The 24-h average ambient particulate matter (PM 10 and PM 2.5) concentrations are sampled concurrently during November 2008-April 2009 at a busy roadside in Chennai City, India. The elemental (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Rb, Se, Sr, Te, Tl, V and Zn) and ionic (Na +, NH 4 +, K +, Ca 2+, Mg 2+, F -, Cl -, NO 2 -, NO 3 - and SO 4 2-) composition of PM 10 and PM 2.5 are determined using an inductively coupled plasma-optical emission spectrometer (ICP-OES) and an ion chromatograph (IC), respectively. The emission inventory at the study area is also carried out to identify the likely PM emission sources. The U.S. EPA's-CMB (chemical mass balance) version 8.2 is applied to identify the source contribution of ambient PM 10 and PM 2.5 concentrations at the study area. Results indicated that diesel exhausts (43-52% in PM 10 and 44-65% in PM 2.5) and gasoline exhausts (6-16% in PM 10 and 3-8% in PM 2.5) are found to be the major source contributors at the study site followed by the paved road dusts (PM 10=PM 2.5=0.-2.3%), brake lining dusts (0.1% in PM 10 and 0.2% in PM 2.5), brake pad wear dusts (0.1% in PM 10 and 0.01% in PM 2.5), marine aerosols (PM 10=PM 2.5=0.1%) and cooking (~0.8% in PM 10 and ~1.5% in PM 2.5). © 2012 Elsevier B.V.