Sign up & Download
Sign in

Observations of the diurnal and seasonal trends in nitrogen oxides in the western Sierra Nevada

by J. G. Murphy, D. A. Day, P. A. Cleary, P. J. Wooldridge, R. C. Cohen
Atmospheric Chemistry and Physics Discussions ()

Abstract

Observations of speciated nitrogen oxides, namely NO2, total peroxy nitrates (?PNs), total alkyl nitrates (?ANs), and HNO3 by thermal dissociation laser induced fluorescence (TD-LIF), and supporting chemical and meteorological measurements at Big Hill (1860m), a high elevation site in California's Sierra Nevada Mountains, are described. From May through October, terrain-driven winds in the region routinely bring air from Sacramento, 100km southwest of the site, upslope over oak and pine forests to Big Hill during the day, while at night, the site often samples clean, dry air characteristic of the free troposphere. Winter differs mainly in that the meteorology does not favour the buildup of Sacramento's pollution over the Sierra Nevada range, and the urban-influenced air that is seen has been less affected by biogenic VOC emissions, resulting in longer life-time for NO 2 and a predominance of the inorganic forms of nitrogen oxides. Summertime observations at Big Hill can be compared with those from Granite Bay, a Sacramento suburb, and from the University of California's Blodgett Forest Research Station to examine the evolution of nitrogen oxides and ozone within the urban plume. Nitrogen oxide radicals (NO and NO2), which dominate total nitrogen oxides (NOy) at Granite Bay, are rapidly converted into HNO3, ?PNs, and ?ANs, such that these compounds contribute 29, 30, and 21% respectively to the NOy budget in the plume at Big Hill. Nevertheless, the decreasing concentrations of NO2 as the plume is advected to Big Hill lead to decreases in the production rate of HNO3 and ozone. The data also demonstrate the role that temperature plays in sequestering NO2 into peroxy nitrates, effectively decreasing the rate of ozone production. The important contribution of ?AN s to NOy in the region suggests that they should be considered with regards to ex port of NOy from the boundary layer. Nocturnal observations of airmasses characteristic of the free troposphere showed lower NOy concentrations, which were dominated by HNO 3 with a relatively small contribution from the organic nitrates.

Cite this document (BETA)

Readership Statistics

16 Readers on Mendeley
by Discipline
 
 
 
by Academic Status
 
25% Ph.D. Student
 
25% Post Doc
 
6% Other Professional
by Country
 
6% United Kingdom
 
6% Peru
 
6% Argentina

Sign up today - FREE

Mendeley saves you time finding and organizing research. Learn more

  • All your research in one place
  • Add and import papers easily
  • Access it anywhere, anytime

Start using Mendeley in seconds!

Already have an account? Sign in