Distribution and source apportionment of atmospheric non–methane hydrocarbons in Mumbai, India

Concentrations of non–methane hydrocarbons (NMHCs) in atmosphere were measured at six urban sites in Mumbai from February 2005 to January 2006. Seventeen hydrocarbons, i.e., ethane, ethylene, acetylene, propane, propylene, iso–butane, n–butane, iso–pentane, n–pentane, hexane, benzene, heptane, toluene, ethyl benzene, p–xylene, o– xylene and n–decane have been identified in 254 urban air samples using a cryogenic pre–concentration system attached to a Gas Chromatograph (GC) with a Flame Ionization Detector (FID). C2–C5 hydrocarbons were determined on 2 m x 2 mm i.d., stainless steel (S.S.) column packed with n–octane/Poracil C. The components of C6 and above are determined on a 3 m x 2 mm i.d., S.S. column filled with 10% OV – 101 on chromosorb WAW. All these species show well–defined winter season (November–February) high and summer season (March–June) low values. Factor analysis (FA), a receptor modeling technique, has been used for quantitative source apportionment. Varimax rotated factor analysis identified five possible sources. The mean percent contribution from the vehicular exhausts was found to be 33% while that from refinery sources contribute 21%. Petrochemical industries and paint solvent contributed 15% and 11% respectively. Eight percent of the NMHCs were coming from polymer manufacturing industries. The remaining 12% is contributed by other unidentified sources.