Mass balance of carbon

Table IV. Mass Balance of Carbon in Dry Oxidation, Expressed as Mass % Relative to Original Mass of Carbon (Distillation) and Available Mass of Carbon (Final Products)...

The mass balance for carbon during dry oxidation of bitumen in our calorimeter can be calculated from the above results in combination with some of our chemical results for oxidized samples reported elsewhere ( 2). This mass balance is summarized in Table IV, where the following relationships have been used ... 

Expired air. For 14C-labeled chemicals, the tracer carbon may be incorporated in vivo into carbon dioxide, a possible metabolic product. Therefore, when the position of the radiolabel indicates the potential for biological instability, a pilot study to collect expired air and monitor its radioactivity content should be conducted prior to initiating a full-scale study. Expired air studies should also be performed in situations where the radiolabel has been postulated to be stable but analyses of urine and feces from the toxicokinetic study fail to yield complete recovery (mass balance) of the dose. 

The gas channels contain various gas species including reactants (i.e., oxygen and hydrogen), products (i.e., water), and possibly inerts (e.g., nitrogen and carbon dioxide). Almost every model assumes that, if liquid water exists in the gas channels, then it is either as droplets suspended in the gas flow or as a water film. In either case, the liquid water has no affect on the transport of the gases. The only way it may affect the gas species is through evaporation or condensation. The mass balance of each species is obtained from a mass conservation equation, eq 23, where evaporation/condensation are the only reactions considered. 

Khalil, M.A.K. and Rasmussen, R.A. Global sources, lifetimes and mass balances of carbonyl sulfide (OCS) and carbon disulfide (CS2) in the earth s atmosphere, Atmos. Environ., 18(9) 1805-1813, 1984. 

Other products can be produced in fermentative bacteria but the central feature of all these pathways is the strict maintenance of the oxidation-reduction balance within the fermentation system. This gives rise to another important tool in assessing fermentation pathways—a mass balance of the substrate and products. The amount of carbon, hydrogen and oxygen in the fermentation products (including cells) must correspond to the quantities in the substrate utilised. 

In this paper we have brought together much of the information that is presently available on certain pollutants in Narragansett Bay (Rhode Island, U.S.A.) in an attempt to develop annual mass balances for carbon, nitrogen and phosphorus as well as some heavy metals (Mn, Cd, Pb, Cu) and petroleum hydrocarbons under conditions of recent input. We cannot pretend complete knowledge of the quantities or behavior of any of these substances in the Bay, but they have all been subjected to considerable study and it seemed that it would be interesting and instructive to compare the effectiveness of this one system as a trap for a variety of different materials. 

Fig. 9. Mass balances of (a) Carbon and (b) Nitrogen in a pile of decomposing kelp, Ecklonia maxima. Figures are g carbon or nitrogen derived from 100 g carbon or nitrogen kelp. Note that 69.8% of the carbon is lost from the microcosm but only 2.3% of the nitrogen.

At the ecosystem level, the principal goals of the biogeochemical process approach are to trace the mass flow of carbon and nutrients along particular process paths and to estimate mass balances. If we reduce the scale of interest from the ecosystem to the community, the focus shifts to descriptions of the extracellular biochemical pathways that process specific DOM components (Fig. 5). For this overview, we restrict our discussion to general observations and conjectures about various classes of substrates rather than attempt to review each of the pathways shown in Fig. 5. 

The first step of this study is to optimize the desorption experiments particularly the mass balance of the desorption process expecially the separation between the solutes and C02. The first step of the process is the adsorption at atmospheric conditions of VOC (butyl acetate and/or xylenes). Two adsorbants were chosen to realize a comparison activated carbon and zeolithe. We studied the desorption characteristics as a function of pressure, temperature and C02 flow rate. 

The VUV-initiated oxidation of 2,4-dichlorophenol (2,4-DCP) led to an excellent cr mass balance of 98% and to the diminution of the total organic carbon content (TOC) of the solution (Fig. 7-14). Clearly, the TOC diminution kinetics was much slower than that of the substrate oxidation. It was shovm that the observed kinetics of the TOC degradation of 2,4-DCP was strongly dependent on the electric input power of the Xe2 excimer lamps used (Baum and Oppenlander, 1995). 

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