TSP were collected on 47-mm diameter quartz fibre filters (QMA Whatman) at a flow rate of 1 m3 h?1. In order to avoid the filter overloading (which would introduce uncertainties in carbon analyses), discontinuous sampling was adopted here (1 min every 5 min). Sampling duration was typically of the order of 3–4 days (8 filters per month). A total number of 146 samples were collected at this site from November 2004 to May 2006.der to partly make up for this lack of information on the chemical composition of Cairo aerosols and on their optical properties.