Anthropogenic VOCs

Although the global release of anthropogenic VOCs into the atmosphere is significantly less than from biogenic sources, they are generally concentrated in densely populated and industrialized areas. The most densely populated areas are, of course, our cities, and it is with the applications of PTR-MS in cities that we shall begin this account of PTR-MS 

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FIGURE 2.5 Contribution of various sources to total anthropogenic VOC emissions in the United States in 1996 (from EPA, 1997). 

Figure 6 Ozone production efficiency, expressed as the rate of production of odd oxygen (O3 -h NO2) divided by the loss of NO . from steady state calculations. The calculations assume (i) CO and CH4 only (solid line) (ii) anthropogenic VOC with VOC/ NO = 10 (dashed line) (iii) anthropogenic VOC with VOC/NO c = 20 (short dashed line) (iv) CH, CH4 and 1 ppb isoprene (circles) and (v) anthropogenic VOC/NO = lOand 1 ppb isoprene (asterisks) (source Sillman, 1999 (reproduced by permission of Elsevier from Atmos. Environ. 1999, 33, 1821-1845) based on similar unpublished analyses by Greg Frost, NOAA Aeronomy lab).

USA had been underestimated by a factor of 4 (Geron et al., 1994). This discovery led to a major change in model predictions for the impact of NOjc and VOCs on ozone formation in the eastern USA (Pierce et al., 1998 see also Chameides et al., 1988) and led to greater emphasis on the control of NO c emission sources. Recent results from the Texas Air Quality study also suggest that emissions of anthropogenic VOC from industrial sources are much larger than represented in emission inventories. The accuracy of emission inventories effectively limits our ability to understand the process of smog formation. 

Concluding for new particle formation it can be stated that new particles form gaseous precursors are expected to be formed by the interaction of sulphuric acid and anthropogenic VOCs in urban areas. Solar radiation and OH production are important too, in order to initiate a strong oxidation and precursor formation for aerosol production. 

Real-time continuous monitoring of VOCs at a site near the Houston Ship Channel during the Texas Air Quality Study 2(X)0 was reported by Karl et al. [118]. The anthropogenic VOCs that were observed included aromatic compounds (e.g. benzene, toluene and xylenes), aliphatic hydrocarbons (e.g. propene and isoprene), oxygenated VOCs... 

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