Emissions biogenic organics

Gas-phase chemistry in remote areas is, in most cases, analogous to that in more polluted regions. The major difference is in lower NOx emissions and hence concentrations. In addition, in continental regions, there are substantial emissions of biogenic organics, many of which are highly reactive toward OH, 03, N03, and Cl atoms and in oceanic regions, dimethyl sulfide (DMS), which reacts with OH, N03, and Cl atoms. 

In short, while a variety of oxygen-containing biogenic organics have been obseived to be generated from plants and most are likely direct emissions, care must be taken to distinguish such direct emissions from... 

For example, Taha (1996) suggests that increased urban vegetation with low organic emission rates may lead to a net decrease in 03 formation by lowering surface temperatures and biogenic emission rates as well as increasing dry deposition of pollutants. 

A hypothetical aerosol size/composition distribution is shown in Figure 12.1, indicating that crustal materials (e.g., COf, Si, Al, Fe, Ca, and Mn), sea spray (e.g., Mg, Na, and Cl), and biogenic organic particles (e.g., pollen, spores, and plant fragments) are usually found in the coarse aerosol fraction (2.5 < r/ae < 10pm) (Meszaros et al., 1997 Krivacsy and Molnar, 1998 Matsumoto et al., 1998 Seinfeld and Pandis, 1998 Maenhaut et al., 2002 Smolik et al., 2003). Wind erosion, primary emissions, mechanical disruption, sea spray, and volcanic eruptions all contribute to the concentrations of these species (Seinfeld, 1986 Seinfeld and Pandis, 1998). 

The total organic carbon balance for lakes on the central Amazon floodplain can be examined by comparing total inputs due to primary production and external loading with total losses (Table 14.4). The combined input of organic carbon due to primary production, river import and local runoff was estimated at 117.3 Tg C yr. Combined losses due to biogenic gas emission and... 

Simoneit BRT, Organic matter of the troposphere—V Appfication of molecular marker analysis to biogenic emissions into the troposphere for source reconcih-xtions, JAtmos Chem 8 251—275, 1989. 

Fall, R Biogenic Emissions of Volatile Organic Compounds from Higher Plants, in Reactive Hydrocarbons in the Atmosphere (C. N. Hewitt, Ed.), Chap. 2, Academic Press, San Diego, 1999. 

FIGURE 6.26 Structures of some oxygen-containing organics with biogenic emission sources. 

Puxbaum, H., Biogenic Emissions of Alcohols, Ester, Ether, and Higher Aldehydes, in Biogenic Volatile Organic Compounds in the Atmosphere (G. Helas, J. Slanina, and R. Steinbrecher, Eds.), pp. 79-99, SPB Academic Publishing, Amsterdam, 1997. 

Street, R. A., S. C. Duckham, and C. N. Hewitt, Laboratory and Field Studies of Biogenic Volatile Organic Compound Emissions from Sitka Spruce (Picea sitchensis Bong.) in the United Kingdom, J. Geophys. Res., 101, 22799-22806 (1996). 

Particles collected in regions influenced by anthropogenic emissions and those in aged air masses where there has been ample opportunity for oxidation are even more complex than those in remote regions. Thus, they may contain not only the organics from biogenic emissions but also complex organics that either have been directly emitted from sources associated with human activities or have been formed in air from reactions of primary emissions. 

Simoneit, B. R. T., Organic Matter of the Troposphere—V Application of Molecular Marker Analysis to Biogenic Emissions into the Troposphere for Source Reconciliations, . /. Atmos. Chem., 8, 251-275 (1989). 

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