Bulk filters were used to collect samples of airborne dust. The aerosol sampling system used onboard the BAe146 is identical to that previously used onboard the UK Met Office C-130 and described in detail in Andreae et al. [2000]. Aerosol particles were sampled by filtration onto two stacked-filter units (SFUs) mounted in parallel. Each SFU can hold a maximum of three filters on sequential 47-mm diameter polyethylene supports, but only one stage was used during DODO. Samples were collected only during horizontal flight legs lasting not less than 20–30 minutes in order to guarantee sufficient loading of the filter samples. One SFU consisted of a Nucleopore filter (nominal pore size 0.4 ?m) measuring the inorganic composition. The second SFU was used for measuring carbonaceous aerosols on one quartz filter.