Sulfur, abundance global

H2O, CO, OCS, and SO have spatially and temporally variable abundances. Variations in the abundances of water vapor, CO, and sulfur gases are of particular interest because they result from the solar UV-diiven photochemistry that maintains the global sulfuric acid cloud cover. 

This global cycling of sulfur is closely linked to other geochemical cycles as well. In particular, it is tied to the abundance of atmospheric oxygen. 

The potential use of sulfur isotope abundances in identifying reductive processes and the origin of sulfide minerals is discussed in Chapter 6.2. Although the majority of laboratory experiments have been carried out with reducing bacteria, there have been a sufficient number of studies with other bacteria to indicate that stable isotopes can play a role in elucidating the whole sulfur cycle. Indeed attempts have been made to use isotopic and mass balances to estimate global sulfur shifts with time (Holser and Kaplan, 1966). 

The diversity of polysaccharides at the molecular level is due to the simple basic elements from which they are built. Abundant and ubiquitously available carbon (dioxide), oxygen, hydrogen, and H2O, with contributions from phosphorus (P), sulfur (S), and nitrogen (N) at different states of oxidation (global distribution of C 9.5%, H 63%, O 25.5%, N 1.4%), are the building blocks for on-demand formation and transformation of natural carbohydrates, primarily by green plants and algae. The polysaccharides... 

The SO2 abundance in Venus atmosphere decreases at high altitudes due to the formation of the global sulfuric acid cloud layer (45-70 km), which is produced through SO2 photolysis via the net photochemical reaction ... 

Carbonyl sulfide is the most abundant sulfur gas in the global background atmosphere because of its low reactivity in the troposphere and its correspondingly long residence time. It is the only sulfur compound that survives to enter the stratosphere. (An exception is the direct injection of S02 into the stratosphere in volcanic eruptions.) In fact, the input of OCS into the stratosphere is considered to be responsible for the maintenance of the normal stratospheric sulfate aerosol layer. 

Dimethylsulfide (DMS) is the most abundant volatile sulfur compound in sea water and constitutes about half of the global biogenic sulfur flux to the atmosphere. Studies of the concentration of DMS in the ocean have shown that average surface water concentrations may vary by up to a factor of 50 between summer and winter in mid and high latitudes. Furthermore, there are large-scale variations in DMS concentration associated with phytoplankton biomass, although there are generally poor correlations between local oceanic DMS concentrations and the biomass and productivity of phytoplankton (due to differences between plankton species in ability to produce DMS). 

Sulfur has four stable isotopes , gS, j S, which are -95.02%, -0.75%, -4.21% and 0.02% abundant, respectively. Sulfur is ubiquitous in the global environment and major sulfur reservoirs include sulfate in the oceans, evaporites, sulfide ore deposits, and organic sulfur compounds. Sulfur isotope abundance variations are shown in Figure 11. 

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