NCAR Isoprene Oxidation (2009, 2011, 2012)

The CU LED-CE-DOAS instrument was taken to the lab of Geoff Tyndall and John Orlando at the National Center for Atmospheric Research to investigate isoprene oxidation at their reaction chamber. Measurements by the CE-DOAS were complimented by the FT-IR which is permanently installed in the chamber as well as proton-transfer reaction Mass Spectrometry measurements of VOC’s from another group at NCAR. More than 150 experiments were carried out in October 2009, January-March 2011 and March and April of 2012. Primary yields of glyoxal, methyl glyoxal, glycolaldehyde and hydroxyacetone (the minor carbonyl products) were measured at three temperatures (260, 295, 320 K) and at high and low NOx. Room temperature primary yields of the minor products of 2.1, 1.8, 2.3 and 2.3% were measured for glyoxal, methyl glyoxal, glycolaldehyde and hydroxyacetone respectively. In addition no secondary formation of glyoxal from isoprene was observed.

Reaction chamber at NCAR. The FT-IR beam path is incased in the triple-walled stainless steel chamber. The LED-CE-DOAS and PTR instruments sampled and diluted small flows from the chamber.

Production of glyoxal from isoprene compared to glyoxal formation from 1,3 butadiene. Primary and secondary production are shown separated for isoprene and combined for both isoprene and 1,3 butadiene, compared with the experimental results.