Organic compounds burial

There are several other processes that modify the Cl-Br systematics in formation waters. These include the incongruent dissolution of halite, the incongment dissolution of chloride salts other than halite, differential rates of molecular diffusion, and the introduction of bromide from organic compounds (Land and Prezbindowski, 1981). Br/ Cl ratios in excess of those normally associated with subaerial evaporation may result from the incongment dissolution of Na-K-Mg-Cl mineral assemblages during progressive burial (Hanor, 1987 Land et al., 1995). 

Sediments are important compartments for many organic contaminants in the aquatic environment, in particular for hydrophobic POPs such as PAHs and PCBs. Sediments have been recognised as important sinks for these compounds but with the reduction in levels of them in water, the question arises of whether the older highly contaminated sediments will function in the future as secondary sources of the compounds or whether burial by recent, cleaner sediment will prevent exchange with the water phase. This will depend on the strength of turbulence/bioturbation and on anthropogenic influences such as dredging. 

Due to the complexity of organic matter sources in estuaries and the aforementioned problems associated with making only bulk measurements to constrain them, the application of chemical biomarkers has become widespread in estuarine research (see review, Bianchi and Canuel, 2001). The term biomarker molecule has recently been defined by Meyers (2003, p. 262) as compounds that characterize certain biotic sources and that retain their source information after burial in sediments, even after some alteration. This molecular information is more specific and sensitive than bulk elemental and isotopic techniques in characterizing sources of organic matter, and further allows for identification of multiple sources (Meyers, 1997, 2003). 

The insolubility of iron sulfides offers the potential for the burial and mineralization of large amounts of sulfur in sediments. However, sulfur shares with nitrogen a complex organic chemistry, but organosulfur compounds have not always been widely studied. Nevertheless the discovery of large fluxes of DMS to the atmosphere has revealed just how important organosulfur compounds can be. 

---