Elemental composition of airborne aerosols at a traffic site and a suburban site in Hong Kong

Forty elemental concentrations in different size particles were measured at a roadside site and a suburban site of Hong Kong using a ten-stage MOUDI impactor (Mode 110). Some elements (Cr, Fe, Co, Cu, As and Ba) have clear spatial variability, with ∼100% higher concentrations in roadside atmosphere than in suburban atmosphere, showing obviously vehicle-related sources for those elements. However, it is contrary for three typical sea salt elements (Na, Cl and Br), showing more than 100% higher concentrations in suburban environment than in roadside environment, which is due to the influence of marine aerosols. The size distributions of elements are generally similar between roadside and suburban site. The elements Na, Mg, Al, Si, Cl, Ca, Ti, Mn and Fe mainly present in coarse mode (10 μm > diameter > 1 μm). The mass concentrations of K, V and Ni are distributed in both fine (diameter > 1 μm) and coarse mode. The size distributions of S, Pb, As, Se, Zn, Cu, Cd and Ba show a single peak at around 1 μm or less. The contributions of mineral dust to Total Suspended Particles (TSP) are similar for the traffic and suburban site, ∼13.8% and ∼14.2%, respectively. Sea salts account for ∼1.6% of TSP for the traffic site, and ∼6.0% for the suburban site.