Deep carbon transport

With respect to the sequestration of carbon in deep water, bioreactive COC is either caught up into aggregates that can sediment out (to fuel the deep ocean ecosystem) or is converted to less reactive LMWOC that can accumulate prior to deep transport by winter mixing (Fig. 7). The degree to which aggregation or accumulation is coupled to the production of DOC is a prime regulator of deep carbon transport. This balance between DOC production and accumulation may, in the words of Things tad et al. [117], allow deep carbon sequestration to indeed function very well . 

Under some circumstances transport processes other than fluid motion and molecular diffusion are important. One important example is sedimentation due to gravity acting on particulate matter submerged in a fluid, e.g., removal of dissolved sulfur from the atmosphere by precipitation scavenging, or transport of organic carbon from the surface waters to the deep... 

From a geochemical perspective, sinking POM is an important mechanism by which carbon and other elements are transferred from the sea surfece into the deep sea and onto the sediments. This transport is termed the biological pump and includes the sinking of inorganic particles that are of biogenic origin, namely calcium carbonate and silicate shells. 

The initial decrease in ocean uptake rate will eventually be reversed once enough time has passed (millennia) for meridional overturning circulation to recycle the subsurface waters. This will serve to inject CO2 below the mixed layer. Once the surface waters have been sufficiently acidified and are transported into the deep sea, they will eventually start dissolving sedimentary calcium carbonate. The resupply of alkalinity via this route will provide sufficient enhancement to ocean carbon uptake capacity to... 

Inorganic carbon pump The transport of carbon into the deep sea as a result of the sinking of detrital calcium carbonate formed by cococcolithophorids and foraminiferans. 

Two bioassays are employed to evaluate the effect of samples on terrestrial life forms. For gas samples, the plant stress ethylene test is presently recommended. This test is based on the well-known plant response to environmental stress release of elevated levels of ethylene (under normal conditions plants produce low levels of ethylene). The test is designed to expose plants to various levels of gaseous effluents under controlled conditions. The ethylene released during a set time period is then measured by gas chromatography to determine toxicity of the effluent. For liquid and solid samples, a soil microcosm test is employed. The sample is introduced on the surface of a 5 cm diameter by 5 cm deep plug of soil obtained from a representative ecosystem. Evolution of carbon dioxide, transport of calcium, and dissolved oxygen content of the leachate are the primary quantifying parameters. 

Despite the difficulty of interpreting 14C measurements on surface ocean water such measurements are of great interest. The net transport of excess 14C from the atmosphere to the sea depends on the difference between the 14C concentration in atmospheric C02 and that in the carbonate system at the sea surface. The decline in the atmospheric reservoir of excess 14C is therefore controlled by the 14C concentration at the sea surface. This in turn depends upon diffusion and advection into the deep sea. As the levels of excess 14C in the troposphere and the mixed layer of the sea begin to approach each other, mixing from the mixed layer of the sea into the deep sea will be the factor controlling the levels of excess 14C in the atmosphere. 

The probable absence of any pre-Martinsburg carbon concentrations precludes a clastic origin for the nodules. In any case, they are found in the uniform gray slate (originally mud), which was precipitated in the deep, still basin very slowly and are not associated with the clastic debris of the turbidite sequences. Turbulent conditions would have been needed for transport of such pebbles into the environment. 

An increase of C02 concentration in the atmosphere does not determine substantial fertilization of marine bioproductivity—but does lead to pH decrease. As temperature grows, C02 assimilation by the ocean decreases, but C02 emissions due to upwellings are reduced and the transport of excess carbon to deep layers of the ocean diminishes. The anthropogenically induced input of nutrients to the oceans through river run-off and deposition of atmospheric aerosols (especially nitrate and iron as elements of atmospheric aerosols) can affect bioproductivity. 

Due to bioproductivity processes, carbon is transported from the surface to deep layers of the ocean, where it is re-mineralized. This process maintains the inorganic carbon concentration gradient and preservation of C02 concentration in the atmosphere at a level which is (100-200) 106 lower than it would be without bioproductivity. 

A single neuron-like PC 12 cell was trapped in an etched glass (30 pm deep) pocket sealed against a PDMS channel layer (20 pm). Quantal release of dopamine (in transient exocytosis) from the cell as stimulated by nicotine was amper-ometrically detected with a carbon fiber electrode. The cells flow into the channels caused by the liquid pressure which was provided by a liquid height at the sample reservoir (e.g., 0.5-2 mm). To facilitate transport of cells in the microchannels, the cell density should not be higher than lOVmL. Serious cell adhesion occurred if the transport speed was low (as provided by liquid height below 0.5 mm),... 

Transport of shoal-water carbonates to the deep ocean and to the slope, and their dissolution require more extensive study. 

Heath K.C. and Mullins H.T. (1984) Open-ocean, off-bank transport of finegrained carbonate sediment in the northern Bahamas. In Fine-Grained Sediments Deep Water Processes and Facies (eds. D.A.B. Stow and D.J.W. Piper), pp. 199-208. Blackwell Scientific Publication, London. 

The use of fossil fuels to meet variable electrical demands may be limited in the future because of concerns about the price of natural gas and climate change. With any deep reduction in greenhouse gas emissions, carbon dioxide emissions will likely be limited to transportation, consumer products and other mobile applications - not stationary applications such as peak power production. While carbon dioxide from fossil power plants may be sequestered underground, such fossil power plants are likely to be uneconomic for the production of intermediate and peak electricity because of their high capital costs (MIT, 2007) and the difficulties in operating such plants with variable output. 

In the opinion of most investigators, in connection with the prevalent chloride-sulfuric acid composition of volcanogenic waters iron is transported in them mainly in the form of hydrochloric and sulfuric acid complexes. Only in deep hot springs containing a large amount of COj does iron presumably migrate in the form of bicarbonate complexes. Evidence for this is the formation of iron-bearing carbonate (ankerite) in zones below the limit of steam formation, while chiefly carbonates without iron (cdlcite) are formed in the near-surface zone. 

---