Number and Size Distribution of Airborne Nanoparticles during Summertime in Kuwait: First Observations from the Middle East

摘要

We made fast response measurements of size-resolved particle number concentrations (PNCs) and distributions (PNDs) in the 5-1000 nm range close to a busy roadside, continuously for 31 days, in Kuwait. The aims were to understand their dispersion characteristics during summertime and dust events, and association with trace pollutants (NO_x, O_3, CO, SO_2, and PM_(10)) and meteorological parameters. PNC_5 were found up to ～19-times higher (5.98 × 10~5 cm~(-3)) than those typically found in European roadside environments. Size distributions exhibited over 90% of PNCs in ultrafine size range (＜100 nm) and a negligible fraction over 300 nm. Peak PNDs appeared at ～12 nm, showing an unusually large peak in nucleation mode. Diurnal variations of PNCs coincided with the cyclic variations in CO, NO_x, and traffic volume during morning and evening rush hours. Despite high traffic volume, PNC peaks were missing during noon hours due to high ambient temperature (～48 ℃) that showed an inverse relationship with the PNCs. Principal Component Analysis revealed three probable sources in the area-local road traffic, fugitive dust, and refineries. Dust events, categorized by PM_(10) with over 1000 μg m~3, decreased PNCs by ～25% and increased their geometric mean diameters (GMDs) by ～66% compared with nondust periods.