Irradiation chamber conditions

Photolytic. Major products reported from the photooxidation of butane with nitrogen oxides under atmospheric conditions were acetaldehyde, formaldehyde, and 2-butanone. Minor products included peroxyacyl nitrates and methyl, ethyl and propyl nitrates, carbon monoxide, and carbon dioxide. Biacetyl, tert-butyl nitrate, ethanol, and acetone were reported as trace products (Altshuller, 1983 Bufalini et al, 1971). The amount of sec-butyl nitrate formed was about twice that of n-butyl nitrate. 2-Butanone was the major photooxidation product with a yield of 37% (Evmorfopoulos and Glavas, 1998). Irradiation of butane in the presence of chlorine yielded carbon monoxide, carbon dioxide, hydroperoxides, peroxyacid, and other carbonyl compounds (Hanst and Gay, 1983). Nitrous acid vapor and butane in a smog chamber were irradiated with UV light. Major oxidation products identified included 2-butanone, acetaldehyde, and butanal. Minor products included peroxyacetyl nitrate, methyl nitrate, and unidentified compounds (Cox et al., 1981). 

Irradiation conditions Irradiation was conducted in a climatic chamber at 20°C and 60% humidity using UVA radiation (320-400 nm) with maximum mission at 365 nm. The intensity of radiation was determined by means of radiometer, to be each time of 3.89 W/m. The distance of the samples from radiation source was 13 cm. 

Figure 4. (a) Volume-based and (B) chlorophyll-based photosynthesis-irradiance data for phytoplankton sampled on December 6, 1987 from the experimental chambers (after flow had been stopped for 24 h). Samples were incubated for 4 h under the four treatment conditions described in the text. (Reproduced with permission from reference 23. Copyright 1990 Springer-Verlag, Berlin.)... 

FIGURE 2-8 Photooxidation of propylene in irradiated CjH -NO-NO, mixtures in moist air. A. experimental rate data from smog-chamber experiment of Altshuller et al. Initial concentrations C,H, 2.09 ppm NO. 0.90 ppm NOj. 0.09 ppm. Relative humidity at 31.S C, 50%. B. computer simulation of product concentration-tinte curves for same initial conditions. Reprinted with permission from Demeijian et al. 

Data on c clohexene and a pinene aerosols were reported by Schwartz after a preliminary report from the Battelle Institute group. The experimental conditions and analytic techniques were identical with those just described for the toluene aerosol study. Here again, only the methylene chloride-soluble, water-insoluble fractions were studied. They accounted for about 7% and 65% of the total aerosol mass generated from cyclohexene and a pinene, respectively. Grosjean (unpublished data) has investigated the chemical composition of cyclopentene, cyclohexene, and 1,7-octadiene aerosols. Experiments were conducted in an 80-m Teflon smog chamber filled with ambient air, with irradiation by... 

Calculated coocentratioas for oxidants in smog chamber under conditions outlined in Chapter 2 for 60-niin irradiation (see Table 2-2). 

Perhaps the most direct experimental means of examining the relationship between emissions and air quality is to simulate atmospheric conditions using large chambers. Measured concentrations of the primary pollutants are injected into these environmental (or smog) chambers, as they are called. These are then irradiated with sunlight or lamps used to mimic the sun, and the time-concentration profiles of the primary pollutants as well as the resulting secondary pollutants are measured. The primary pollutant concentrations as well as temperature, relative humidity, and so on can be systematically varied to establish the relationship between emissions and air quality, free from the complexities of continuously injected pollutant emissions and meteorology, both of which complicate the interpretation of ambient air data. 

As discussed in Sections B.3 and C of Chapter 7, this reaction has been shown to be too slow in aqueous solution to be significant in the atmosphere it is faster on surfaces and has been proposed as a source of HONO in smog chambers (e.g., see Sakamaki et al., 1983 Pitts et al., 1984 Leone et al., 1985 and Chapter 7.0. Since HONO is a major OH source in the early stages of irradiation in smog chambers, it is important to understand the mechanism of its formation and to quantify its rate of production under various experimental conditions. Thus, if this reaction only occurs at... 

Irradiation procedure. The LDPE samples (size 40 mm x 20 mm, thickness 37 pm) were purified in an ultrasonic bath (10 minutes, 30 °C) using a mixture of acetone/water and then dried in vacuo (20 mbar, 1 hour at 40 °C). The samples were positioned in the reaction chamber, which was then purged with a mixture of SO2 and synthetic air (1 1, volume) for about 10 minutes for conditioning. Subsequently, the polyethylene samples were irradiated with the Hg lamp for different periods of time (1 to 5 minutes) maintaining the gas flow. Finally the chamber was purged... 

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