About this Research Topic
Mercury is a volatile metal, which is of global interest to environmental chemistry researchers and societies, due to its toxicity and bioaccumulation in the food chain. In the last decade, mercury isotope geochemistry has been largely developed as a useful tool to trace the sources and processes of this metal in the environment. More interestingly, in recent years, geologists also showed that mercury can be a new tracer for understanding Large Igneous Province (LIP) events and Oceanic Anoxic Events (OAEs) in the Earth’s history. LIP events and OAEs are associated with significant ocean/climate changes, which affect the biosphere and often cause mass extinctions. Understanding the climate-ocean feedbacks during LIP events and OAEs is critical to revealing the evolution of the global environment and life. Climate-ocean feedbacks are difficult to constrain (or test) in most paleoenvironmental studies. Mercury can be a potential paleoceanographic proxy to track the climate impact on the paleomarine and terrestrial environments.
Through geological history, the primary source of mercury to the environment is volcanic emissions. Once emitted, mercury can undergo complex cycling between the atmosphere, land, and ocean, and then ultimately, burial in ocean sediments. Mercury enters the ocean primarily through (1) direct atmospheric deposition and (2) the runoff of mercury from terrestrial soil. The sources and emission rates of Hg to the environment were not always in a steady-state in the Earth’s history. Signals of transient Hg emission events, such as those related to OAEs and LIP events, have been documented in ocean sediments. Total Hg (THg) concentration, THg and total organic carbon ratios (THg/TOC), and Hg isotopic signals can jointly be used to define whether the enrichment of Hg was caused by direct atmospheric deposition and/or erosion of terrestrial soil during OAEs and LIP-related mass extinction events. The Earth has experienced a large number of OAEs and LIP events, which would presumably result in a dramatic change in sedimentary Hg levels. The application of sedimentary Hg in constraining OAEs, LIP events, and climate-ocean feedbacks remains an active area of research. Even more recently, Hg records have been examined in terrestrial records and used as a tool to link marine and terrestrial extinction processes driven by large volcanic eruptions.
This Research Topic aims to attract Original Research Articles, Reviews, Data Reports, or Brief Research Reports using mercury as a geochemical proxy to understand ancient volcanic emissions, oceanic anoxic events, and ocean/climate feedbacks in Earth history. Contribution of field and model studies on Hg (and Hg isotopes) covering the following themes are especially encouraged:
• Ocean productivity and redox conditions during LIP events and OAEs;
• Climate-ocean feedbacks during LIP events and OAEs;
• Volcanic or non-volcanic causes of mass extinctions;
• Ocean productivity and redox conditions during the recovery from mass extinctions;
• Terrestrial records and linking terrestrial and marine extinction events.
Keywords: mercury, volcanism, ocean, climate, geochemistry
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