Isoprene global

Currently, important TPE s include blends of semicrystalline thermoplastic polyolefins such as propylene copolymers, with ethylene-propylene terepolymer elastomer. Block copolymers of styrene with other monomers such as butadiene, isoprene, and ethylene or ethylene/propy-lene are the most widely used TPE s. Styrene-butadiene-styrene (SBS) accounted for 70% of global styrene block copolymers (SBC). Currently, global capacity of SBC is approximately 1.1 million tons. Polyurethane thermoplastic elastomers are relatively more expensive then other TPE s. However, they are noted for their flexibility, strength, toughness, and abrasion and chemical resistance. Blends of polyvinyl chloride with elastomers such as butyl are widely used in Japan. ... 

Table 6.24, for example, shows one estimate of the annual global emissions of isoprene, other monoterpenes, and VOCs as well as methane (Guenther, 1999). Emissions of isoprene are believed to be about four times those of the other monoterpenes and about equal to all other VOCs. 

Isoprene occurs in the environment as emissions from vegetation, particularly from deciduous forests, and as a by-product in the production of ethylene by naphtha cracking. In the United States, the total emission rate of isoprene from deciduous forests has been estimated at 4.9 tonnes per year, with greatest emissions in the summer. The global annual emission of isoprene in 1988 was estimated to be 285 000 thousand tonnes. Isoprene is produced endogenously in humans. It has also been found in tobacco smoke, gasoline, turbine and automobile exhaust, and in emissions from wood pulping, biomass combustion and rubber abrasion (United States National Library of Medicine, 1997). 

Note that biogenic hydrocarbons, in particular isoprene, dominate the above outlined impact of NMHC on global tropospheric chemistry. Moreover, convection of... 

Guenther A, Zimmerman PR, Harley P et al (1993) Isoprene and monoterepene emission rate variability Model evaluations and sensitivity analyses. J Geophys Res 98D 12609-12617 Holslag A, Boville B (1993) Local versus nonlocal boundary-layer diffusion in a global climate model. J. Climate 6 1825-1842... 

Guenther A, Karl T, Harley P, Wiedinmyer C, Palmer PI, Geron C. Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature). Atmos. Chem. Phys. Dis. 2006 6 3181-3210. 

Non-methane hydrocarbons (NMHCs such as ethane, ethene, propane, propene, and isoprene) are trace atmospheric constituents that play an important role in both providing a sink for hydroxyl radicals and in controlling ozone concentrations (Donahue and Prinn, 1990). The oceans are known to be a source of NMHCs to the atmosphere, although globally they are significantly smaller than terrestrial sources. However, the main marine-produced NMHCs, ethane and propene, may have an important local impact on atmospheric photochemistry (Plass-Dulmer et al., 1995), particularly in... 

Fig. 13.10. Superposition of retinol, retinal, and retinoic acid in the conformations adopted at the active site of RBP, and in various small molecule crystal structures. For clarity, the H atoms have been omitted. TVvo distinct conformations are observed for the single bond between the )8-ionone ring and the isoprene chromophore. The synclinal conformation, adopted at the receptor site, corresponds to the global energy minimum of the isolated molecule...

Monson, R. K., Guenther, A. B and Fall, R. (1991). Physiological reality in relation to ecosystem- and global-level estimates of isoprene enii.ssion. In Trace Gas Emissions by Plants (T. D. Sharkey, E. A. Holland, and H, A, Mooney, Eds,), pp. 185-207. Academic Pre.ss, New York. 

Green plants also release substantial quantities of isoprene (2) as well as monoterpenoid hydrocarbons such as a-pinene (3), myrcene (4), and limonene (5). These compounds contribute significantly to atmospheric organic concentrations in remote or forested areas (Altshuller, 1983 Hutte et al., 1984). It has been estimated that the global output of these substances may equal about 28% of the annual output of methane (Rasmussen and Went, 1965). 

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