In a pivotal study, scientists from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have found that human emissions have surged the mercury concentration in the atmosphere sevenfold since 1500 C.E. This discovery has amplified concerns about the environmental impacts and long-term exposure associated with mercury. The study was published on November 1, in Geophysical Research Letters.
This new study is the first to provide a natural reference point for atmospheric mercury levels by quantifying emissions from the most significant natural source - volcanic eruptions. Led by Elsie M. Sunderland, the research team developed a novel method that employs sulfur dioxide as an indicator for mercury emissions, enabling them to estimate volcanic mercury discharge accurately. The researchers found that the atmosphere contained an average of about 580 megagrams of mercury, sans human intervention. A 2015 study reported the atmospheric mercury reservoir at approximately 4,000 Mg – marking a near sevenfold increase compared to pre-anthropogenic levels.
Industrial activities, such as coal-based power generation, waste incineration, mining, and manufacturing processes, are deemed responsible for this significant mercury concentration spike. To adopt effective policies for curbing mercury emissions, researchers first had to comprehend the natural mercury cycle, driven by volcanic emissions. This understanding facilitated the establishment of an atmospheric baseline against which to gauge the full scale of human-induced environmental impacts explained Sunderland.
The study's results indicate that despite its propensity for dissolving into the atmosphere and being transported over long distances, volcanic emissions account only for a negligible percentage of ground-level mercury concentrations in most regions. This recognition led researchers to pin human activity as the chief contributor to increased mercury levels. Conversely, in regions with significantly high volcanic emissions like South America, the Mediterranean, and the Pacific's Ring of Fire, identifying the precise mercury source becomes more complex, emphasizing the need to understand natural emission distribution and variability.
As Benjamin Geyman, a Ph.D. student in Environmental Science and Engineering at SEAS and the study's first author, clarified, in regions such as Boston, where volcanic emissions are negligible, tracking mercury levels and determining human-induced atmospheric impacts are relatively easy. However, in regions like Hawaii, where natural mercury emissions are higher and variable, taking into account both natural and anthropogenic sources becomes essential to monitor mercury levels accurately.
The study's conclusions carry substantial implications for examining long-term mercury contamination trends in fish, the atmosphere, and bodies of water. By distinguishing between natural and man-made mercury emissions, researchers and policymakers can plot targeted strategies to neutralize rising mercury concentrations' harmful effects on health and the environment.
The National Science Foundation backed this research with grants 2210173 and 2108452. Contributing researchers included Colin Thackray and Daniel J. Jacob, the Vasco McCoy Family Professor of Atmospheric Chemistry and Environmental Engineering. Fundamentally, this released study serves as a crucial foundation for understanding, and subsequently combating, the deleterious impacts of human-made atmospheric mercury concentration - which, as evidenced by the research, have soared sevenfold since the dawn of the modern era, thereby underscoring the urgent need for targeted policies and actions.
