Atmospheric resids

The StabUity or persistence of a poUutant in the atmosphere depends on the poUutant s atmospheric residence time. Mean residence times and principal atmospheric sinks for a variety of species are given in Table 2. Species like SO2, (NO and NO2), and coarse particles have lifetimes less than... 

Table 2. Mean Atmospheric Residence Times (t) and Dominant Sinks of Air Pollutants...

Gas CAS Registry Number 1990 Concentrations Concentration increases, %/yr Greenhouse efficiency Atmospheric residence times, c yrs... 

Effect of Pressure Figure 3 shows the effect of pressure on product sulfur. In the 400-800 psig range, doubling the pressure reduces the product sulfur by about one third. Pressure also has an effect on catalyst life. In general, as the pressure is increased the catalyst deactivates at a lower rate. However, beyond a certain point, further increases in pressure have only a small effect on deactivation rate. An example of this is for atmospheric resids typical data... 

Pollutants have various atmospheric residence times, with reactive gases and large aerosols being rapidly removed from air. In the London air pollution episode of December 1952, the residence time for sulfur dioxide was estimated to be five hours daily emissions of an estimated 2,000 tons of sulfur dioxide were balanced by scavenging by fog droplets, which were rapidly deposited. Most relatively inert gases remain in the atmosphere for extended periods. Sulfur hexafluoride, used extensively in the electric power industiy as an insulator in power breakers because of its inertness, has an estimated atmospheric lifetime of 3,200 years. 

Transformation of parent contaminants into secondary products may occur during the processes of atmospheric diffusion and transport as a result of physical, chemicjd, and photochemical processes (22). Chemical conversion within the atmosphere may also change the physico-chemical characteristics of contaminants, dramatically altering their atmospheric residence times and fates from those of the parent contaminants. The complex reactions within the atmosphere that are driven by chemical processes such as hydroxyl scavenging... 

The average residence times for mercury in the atmosphere, terrestrial soils, oceans, and oceanic sediments are approximately 1 yr, 1000 yr, 3200 yr, and 2.5 x 10 yr, respectively. (See Bergan et al. (1999) for more details on atmospheric residence times.)... 

Although thermodynamically it is relatively simple to determine the amount of water vapor that enters the atmosphere using the Clausius-Clapeyron equation (see, e.g.. Chapter 6, Equation (1)), its resultant atmospheric residence time and effect on clouds are both highly uncertain. Therefore this seemingly easily describable feedback is very difficult to quantify. 

Although hydrogen sulfide does not react photochemically, it may be transformed to sulfur dioxide and sulfate by nonphotochemical oxidation reactions in the atmosphere. Its atmospheric residence time is typically less than 1 day (Hill 1973), but may be as high as 42 days in winter (Bottenheim and Strausz 1980). 

Lyman, W. 1982. Atmospheric Residence Time. In Handbook of Chemical Property Estimation Methods, Environmental Behavior of Organic compounds. Lyman, W.J., Reehl, W. F., and Rosenblatt D.H., eds. McGraw Hill Book company, New York, NY. 10-2-10-33. 

The most important transformation process for di-w-octylphthalate present in the atmosphere as an aerosol is reaction with photochemically produced hydroxyl radicals. The half-life for this reaction has been estimated to be 4.5 14.8 hours (Howard et al. 1991). Actual atmospheric half-lives may be longer since phthalate esters sorbed to wind-entrained particulates may have long atmospheric residence times (Vista Chemical 1992). Direct photolysis in the atmosphere is not expected to be an important process (EPA 1993a HSDB 1995). 

The atmospheric and chemical processes controlling the spatial and temporal variability of psychoactive substances in urban atmospheres are largely uncertain, mostly due to the fact that the atmospheric residence time of these compounds is so far unclear. The transport, transformation and deposition/atmospheric removal... 

The physical characteristics of individual particles also are of environmental significance. For example, the smaller particles (diameters on the order of 1 micrometer of less) generally are most important in that they have very long atmospheric residence times (18), are least effectively controlled by pollution control devices (19), are preferentially deposited in the pulmonary regions of the lung (20,21), and may be most enriched in toxic species on a specific concentration (iig/g) basis (22-24). 

Statfjord atmospheric resid (1). Atmospheric resid (2). SRC II (3). Prahoe shale oil (4). Directly liquefied oil from wood chips using the PERC process (5). Molar ratio adjusted assuming that ammonia, water and hydrogen sulfide are formed by the heteroatoms. 

In the atmosphere, the vapor pressure of the isomeric cresols, 0.11+0.30 mmHg at 25.5 °C (Chao et al. 1983 Daubert and Danner 1985), suggests that these compounds will exist predominantly in the vapor phase (Eisenreich et al. 1981). This is consistent with experimental studies that found all three isomers in the gas phase of urban air samples, but they were not present in the particulate samples collected at the same time (Cautreels and Vancauwenbergh 1978). The relatively high water solubility of the cresol isomers, 21,520- 25,950 ppm (Yalkowsky et al. 1987), indicates that wet deposition may remove them from the atmosphere. This is confirmed by the detection of cresols in rainwater (Section 5.4.2). The short atmospheric residence time expected for the cresols (Section 5.3.2.1) suggests that cresols will not be transported long distances from their initial point of release. 

Marine residual fuels bunker fuel oil Grades ISO RMA through RML marine residual fuel and bunker fuel are blended from components such as atmospheric resid, vacuum resid, visbreaker resid, FCC bottoms, low-grade distillate, and cracked components. Bunker fuel has a maximum viscosity of 550 cSt 122°F (50°C), density of 0.990 g/cc, and sediment of 0.1 wt%. ISO marine fuel oil viscosities range from 10 to 55 cSt 212°F (100°C). These fuels are used in slow-speed diesel engines and boilers. 

When determining the pour point of certain heavy residual products such as 6 fuel oils, bunker fuels, vacuum gas oils, vacuum resids, atmospheric resids, and visbreaker bottoms, it is important to pay close attention to the temperature applied to the oil prior to pour point testing. In some cases, preheating an oil to temperatures greater than 212°F (100°C) prior to pour point testing can result in a pour point value which is lower than the value obtained for the same oil preheated to 110°F (43.3°C). 

Colman, J. J., D. R. Blake, and F. S. Rowland, Atmospheric Residence Time of CH2Br Estimated from the Junge Spatial Variability Relation, Science, 281, 392-396 (f998). 

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