Carbon demand

In this process, diamond forms from graphite without a catalyst. The refractory nature of carbon demands a fairly high temperature (2500—3000 K) for sufficient atomic mobiUty for the transformation, and the high temperature in turn demands a high pressure (above 12 GPa 120 kbar) for diamond stabihty. The combination of high temperature and pressure may be achieved statically or dynamically. During the course of experimentation on this process a new form of diamond with a hexagonal (wurtzitic) stmcture was discovered (25). 

Carbon and Phosphorus Burial Efficiencies. The estimate of diatom carbon demand (12-15 g/m2 per year) is consistent with the flux of carbon to the sediment surface. With sediment-trap fluxes corrected for resuspension, we measured a total annual deposition flux of 12.5 g of C/m2. In comparison, Eadie et al. (24) obtained 23 g of C/m2 for a 100-m station, based on three midsummer metalimnion deployments. Of our total, 83% of the carbon was associated with diatoms, and the primary diatom carbon flux was 10.3 g of C/m2. Thus, about 15-30% of the diatom carbon was regenerated in the water column during sedimentation. Approximately 10% of the diatom flux reached the sediment surface encapsulated in copepod fecal pellets the remaining 90% was unpackaged. 

Calculated from data in Bertilsson and Tranvik (1998) by assuming 7.6 h or noontime sun per day. h BCD, bacterial carbon demand. 

Field studies point in a similar direction field comparisons of peptide hydrolysis rates and amino acid turnover in coastal sediments showed that amino acid production could exceed uptake by a factor of approximately 8 (Pantoja and Lee, 1999). A comparison of potential enzyme activities and sedimentary amino acid and carbohydrate inventories in sediments from the Ross Sea also showed that potential hydrolysis rates on time scales of hours should in theory rapidly deplete sedimentary amino acid and carbohydrate inventories (Fabiano and Danovaro, 1998). In deep-sea sediments, Poremba (1995) also found that potential enzyme activities in theory could exceed total sedimentary carbon input by a factor of 200. Finally, Smith et al. s (1992) investigation of potential hydrolysis rates and amino acid uptake in marine snow demonstrated that the particle-associated bacteria were potentially producing amino acids far in excess of their own carbon demand. 

Thingstad TF, Lignell R (1997) Theoretical models for the control of bacterial growth rate, abundance, diversity and carbon demand. Aquat Microb Ecol 13 19-27... 

The chemical half-life of DMSP in seawater is >8 years (Dacey and Blough 1987), which results in high abiotic stability under natural conditions (moderate temperatures and pH). Therefore, most of the DMSP removal is through enzymatic processes. In the microbial food web, dissolved DMSP has many fates and several recent reviews on the microbial pathways and involved mechanisms have been published (Bentley and Chasteen 2004 Kiene et al. 2000 Lomans et al. 2002 Yoch 2002). They all show that DMSP can be readily used in a complex network of enzymatic conversions. This versatility indicates that this single compound is of major importance for the nutrition of the bacterial community. Indeed, several studies have shown that DMSP alone can contribute 1 to 15% of the total bacterial carbon demand in surface waters. Moreover, DMSP assimilation can satisfy most, if not all the, sulphur demand of marine bacteria (Kiene and Linn 2000 Simo et al. 2002 Zubkov et al. 2001). Since the focal point of this section is the quantification of DMSP removal, only the overall effects of the main pathways originating from DMSP (Fig. 1) will be discussed here. 

Thingstad, T. F., and LigneU, R. (1997). A theoretical approach to the question of how trophic interactions control carbon demand, growth rate, abimdance and diversity. Aquat. Mkrob. Ecol. 13, 19-27. 

The precursor DMSP is often present at concentrations an order of magnitude higher than DMS. These concentrations are so high that DMSP could support 1-13% of the bacterial carbon demand in surface waters, making it a... 

The use of activated carbon, or activated charcoal as it is sometimes called, dates back as far as 2000 B.C. when it was first used by the ancient Egyptians. The term activated" refers to the chemical or thermal treatment given to the carbon to increase its adsorptive capacity. Estimates for activated carbon demand in the U.S. vary but a nominal value for current U.S. usage would be 10 kg/yr. 

Consequently, in this procedure, an uncertainty in the carbon demand is given. This means that, depending on the operating conditions, the carbon content of the final product may vary significantly. 

Measurements at sea suggest that the total amount of carbon taken up by the whole phytoplankton community to form new CaCOs is rather small compared to the total amount of carbon taken up to form new organic matter. Both calcification carbon demand and photosynthetic carbon demand have recently been measured on a long transect in the Atlantic Ocean and the ratio of the two was found to average 0.05 or, in other words, for every 20 atoms of carbon taken up by phytoplankton, only one on average was taken up into solid CaCOs. 

Fig. 1. World activated carbon demand in 1000 metric tons [11]...

Stockline index > 32 carbon demand varying/burden basicity varies/furnace filling irregularities. 

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