Grantee Research Project Results
1998 Progress Report: RO2 and HOx Radicals in Urban and Rural Air: Measurements of OH and RO2 Formation From Ozone-Alkene Reactions, and the Rate Coefficients of the Reactions of High Molecular Weight RO2 Radicals with HO2
EPA Grant Number: R826236Title: RO2 and HOx Radicals in Urban and Rural Air: Measurements of OH and RO2 Formation From Ozone-Alkene Reactions, and the Rate Coefficients of the Reactions of High Molecular Weight RO2 Radicals with HO2
Investigators: Paulson, Suzanne , Sander, Stanley
Institution: University of California - Los Angeles
EPA Project Officer: Hahn, Intaek
Project Period: January 15, 1998 through January 14, 2001
Project Period Covered by this Report: January 15, 1998 through January 14, 1999
Project Amount: $440,323
RFA: Ambient Air Quality (1997) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:
The objectives of this project are to: (1) complete proposed OH yield measurements for a series of anthropogenic alkenes (UCLA work component); and (2) continue development of the Infrared Kinetic Spectroscopy (IRKS) system which will be used to study the rates and mechanisms of organic peroxy radicals (RO2) with hydroperoxyl (HO2) radicals (JPL Work Component).Progress Summary:
During the reporting period, the following milestones were reached for the UCLA work component:
- A large series of OH formation yields, together with measurements of carbonyl and other product yields have been made. This work has developed a highly accurate data set characterizing this key HOx source in the polluted troposphere, as well as providing predictive capability for OH formation yields based on alkene structure. The following alkenes were investigated: ethene, propene, 1-butene, 1-pentene, 1-hexene and 1-octene, cis and trans-2-butene, cis and trans-2-pentene, cis and trans-2-hexene, 2-methyl-2-butene, styrene, a-methyl styrene, trans-b-methyl styrene, cyclopentene, cyclohexene, and cycloheptene and butadiene. The results from the first six in this series have been published.
- The detection sensitivity for HO2 was enhanced through development of electronics for frequency modulation of the distributed feedback (DFB) near-IR laser at 7 MHz, and second derivative demodulation of the detected laser signal. The minimum detectable absorbance in a 100 kHz bandwidth after integration of the signal from 100 photolysis laser shots is better than 1x10-6, corresponding to a detection limit for HO2 radicals of about 2x1011 molecules cm-3.
- An optical configuration was developed for the simultaneous detection of organic peroxy radicals (RO2) in the same detection volume as the near-infrared probe for HO2 radicals. The RO2 probe consists of a single pass of a collimated beam from a cw ultraviolet deuterium lamp focused on the entrance slit of a 0.25 m spectrograph. The RO2 radicals are detected in their region of strong absorption near 250 nm.
Future Activities:
Experiments to measure OH formation yields from ozone-alkene reactions, are complete. Data analysis and preparation of publications will continue through the next project periods. Development of the IRKS system for measuring HO2-RO2 rate constants will continue. Assembling the HPLC system to develop the ability to measure peroxides to address Goal 3, measurement of RO2 yields, will commence.Journal Articles on this Report : 2 Displayed | Download in RIS Format
| Other project views: | All 30 publications | 10 publications in selected types | All 10 journal articles |
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Paulson SE, Fenske JD, Sen AD, Callahan TW. A novel small-ratio relative-rate technique for measuring OH formation yields from the reactions of O3 with alkenes in the gas phase, and its application to the reactions of ethene and propene. Journal of Physical Chemistry A 1999;103(13):2050-2059. |
R826236 (1998) R826236 (Final) |
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Paulson SE, Chung MY, Hasson AS. OH radical formation from the gas-phase reaction of ozone with terminal alkenes and the relationship between structure and mechanism. Journal of Physical Chemistry A 1999;103(41):8125-8138. |
R826236 (1998) R826236 (Final) |
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Supplemental Keywords:
atmospheric chemistry, organic radicals, hydroxyl radical, RFA, Scientific Discipline, Air, particulate matter, air toxics, Environmental Chemistry, tropospheric ozone, Atmospheric Sciences, Environmental Engineering, ambient air quality, urban air toxics, particle size, particulates, ozone-alkene reactions, air pollutants, chemical characteristics, ozone occurrence, photochemical radical, ambient air, ozone, ambient measurement methods, ambient monitoring, chemical composition, smog, urban air pollutants, photochemical smog, atmosphere, infrared spectroscopy, chain reactions, Volatile Organic Compounds (VOCs), Alkene reactions, photochemical assessmentRelevant Websites:
http://dx.doi.org/10.1021/jp993611qProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.