Factors Influencing Volatilization

Plants also vary with respect to their uptake of Se and their capacity to accommodate large, potentially toxic concentrations (Rosenfeld and Beath, 1964 Sors et al., 2005). Wetland plants have been reported to volatilize Se (Pilon-Smits et al., 1999 Lin and Terry, 2003 Wu, 2004), and factors influencing volatilization have been reviewed by Terry and Zayed (1994). As stated above, it has been suggested tlrat changes in redox conditions in the rhizosphere of some plants may influence Se speciation in soil. Some species accumulate Se in Se-rich soils, but not to the extent reported for hyperaccumulators of toxic metals such as Cd and Ni (Banuelos et al., 1997 Prasad and Freitas, 2003 Srivastava et al., 2005). There are few recent studies of Se uptake from soils with normal or deficient levels of Se, as would be the probable situation in the case of radio-Se pollution, but the data have been reviewed comprehensively by Coughtrey et al. (1983) and Ihnat (1989). 

Volatilization. The susceptibility of a herbicide to loss through volatilization has received much attention, due in part to the realization that herbicides in the vapor phase may be transported large distances from the point of application. Volatilization losses can be as high as 80—90% of the total applied herbicide within several days of application. The processes that control the amount of herbicide volatilized are the evaporation of the herbicide from the solution or soHd phase into the air, and dispersal and dilution of the resulting vapor into the atmosphere (250). These processes are influenced by many factors including herbicide application rate, wind velocity, temperature, soil moisture content, and the compound s sorption to soil organic and mineral surfaces. Properties of the herbicide that influence volatility include vapor pressure, water solubility, and chemical stmcture (251). 

Zieve, R. and P.J. Peterson. 1981. Factors influencing the volatilization of selenium from soil. Sci. Total Environ. 19 277-284. 

Intermetallic compound formation may be observed as the result from the diffusion across an interface between the two solids. The transient formation of a liquid phase may aid the synthesis and densification processes. A further aid to the reaction speed and completeness may come from the non-negligible volatility of the component(s). An important factor influencing the feasibility of the reactions between mixed powders is represented by the heat of formation of the desired alloy the reaction will be easier if it is more exothermic. Heat must generally be supplied to start the reaction but then an exothermic reaction can become self-sustaining. Such reactions are also known as combustion synthesis, reactive synthesis, self-propagating high-temperature synthesis. 

This chapter is by no means a comprehensive portrait of risk management issues. Many exceedingly complex technical and policy matters, to say nothing of the often volatile political factors, influence decision-making in particular cases. Emphasis here is on certain technical issues that arise in the use of the risk information that has been the subject of this book. 

Due to the movement of the pesticides to the bed surface, air samples were taken to determine any volatilization and subsequent concentration In the air along the berm on the downwind side of the bed. In most Instances, the top of the berm was only about 12 vertical Inches above the bed surface. Spencer and Farmer ( ) have reviewed the literature on the transfer of pesticides Into the atmosphere. Even though pesticide volatility Is related to vapor pressure of the chemical, there are many factors Influencing the effective vapor pressure from soil and water surfaces. 

Several factors influence TGA data. Sample size and shape affect the rate and efficiency of decomposition. Powdered versus solid bulk samples will have different decomposition profiles due to the differing surface areas from which exiting decomposition products can leave the sample and be registered as mass losses. Similarly, the packing of the sample in the pan must be even and reproducible from run to run. Loosely distributed particles will heat more evenly and evolve volatilized products more evenly than mounded or densely packed samples. This can be especially important when looking at determinations of residual solvents, moisture or diffusion controlled losses such as plasticizer in the samples. 

Udayagiri, S. and Jones, R. L. (1992a). Flight behavior of Macrocentrus grandii Goidanich (Hymenoptera, Braconidae), a specialist parasitoid of European corn borer (Lepidoptera, Pyralidae) factors influencing response to corn volatiles. 

