Volatilization significance

As a result of volatilization, significantly elevated indoor air levels of trichloroethylene can occur in homes that use water supplies contaminated with trichloroethylene (Andelman 1985a). The transfer of trichloroethylene from shower water to air in one study had a mean efficiency of 61% which was independent of water temperature (McKone and Knezovich 1991). The study authors concluded that showering for 10 minutes in water contaminated with trichloroethylene could result in a daily exposure by inhalation comparable to that expected by drinking contaminated tap water. Another study using a model shower system found that, in addition to shower spray, shower water collecting around the drain could be an important source of volatilized trichloroethylene, and the fraction volatilized could be affected by spray drop size and flow rate (Giardino et al. 1992). 

Because acrylonitrile is readily volatile, significant releases to air may occur during acrylonitrile production and use (Hughes and Horn 1977 Miller and Villaume 1978). Kayser et al. (1982) estimated that 11,790 kkg/yr (metric tons per year) of acrylonitrile was released from these sources, accounting for 87% of all acrylonitrile released to the... 

In spite of its low vapor pressure, endrin has been found to volatilize significantly (20-30%) from soils within days after application (Nash 1983). In air, endrin will be primarily absorbed to particulates which may be re-entrained to soil or surface water via wet or dry deposition. Laboratory studies have indicated that a predominant mechanism for the transformation and degradation of endrin in air under field conditions is via photochemical reactions and rearrangements to yield primarily endrin ketone, with minor... 

The amounts volatilized in 10 days were extremely low in most cases. Dicamba was the only herbicide exhibiting significant volatilization and that only in the presence of high water evaporation. Apparently the insecticide carbaryl, has the potential to volatilize significantly from the soil with or without water evaporation, particularly when it is present near the soil surface. The reference insecticide, lindane, will appreciably volatilize when it is present near the soil surface, but its volatility decreases markedly when present within the entire 0 - 10 cm depth. Volatilization of the other insecticides will be essentially insignificant due either to their rapid degradation rate or low Kh-... 

The modeling data based on nonsteady-state equilibrium predict that volatilization of 4-nitrophenol will be insignificant (Yoshida et al. 1983). The Henry s law constant (H) values for these two compounds (see Table 3-2) and the volatility characteristics associated with various H values (Thomas 1982) can be used to predict that volatilization from water will not be important. The dissociation constant (pKa) values of the two compounds (see Table 3-2) indicate that significant fractions of these nitrophenols will be dissociated at pHs above 6. Since ionic species do not volatilize significantly from water, the ionization may further limit volatilization. 

It is noteworthy that in practice even the reverse of the above may occur. Often it is necessary to analyse compounds that are too volatile. Significant losses during the preliminary treatment of the sample (e.g., extraction, removal of the solvent), due to this volatility, may introduce errors into the quantitative evaluation. Analysis of volatile carboxylic acids in biological samples is an example. Conversion of these compounds into less volatile derivatives is therefore advantageous from the viewpoint of both GC proper and preliminary isolation of the compounds and sample treatment. 

Nursery pollination systems are examples of reciprocal mutualism between pollinators and plants, in which the female pollinators oviposit on the ovaries of plants and the hatched larvae feed on pollinated fruits and seeds. At least 13 nursery pollination systems have been identified.88 Floral volatiles significantly contribute to attracting... 

It has been shown that the PTV injector is a very useful technique for large-volume injection, especially for the analysis of a dirty sample. Because the vaporization of the solvent is carried out at a low temperature, nonvolatile matrix constituents remaining in the liner will not contaminate the GC column. However, the PTV injection technique is less suited when analyzing volatile compounds because only components with volatility significantly below that of the solvent are trapped in the cold liner, unless liners packed with a selective adsorbent is used [4]. 

Elevated risk of death from cancer and from lung cancer was reported in a retrospective cohort study of 6,635 male workers employed for more than 15 years during the period 1970-1985 in seven factories in China (Liu et al. 1997). The main chemical exposure was to coal tar pitch volatiles. Significantly... 

A similar study was carried out in a coke plant in Zabrze, Poland (Bieniek 1997). The concentrations of 1-naphthol and 2-naphthol in the urine of 102 workers from the coke plant were compared with those of 36 controls not occupationally exposed to coal tar volatiles. Significant differences were found between the concentrations of 1- and 2-naphthols in the urine of exposed and unexposed workers (P<0.05). The correlation between the concentrations of naphthols in urine and napthalene in air were statistically significant (P<0.001). 

PROBABLE FATE photolysis, sensitized process may be important, reacts in the vapor phase with photochemically produced hydroxyl radicals at an estimated half-life of 6.2 hr, suggesting that this reaction is the predominate chemical removal process oxidation photooxidation half-life in air 5.2-51.7 hrs hydrolysis not an important process, first-order hydrolytic half-life >197,000 yrs volatilization probably an important process, can volatilize significantly from soil surfaces from which it is sprayed, particularly moist soil surfaces, volatilization half-life from a model pond, river, and lake is 18-26,3.6-5.2, and 14.4-20.6 days respectively sorption probably an important process biological processes bioaccumulation is an important process... 

A typical trayed column develops a pressure drop of 190 to 250 mm Hg. This system changes relative volatility significantly with temperature. At the column top, with a pressure of 45 mm Hg absolute, the relative volatility between cyclohexanone and cyclohexanol is 2.1. At the bottom of the trayed column, with a pressure of 295 mm Hg absolute, the relative volatility is reduced to about 1.4. It is apparent that the difficulty of separation... 

The term volatility is often used to qualitatively describe a chemical s vapor pressure. Although there are no universally agreed-upon cutoffs, chemicals described as volatile typically have vapor pressures exceeding 1 atm at the boiling point of water (100 °C). Examples of volatile chemicals include solvents, such as TCE, and hydrocarbons present in gasoline, such as benzene. Semivolatile chemicals typically have vapor pressures lower than 1 atm at 100 °C but nevertheless can volatilize significantly at environmental temperatures. Examples include naphthalene (found in mothballs) and other polycyclic aromatic hydrocarbons (PAHs). Chemicals whose vapor pressures are negligible are often called nonvolatile examples include most salts. 

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