Figure 5. Natural (pre-industrial) global sulfur reservoirs, fluxes and turnover times. Major reservoirs are underlined, pool sizes and fluxes are given in Tg (1012 g) S and Tg S yr-1. Turnover times (reservoir divided by largest flux to or from reservoir ) are in parentheses. To convert Tg S to moles S, multiply by 3.1 x 1010.

The lithosphere is the largest reservoir, with turnover times of ~109 yr. Ocean waters, where sulfate is a major consituent, and ocean sediments, where sulfide and sulfate are the major forms, have similar reservoir sizes and turnover times of >106 yr.

Carbonyl sulfide (COS) is the longest-lived gaseous sulfur compound. Large particulate fluxes of seasalt and terrestrial dust are added to the atmosphere, but their abundance is restricted to altitudes of < 1km. The particles have residence times of days, close to rainout times, reflecting their control by precipitation. Some volcanic emissions are injected into the stratosphere, where they have much longer residence times.

Note that the net pre-industrial flux of sulfur (as sulfate aerosol) is from the ocean to land.