Emissions of 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. 

4 being typical (e.g., Dickerson et al., 1989 Chin et al., 1994 Wang et al., 1996 Harris et al., 1998 Parrish et al., 1993b, 1998 Kajii et al., 1998). This relationship is impacted, of course, by other factors as well such as the production of CO in the oxidation of VOC and by the deposition of 03 during transport, for which corrections can be estimated (e.g., Chin et al., 1994). 

FIGURE 6.22 Chemical structures of some biogenically emitted hydrocarbons. 

Ethene is a plant hormone emitted at a rate of several teragrams per year from plants smaller amounts are emitted by soils and oceans (Rudolph, 1997). Interestingly, the emissions of ethene as well as some other VOCs (see later) increase significantly (by as much as factors of one to two orders of magnitude) when the plant is stressed, for example by mechanical means, high temperatures, or lack of water. 

Isoprene is the major single, non-methane VOC emitted by plants  

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