Mercury rising: the scientists tackling a growing environmental threat

The total amount of mercury in the world's atmosphere has increased threefold since the industrial era, driven by climate change as well as human activities such as the burning of fossil fuels, heavy industry and gold-mining.

After being released into the environment, mercury undergoes various changes. One key change is its conversion to organic methylated mercury, a form with substantial impact. Absorbed by marine plankton, it is passed up the food chain, accumulating in large, economically important fish such as tuna and halibut - and the humans who eat them.

"Once you release mercury into the environment, it bounces around the world like a ping-pong ball. It finally bioaccumulates in fish, concentrated a million times more than the surrounding water," explains Milena Horvat, head of Environmental Sciences at the Jožef Stefan Institute in Slovenia and GMOS-Train project coordinator. "And in countries where fish is a large part of the diet, such as European coastal states, this is becoming a problem, as inhabitants exhibit notably elevated mercury levels."

A global response

Recognising the severity of the mercury pollution crisis, the international community took decisive action in 2013 by establishing the Minamata Convention , a global treaty designed to regulate and reduce mercury emissions. EU Member States are among the 140 countries that ratified the convention, signalling a collective commitment to mitigating mercury pollution.

GMOS-Train's main objective was to support the goals of the Minamata Convention, by delivering consistent and comparable mercury monitoring data and modelling tools to inform policy decisions. It was primarily focused on creating a new generation of scientists who will tackle issues pertinent to the global mercury challenge.

Led by the collective efforts of researchers and PhD students worldwide, it was hoped that the collection and analysis of observational data would lead to a better understanding of how human-caused activities contribute to rising mercury levels, particularly in fish.

"One of the main goals was to improve the measurements that were being carried out around the world, in air, water, soils and biota," says Horvat, "and to develop robust, consistent and comparable modelling tools."

To accomplish this objective, the project involved the expertise of 15 PhD students from various regions around the globe to address knowledge gaps pertaining to atmospheric, aquatic and terrestrial mercury dynamics, particularly focusing on the formation and uptake of mercury within the lower levels of the food chain.

The data collected from monitoring stations strategically positioned worldwide in the Atlantic, Pacific, Mediterranean, North Sea and Arctic, along with additional data gathered during ad hoc cruise campaigns, enabled GMOS-Train to gather comprehensive insights into mercury behaviour. This collective effort significantly enhanced the collection, processing and analysis of data, leading to the development of improved modelling tools.

Unravelling a mercury mystery

The GMOS-Train project also concentrated its efforts on deciphering the complexities of mercury's atmospheric chemistry. Its 15 PhD students played a crucial role in shedding light on some of the metal's less-explored characteristics, such as the conversion process from inorganic to organic mercury.

"At the outset, we started with the fundamental question: 'How and why does methylation of mercury happen in the aquatic environment?'" adds Horvat. "The majority of our PhDs were dedicated to this research, and our ongoing efforts persist because we have yet to fully unravel all its complexities."

Compelling results

Thanks to five years of extensive field research, GMOS-Train's detailed observations and improvements to existing methodologies have proven instrumental in understanding the mercury cycle and assessing its implications for ecosystems.

"Through GMOS-Train, we enhanced the measurement infrastructure, ensuring that results are comparable in both time and space.

"We also fostered collaboration with key stakeholders in the field, including instrument producers, standardisation bodies, and national and regional metrology networks," notes Horvat.

The project's new knowledge of the global mercury cycle is expected to significantly influence policy decisions and shape international treaties, notably the Minamata Convention.

This project was funded by the Marie Skłodowska-Curie Actions programme.

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