ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-4-569-2004 Reactive uptake coefficients for heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> with submicron aerosols of NaCl and natural sea salt Stewart D. J. 1 Cox R. A. 1 Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK 26 01 2004 4 1 569 590 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/4/569/2004/acpd-4-569-2004.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/4/569/2004/acpd-4-569-2004.pdf

The kinetics of uptake of gaseous N<sub>2</sub>O<sub>5</sub> on submicron aerosols containing NaCl and natural sea salt has been investigated in a flow reactor as a function of relative humidity (<i>RH</i>) in the range 30-80% at 295+/-2 K and a total pressure of 1 bar. The measured uptake coefficients, &gamma;, were larger on the aerosols containing sea salt compared to those of pure NaCl, and in both cases increased with increasing <i>RH</i>. These observations are explained in terms of the variation in water content and hence size of the salt droplets, which leads to a limitation in the uptake rate into small particles. After correction for this effect the uptake coefficients are independent of relative humidity, and agree with those measured previously on larger droplets. A value of &gamma;=0.025 is recommended for the reactive uptake coefficient for N<sub>2</sub>O<sub>5</sub> on deliquesced sea salt droplets at 298 K and <i>RH</i>&gt;40%.