Measurements of isoprene nitrates above a forest canopy

TitleMeasurements of isoprene nitrates above a forest canopy
Publication TypeJournal Article
Year of Publication2001
AuthorsGrossenbacher JW, Couch TL, Shepson PB, Thornberry TDean, Witmer-Rich M, Carroll MAnne, Faloona I, Tan D, Brune WH, Ostling K, Bertman SB
JournalJournal of Geophysical Research

Measurements of atmospheric organic nitrates derived from isoprene, i.e., "isoprene nitrates", were conducted from July 14 to August 19, 1998, as part of the 1998 summer intensive measurement campaign of the Program for Research on Oxidants: PHotochemistry, Emissions, and Transport (PROPHET) at UMBS in Pellston, Michigan. The measurements were conducted using on-line chromatography in conjunction with a nitrate-selective detection scheme. Measured concentrations of isoprene nitrates ranged from 0.5 parts per trillion (ppt), the detection limit of the method employed, to 35 ppt. In this paper we discuss the contribution of the isoprene nitrates to NOy, which was typically 0.5 to 1.5% of total odd nitrogen, but up to ~4% for well-aged air. Concentrations of isoprene nitrates exhibited a strong diurnal variation consistent with their expected chemical and physical removal rates. In this work we also discuss the chemistry of the precursor peroxy radicals and the NOx dependence of isoprene nitrate formation.