Global boron cycle in the Anthropocene

This paper presents a revised and updated synthesis of the biogeochemical cycle of boron at the Earth's surface, where the largest fluxes are associated with the injection of sea-salt aerosols to the atmosphere (1.44TgB/yr), production and combustion of fossil fuels (1.2TgB/yr), atmospheric deposition (3.48TgB/yr), the mining of B ores (1.1TgB/yr), and the transport of dissolved and suspended matter in rivers (0.80TgB/yr). The new estimates show that anthropogenic mobilization of B from the continental crust exceeds the naturally occurring processes, resulting in substantial fluxes to the ocean and the hydrosphere. The anthropogenic component contributes 81% of the flux in rivers. The mean residence time for B in seawater supports the use of B-11 in marine carbonates as an index of changes in the pH of seawater over time periods of >1 Ma.