Particulate carbon oceans

An alternative method for the determination of particulate organic carbon in marine sediments is based on oxidation with potassium persulfate followed by measurement of carbon dioxide by a Carlo Erba non-dispersive infrared analyser [152,153]. This procedure has been applied to estuarine and high-carbonate oceanic sediments, and results compared with those obtained by a high-temperature combustion method. 

Measurements of radionuclides are also used to determine removal mechanisms and controls for carbon and metal cycling in the ocean. For example, the removal of Th from the euphotic zone is closely coupled to the vertical flux of particulate organic carbon. The deficiency of Th with respect to its parent—near-surface waters is used to estimate the export flux of particulate organic carbon (Buesseler, 1991). Measurements of Th and in the upper water column provided the primary data relahng to particulate carbon fluxes during JGOFS. 

Carbon in Intermediate and Deep Ocean Carbon in Ocean Sediments Marine Particulate Carbon Flux... 

Anita A. N., et al. (2001) Basin-wide particulate carbon flux in the Atlantic Ocean regional export patterns and potential for atmospheric CO2 sequestration. Global Biogeochem. Cycles 15, 845-862. 

Most of the atoms of Th that are produced from decay readily attach to particles and are removed from solution. In the surface ocean there are enough particles formed to create a deficiency in Th activity from that to be expected at secular equilibrium with At steady state, the depth-integrated deficiency of the activity concentrations of Th in the euphotic zone is equal to its flux from the surface ocean on particles. If one then knows the Th C ratio in the particles, the flux of particulate carbon can be calculated. An example of Th measurements in the surface waters of the subtropical Pacific (see Fig. 6.11) indicates that difference in Th activity from that expected at secular equilibrium (equal to the activity of U) is small but readily measurable. 

Llewellyn, C.A. and R.F. C. Mantoura (1996) Pigment biomarkers and particulate carbon in the upper water column compared to the ocean interior of the northeast Atlantic. Deep-Sea Res. 43, 1165-84. 

Antia, N.A., Koeve, W., Fischer, G, Blanz, T., Schulz-Bull, D., Scholten, J., Neuer, S., Kremling, K., Kuss, J., Peinert, R., Hebbeln, D., Bathmann, U., Conte, M., Fehner, U. and Zeitschel, B., 2001. Basin-wide particulate carbon flux in Atlantic Ocean Regional export patterns and potential for atmospheric CO sequestration.- Global Biogeochemical Cycles, 15, 845-862. 

Owing to the stability of the uranyl carbonate complex, uranium is universally present in seawater at an average concentration of ca. 3.2/rgL with a daughter/parent activity ratio U) of 1.14. " In particulate matter and bottom sediments that are roughly 1 x 10 " years old, the ratio should approach unity (secular equilibrium). The principal source of dissolved uranium to the ocean is from physicochemical weathering on the continents and subsequent transport by rivers. Potentially significant oceanic U sinks include anoxic basins, organic rich sediments, phosphorites and oceanic basalts, metalliferous sediments, carbonate sediments, and saltwater marshes. " ... 

The quantity of primary production that is exported from the upper ocean is said to be equivalent to new production (18, 19) New primary production is that associated with allocthonous nutrients (i.e., those upwelled or mixed into the euphotic zone or input via rivers and rain). In order for steady state to be maintained, an equivalent flux out of the euphotic zone is required. Earlier studies (19) suggested that sediment-trap measurements of particulate organic carbon (POC) flux were equivalent to new primary production however, recently it has become clear that these measurements probably represent only a... 

As shown in Fig. 10-13, there is also a flux of O2 produced during net photosynthesis from the ocean to the atmosphere and an export flux of particulate and dissolved organic matter out of the euphotic zone. For a steady-state system, new production should equal the flux of O2 to the atmosphere and the export of organic carbon (Eppley and Peterson, 1979) (when all are expressed in the same units, e.g., moles of carbon). Such an ideal state probably rarely exists because the euphotic zone is a dynamic place. Unfortunately, there have been no studies where all three fluxes were measured at the same time. Part of the difficulty is that each flux needs to be integrated over different time scales. The oxygen flux approach has been applied in the subarctic north Pacific (Emerson et al, 1991) and subtropical Pacific (Emerson et al, 1995, 1997) and Atlantic (Jenkins and Goldman, 1985). The organic carbon export approach has... 

Fig. 10-15 Organic carbon fluxes with depth in the water column normalized to mean annual primary production rates at the sites of sediment trap deployment. The undulating line indicates the base of the euphotic zone the horizontal error bars reflect variations in mean annual productivity as well as replicate flux measurements during the same season or over several seasons vertical error bars are depth ranges of several sediment trap deployments and uncertainities in the exact depth location. (Reproduced with permission from E. Suess (1980). Particulate organic carbon flux in the oceans - surface productivity and oxygen utilization, Nature 288 260-263, Macmillan Magazines.)...

The distribution of dissolved, total particulate, and living particulate organic carbon in the surface (0-300 m) and deep ocean (>300 m) are summarized in Table 10-6. Recent analytical advances have greatly improved our understanding of the distributions of DOC in the ocean (Hedges and Lee, 1993). The important aspects of this compilation are ... 

To a first approximation the deep ocean distributions shown in Fig. 10-20 can be reproduced if the particulate material dissolving in the deep sea has the ratio of 1 mol CaCOs to 4 mol organic carbon (Broecker and Peng, 1982). 

Suess, E. (1980). Particulate organic carbon flux in the oceans-surface productivity and oxygen utilization. Nature 288, 260-263. 

Buesseler KO, Ball L, Andrews J, Benitez-Nelson C, Belastock R, Chai F, Chao Y (1998) Upper ocean export of particulate organic carbon in the Arabian Sea derived from thorium-234. Deep-Sea Res II 45 2461-2487... 

Charette MA, Moran SB (1999) Rates of particle scavenging and particulate oiganic carbon export estimated using as a tracer in the subtropical and equatorial Atlantic Ocean. Deep-Sea Res II 46 885-906... 

Figure 8. Partition coefficients (Kd) for Th and Pa and the fractionation factor (F) between Th and Pa plotted as a function of the opal and calcium carbonate percentage in settling particulate material. Note the tendency for the Kd for Th to increase with increasing carbonate fraction and decrease with increasing opal fraction. Pa shows the opposite behavior so that F increases with low opal fraction or high carbonate fraction. This plot is modified from Chase et al. (in press-b) but excludes the continental margin data also shown in that study and instead focuses exclusively on open-ocean sites.

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