Our results have important implications for the role of volcanism in the global atmospheric Hg budget. They show that terrestrial volcanism, generally assumed to be a source of Hg to the atmosphere, may also have a significant sink effect on atmospheric Hg through the co-emission of Hg-scavenging aerosols. While this process would tend to reduce the global atmospheric Hg pool, it would also tend to enhance Hg deposition and the potential for Hg exposure in volcanic regions inhabited by human populations.