Sources and contribution of terrigenous organic carbon to surface sediments in the Gulf of Mexico

Article Abstract:

A study of terrigenous organic matter in offshore surface sediments in the Gulf of Mexico revealed that offshore sediments originate from grassland soils in the Mississippi River drainage basin and that nearshore sediments derive from coastal forests and swamps. The study examined the chemical and stable isotope signatures of oxidation from lignins in the organic matter. It enabled researchers to differentiate between matter which originated from plants which use the C4 mechanism in photosynthesis and those which use the C3 mechanism. These results significantly expand knowledge of the nature and fraction of terrigenous organic carbon in marine sediments.

Composition, Marine sediments, Gulf of Mexico

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Global and hemispheric CO2 sinks deduced from changes in atmospheric O2 concentration

Article Abstract:

The changes in the temporal and spatial pattern of CO2 and O2 sources and sinks affect the north-south gradients in atmospheric CO2 concentrations and the O2/N2 ratio. Fossil-fuel burning, and the natural pumping of O2 and CO2 from the northern to southern hemisphere are some of the main sources and sinks causing the gradients. The exchange of the gases with land biota plus the ocean's uptake of excess anthropogenic CO2 are also responsible for the gradients. An analysis of O2/N2 data and its comparison with results of different studies are given.

Observations, Atmospheric carbon dioxide

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Dynamics of the carbon cycle

Article Abstract:

The atmospheric CO2 concentration varies constantly and these variations have a direct influence on global carbon cycle. The present and future climate of the Earth is dependent on CO2 concentration, a record of which is kept at Mauna Loa Observatory on Hawaii. A record of the 13C/12C ratio of stable carbon isotopes for determining the source of atmospheric CO2 is also kept. The direct anthropogenic effects and climate-induced perturbations of natural carbon cycle are studied.

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