Sulfur is one of the major elements in the environment. It exists in a variety of forms, including organic compounds, gases, and aqueous species. In the biological realm, sulfur is found in B vitamins, amino acids, and polysaccharides. There are also a number of sulfur-containing solids in the Earth, including pyrite, a common meteorite.
The main sources of sulfur in the atmosphere are soil and aquatic. Plants use it to produce a variety of organic compounds. Some of these compounds are metabolized to sulfur dioxide. Biologically, organic sulfur is allocated into a variety of different compounds, primarily proteins and secondary metabolites.
The chemistry of the Earth’s atmosphere and biosphere is complex. However, it is possible to trace the pathways by which sulfur is oxidized. For example, we can use stable isotope ratios to track sulfur’s movement in plants. These measurements are often performed with an EA-IRMS.
Sulfur isotopes in the atmosphere are composed of four stable isotopes and one radioactive isotope. The radioactive isotope isotopes have short half-lives (typically less than a minute). They are mainly used for medical applications.
Sulfur isotopic compositions in the atmosphere are largely normal within error. However, the behavior of the isotopes in the troposphere is not completely understood. This makes it difficult to interpret signals.
The origins of the D33S/D36S relationship are not well understood. However, their slopes can be correlated to thermal processes. Whether this relationship is related to thermochemical S-MIF processes or photochemical S-MIF processes remains unclear.