Dolomite: occurrence, evolution and economically important associations

Neoproterozoic variations in the C-isotopic composition of seawater: stratigraphic and biogeochemical implications.

3.3.7. Nucleation of Calcium Carbonate 357 3.4. Dissolution Reactions 359 3.4.1. Calcite Dissolution Kinetics 359 3.4.2. Aragonite Dissolution 360 3.4.3. Magnesian Calcite Dissolution Kinetics 360 3.5. Biominerals and Nanophase Carbonates 361 3.5.1. General Considerations 361 3.5.2. Biomineralization 361 3.5.3. Biogeochemistry, Geomicrobiology 361 3.5.4. Nanophase Carbonates 362 3.6. Calcium Carbonate−Organic Matter Interactions 363

Calcium Carbonate Formation and Dissolution

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Atmospheric methane and global change

Present-day production of CaCO3 in tne world ocean is calculated to be about 5 billion tons (bt) per year, of which about 3 bt accumulate in sediments; the other 40% is dissolved. Nearly half of the carbonate sediment accumulates on reefs, banks, and tropical shelves, and consists largely of metastable aragonite and magnesian calcite. Deep-sea carbonates, predominantly calcitic coccoliths and planktonic foraminifera, have orders of magnitude lower productivity and accumulation rates than shallow-water carbonates, but they cover orders of magnitude larger basin area. Twice as much calcium is removed from the oceans by present-day carbonate accumulation as is estimated to be brought in by rivers and hydrothermal activity (1.6 bt), suggesting that outputs have been overestimated or inputs underestimated, that one or more other inputs have not been identified, and/or that the oceans are not presently in steady state. One “missing” calcium source might be groundwater, although its present-day input is probably much smaller than that of rivers. If, as seems likely, CaCO3 accumulation presently exceeds terrestial and hydrothermal input, this imbalance presumably is offset by decreased accumulation and increased input during lowered sea level: shallow-water accumulation decreases by an order of magnitude with a 100 m drop in sea level, while groundwater influx increases because of heightened piezometric head and the diagenesis of metastable aragonite and magnesian calcite from subaerially exposed shallow-water carbonates.

Production and accumulation of calcium carbonate in the ocean: Budget of a nonsteady state

Dissolution of Recent platform carbonate sediments in marine pore fluids

Controls on marine carbonate cement mineralogy: review and reassessment

Rates and controlling variables for methanotrophic oxidation of methane at a northeastern Illinois landfill with pumped gas recovery were examined in a field study from June to December 1995. Cover materials consisted of a simple clay-topsoil sequence without geomembranes. Through use of a static enclosure (closed chamber) technique supplemented by soil gas concentration profiles and field incubations, the study concentrated on proximal (near gas recovery well) and distal (between well) sites established in 1994. A personal computer-based three-dimensional finite−difference model was also developed which includes both gaseous mass transfer (CH4, CO2, O2) and microbial CH4 oxidation. Mass transfer is modeled through a modified chemical potential gradient within a cubic network of nodes; a strict mass balance for each gas is maintained through successive timesteps. Methane-oxidizing conditions with no net CH4 emissions to the atmosphere persisted into full winter conditions in December, 1995. Rates of CH4 o...

Elizabeth A. Burton

Papers

Dissolution of Recent platform carbonate sediments in marine pore fluids

Controls on marine carbonate cement mineralogy: review and reassessment

Kinetics of Methane Oxidation in a Landfill Cover Soil: Temporal Variations, a Whole-Landfill Oxidation Experiment, and Modeling of Net CH4 Emissions

Landfills as atmospheric methane sources and sinks

The role of pH in phosphate inhibition of calcite and aragonite precipitation rates in seawater