Hydrocarbons atmospheric concentrations

Square brackets around a molecular species indicate atmospheric concentration. The rate constants k times the reactant concentration product refers to the rates of the chemical reactions of the indicated number. The photolytic flux term /l4 refers to the photodissociation rate of N02 in Reaction R14, its value is proportional to solar intensity.]. RO2 stands for an organic peroxyl radical (R is an organic group) that is capable of oxidizing NO to NO2. Hydrocarbons oxidize to form a very large number of different RO2 species the simplest of the family is methylperoxyl radical involved in R5, R6 and R8. 

The reaction of volatile chlorinated hydrocarbons with hydroxyl radicals is temperature dependent and thus varies with the seasons, although such variation in the atmospheric concentration of trichloroethylene may be minimal because of its brief residence time (EPA 1985c). The degradation products of this reaction include phosgene, dichloroacetyl chloride, and formyl chloride (Atkinson 1985 Gay et al. 1976 Kirchner et al. 1990). Reaction of trichloroethylene with ozone in the atmosphere is too slow to be an effective agent in trichloroethylene removal (Atkinson and Carter 1984). 

Clark Al, McIntyre AE, Perry R, et al. 1984. Monitoring and assessment of ambient atmospheric concentrations of aromatic and halogenated hydrocarbons at urban, rural, and motorway locations. Environmental Pollution (Series B) 7 141-158. 

Our knowledge of the chemical and physical processes that govern aerosol formation in the atmosphere is limited, and further research in the field is badly needed. Attention should be focused on laboratory studies of aerosol formation from aromatic hydrocarbons. The concentrations of aerosol precursors in the atmosphere should be determined more data on organic compounds in ambient aerosols are needed to estimate the relative importance of olefinic and aromatic hydrocarbons as aerosol precursors. 

The main purpose of this chapter is to survi atmospheric concentrations of photochemical oxidants, with emphasis on surface concentrations and the distribution patterns associated with them. The reason for that em> phasis is that the photochemical oxidants that affect public health and welfare are largely concentrated in this region. The whole subject of stratospheric ozone (and its filtering of ultraviolet light and interactions with supersonic-transport exhaust products), nuclear weapon reaction products, and halogenated hydrocarbon decomposition pr ucts is not treated here. 

North Atlantic Treaty Organization. Committee on the Challenges of Modem Society. Atmospheric concentrations, pp. 2-1-2-52. In Air Quality Criteria for Photochemical Oxidants and Related Hydrocarbons. N.29. 1974. 

Atmospheric concentrations of polycyclic aromatic hydrocarbons have been measured since 1991 as part of the Integrated Atmospheric Deposition Network (e.g. [122]). Buehler et al. [35] report PAH concentrations from five US IADN sites (Table 2). 

A recent study by Omar et al. (2002) showed that the total polycyclic aromatic hydrocarbons (PAHs) concentrations in the atmospheric particles and roadside soil particles collected in Kuala Lumpur were 6.28 ng m-3 and 0.22 pg g-1, respectively. 

An apparatus suitable for human breath collection was described by Lemoyne et al. (1987). Subjects were allowed to breathe for 4 min through a mouth piece connected to a Rudolph Valve from a Tedlar bag (Analygas Systems Ltd., Scarborough, Ontario, Canada) containing hydrocarbon-free air. Atmospheric air was hushed from the lungs and an aliquot of exhaled air collected during the succeeding 2 min while the hydrocarbon-free air was inspired. Hydrocarbons were concentrated by a loop-concentrator similar to that previously described and then injected into the GLC. 

Gigliotti, C.L., Totten, L.A., et al (2005) Atmospheric concentrations and deposition of polycychc aromatic hydrocarbons to the Mid-Atlantic East Coast Region. Environmental Science and Technology, 39(15) 5550-5559. 

The primary tropospheric oxidants are OH, O3, and NO3, with "OH and O3 reactions with hydrocarbons dominating primarily during daytime hours, and NO3 reactions dominating at night. Rate constants for the reactions of many different aromatic compounds with each of the aforementioned oxidants have been determined through laboratory experiments [16]. The rate constant data as well as atmospheric lifetimes for the reactions of toluene, m-xylene, p-xylene, m-ethyl-toluene, and 1,2,4-trimethylbenzene appear in Table 14.1. Only these particular aromatic compoimds will be discussed in this review paper, since much of the computational chemistry efforts have focused on these compounds. When considering typical atmospheric concentrations of the major atmospheric oxidants, OH, O3, and NO3 of 1.5 x 10, 7 x 10, and 4.8 x 10, molecules cm , respectively [17], combined with the rate constants, it is clear that the major atmospheric loss process for these selected aromatic compounds is reaction with the hydroxyl... 

