Organic sulfur as part of the sulfur cycle from early diagenesis through catagenesis

Abstract

During the diagenetic stage the sulfur–organic matter (S-OM) chemical environment is dominated by the aquatic media. The pH variations of the interstitial water and the redox potential prevailing control the various sulfur species hence their chemical activity. Some of the more polar organic matter being hydrophilic is exposed to the reduced active sulfides (e.g. S_x^(-2), HS^-,RS^-) that are very active nucleophiles. In the last four years we have extended the research to decipher the mechanisms controlling these reactions. The more hydrophobic organic matter can be exposed to similar reactions in the presence of phase transfer catalysts (PTC). However, under these conditions the actual environment for the reaction is the organic phase. Since the diagenetic stage is considered to pertain to ambient to mild increased temperatures range all laboratory simulations indicate equilibration controlled mechanisms for both sulfur introduction into the (OM) as well as nucleophilicity controlled exchange. The only kinetic controlled reactions were either due to thermal stress or easily removed (substituted) groups most of which are rare in young sedimentary OM. We consider for these transformations the sulfate as un-reactive sulfur specie.

Additional details