Alkalinity, near sediment-water interface

In sUiciclastic sediments, the major source of carbonates is also primarily derived from benthic organisms. These include bivalves, other mollusks, sea urchins, and foraminifera. In these sediments there is often a zone of considerable under saturation produced near the sediment-water interface, where the oxidation of organic matter and bacterially produced sulfides can result in almost complete dissolution of sediment carbonate. Carbonates from organisms that burrow beneath this zone of intense diagenetic activity are often well preserved. In organic-rich siliciclastic sediments sulfate reduction may be very extensive, with the increase in alkalinity outweighing the decrease in pH, resulting in the precipitation of calcium carbonate. 

The study has been broken into two parts the first concentrates on describing diagenetic processes involving organic-matter decomposition and production or consumption of the nutrients SO ", NH4, alkalinity, and HP04. The second emphasizes the associated chemical behavior of Fe and Mn (Part II). Several types of measurements were made (1) seasonal pore water and solid-phase analyses, (2) direct measurement of solute fluxes out of the sediment, (3) rates of reaction as a function of depth and temperature, and (4) the abundance and composition of the fauna at each station. Taken together, these measurements provide one of the most detailed descriptions of controls on diagenesis near the sediment-water interface that is presently available. 

In summary, theoretical predictions indicate that Fe can be released by oxidation of FeS and FeS2 near the sediment-water interface. A destruction of alkalinity is associated with these reactions. The preliminary... 

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