Regional-scale influences on urban air quality : a field study in Phoenix, Arizona.
Regional air quality can play an important role in determining whether urban ozone or PM-2.5 standards are exceeded. Background levels of nitrogen oxide species (NO{sub x}) and their interactions with natural organics can generate secondary aerosol products via formation of nitric acid and its subsequent reaction with ammonia to form ammonium nitrate. Natural organics and reactive anthropogenic organic compounds, particularly aromatic species and monoterpenes, can also lead to the formation of secondary organic aerosols, contributing to the formation of PM-2.5. Long-range transport and chemical transformation of hydrocarbons and NO{sub x} via both photochemical reactions and nighttime chemistry can yield significant regional levels of ozone and other oxidants, such as peroxyacyl nitrates (R-C=O-O-O-NO{sub 2}; PANs). The PANs are key species in determining the apparent age of an air parcel (Gaffney et al., 1989, 1993, 1997). The most common member of the family is peroxyacetyl nitrate (R=CH3-; PAN), which typically accounts for more than 85% of the PANs found in an urban or rural site. The PANs are in equilibrium with NO{sub 2}. Peroxyacyl radicals (R-C=O-O-O) are typically produced by the photooxidation reactions of organics, particularly those of aldehyde oxidation products with OH radical during the daytime (photochemically active) periods. Proposed mechanisms for nighttime formation of PANs (Gaffney et al., 1989) include abstraction reactions of nitrate radical (NO{sub 3}) and the initiation of OH chemistry by olefin-ozone reactions.
- Research Organization:
- Argonne National Lab., IL (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 11028
- Report Number(s):
- ANL/ER/CP-96886
- Country of Publication:
- United States
- Language:
- English
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