Hydrospheric Cycle of Sulfur

Comparison of Figs 13-6a and 13-6b clearly demonstrates the degree to which human activity has modified the cycle of sulfur, largely via an atmospheric pathway. The influence of this perturbation can be inferred, and in some cases measured, in reservoirs that are very distant from industrial activity. Ivanov (1983) estimates that the flux of sulfur down the Earth s rivers to the ocean has roughly doubled due to human activity. Included in Table 13-2 and Fig. 13-6 are fluxes to the hydrosphere and lithosphere, which leads us to these other important parts of the sulfur cycle. 

The ocean plays a central role in the hydro-spheric cycling of sulfur since the major reservoirs of sulfur on the Earth s surface are related to various oceanic depositional processes. In this section we consider the reservoirs and the fluxes focusing on the cycling of sulfur through this oceanic node. 

Various workers have estimated the rate of pyrite formation. Berner (1972) summed the 

Ocean sediments Gypsum (CaS04) Pyrite (FeS2) 3 X 10  

Rest of lithosphere Pyrite (FeS2) Gypsum (CaS04) 2.4 X 10 ° 

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