Carbonate contamination, amount variation

It is clear from the analysis of gaseous reactor effluent that there were variations in the extent of organic contaminant combustion. Some carbon dioxide was observed in the effluent gas from the reactor in most of the tests. However, with fluorobenzene at 300°C we estimate that only about 2.5 % of the fluorobenzene was combusted based on the amount of CO2 observed. This is in contrast to the 30 to 50 % combustion of dibromoethane, dibromoethene, dichloroethane,... 

Variation of the content of impurities in the different CNT preparations [21] offers additional challenges in the accurate and consistent assessment of CNT toxicity. As-produced CNTs generally contain high amounts of catalytic metal particles, such as iron and nickel, used as precursors in their synthesis. The cytotoxicity of high concentrations of these metals is well known [35, 36], mainly due to oxidative stress and induction of inflammatory processes generated by catalytic reactions at the metal particle surface [37]. Another very important contaminant is amorphous carbon, which exhibits comparable biological effects to carbon black or relevant ambient air particles. 

Fig. 10.5. Models showing Sr-0 isotope variation during mixing between upper crustal rocks (full triangle), mantle peridotite (star) and mantle-derived basaltic magma (full square). Solid line represents the trend of magma contamination by upper crust. Dotted line is mantle contamination trend. Dashed line represents contamination trend of Roman Province magmas by sedimentary carbonates. Numbers along the lines indicate amounts of crustal end-member. For discussion, see text.

In the current investigation we have extended these types of experiments to cover the influence of sulfur on the catalytic properties of iron. Since C2H4 does not readily undergo decomposition on iron surfaces we elected to use the decomposition of CO/H2 and CO/C2H4/H2 mixtures at 600 0 as the probe reactions in this work. For this purpose, both the amount of solid carbon and the gas phase product distribution arising from the decomposition of these mixtures have been used to monitor variations in the catalytic behavior of both pure and sulfur contaminated iron particles. 

The estimated arnounts show how difficult it is to measure such an amount of carbon accurately. Combe et al. (1999) reported that this amount adsorbed could not be measured by mass balance (total amount adsorbed about 10 pg on a 28.7 10 trF membrane section (Clark (1999)). This amount is very close to the estimated monolayer adsorption value. The organic carbon was desorbed from the membranes with NaOH and then measured with UV. Despite the results being very close to the calculated monolayer value, this method is subject to errors from (i) the contamination of the NaOH with membrane components, (ii) the erratic concentration detetmination using UV (the selective adsorption of UV absorbing compounds could lead to an overestimation), and (ill) possibly the modification of UV absorbance characteristics of the organics due to the extreme pH variation. 

Similar results are obtained in the cases of soil contamination by other agrochemicals. Figure 10.2 presents the variation of enthalpy with time, obtained for samples of Red Latosol soil that contained certain ammount of glucose as degradable source of carbon and variable amounts of herbicide diquat. These results are presented as the integral heats vs. time. The curves show that the increase of the applied agrochemicals doses produces the decreases in activity generated by microbes. 

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