Unveiling the Natural Mercury Cycle
Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have shed light on the natural mercury cycle by estimating emissions from volcanic eruptions, the primary natural source of this element. Their findings reveal that since the start of the modern era around 1500 C.E., human activities have increased the concentration of potentially toxic mercury in the atmosphere by a staggering sevenfold.
Reconstructing Pre-Industrial Mercury Levels
The research team, led by Professor Elsie M. Sunderland, developed a novel methodology to accurately estimate the annual mercury emissions from volcanoes. This estimate, along with a sophisticated computer model, enabled them to reconstruct pre-anthropogenic atmospheric mercury levels.
A Dramatic Surge in Mercury Levels
Prior to human intervention, the average atmospheric mercury content was approximately 580 megagrams. However, in 2015, independent research revealed that the atmospheric mercury reservoir had ballooned to around 4,000 megagrams – nearly seven times larger than the natural baseline estimated in this study.
The Culprits Behind Mercury Pollution
Human emissions from coal-fired power plants, waste incineration, industrial processes, and mining are the primary culprits behind this drastic surge in atmospheric mercury. These activities release mercury into the air, where it spreads across the globe, posing significant health risks to humans and ecosystems.
The Perils of Methylmercury
“Methylmercury, a potent neurotoxin, bioaccumulates in fish and other organisms, including us,” explained Professor Sunderland, the senior author of the study. Understanding the natural mercury cycle driven by volcanic emissions provides a baseline for policies aimed at curbing mercury emissions and allows us to fully grasp the human impact on the environment.”
The Challenges of Measuring Atmospheric Mercury
Measuring mercury in the atmosphere is a formidable challenge due to its scarcity, despite its substantial impact on human health. In a cubic meter of air, there may be only a nanogram of mercury, rendering it virtually undetectable via satellite.
Leveraging Sulfur Dioxide as a Proxy
To overcome this obstacle, the researchers employed sulfur dioxide, a major component of volcanic emissions, as a proxy for mercury. Sulfur dioxide is readily detectable by satellites, enabling them to track volcanic mercury emissions from space.
Volcanic Emissions and Atmospheric Mercury Distribution
The research team discovered that while mercury can travel long distances from its source, volcanic emissions directly contribute to only a small fraction of ground-level mercury concentrations in most regions. However, in areas like South America, the Mediterranean, and the Pacific Ring of Fire, volcanic mercury emissions significantly complicate the tracking of human emissions.
Implications for Mercury Monitoring and Mitigation Strategies
“In Boston, we can rely on local monitoring without worrying about volcanic activity,” explained Benjamin Geyman, a PhD student in Environmental Science and Engineering at SEAS and the study’s first author. “But in a place like Hawaii, volcanic mercury emissions are highly variable, making it challenging to track human emissions. This map helps us identify regions where volcanos play a significant role and those where their influence is negligible. This information is crucial for understanding the long-term impact of human activities on mercury levels in fish, air, and the ocean.”
The Path Forward
The study’s findings underscore the urgent need to curb human-driven mercury emissions, safeguarding human health and environmental integrity. By understanding the natural mercury cycle and the challenges of measuring atmospheric mercury, policymakers and scientists can develop more effective strategies to mitigate mercury pollution and protect our planet.
