FOAM sites

One major paper attacking the problem of the relationship between the preservation of calcium carbonate in shallow anoxic marine sediments and their chemistry was by Aller (1982). The study was conducted at sites in Long Island Sound. The calcium carbonate content of the sediments decreased with increasing water depth. At the shallow FOAM (Friends of Anaerobic Muds) site shell layers associated with storms resulted in irregular variations in the carbonate content of the sediment. Ca2+ loss from the pore waters, indicative of calcium carbonate precipitation, was found only at the FOAM site below -20 cm depth. During the winter, elevated Ca2+ to CL ratios were observed near the sediment-water interface... 

The rates of sulfate reduction at the different sites were similar, but concentrations of reactant products varied owing to differences in exchange rates, which were controlled by the extent of benthic community development. More highly developed infaunal communities occurred at the deeper sites. The aggregation of shells into layers by storms also helped preserve shell material in the shallow FOAM site. 

Certain smaller suboxic environments within larger estuarine systems also show unbioturbated sections of sediments. Because of their generally rapid rate of accumulation, the cosmogenic nuclide Be (53 d half-life) may be used in addition to °Pb for sediment accumulation rate assessment for the more recently deposited sediments. Similarly the pattern of bomb-produced Cs in sediments can serve as a chronometer. In addition, radiocarbon ages commonly can be obtained from calcareous fractions in the accumulating sediment. All these approaches were used at the FOAM site in Long Island Sound by Krishnaswami et al. (1984). 

Aerosol products are hermetically sealed, ensuring that the contents caimot leak, spill, or be contaminated. The packages can be considered to be tamper-proof. They deUver the product in an efficient manner generating Httie waste, often to sites of difficult access. By control of particle size, spray pattern, and volume deUvered per second, the product can be appHed directiy without contact by the user. For example, use of aerosol pesticides can minimize user exposure and aerosol first-aid products can soothe without applying painful pressure to a wound. Spray contact lens solutions can be appHed directiy and aerosol lubricants (qv) can be used on machinery in operation. Some preparations, such as stable foams, can only be packaged as aerosols. 

Natural Waters. Many water systems have a natural tendency to produce foam upon agitation. The presence of poUutants exacerbates this problem. This was particularly severe when detergents contained surfactants that were resistant to biodegradation. Then, water near industrial sites or sewage disposal plants could be covered with a blanket of stable, standing foam (52,59). However, surfactant use has switched to biodegradable molecules, which has gready reduced the incidence of these problems. 

Silicone foam thus formed has an open ceU stmcture and is a relatively poor insulating material. Cell size can be controlled by the selection of fillers, which serve as bubble nucleating sites. The addition of quartz as a filler gready improves the flame retardancy of the foam char yields of >65% can be achieved. Because of its excellent dammabiUty characteristics, siUcone foam is used in building and constmction fire-stop systems and as pipe insulation in power plants. Typical physical properties of siUcone foam are Hsted in Table 10. 

The water reaction evolves carbon dioxide and is to be avoided with solid elastomers but is important in the manufacture of foams. These reactions cause chain extension and by the formation of urea and urethane linkages they provide sites for cross-linking, since these groups can react with free isocyanate or terminal isocyanate groups to form biuret or allophanate linkages respectively (Figure 27.5). 

The effeet of temperature satisfies the Arrhenius relationship where the applieable range is relatively small beeause of low and high temperature effeets. The effeet of extreme pH values is related to the nature of enzymatie proteins as polyvalent aeids and bases, with aeid and basie groups (hydrophilie) eoneentrated on the outside of the protein. Einally, meehanieal forees sueh as surfaee tension and shear ean affeet enzyme aetivity by disturbing the shape of the enzyme moleeules. Sinee the shape of the aetive site of the enzyme is eonstrueted to eoirespond to the shape of the substrate, small alteration in the strueture ean severely affeet enzyme aetivity. Reaetor s stirrer speed, flowrate, and foaming must be eontrolled to maintain the produetivity of the enzyme. Consequently, during experimental investigations of the kineties enzyme eatalyzed reaetions, temperature, shear, and pH are earefully eontrolled the last by use of buffered solutions. 

Groupe TBI is investing about FFr3m to build a 15,0001/ y aromatic polyester polyols plant on a greenfield site at Issoire, near Lyons. The novel, patented process uses postconsumer waste bottles made from PETP as feedstock. PU and modified PIR foams made using the APPs have excellent fire performance and good dimensional stability. GROUPE TBI... 

Ethylhexanol can be epoxidized with 1-hexadecene epoxide. This additive also helps reduce or prevent foaming. By eliminating the need for traditional oil-based components, the composition is nontoxic to marine life, biodegradable, environmentally acceptable, and capable of being disposed of at the drill site without costly disposal procedures [44]. 

Several surfactants were studied in ambient-pressure foam tests, including alcohol ethoxylates, alcohol ethoxysulfates, alcohol ethoxyethylsulfonates, and alcohol ethoxyglycerylsuUbnates [210]. Surfactants that performed well in the 1-atm foaming experiment were also good foaming agents in site cell and core flood experiments performed in the presence of CO2 and reservoir fluids under realistic reservoir temperature and pressure conditions. 

J. J. Kilbane, II, P. Chowdiah, K. J. Kayser, B. Misra, K. A. Jackowski, V. J. Srivastava, G. N. Sethu, A. D. Nikolov, and D. T. Wasan. Remediation of contaminated soils using foams. In Proceedings Volume. 10th Inst Gas Technol Gas, Oil Environ Biotechnol Site Remediation Technol Int Symp (Orlando, FL, 12/8-12/10), 1997. 

This Web site provides a collection of science experiments you can do at home, including making a red cabbage pH indicator, removing tarnish from silver, and making things fizz and foam. 

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