Volatile loss mechanisms

R. J. Keeling, "The Effect of Volatile Loss During Analysis on the Mechanical Spectra of PhenoHc/Kraft Composites," Conference Proceedings, Society... 

Loss of compound by sorption onto the walls of the equilibration vessels, volatilization, and chemical or biological degradation also can affect the experimental determination of sorption coefficients. These potential loss mechanisms must be eliminated or accounted for if accurate sorption coefficients are to be determined. It is preferable to measure the concentration of the chemical in both phases and determine the mass balance to quantify potential loss mechanisms. Singh et al., (1990) found that Koc values obtained by measuring only the concentration in the solution phase were consistently higher than with those generated using a mass balance approach when the concentrations in both phases are measured. 

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... 

For the more volatile compounds such as HCB and the HCHs, evaporation will be the major loss mechanism over a relatively short period of time. For compounds with higher adsorption, such as DDT, residual quantities may... 

PAHs may also volatilize from soil. Volatilization of acenaphthene, acenaphthylene, anthracene, fluorene, and phenanthrene (low molecular weight PAHs) from soil may be substantial (Coover and Sims 1987 Southworth 1979 Wild and Jones 1993). However, of 14 PAHs studied in two soils, volatilization was found to account for about 20% of the loss of 1 -methyinaphthalene and 30% of the loss of naphthalene volatilization was not an important loss mechanism for anthracene, phenanthrene, fluoranthene, pyrene, chrysene, benz[a]anthracene, benzo[b]fluoranthene, dibenz[a,h]anthracene, benzo[a]pyrene, and indeno[1,2,3-c,d]pyrene (Park et al. 1990). 

Erie (0.2), and Ontario (1.1) and the percent loss of PCBs from these lakes due to sedimentation, volatilization, and outflow to other water bodies are summarized in Table 6-2 (Arimoto 1989 Eisenreich et al. 1992). Eor PCBs in the Great Lakes, sedimentation and volatilization were the primarily loss mechanisms, while the contribution of outflow was comparatively low. Eor Lake Michigan between 1980 and 1991, the calculated half-lives for the PCB homologs (assuming a first-order processes in years) due to both sedimentation and volatilization were di- (11), tri- (15), tetra- (10), penta- (12), hexa-... 

Therefore, it is expected that chlordane mobility will be enhanced at this site. Volatilization from soil is a major loss mechanism for chlordane the rate depends on such parameters as the soil... 

By comparison with spectrophotometric procedures, amperometric methods require somewhat greater skill. The solution must be well mixed and contain sufficient inert supporting electrolyte to reduce the ohmic potential gradients that interfere with the development of a uniform diffusion layer through which the electroactive species must diffuse in order to reach the working electrode. For accurate work, howevei care must also be taken to avoid volatilization losses of chlorine from solution by mechanical stirring. 

Bio-based PHAs (polyhydroxyalkanoates) show improved mechanical and environmental performance over PVC. Since some versions may be miscible with PVC, it is possible to produce blends that have superior plasticization, impact strength, and processability. Acting as a plasticizer in the PVC, the PHA provides low migration and extractability, volatile loss, and staining. Toughness can exceed that afforded by traditional MBS core/shell impact modifiers without compromising transparency or UV stability (Anon 2013a). 

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