Biomass burning and vehicle emissions have been identified as two major sources of brown carbon (BrC) (Saleh et al., 2013). Identifying the contributions of BrC sources to the total aerosol and interpreting the optical properties of these sources in the context of atmospheric processing is one of the key objectives of ambient measurements. The main objectives of this work includes measurement of the water and methanol soluble organic aerosol (OA) absorbance at two different sites followed by apportionment of the most important sources of BrC using advanced receptor models such as positive matrix factorization (PMF).