Chapter 2 Early Diagenesis and Marine Pore Water

Abstract

Publisher Summary This chapter discusses the degradation of organic matter by a suite of redox processes in marine sediments, with an emphasis on the effect on pore water chemistry, the modeling of concentration profiles, and the calculation of the concomitant fluxes across the sediment, water interface. Labile organic compounds are decomposed at more moderate rates and become buried in the sediment. The accumulation of organic matter in the sediments is a function of: (1) primary production in the photic zone above; (2) the total sedimentation rate; and (3) the porosity of the sediment. Decomposition of organic matter occurs mainly by micro-biota under oxic, suboxic, and anoxic conditions. As a result of the decomposition of carbonic acid, may be either produced or consumed, bicarbonate is formed. This affects the pH of the interstitial water. In addition to the role played by the degradation of organic matter, other reactions may also have an impact on changes in pore-water chemistry. Sediments consist of a mixture of solid particles immersed in pore waters. Studies of pore-water chemistry are used to estimate the consumption of oxygen, nitrate, and sulphate, as well as to estimate the methane production involved in the breakdown of organic matter. Finally, the chapter also presents several models that have been applied to measure profiles for oxygen, nitrate, manganese, sulfate, sulfide, methane, bicarbonate, phosphate, and silica in pore water.