Uptake of NO3 and N2O5 to Saharan dust, ambient urban aerosol and soot: a relative rate study Max-Planck-Institute für Chemie, Atmospheric Chemistry Division, Mainz, Germany
Received: 02 Dec 2009 – Published in Atmos. Chem. Phys. Discuss.: 08 Jan 2010Abstract. The uptake of NO3 and N2O5 to Saharan dust, ambient aerosols
and soot was investigated using a novel and simple relative rate method with
simultaneous detection of both NO3 and N2O5. The use of
cavity ring down spectroscopy to detect both trace gases enabled the
measurements to be carried out at low mixing ratios (<500 pptv or 1×1010 molecule cm−3). The uptake coefficient ratio,
γ(NO3)/γ(N2O5), was determined to be 0.9±0.4 for Saharan dust, independent of relative humidity, NO3 or
N2O5 mixing ratio and exposure time. Ambient (urban) aerosols
showed a very limited capacity to take up N2O5 but were reactive
towards NO3 with γ(NO3)/γ(N2O5)>15.
A value of γ(NO3)/γ(N2O5)~1.5–3 was obtained when using candle generated soot. The relative rate obtained
for Saharan dust can be placed on an absolute basis using our recently
determined value of γ(N2O5)=1×10−2 to
give γ(NO3)=9×10−3, which is significantly
smaller than the single previous value. With the present uptake coefficient,
reaction of NO3 with mineral dust will generally not contribute
significantly to its NO3 loss in the boundary atmosphere or to the
nitration of mineral dust.
Revised: 18 Mar 2010 – Accepted: 23 Mar 2010 – Published: 29 Mar 2010
Citation: Tang, M. J., Thieser, J., Schuster, G., and Crowley, J. N.: Uptake of NO3 and N2O5 to Saharan dust, ambient urban aerosol and soot: a relative rate study, Atmos. Chem. Phys., 10, 2965-2974, doi:10.5194/acp-10-2965-2010, 2010.