Suppression of new particle formation from monoterpene oxidation by NOx 1Institut für Bio- und Geowissenschaften, IBG-2, Forschungszentrum Jülich, 52425, Jülich, Germany
18 Mar 2014
2Institut für Energie- und Klimaforschung, IEK-8, Forschungszentrum Jülich, 52425, Jülich, Germany
3Institut für Anorganische und Analytische Chemie, Johannes Gutenberg Universität Mainz, 55128, Mainz, Germany
4Weizmann Institute of Science, Rehovot, 76100, Israel
*now at: Department of Physics, Division of Atmospheric Sciences, Helsinki University, PL 64, 00014 Helsingin yliopisto, Finland
**now at: Frankenstrasse 8, 52382, Niederzier, Germany
Received: 25 Jun 2013 – Published in Atmos. Chem. Phys. Discuss.: 08 Oct 2013Abstract. The impact of nitrogen oxides (NOx = NO + NO2) on new particle
formation (NPF) and on photochemical ozone production from real plant
volatile organic compound (BVOC) emissions was studied in a laboratory setup. At high NOx conditions ([BVOC] / [NOx] < 7, [NOx] > 23 ppb) new particle formation was suppressed. Instead,
photochemical ozone formation was observed resulting in higher hydroxyl
radical (OH) and lower nitrogen monoxide (NO) concentrations. When [NO] was
reduced back to levels below 1 ppb by OH reactions, NPF was observed. Adding
high amounts of NOx caused NPF to be slowed by orders of magnitude compared
to analogous experiments at low NOx conditions ([NOx]
~300 ppt), although OH concentrations were higher. Varying
NO2 photolysis enabled showing that NO was responsible for suppression
of NPF. This suggests that peroxy radicals are involved in NPF. The rates of
NPF and photochemical ozone production were related by power law dependence
with an exponent approaching −2. This exponent indicated that the overall
peroxy radical concentration must have been similar when NPF occurred. Thus,
permutation reactions of first-generation peroxy radicals cannot be the rate
limiting step in NPF from monoterpene oxidation. It was concluded that
permutation reactions of higher generation peroxy-radical-like intermediates
limit the rate of new particle formation.
Revised: 23 Jan 2014 – Accepted: 10 Feb 2014 – Published: 18 Mar 2014
In contrast to the strong effects on the particle numbers, the formation of
particle mass was substantially less sensitive to NOx concentrations.
If at all, yields were reduced by about an order of magnitude only at very
high NOx concentrations.
Citation: Wildt, J., Mentel, T. F., Kiendler-Scharr, A., Hoffmann, T., Andres, S., Ehn, M., Kleist, E., Müsgen, P., Rohrer, F., Rudich, Y., Springer, M., Tillmann, R., and Wahner, A.: Suppression of new particle formation from monoterpene oxidation by NOx, Atmos. Chem. Phys., 14, 2789-2804, doi:10.5194/acp-14-2789-2014, 2014.