Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 6 3 2006 10.5194/acpd-6-5505-2006 http://www.atmos-chem-phys-discuss.net/6/5505/2006/ http://www.atmos-chem-phys-discuss.net/6/5505/2006/acpd-6-5505-2006.html http://www.atmos-chem-phys-discuss.net/6/5505/2006/acpd-6-5505-2006.pdf 5505 5542 2006-06-27 Size distributions of non-volatile particle residuals (Dp<800 nm) at a rural site in Germany and relation to air mass origin C. Engler D. Rose B. Wehner A. Wiedensohler E. Brüggemann T. Gnauk G. Spindler T. Tuch W. Birmili Leibniz Institute for Tropospheric Research, Leipzig, Germany UFZ Center for Environmental Research, Department of Human Exposure Research and Epidemiology, Leipzig, Germany Atmospheric aerosol particle size distributions at a continental background site in Eastern Germany were examined for a one-year period. Particles were classified using a twin differential mobility particle sizer in a size range between 3 and 800 nm. As a novelty, every second measurement of this experiment involved the removal of volatile chemical compounds in a thermodenuder at 300°C. This concept allowed to quantify the number size distribution of non-volatile particle cores – primarily associated with elemental carbon, and to compare this to the original ambient size distribution. A general result was that practically every ambient particle in continental background air contained a non-volatile core. The volume fraction of non-volatile particulate matter (ambient Dp<800 nm) varied between 10 and 30% and was largely consistent with the experimentally determined mass fraction of elemental carbon. The average size of the non-volatile particle cores was estimated as a function of original ambient size using a summation method, which showed that larger particles (>200 nm) contained more non-volatile compounds than smaller particles (<50 nm), thus indicating a significantly different chemical composition. Two alternative air mass classification schemes based on either, synoptic chart analysis (Berliner Wetterkarte) or back trajectories showed, that the volume and number fractions of non-volatile cores were less dependent on air mass than the absolute concentrations in the particle size distributions. In all air masses, the non-volatile size distributions showed a more and a less volatile ("soot") mode, which is located in the size range of about 50 nm. During unstable conditions and in maritime air masses, smaller values were observed compared to continental or stable conditions. This reflects the significant emissions of non-volatile material over the continent and, depending on atmospheric stratification, increased concentrations at ground level.