetal and infant cognitive development.

Another study by McLagan took him to a shuttered mercury mine in Italy to measure concentrations in the buildings and surrounding area. Emissions from this mine remain a concern because it’s located close to the community of Abbadia San Salvatore in Southern Tuscany.

He also witnessed small droplets of liquid mercury on the ground inside old mining buildings.

“In terms of exposure, there is a lot of mercury there so I wouldn’t want to spend a lot of time in those mining buildings,” he says. “We’re careful not to spend more than five minutes or so.”

While mining for mercury is no longer allowed in most parts of the world, McLagan says there’s been a rise in emissions from small-scale gold mining operations in the developing world.

He adds while active air sampling of mercury is common in affluent countries in the northern hemisphere, there are fewer than ten remote sites in the southern hemisphere that are currently monitoring mercury. The ultimate goal of his research, he says, is to help resolve these spatial imbalances that exist in mercury monitoring across the globe.

“Being able to go to these places and collaborate with researchers from around the world, it’s just a great professional and personal experience.”

U of T invites the public to watch the transit of Mercury

lavende4 — Mon, 09 May 2016 20:00:09 +0000

U of T invites the public to watch the transit of Mercury lavende4 Mon, 05/09/2016 - 16:00

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Mike Reid from the department of astronomy & astrophysics and some of his undergrad students took their telescopes outside so the public could view the transit of Mercury on Monday (Johnny Guatto photo)

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Our Community

Astronomy & Astrophysics

Mercury