Project at a Glance
Project Status: complete
Report Published December 1998:
Title: Biogenic hydrocarbon inventories for California: generation of essential databases. Final report.
Principal Investigator / Author(s): Winer, Arthur M
Contractor: UC Los Angeles
Contract Number: 95-309
Research Program Area: Atmospheric Processes
Topic Areas: Chemistry & Reactivity, Modeling, Natural (Biogenic) Sources
Volatile organic compounds (VOC) of biogenic origin (BHC, biogenic hydrocarbons) were measured in California's South Coast Air Basin (SoCAB) during the Southern California Ozone Study (SCOS97) conducted in the summer of 1997. Anthropogenic hydrocarbons are measured on a routine basis in the SoCAB, but few ambient measurements of biogenic hydrocarbons or their atmospheric reaction products have been conducted in the basin. While on a global scale the dominance of BHC over anthropogenic VOC is estimated to be as much as a factor of ten (WMO, 1995), U.S. emission inventories put the two sources of VOC at comparable strengths (Guenther et al., 1994) and in urban areas such as the SoCAB anthropogenic VOC clearly dominate (Benjamin et al., 1997). Biogenic hydrocarbons are generally highly reactive in the atmosphere (Carter, 1994; Atkinson, 1997; Atkinson and Arey, 1998) and thus can play an important role in tropospheric chemistry (Trainer et al., 1987; Chameidies et al., 1988). Because of their rapid atmospheric reactions, however, the ambient concentrations of BHC are generally low and additional measurements of their atmospheric reaction products are necessary to understand the full impact of BHC on photochemical processes such as ambient ozone formation (Montzka et al., 1993; 1995). For this reason, measurements of isoprene, the BHC emitted in greatest quantity by vegetation (Guenther et al., 1995), and its principal reaction products, methacrolein (MACR) and methyl vinyl ketone (MVK), were undertaken during the SCOS97 campaign. Additionally, the following monoterpenes were measured: a-pinene, camphene, sabinene, Ŗ-pinene, limonene, 1,8-cineole and camphor. Figure 1 shows the structures of these biogenic hydrocarbons.
The SCOS97 campaign took place during June 16- October 15, 1997, with six intensive sampling periods and a total of 13 days of intensive sampling. Sampling for biogenic VOC was generally conducted simultaneously at three sites chosen as a mid-basin receptor site for anthropogenic VOC (Azusa), a down-wind receptor site (Banning) and a high elevation site impacted by biogenic VOC (Pine Mountain or Mount Baldy).
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