Role of Hydrocarbons

A major component of the reactive hydrocarbon loading are the biogenic hydrocarbons. As previously indicated, the hydrocarbon oxidation chemistry is integral to the production of ozone. Globally, the contribution of NMHC to net photochemical production of ozone is estimated to be about 40%.  

There are a number of inorganic molecules such as NO2 and SO2 (See Table 3) which are also lost via reaction with OH. A number of halocarbons also exist that posses insubstantial tropospheric sinks and have importance in the chemistry of the stratosphere (see Section 2.10). 

As both reactions (2.37) and (2.19) lead to the oxidation of NO to NO2 the subsequent photolysis leads to the formation of ozone (see reactions (2.2) and (2.20)). The individual reaction mechanism depends on the identity of the organic compounds and the level of complexity of the mechanism. Although OH is the main tropospheric oxidation initiator, reaction with NO3, O3, 0( P) or photolysis may be an important loss route for some NMHCs or the partially oxygenated products produced as intermediates in the oxidation (see reaction (2.38)). 

In summary, the rate of oxidation of VOCs and therefore by inference the production of ozone is governed by the concentration of the catalytic HO c radicals. There are a large variety of VOCs with a range of reactivities therefore this remains a complex area. 

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Describe the role of hydrocarbons in photochemical oxidant formation. 

CO oxidation and the reaction between CO -t NO have been extensively studied. Much less is known about hydrocarbon oxidation, and the role of hydrocarbons in reducing NO is only beginning to be explored. Surface science studies with reactions on well-defined single-crystal surfaces have contributed significantly to our understanding, for an overview see B.E. Nieuwenhuys, Adv. Catal. 44 (1999) 259. 

The free-radical chemistry was studied using a zerodimensional box-model based upon the Master Chemical Mechanism (MCM). Two versions of the model were used, with different levels of chemical complexity, to explore the role of hydrocarbons upon free-radical budgets under very clean conditions. The detailed model was constrained to measurements of CO, CH4 and 17 NMHCs, while the simple model contained only the CO and CH4 oxidation mechanisms, together with inorganic chemistry. The OH and HO2 (HOx) concentrations predicted by the two models agreed to within 5-10%. 

Class II oenocytes produce hydrocarbons in grasshoppers (Diehl, 1975) other than its involvement in waterproofing the cuticle and the ootheca, the role of hydrocarbons in the sexual behavior of the grasshopper is not known, unlike in some arctiids, cockroaches, and flies (Schal et al., 1998 a or b). Similarly, while the biochemical processes involved in the cycling of hydrocarbons between oenocytes and target tissues has been described (e.g. Schal et al., 1998), little information is available on such processes in grasshoppers nor is information available on their ultrastructure. 

Nestmate recognition in social insects and the role of hydrocarbons... 

Singer, T.L. (1998). Roles of hydrocarbons in the recognition systems of insects. Am. 

The economic significance of the Black Sea region is determined, first of all, by its transport and pipeline potentialities and recreation resources. Fishery is also retained in the region s economy, although, under the present-day conditions, its significance has strongly decreased. The role of hydrocarbon resources, to date, has been restricted to oil and gas prospecting in the shelf areas of the sea. 

Brooks J., Cornford C., and Archer R. (1987) The role of hydrocarbon source rocks in petroleum exploration. In Marine Petroleum Source Rocks (eds. J. Brooks and A. J. Fleet). Blackwell, Oxford, pp. 17-46. 

Aside from glomerulonephritis, the impact of solvent exposure in other renal diagnoses needs to be explored. Indeed, it is of particular note that all these studies are limited to the former type of renal disease while the role of hydrocarbons in the other renal diagnoses such as diabetic nephropathy should be considered [27, 28]. Interestingly in this context is the recent observation by Nuyts et al. [28] in a group of patients with diabetic nephropathy where hydrocarbon exposure was found in 39% of the patients with that particular type of renal disease. This corroborates the results of Yaqoob et al. [27] who found higher exposure scores to hydrocarbons in patients with incipient (odds ratio 4.0) and overt (odds ratio 5.8) diabetic nephropathy as compared to diabetic individuals without clinical evidence of nephropathy. 

The Environmental Protection Agency has promulgated a national ambient air quality standard for hydrocarbons 160 is the maximum 3-hr concentration not to be exceeded more than once a year. It was arrived at by considering the role of hydrocarbons in the formation of photochemical smog. Suppose that in an exhaust gas benzene vapor is mixed with air at 25°C such that the partial pressure of the benzene vapor is 2.20 mm Hg. The total pressure is 800 mm Hg. Calculate ... 

Nemanich, G. (2003). The Continuing Role of Hydrocarbons in the Future of Hydrogen Supply Infrastructure. Proceedings of the University of California at Davis Institute of Transportation Studies IX Biennial Conference on Transportation and Energy. 

McIntosh S, Vohs JM, Gorte RJ (2003) Role of hydrocarbon deposits in the enhanced performance of direct-oxidation SOFCs. J Electrochem Soc 150 A470-A476... 

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