Mercury, a toxic metallic element that remains liquid at standard Earth temperature and pressure, poses a considerable threat to human health, particularly to children. Over the course of history, mercury has been extensively used in various human activities, including gold and silver mining, the production of vermilion pigment, felt production, and the manufacturing of devices such as thermometers and pressure gauges. Its use even extended to creating a mesmerizing mercury fountain for the Spanish Pavilion at the 1937 World Exhibition in Paris, which is now on display at the Fundació Joan Miró in Barcelona. Due to the significant industrial use of mercury throughout centuries, researchers have recognized the importance of accounting for its legacy in order to address its enduring toxic implications on humans and the environment.
Saul Guerrero and Larissa Schneider from the Australian National University have undertaken an ambitious research endeavor, aiming to create a comprehensive historical dataset on the global trade and production of mercury prior to the year 1900. The authors compiled primary source data from various archives, including governmental records, documents from local trade associations, newspaper reports on ship cargoes, and other relevant sources. By considering the net import/export balance and accounting for domestically produced mercury that remained within each country, the researchers were able to create a “mercury source pool” that encompasses the total historic anthropogenic mercury present within and outside the global mercury biogeochemical cycle. Their study, published in the Proceedings of the National Academy of Sciences, provides an unprecedented level of detail, allowing for a chronological and regional understanding of the environmental impact of legacy mercury.
Between 1500 and 1900, the use of mercury underwent a significant evolution, transitioning from a monopoly held by silver refiners in the New World to a vast global market that encompassed regions such as the western world, China, and India. Importantly, a substantial amount of anthropogenic mercury during this period was chemically sequestered, either in industrial products like felt and vermilion or as a byproduct in the form of calomel, a solid mercury chloride mineral, buried within a mineral matrix. Notably, China played a prominent role in the global mercury market, accounting for 20% of the market share in the 19th century as both a consumer and exporter. This implies that a significant portion of mercury was sequestered as vermilion, thereby not participating in the global mercury biogeochemical cycle.
Contrary to previous beliefs, gold rushes were found to contribute less to anthropogenic mercury deposits than anticipated. The authors cite the unexpectedly low use of mercury by gold miners in Australia, challenging the notion of gold mining as a major source of mercury emissions. They argue that previous overestimations of mercury emissions from gold and silver mining failed to consider the sequestered mercury in the form of calomel. Additionally, previous models neglected to account for significant mercury exports from California and China.
To facilitate more accurate future studies, the authors emphasize the need for comprehensive data on all mercury hotspots unrelated to precious metal mining. This would enable a more nuanced understanding of mercury emissions and losses across different industries and regions. Additionally, a better-documented historical estimation of mercury losses at production sites would be invaluable in refining future modeling efforts. By continuing to investigate the historical trade and production of mercury, researchers can gain insights into the legacy and environmental magnitude of this hazardous element, ultimately paving the way for effective mitigation strategies in the future.
The study conducted by Guerrero and Schneider sheds light on the historical trade and production of mercury, providing a comprehensive dataset that offers invaluable insights into its environmental impact. By challenging previous assumptions and uncovering the role of chemical sequestration, the authors have redefined our understanding of mercury emissions and losses. Moving forward, continued research in this field is crucial for developing comprehensive strategies to mitigate the toxic hazards posed by mercury.
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