Aerosol Science 34 (2003) 747–764 www.elsevier.com/locate/jaerosci Analysis of measurement techniques to determine dry deposition velocities of aerosol particles with diameters less than 100 nm G. Buzorius a; c ; * ,  U. Rannik b , E.D. Nilsson c , T. Vesala b , M. Kulmala b a Atmospheric Sciences Division, Brookhaven National Laboratory, Upton, NY 11973, USA b Department of Physical Sciences, Helsinki University, Helsinki, Finland c Department of Meteorology, Stockholm University, S-10691 Stockholm, Sweden Received 26 August 2002; accepted 13 December 2002 Abstract Modeled aerosol dry deposition velocities to natural surfaces have not been veried against experimental data because data is not available. However due to recent instrumentation developments measuring vertical number uxes of aerosols with sizes down to 10 nm became possible. Additional instrument modications which are discussed here allows measuring size dependent uxes of 10–100 nm aerosols and would fulll the data gap. This study analyzes uncertainties in such measurements. Low particle count is identied as a major contributor to the measurement uncertainty, limiting the accurate estimation of size-resolved dry deposition velocities in remote environment to particles with diameters less than 50 nm using current instrumentation. Even in this size range high concentrations are required. In the case of two particle counters with dierent detection limits dry deposition velocity estimates can be also systematically biased, depending on the aerosol size distribution. A dierence in detection limits of counters about 10 nm is narrow enough to avoid bias in size-dependent dry deposition velocities in most circumstances. Published by Elsevier Science Ltd. 1. Introduction The literature reports dry deposition data for super-micron and sub-micron ambient aerosols down to 100 nm. A summary of model ts to experimental data for aerosol particles with diameters larger ∗ Corresponding author. E-mail address: gintas@misu.su.se (G. Buzorius). 0021-8502/03/$ - see front matter. Published by Elsevier Science Ltd. doi:10.1016/S0021-8502(03)00025-9