How Volcanic Emissions Affect Global Mercury Cycle

The impact of human activities on the environment has been a subject of concern for many years. One area of particular interest is the increase in atmospheric mercury levels and its potential toxicity. Recent research from the Harvard John A. Paulson School of Engineering and Applied Sciences has shed light on the role of volcanic emissions in the global biogeochemical mercury cycle. This article will explore the insights gained from satellite observations and chemical transport modeling, highlighting the impacts of volcanic emissions on the mercury cycle.

Understanding Mercury Emissions

Before delving into the impacts of volcanic emissions, it is essential to understand the sources of mercury in the atmosphere. Human activities, such as coal burning, waste incineration, industrial processes, and mining, are the primary contributors to the current high levels of atmospheric mercury. However, volcanic emissions also play a significant role in the release of mercury into the environment. Volcanos are the largest single natural emitter of mercury, making them an essential factor to consider in assessing the overall mercury cycle.

The Challenge of Mercury Detection

Measuring mercury in the atmosphere poses a significant challenge due to its low concentrations. In a cubic meter of air, there may be only a nanogram of mercury, making it virtually impossible to detect directly using satellite observations. To overcome this challenge, researchers have developed alternative methods to estimate mercury emissions indirectly.

The Role of Sulfur Dioxide as a Proxy

One such method involves using sulfur dioxide as a proxy for mercury emissions. Sulfur dioxide is a major component of volcanic emissions and can be easily detected using satellite observations. By measuring the ratio of mercury to sulfur dioxide in volcanic gas plumes, researchers can estimate the amount of mercury attributed to volcanic eruptions. This information, coupled with atmospheric modeling, allows for a better understanding of how volcanic emissions impact the global mercury cycle.

Estimating Pre-Industrial Mercury Levels

To establish a baseline for mercury levels before human activities significantly influenced the environment, researchers reconstructed pre-anthropogenic atmospheric mercury levels. The study estimated that before human intervention, the atmosphere contained approximately 580 megagrams of mercury. In contrast, independent research conducted in 2015 suggested that the atmospheric mercury reservoir had increased to around 4,000 megagrams, nearly seven times larger than the natural condition estimated in this study.

Impact of Volcanic Emissions on Atmospheric Mercury

While volcanic emissions contribute to the overall mercury levels in the atmosphere, their direct impact on ground-level concentrations is relatively small in most areas. The study found that volcanic emissions are responsible for only a few percent of ground-level concentrations worldwide. However, certain regions, such as South America, the Mediterranean, and the Ring of Fire in the Pacific, experience higher levels of volcanic emissions, making it more challenging to separate the contributions of natural and human-induced mercury.

Tracking the Movement of Mercury

Understanding the movement of mercury from volcanic emissions is crucial in assessing its overall impact on the environment. The researchers utilized the GEOS-Chem atmospheric model to simulate the transport of mercury across the globe. The model revealed that while mercury can mix into the atmosphere and travel long distances from its source, volcanic emissions alone are not the primary drivers of ground-level concentrations. Human emissions from various sources, including coal-fired power plants, waste incineration, industry, and mining, contribute significantly to the levels of mercury observed on the ground.

Importance of Correcting for Natural Variability

In regions heavily influenced by volcanic emissions, such as Hawaii, natural variability in mercury emissions becomes a crucial factor to consider. Understanding the extent of this variability allows for more accurate assessments of the long-term trends in mercury levels. By distinguishing between natural and human-induced mercury, policymakers and researchers can develop strategies to reduce mercury emissions effectively.

Implications for Human Health

Mercury, particularly in its methylmercury form, is a potent neurotoxicant that bioaccumulates in fish and other organisms, including humans. The increased concentrations of atmospheric mercury due to human activities have raised concerns about the potential health risks associated with the consumption of contaminated fish. By understanding the natural mercury cycle driven by volcanic emissions, researchers and policymakers can establish a baseline for reducing human-induced mercury emissions and protecting human health.

The research conducted at the Harvard John A. Paulson School of Engineering and Applied Sciences has provided valuable insights into the impacts of volcanic emissions on the global biogeochemical mercury cycle. By utilizing satellite observations and chemical transport modeling, researchers have established a baseline for pre-industrial mercury levels and identified the contributions of volcanic emissions. These findings underscore the importance of reducing human-induced mercury emissions and highlight the need for ongoing monitoring and research to protect both the environment and human health.