Organic contaminants phase distribution

Phase Distribution of Organic Contaminants in the Vadose Zone... 

FIGURE 14.2 Phase distribution of organic contaminants in the vadose zone. The solid arrows in the three-and four-phase models represent the equilibria taken into consideration in the equations of Table 14.3. 

The presence of a residual hydrocarbon phase in soils or sediments has been shown to increase the soil- or sediment-water distribution coefficients of poorly water-soluble organic contaminants [463,464]. Such petroleum-hydrocarbon-based phases have been shown to function as effective partition media for PCB congeners [467]. In general, sorption of contaminants by soils and sediments reduces their bio availability to microorganisms [468,469]. In this fashion, the... 

Surfactant-enhanced aquifer remediation for both sorbed pollutants and nonaqueous phase liquids is addressed in Chapters 9 through 13. Chapters 9 and 10 discuss the effects of surfactants on the sorption of organic contaminants to natural soil. Seok-Oh Ko and co-workers present data on the equilibrium distribution of pollutants in the presence of surfactants, whereas James Deitsch and Elizabeth Rockaway discuss how surfactants can increase... 

Organic contaminants in surface and subsurface systems are typically distributed by sorption between the aqueous phase and natural solid phases. The extent to which such contaminants are sorbed significantly affects their transport and distribution, their impacts on the ecosystem, and the selection of strategies for their removal. In cases of hydrophobic contaminants, sorption is governed by a complex combination of interactions associated with solute repulsion from the aqueous phase and solute attraction to particular solid phases and interfaces. The variety of thermodynamically driven and kinetic or mass-transport-controlled solute-sorbent interactions that may occur in natural systems were summarized by Weber et al. (1). 

Heberer Th, Gramer S, Stan HJ (1999b) Occurrence and distribution of Organic contaminants in the aquatic system. Part III Determination of synthetic musks in Berlin surface water applying solid phase microextraction (SPME) and gas chromatography-mass spectrometry in the full-scan mode. Acta Hydrochim Hydrobiol 21, 150-156. 

FIGURE 5 Organic contaminant distribution resulting from interactions between geoiogic heterogeneities and types of sources. Stippling represents dissolved or vapor phase contaminants. Solid black represents nonaqueous phase liquids (NAPLs). 

Karanfil and Kilduff studied the adsorption of two synthetic organic contaminants, trichloroethylene (TCE) and trichlorobenzene (TCB), on coal-based and wood-based granulated activated carbons. The activated carbon surface was modified by liquid-phase oxidation with nitric acid and by degassing in an inert atmosphere. The activated carbons were characterized by elemental analysis, surface area and pore-size distribution, and acid-base adsorption techniques. The adsorption isotherms were determined by equilibrating a known weight of the carbon sample with different concentrations of TCE and TCB solutions, and analyzing the solution by gas chromatography. 

The distribution between the aqueous (mobile) phase and the various sediment or soil (stationary) phases is one of the key parameters determining both transport and transformation of contaminants in subsurface systems. While the impact of adsorp-tion/desorption processes on subsurface transport is obvious and has been the subject of numerous investigations, their effects on transformation reactions of organic contaminants has been widely ignored in the past. It is important to realize that both the extent and the type of distribution of a contaminant between aqueous and solid phase(s) may determine its availability as well as its reactivity towards abiotic and microbial transformation reactions. For instance, it has been shown for a series of / ar -substituted n-alkyl-nitrobenzenes that the abiotic reduction of these compounds in natural sediments is strongly affected by the... 

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