The Budget and Cycle of Earth's Natural Chlorine

Abstract

Earth's chlorine, retained when the planet was formed from the Solar nebula, is contained largely in three reservoirs: the mantle (99.6%), the crust (0.3%), and the oceans (0.1%). Only oceanic chlorine is readily mobile, cycling among the lower and middle atmosphere, the pedosphere, freshwaters, and the cryosphere. Inter-reservoir chlorine fluxes are estimated for all transitions of interest; by far the most important on a mass basis is the injection of seasalt from the oceans to the atmosphere, and its return to the planetary surface by wet and dry deposition.