Mass, and carbon

June, decreased by late July, and then reached maximal levels during late stratification. These fluxes somewhat tracked mass and carbon deposition trends. 

Particle-bound Hg concentrations of sediment trap material exhibited strong seasonal response and accounted for the differences between the Hg flux and mass and carbon fluxes late in the summer. Particle-bound HgT content in spring and early summer was below 200 ng/g, but during late summer stratification it reached levels between 200 and 400 ng/g. Levels were highest following breakdown of thermal stratification and remained high throughout the fall (>350 ng/g). The elevated HgT levels after overturn most likely represented a shift from dissolved to particle-bound Hg. 

Using regression analysis to quantify the intrinsic cellulose, lignin, and ash fractions effects on a few products, MacKay and Roberts (1982) studied the pyrolytic behavior of 20 unmodified or native powdered Hgnocellulosic materials. Linear regression models for total mass and carbon yields of the products were developed, assuming each constituent fraction of the biomass was pyrolyzed independently. They concluded that char yield increased with substrate ca n content char yield from lignin content was found to be three times that of cellulose content. They did not study the gas nor tar composition in their experiments. In addition their particle sizes... 

The catalytic oxidation of ethane at 573-648 K was carried out at atmospheric pressure in a fixed bed flow reactor. Mbftures of ethane (4 mol%), oxygen (4-12 mol%), and helium (balance) were fed to the reactor with a residence time of 38 g. h/mol C2H6, using a catalyst load of 0.36 g, (particle size 0.25-0.42 mm) mixed with SiC bits (dilution 1 4 vA) to reduce the heat release per imit volume. Reactants and products were analysed by gas chromatography on a Vaiian 3400, equ ped with a thennal conductivity detector, using Porapak QS (3 m) and molecular sieve 13X (1 m) columns. In all reaction conditions, the mass and carbon balances were within 10012 %. 

Figure 1 shows the apparatus used in the cracking experiments. This assay apparatus is a modification of the LLNL modified Fischer assay apparatus described previously (17). It is used for a complete mass- and carbon-balanced assay under various heating schedules. For the cracking experiments, a second furnace and reactor were added. Both reactors were made of Type 304 stainless steel. A 165-pm stainless steel frit (6.3 mm high by 32 ram in diam) allowed gases but not shale to pass through the bottom of the reactors. 

Product formation in a fermenter can be characterized using the most common metric(s) such as titer (product concentration), yield (product per substrate), and rate (productivity). Equations 6.1-6.3 can be explicitly written for product formation, cell growth, and maintenance. These equations assume that the only fermentation products containing carbon are product, cell mass, and carbon dioxide, though there are often additional side products that can be taken into account to improve the accuracy of the model. For production of enzyme(s). Equation 6.1 can be used ... 

The measured solubilities were compared to literature values for polyethylene glycols of different molar mass and carbon dioxide [17, 18]. The results are presented in Fig. 15.10. It can be observed that for polyethylene glycols the molar mass does not have a strong influence on the solubility of CO2. Wiesmet observed that polyethylene glycols with molecular masses lower than 1500 g/mol... 

These isotope masses and their ratio of abundances are characteristic of carbon. Similarly, the isotopes of other elements that occur naturally have fixed ratios of isotopes, as given in Tables 47.1 and 47.2 at the end of the accompanying full text. 

The deterrnination of hydrogen content of an organic compound consists of complete combustion of a known quantity of the material to produce water and carbon dioxide, and deterrnination of the amount of water. The amount of hydrogen present in the initial material is calculated from the amount of water produced. This technique can be performed on macro (0.1—0.2 g), micro (2—10 mg), or submicro (0.02—0.2 mg) scale. Micro deterrninations are the most common. There are many variations of the method of combustion and deterrnination of water (221,222). The oldest and probably most reUable technique for water deterrnination is a gravimetric one where the water is absorbed onto a desiccant, such as magnesium perchlorate. In the macro technique, which is the most accurate, hydrogen content of a compound can be routinely deterrnined to within 0.02%. Instmmental methods, such as gas chromatography (qv) (223) and mass spectrometry (qv) (224), can also be used to determine water of combustion. 

Design criteria for carbon adsorption include type and concentration of contaminant, hydrauhc loading, bed depth, and contact time. Typical ranges are 1.4—6.8 L/s/m for hydrauhc loading, 1.5—9.1 m for bed depth, and 10—50 minutes for contact time (1). The adsorption capacity for a particular compound or mixed waste stream can be deterrnined as an adsorption isotherm and pilot tested. The adsorption isotherm relates the observed effluent concentration to the amount of material adsorbed per mass of carbon. 

A number of analytical methods have been developed for the determination of chlorotoluene mixtures by gas chromatography. These are used for determinations in environments such as air near industry (62) and soil (63). Liquid crystal stationary columns are more effective in separating m- and chlorotoluene than conventional columns (64). Prepacked columns are commercially available. ZeoHtes have been examined extensively as a means to separate chlorotoluene mixtures (see Molecularsieves). For example, a Y-type 2eohte containing sodium and copper has been used to separate y -chlorotoluene from its isomers by selective absorption (65). The presence of ben2ylic impurities in chlorotoluenes is determined by standard methods for hydroly2able chlorine. Proton (66) and carbon-13 chemical shifts, characteristic in absorption bands, and principal mass spectral peaks are available along with sources of reference spectra (67). 

Mass Spectrometer. The mass spectrometer is the principal analytical tool of direct process control for the estimation of tritium. Gas samples are taken from several process points and analy2ed rapidly and continually to ensure proper operation of the system. Mass spectrometry is particularly useful in the detection of diatomic hydrogen species such as HD, HT, and DT. Mass spectrometric detection of helium-3 formed by radioactive decay of tritium is still another way to detect low levels of tritium (65). Accelerator mass spectroscopy (ams) has also been used for the detection of tritium and carbon-14 at extremely low levels. The principal appHcation of ams as of this writing has been in archeology and the geosciences, but this technique is expected to faciUtate the use of tritium in biomedical research, various clinical appHcations, and in environmental investigations (66). 

SSIMS has been used in the TOP SSIMS imaging mode to study very thin layers of organic materials [3.32-3.36], polymeric insulating materials [3.37], and carbon fiber and composite fracture surfaces [3.38]. In these studies a spatial resolution of ca. 80 nm in mass-resolved images was achieved. 

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