Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 1 2004 10.5194/acpd-4-569-2004 http://www.atmos-chem-phys-discuss.net/4/569/2004/ http://www.atmos-chem-phys-discuss.net/4/569/2004/acpd-4-569-2004.html http://www.atmos-chem-phys-discuss.net/4/569/2004/acpd-4-569-2004.pdf 569 590 2004-01-26 Reactive uptake coefficients for heterogeneous reaction of N₂O₅ with submicron aerosols of NaCl and natural sea salt D. J. Stewart R. A. Cox Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK The kinetics of uptake of gaseous N₂O₅ 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 N₂O₅ on deliquesced sea salt droplets at 298 K and <i>RH</i>&gt;40%.