Surface waters, volatile aromatics

The rate of volatilization will also increase with an increase in temperature, ten Hulscher et al. (1992) studied the temperature dependence of Henry s law constants for three chlorobenzenes, three chlorinated biphenyls, and six polynuclear aromatic hydrocarbons. They observed that within the temperature range of 10 to 55 °C, Henry s law corrstant doubled for every 10 °C increase in temperature. This temperature relationship should be corrsidered when assessing the role of chemical volatilization from large surface water bodies whose temperatines are generally higher than those typically observed in groimdwater. 

On the other hand, the quality of the permeate is independent of the feed concentration. Whereas in seawater desalination reverse osmosis is strongly affected by the osmotic pressure of the (highly) concentrated feed solutions, membrane disdilation can handle even higher salt concentrations without a substantial decrease in membrane performance. The removal of volatile organic components (VOCs). such as chlorinated hydrocarbons or aromatics, from an aqueous solution is another application. These volatile contaminants are often present in very low concentrations in surface water or industrial effluent. 

Benzene, toluene, and their derivatives enter the atmosphere by various mechanisms such as controlled emissions from consumer industries, volatilization from waste dumps and landfill sites, intentional spraying and dusting, and from automobile exhaust. Since such compounds are moderately soluble in water, they are probably washed out of the atmosphere with rainfall, deposited in surface waters, and then evaporated back into the atmosphere. Although this recycling process may be a significant source of aromatic... 

Only insufficient information is available concerning the exchange of volatile aromatics between the atmosphere and water. It can be reliably assumed that rainfall precipitates volatile aromatics from the atmosphere, whereupon they are introduced directly or indirectly into surface water. The occurrence of aromatic fractions from automobile exhaust gases in Lake Zurich and the river Glatt, mentioned above, provides evidence that such an exchange actually does take place [64, 65] for other water ways see [67,68] and a later section [see also 291, 292]. 

There are indications that gasoline fractions from oil spillages disappear from the sea completely within six hours by evaporation [69] this in contrast to higher boiling fractions. Of the approx. 6 million t petroleum fractions introduced into the sea per annum, approx. 600,000 t originate from natural sources [5, 6], approx. 600,000 t are precipitated from the atmosphere and some 1.9 million t originate from rivers. However, the proportion of volatile fractions is not known [6]. Volatile aromatics may perhaps account for about one-fifth of these quantities or - in relation to their vapour pressure - less. Near the surface of the sea one finds 1-10 ppb of natural hydrocarbons, less in deeper waters [6]. Organic pollutants may increase the absorption of hydrocarbons in water [13]. Aromatic hydrocarbons are the relatively best water soluble components of crude oil and petroleum fractions. Therefore they have an increased mobility in waters. 

Surface waters contain in addition to other organic compounds relatively small quantities of volatile aromatics, and these are important mainly when they change... 

Table 3. Concentrations of volatile aromatics in American surface, tap, and drinking waters ... 

Sauer, T.C., Jr, Sackett, W.M. Jeffrey, L.M. (1978) Volatile liquid hydrocarbotrs in the surface coastal waters of the Gulf of Mexico. Marine Chem., 1, 1-16 Seifert, B. Abraham, H.-J. (1982) Indoor air concentratiotrs of benzene and some other aromatic hydrocarbons. Ecotoxicol. environ. Saf, 6, 190-192 Shah, J.J. Heyerdahl, E.K. (1988) National Ambient Volatile Organic Compounds (VOCs) Data Base Update (EPA 600/3-88/0 lOA), Research Triangle Park, NC, Environmental Protection Agency, Atmospheric Sciences Research Laboratory ... 

The results for other conditions for polystyrene pyrolysis were reported. For example, pyrolysis on different catalysts was shown to lead to modifications of the yield of specific components in the pyrolysate. During the pyrolysis of PS on solid acid catalysts, the increase of contact time and surface acidity enhanced the production of ethylbenzene. Pyrolysis in the presence of water increases the yield of volatile products and that of monomer [30]. Studies on the generation of polycyclic aromatic hydrocarbons (PAHs) in polystyrene pyrolysates also were reported [36]. It was demonstrated that the content in PAHs in polystyrene pyrolysates increases as the pyrolysis temperature increases. The analysis of the end groups in polystyrenes with polymerizable end groups (macromonomers) was reported using stepwise pyrolysis and on-line methylation [46]. 

Properties Colorless, volatile, mobile liquid. Hygroscopic, aromatic odor, burning and sweet taste. Bp 34.5C, fp -116.2C, d 0.7147 (20/20C), surface tension 17.0 dynes/cm (20C), refr index 1.3526 (20C), viscosity 0.00233 cP (20C), vap press 442 mm Hg (20C), specific heat 0.5476 cal/g (30C), flash p -49F (-45C), autoign temp 356F (180C), latent heat of evaporation 83.96 cal/g at bp, electric conductivity 4 X 10 3mho/cm (25C), bulk d 6 lb/gal (20C). Soluble in alcohol, chloroform, benzene, solvent naphtha, and oils slightly soluble in water. 

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