An updated database of mercury emissions based on remote sensing, geochemical surveys and laboratory experiments

Mercury (Hg) represents one of the top ten chemical elements of significant public concern according to the World Health Organization. In 2013, the Minamata Convention was established aiming to reduce, control and possibly eliminate the use and release of mercury in the environment. The Global Mercury Assessment 2018 estimated annual global mercury anthropogenic emissions at around 2200 tons, while the contributions of primary natural sources (e.g., volcanic activity) appear significantly uncertain.

The aim of this study is to better constrain the origin and quantity of mantle-derived Hg by integrating the current available data from experimental petrology, geochemical analyses of sedimentary rocks the Hg anomaly of which is linked to large-scale magmatic events, chemical data of igneous rocks and Hg measurements from volcanoes and minerals by in situ and in satellite remote sensing.

The volcanic Hg is known to be characterized by an atmospheric residence period of 0.5-2 years (Bagnato et al., 2007) that allows it to distribute over the globe in the form of Hg⁰ and Hg²⁺.Inizio modulo The oxidation of Hg⁰ to Hg²⁺ causes mercury to dissolve into aqueous fluids. Part of Hg directly migrates to the atmosphere, precipitate into sedimentary basins and eventually long-term sequestrate in marine sediments (Grasby et al., 2019).

Sharp Hg anomalies have been detected in several stratigraphic layers with concentrations varying from 20 ppb (La Bédoule, France) to 90 ppm (Grane field, southern Viking Graben, Norwegian North Sea) to be representative of mass extinction anoxic and Large Igneous Province events (i.e. Greater Ontong Java and North Atlantic Igneous Province) such as Selli oceanic anoxic event and Palaeocene-Eocene Thermal Maximum, respectively (Grasby et al., 2019 and reference therein). The analyses of current Hg volcanic emissions along with stratigraphic geochemical anomalies highlight transport processes of deeply seated Hg of mantle origin (Shen et al., 2023). The interior of Earth is proposed to store about 10 ppb of Hg (BSE model, McDonough and Sun 1995) within a variety of igneous rocks both intrusive (peridotites, pyroxenites and gabbros) and effusive (basalts), the majority of which (about 5 ppb) is hosted by ophiolites (Canil et al., 2015).

Further, the current global volcanic Hg flux ranges from 0.6 ton·yr^-1 to over 1000 ton·yr^-1 (Edwards et al., 2021) pointing out the high volatility of mantle-derived Hg that is confirmed by the established link between volatile-driven LIP events and Hg anomalies distributed worldwide. Additional sources of natural Hg emissions are represented by hydrothermal mineralization (e.g. cinnabar) that testify the dominant role of SO₂ and H₂S emissions in volcanic and hydrothermal systems, respectively.

We will present a preliminary database of global Hg concentration that allows to model the deep Hg cycle based on the effect of magma-mineral element distribution and the role of pressure-temperature-mantle redox state through space and time.