Contaminant mixtures

Chlorine-enhancement may offer a partial solution. The addition of the chlorinated olefin TCE, PCE, or TCP to air/contaminant mixtures has recently been demonstrated to increase quantum yields substantially [1, 2, 6]. We recently have extended this achievement [3], to demonstrate TCE-driven high quantmn efficiency conversions at a reference feed concentration of 50 mg contaminant/m air not only for toluene but also for other aromatics such as ethylbenzene and m-xylene, as well as the volatile oxygenates 2-butanone, acetaldehyde, butsraldehyde, 1-butanol, methyl acrylate, methyl-ter-butyl-ether (MTBE), 1,4 dioxane, and an alkane, hexane. Not 1 prospective contaminants respond positively to TCE addition a conventional, mutual competitive inhibition was observed for acetone, methanol, methylene chloride, chloroform, and 1,1,1 trichloroethane, and the benzene rate was altogether unaffected. 

Abstract As the world has become ever more industrialized, an alarmingly large number of chemicals have entered as contaminant mixtures in waste, air, water, and soil. 

The contaminant mixture may have been altered by metabolism and subsequent partition into multiple environmental compartments that may be further changed by weathering or degradation. 

Thin-film and surface renewal evaporators are mostly applied to materials with medium to high viscosity, or to high-boiling contaminated mixtures. A typical thin-film evaporator employs a unique rotor with an array of discrete, plowlike blades attached to the rotor core. The blades transport the viscous concentrate or melt through the evaporator while simultaneously forming films to facilitate heat and mass transfer. 

Lower Explosive Limit (LEL) (Also known as Lower Flammable Limit). The lowest concentration of a substance that will produce a fire or flash when an ignition source (flame, spark, etc.) is present. It is expressed in percent of vapor or gas in the air by volume. Below the LEL or LFL, the air/contaminant mixture is theoretically too lean to burn. (See also UEL)... 

The ability to measure the isotopic composition of individual compounds can be used to determinate whether or not some contaminants are being affected by surface/subsurface processes. In comparison, monitoring the isotopic composition of total carbon can only provide information concerning the processes affecting the contaminant mixture as a whole rather than individual compounds. 

Aging of soil-contaminant mixtures prior to the addition of microbes reduced bio availability of such contaminants in laboratory studies and aging reduced herbicidal activity in various field studies. 

Under natural conditions, subsurface contaminants can be composed of single organic or inorganic compounds or mixtures thereof. These compounds have different properties, so they react differently, even if they reach the subsurface simultaneously. Therefore, knowledge of subsurface partitioning among individual components in a contaminant mixture is of major importance. 

Composition of Contaminant Mixture Administered to Male Rats... 

Eadon G et al Calculation of 2,3,7,8-TCDD equivalent concentrations of complex environmental contaminant mixtures. Environ Health Perspect 70 221-7, 1986... 

Because advanced oxidation processes are based on hydroxyl free-radical chemistry, chemical interactions are highly nonselective. Rates of destruction vary with such factors as the nature of the contaminant mixture, pH, concentration of contaminants, presence of scavengers, and inorganic nature. 

Is applicable to complex contaminant mixtures in a single integrated process. 

The Metcalf Eddy HYDRO-SEP soil washing system is an ex situ, water-based technology that separates contaminants from soil matrices. The HYDRO-SEP modular system uses screening and hydraulic classification processes to separate uncontaminated soil particles from a contaminated mixture. 

Additivity Toxicity of a contaminant mixture equal to the sum of toxic effects of the individual contaminants. See also Additive effects, Antagonism and Synergy. Volume 2(1,10). 

No reaction Contaminant layer determines bond strength Properties of adhesive-contaminant mixture determine bond strength ... 

Ankley GT, Mount DR. 1996. Retrospective analysis of the ecological risk of contaminant mixtures in aquatic sediments. Human Ecol Risk Assess 2 434-440. 

This pathway is supported by related results. For example, clean halogenations of carbanions with perhaloethanes, reported by De Waard and coworkerslllb for the chlorination of the a-carbanion of sulfolane with hexachloroethane, were demonstrated and worked out by Meyers coworkers112,113. They have the advantage over perhalomethanes in that they do not form dihalocarbenes as byproducts which lead to contaminated mixtures. Li and co workers themselves proved unequivocally that the addition reaction in step 3 readily occurs when more CF2=CC12 was added, their reaction was greatly accelerated. 

Fay M. 2005. Exposure to contaminant mixtures at US hazardous waste sites. In Aral MM, Brebbia CA, Maslia ML, Sinks T, editors, Environmental exposure and health. WIT transactions on ecology and the environment. Vol. 85. Southhampton (UK) WIT Press, p 227-232. 

Haws NW, Ball WP, Bouwer EJ. 2006. Modeling and interpreting bioavailability of organic contaminant mixtures in subsurface environments. J Contain Hydrol 82 255-292. 

Riley, R.G. and Zachara, J.M., Chemical Contaminants on DOE Lands and Selection of Contaminant Mixtures for Subsurface Science Research, DOE/ER-0547T, U.S. Government Printing Office, Washington, DC, 1992. 

Wormley, D.D., Ramesh, A., Hood, D.B. (2004). Environmental contaminant-mixture effects on CNS development, plasticity, and behavior. Toxicol. Appl. Pharmacol. 197 49-65. 

SAFETY PROFILE Mutation data reported. Can evolve toxic formaldehyde fumes when heated strongly or in contact with strong acids or acid fumes. Flammable liquid when exposed to heat, flame, or oxidizers. May explode when heated. Explosive in the form of vapor when exposed to heat or flame. Explodes on impact, possibly due to peroxide contamination. Mixtures with hydrogen peroxide are explosives sensitive to heat, shock, or contact with lead. 

Figure 2a shows a spectrum of the contaminated mixture combined with matrix and loaded onto a stainless steel surface. The contamination, while small by biochemical standards, was significant... 

Eadon, G., L. Kaminsky, J. Silkworth, K. Aldous, D. Hilker, P. O Keefe, R. Smith, J. Gierthy, J. Hawley, N. Kim and A. DeCaprio. Calculation of 2,3,7,8-TCDD equivalent concentrations of complex environmental contaminant mixtures. Environ. Health Perspect. 70 221-227, 1986. 

Riley, R. G. Zachara, J. M., "Nature of Chemical Contaminants on DOE Lands and Identification of Representative Contaminant Mixtures for Basic Subsurface Science Research," Office of Energy Research, U.S. Department of Energy, Washington, DC, 1992, DOE/ER-05A7T. 

DOE. 1992. Chemical contaminants on DOE lands and selection of contaminant mixtures for subsurface science research. Washington, DC U.S. Department of Energy. DE92-014826. 

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