Toxicity. Methoxychlor is the least toxic of the chlorinated hydrocarbon insecticides. The maximum permissible atmospheric concentration is 10 mg/m and the maximum permissible concentration in food is 14 pg/g. 

The combustion of alkanes and other hydrocarbons obtained from fossil fuels adds a tremendous amount of CO2 to the atmosphere each year. Quantitatively, data show a 20% increase in the atmospheric concentration of CO2 in the last 46 years (from 315 parts per million in 1958 to 377 parts per million in 2004 Figure 4.19). Although the composition of the atmosphere has changed over the lifetime of the earth, this may be the first time that the actions of humankind have altered that composition significantly and so quickly. 

Workplace air concentration data are discussed in Section 6.5. Data on ambient atmospheric concentrations of PAHs derived from other sources can be found in the ATSDR Toxicological Profile for Polycyclic Aromatic Hydrocarbons (Agency for Toxic Substances and Disease Registry 1995). 

The atmosphere above the ocean contains C9-C28 n-alkanes in addition to low-weight hydrocarbons. Eichmann et al. (1980) have estimated that the ocean might emit 26 Tg of higher alkanes each year. The value is based on the measured total atmospheric concentration for C9-C28 n-alkanes of 300-400 ng/m3 over the Indian and the North Atlantic Oceans, coupled with an assumed residence time of the alkanes of 5 days resulting from their reactions with OH radicals. From measurements at Enewetak Atoll (Marshall Islands), however, Duce et al. (1983) reported atmospheric concentrations of C,2-C28 alkanes that were an order of magnitude lower than those found by Eichmann et al. (1980). It is questionable, therefore, whether their data can be extrapolated to the whole ocean area, so that the emission rate derived must be regarded an upper limit. 

Balasubramanian R, He J (2010) Fate and transfer of persistent organic pollutants in a multi-media environment. In Zereini F, Wiseman CLS (eds) Urban airborne particulate matter origins, chemistry, fate and health impacts. Springer, Heidelberg Bozlaker A, Muezzinoglu A, Odabasi M (2008) Atmospheric concentrations, dry deposition and air-soil exchange of polycyclic aromatic hydrocarbons (PAHs) in an industrial region in Turkey. J Hazard Mater 153 1093-1102... 

Agrell C, ter Schure AFH, Sveder J et al (2004) Polybrominated diphenyl ethers (PBDEs) at a solid waste incineration plant I atmospheric concentrations. Atmos Environ 38 5139-5148 Allen JO, Dookeran MM, Smith KA et al (1996) Measurement of polycyclic aromatic hydrocarbons associated with size-segregated atmospheric aerosols in Massachusetts. Environ Sci Technol 30 1023-1031... 

Cetin B, Odabasi M (2008) Atmospheric concentrations and phase partitioning of polytaominated diphenyl ethers (PBDEs) in Izmir, Turkey. Chemosphere 71 1067-1078 Chen S-J, Hsieh L-T, Hwang P-S (1996) Concentration, phase distribution, and size distribution of atmospheric polychlorinated biphenyls measured in southern Taiwan. Environ Int 22 411-423 Chen L-G, Mai B-X, Bi X-H et al (2006) Concentration levels, compositional profiles, and gas-particle partitioning of polybrominated diphenyl ethers in the atmosphere of an urban city in South China Environ Sci Technol 40 1190-1196 Chuang JC, Mack GA, Kuhlman MR et al (1991) Polycyclic aromatic hydrocarbons and then-derivatives in indoor and outdoor air in an eight-home study. Atmos Environ B 25 369-380 Cotham WE, Bidleman TF (1995) Polycyclic aromatic hydrocarbons and polychlorinated biphenyls in air at an urban and a rural site near Lake Michigan. Environ Sci Technol 29 2782-2789... 

P) can react with many organic and inorganic molecules but the reactivity is much lower than 0( D). Thus, although hydrocarbons existing in the clean and polluted troposphere can all react with 0( P), the reactions can in general be neglected as compared to those with OH radicals when atmospheric concentrations of 0( P) and reaction rates are considered, and only the reaction with the atmospheric main species O2 is necessary to be considered as the 0( P) reaction in the troposphere. In the stratosphere, reactions with O2 and O3 are predominant, but those with OH, HO2, NO2, CIO are also important in the chain reaction system. 

When gases that are somewhat soluble in a Hquid concentrate are used, both concentrate and dissolved gas are expeUed. The dissolved gas then tends to escape into the atmosphere, dispersing the Hquid into fine particles. The pressure within the container decreases as the product is dispersed because the volume occupied by the gas increases. Some of the gas then comes out of solution, partially restoring the original pressure. This type of soluble compressed gas system has been used for whipped creams and toppings and is ideal for use with antistick cooking oil sprays. It is also used for household and cosmetic products either where hydrocarbon propeUants cannot be used or where hydrocarbons are undesirable. 

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