The main factors influencing CP remediation include temperature, the properties of the environmental matrix, the toxicity of CPs or other compounds, and the composition of indigenous or added microbial cultures (Crawford Mohn, 1985). Unlike many other xenobiotics, CPs undergo insignificant volatilization (Valo Salkinoja-Salonen, 1986 Lamar et al., 1990b Mueller et al., 1991a). The temperature, the contaminant bioavailability, the possible process amendments and the effects of additional contaminants are discussed below. 

The more advanced instrumental methods of analysis, including GC, for the detection and identification of expls are presented (Ref 90) Pyrolysis of expls in tandem with GC/MS was used for the identification of contaminant expls in the environment (Ref 108). Isomer vapor impurities of TNT were characterized by GC-electron capture detector and mass spectrometry (Ref 61). Volatile impurities in TNT and Comp B were analyzed using a GC/MS the GC was equipped with electron capture and flame ionization detectors (Ref 79). The vapors evolved from mines, TNT, acetone, toluene, cyclohexanone and an organosilicon, were analyzed by GC/MS (Ref 78). Red water produced by the sellite purification of crude TNT was analyzed by GC/MS for potentially useful organic compds, 2,4-dinitrotoluene, 3- and 4-sulfonic acids (Ref 124). Various reports were surveyed to determine which methods, including GC/MS, are potential candidates for detection of traces of TNT vapors emitted from land mines factors influencing transportability of TNT vapors thru soil to soil/air interface are dis-... 

No direct measurements of volatilization losses of any pesticide has been made following applications to forests. However, Grover et al. (7) recently measured the volatilization of 2,4-D after application as the isooctyl ester to a wheat field. This same low-volatile ester is used in forest vegetation control. The total vapor loss within 3 days after application of the isooctyl ester of 2,4-D was 20% of the amount applied. The applicability of these findings to volatilization of like pesticides in the forest environment will be discussed. We will indicate how volatilization in forests may differ from that reported from agricultural applications to open fields. The paper also will discuss the transfer of pesticides into the atmosphere from the standpoint of mechanisms involved, factors influencing rates of... 

In addition to in vivo and in vitro experimentation, mathematical models and quantitative structure-permeability relationship (QSAR) methods have been used to predict skin absorption in humans. These models use the physico-chemical properties of the test compound (e.g. volatility, ionization, molecular weight, water/lipid partition, etc.) to predict skin absorption in humans (Moss et al 2002). The models are particularly attractive because of the low cost and rapidity. However, because of the above-mentioned factors influencing dermal absorption, mathematical models are of limited use for risk assessment purposes. Since these models are currently not accepted by regulatory agencies involved in pesticide evaluations, they will not be further discussed in this chapter. 

Mosesman NH, Sidisky LM, Corman SD. 1987. Factors influencing capillary analyses of volatile pollutants. J Chromatorger Sci 25 351-355. 

The former variables affect the deposition of heat in the solid fuel and its transient temperature-profile, as well as the diffusion of the volatile pyrolysis products and their distribution and mixing with the surrounding atmosphere. The latter factors influence the nature and sequence of the primary and secondary reactions involved, the composition of the flammable volatiles, and, ultimately, the kinetics of the combustion. Consequently, basic study of the combustion of cellulosic materials or fire research has been channeled in these two directions. 

Volatiles composition is an important factor influencing the conversion of volatile nitrogen to NO and N O. The high CO content in biomass volatiles seems also to be partly responsible for the low levels of NjO emissions in biomass combustion. As the effect of most parameters is contrary a simultaneous reduction of NO and N O by primary measures is difficult, especially as other emission limits (e.g. for CO) have also to be captured. However, affecting devolatilization conditions to favor NH3 to HCN release and minimizing air-to-fuel ratio seems promising. 

I. Factors influencing production of volatile fatty adds from casein hydrolyzate. /. Dairy Sci. 48,287-292. 

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