Mercury, the only known metallic element that is liquid at standard Earth temperature and pressure, poses a significant hazard to humans. Although it is a cool element, it is toxic and can cause harm, particularly to children. Throughout history, numerous human activities have involved the use of mercury, including gold and silver mining, the production of vermilion pigment, felt production, and the manufacture of various devices. The extensive industrial use of mercury over the centuries has led to its accumulation in the environment, posing a persistent toxic threat to humans and other forms of life.
Constructing a Comprehensive Historical Dataset
Researchers Saul Guerrero and Larissa Schneider from the Australian National University embarked on a mission to create a comprehensive and country-by-country historical dataset on the global trade and production of mercury before 1900. Their study, published in the Proceedings of the National Academy of Sciences, aims to shed light on the legacy of mercury and its environmental impact with unprecedented detail.
To compile their dataset, Guerrero and Schneider delved into primary sources such as government records, documents from local trade associations, newspaper reports on ship cargoes, and various other sources. They meticulously collected data on the mercury market, considering the net import/export balance of each country and accounting for domestically produced mercury that remained within the country. This compilation of data, referred to as the “mercury source pool,” provides a comprehensive overview of the total historic anthropogenic mercury within and outside the global mercury biogeochemical cycle.
The use of mercury has evolved significantly from the 1500s to the 1900s. Initially monopolized by silver refiners in the New World, mercury transformed into a global market that encompassed the western world, China, and India. The study highlights the substantial amount of anthropogenic mercury before 1900 that was chemically sequestered, either as industrial products like felt and vermilion or as an industrial byproduct in the form of calomel, a solid mercury chloride mineral often buried within a mineral matrix.
The Role of China
China, as both a consumer and exporter of mercury, played a significant role in the global mercury market during the 19th century. The study reveals that China alone accounted for 20% of the global market share. Considerable amounts of mercury were chemically sequestered as vermilion, and therefore were not part of the global mercury biogeochemical cycle. This finding challenges the notion that gold rushes, previously believed to contribute significantly to anthropogenic mercury deposits, were major drivers. The authors point to the unexpectedly low use of mercury by gold miners in Australia as evidence contradicting this commonly held belief.
The study challenges previous models that overestimated mercury emissions from gold and silver mining activities. It argues that these models failed to account for sequestered mercury in the form of calomel, leading to inflated emission estimates. Furthermore, the previous models did not adequately consider major mercury exports from California and China, which further skewed the data.
The authors contend that future studies must consider all mercury global hotspots, not solely those related to precious metal mining. Additionally, a better-documented historical estimate of mercury losses at production sites is crucial for more accurate assessments in the future.
The groundbreaking study by Guerrero and Schneider provides a comprehensive analysis of the historical trade and production of mercury, shedding light on the legacy of this toxic element. Their dataset offers unprecedented details and boundaries on the environmental impact of legacy mercury. By challenging established beliefs and highlighting the role of chemical sequestration, the study paves the way for more accurate assessments of mercury emissions and environmental hazards. Understanding the historical context of mercury usage is vital in developing effective strategies for managing and mitigating its impact on humanity and the environment.
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