Volatile metal emissions from volcanic degassing and lava-seawater interactions at Kīlauea Volcano, Hawai’i

Abstract:

Volcanoes represent one of the largest natural sources of metals to Earth’s surface. Emission of these pollutants and/or nutrients has important implications for the biosphere. We report and compare the gas and particulate chemistry, including trace metals, of the substantial magmatic (≥ 200 kt/day SO₂) and lava-seawater interaction (laze) plumes from the 2018 eruption of Kīlauea, Hawai’i. The magmatic plume contains abundant volatile chalcophile metals and metalloids such as Se, whereas the laze plume contains abundant seawater components (e.g. Cl), yet concentrations of Cu are 10⁵ times higher than typical seawater. High-temperature speciation modelling of the magmatic plume as it is emitted at the lava-air interface emphasises chloride’s critical role in metal and metalloid complexation during degassing. In the laze plume, concentrations of moderately (Cu, Zn, Ag) to highly volatile (Bi, Cd) metals are elevated compared to seawater. These metals have an affinity for chloride and are derived from late-stage degassing of distal lava flows, potentially facilitated by elevated chloride (as HCl gas) formed as seawater boils. Understanding these processes yields important insights into the environmental impacts of volcanism in the present day and geological past.