Atmospheric Measurement Techniques www.atmos-meas-tech.net 1867-1381 1867-8548 2 1 2009 10.5194/amt-2-313-2009 http://www.atmos-meas-tech.net/2/313/2009/ http://www.atmos-meas-tech.net/2/313/2009/amt-2-313-2009.html http://www.atmos-meas-tech.net/2/313/2009/amt-2-313-2009.pdf 313 318 2009-06-30 Development of an H-TDMA for long-term unattended measurement of the hygroscopic properties of atmospheric aerosol particles E. Nilsson erik.nilsson@nuclear.lu.se E. Swietlicki S. Sjogren J. Löndahl M. Nyman B. Svenningsson Div. of Nuclear Physics, Dept. of Physics, Lund University, P.O. Box 118, 22100, Lund, Sweden A new hygroscopic tandem differential mobility analyzer (H-TDMA) has been constructed at Lund University within the frameworks of the EU FP6 Infrastructure Project EUSAAR (<a href="http://www.eusaar.org/" target="_blank">http://www.eusaar.org/</a>). The aim of this coordinated H-TDMA development is to design and evaluate a new generation of H-TDMAs that are capable of conducting long term measurements of the hygroscopic growth and state of mixing of sub-micrometer atmospheric aerosol particles at the EUSAAR aerosol super-sites across Europe. The H-TDMA constructed for this project has been validated with respect to hygroscopic growth factor, stability of relative humidity (RH), temperature stability and its ability to operate unattended for longer periods of time. When measuring growth factors of ammonium sulphate, the new H-TDMA system was found to measure within a growth factor deviation of &plusmn;0.05 compared to previously recorded data by Tang et al. (1994). The long term RH of the system has been found stable at 90.0% with a standard deviation of &plusmn;0.23% and an average temperature variability of the second DMA less than &plusmn;0.1 K. 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