Contamination effects on ozone formation in smog chambers

Abstract

Ozonation, on the other hand, did not result in the formation of any of these volatile halogenated compounds. The concentration of these compounds actually decreased during ozonation, possibly resulting from both stripping and oxidation of these compounds by the ozone.Therefore, with the ozonation process, organic compounds can ultimately be converted to harmless carbon dioxide by intensive ozonation of water. Cost, however, appears to be the major obstacle to the wide application of ozonation. Effective coagulation and sedimentation in the early stages of water treatment would tend to decrease ozone demand; incorporating UV irradiation and catalysts would enhance organic removal. These approaches would lower the ozonation cost.Further cost reductions can be realized through the development of efficient ozone generators and contactors and by obtaining knowledge about optimal conditions for ozonation reactions including such factors as reactor design, pH adjustment, temperature control, and application of UV. Future studies should therefore be directed toward minimizing costs by optimizing ozonation processes and toward assessing the health hazards associated with ozonation. ConclusionsUpon ozonation, 2-propanol was converted to acetone that

Otimização de um mecanismo fotoquímico para a simulação da atmosfera urbana brasileira

“…Especialmente nas últi-mas amostragens, quando o volume da câmara já ficou sensivelmente reduzido, é de se esperar um efeito bastante alto. A literatura cita este efeito (aumento sensível da relação S/V) 12 e, também a possibilidade de perda de fluoro-hidrocarbonetos leves através da parede, assim como adsorção de compostos nitrogenados e orgânicos nas paredes 13 , dessorção posterior destas espécies 13 e aumento da concentração de radicais OH em várias ordens de grandeza 14 . Este último efeito pode alterar em forma notória os resultados das simulações quando se torna necessária a modelagem durante várias horas (como é o caso Para avaliar este efeito foram realizadas uma série de simulações, mudando as velocidades das "reações de parede":…”

Smog chamber studies of temperature effects in photochemical smog

“…In this paper three categories of hydrocarbons are treated: (a) mixtures designed to resemble as closely as possible the composition and concentration ranges occurring in a polluted urban airshed [in our studies, these consist of sub-parts per million concentrations of oxides of nitrogen (NOx) and a "surrogate" hydrocarbon mixture consisting of 12 alkanes, olefins, and aromatics designed to represent hydrocarbon emissions from all sources in the Los Angeles air basin (18)]; (b) mixtures consisting of sub-parts per million concentrations of NOx and the single hydrocarbons propene or toluene; (c) mixtures consisting of NO, and propene in concentration ranges greater than ambient. Studies of high concentration systems are useful because chamber effects relating to unknown radical sources, known to be important in ambient concentration smog chamber studies (19)(20)(21), are minimized by increasing the relative importance of known homogeneous radical sources. This also allows tests of detailed models under a wider variety of conditions, and allows a larger number of trace intermediates and products to be detected.…”

Atmospheric Process Evaluation of Mobile Source Emissions

“…However, individual VOCs are not emitted in the absence of other reactive organics, so such experiments do not represent atmospheric conditions. Furthermore, chamber effects such as unknown radical sources (Carter et al, 1982), affect the results of such experiments (Bufalini et al, 1977;Joshi et al, 1982;Carter et al, 1982;Lurmann, 1990, 1991;Jeffries et al, 1993), particularly if the compound reacts slowly or has radical sinks in its mechanism (Carter et al, 1986a;Lurmann, 1990, 1991). Therefore, single organic-NOx-air experiments do not reliably quantify reactivity.…”