Volume 12, No. 6, December 2012, Pages 1247-1260 PDF(1.24 MB)
Chemical Speciation and Source Assignment of Particulate (PM10) Phase Molecular Markers in Mumbai
Mihir Herlekar, Abba Elizabeth Joseph, Rakesh Kumar, Indrani Gupta
National Environmental Engineering Research Institute, 89-B, Dr. A.B. Road, Worli, Mumbai – 400 018, India
Particulate matter (PM10) has emerged as the single most important pollutant across Indian cities, as its levels exceed the regulated standards at most places. PM10 was collected and analyzed at seven sites representing different land use patterns in Mumbai during 2007–08 for organic carbon (OC) and elemental carbon (EC). OC was further speciated for organic markers, which are useful for identifying sources. Average PAH concentration ranged from 47.84 ± 14.07 to 247.70 ± 163.19 ng/m3. n-alkanes concentration varied from 157.20 ± 35.28 to 759.13 ± 451.65 ng/m3. Hopanes and steranes showed the highest concentrations of 94.14 ± 28.66 and 32.64 ± 11.79 ng/m3 and lowest concentrations of 7.81 ± 2.00 ng/m3 and 2.83 ± 0.73 ng/m3, respectively. The values for levoglucosan varied from 0.69 ± 0.46 to 3.23 ± 2.07 µg/m3. The percentage contribution of the sum of the concentrations of these compounds to the total organic carbon varied from 1.7–5.1%. The sources contributing to particulate PAHs were identified using diagnostic ratios. Indicators like the Carbon Preference Index (CPI), Cmax and Plant Wax Number (%WNA) were used to identify the relative contributions to n-alkanes from anthropogenic and biogenic emissions. The source apportionment results and also the concentration trends for these molecular markers indicate that anthropogenic sources, especially vehicular exhaust, wood combustion and coal combustion, are mainly responsible for the organic fraction of particulate matter in Mumbai city. The sources identified qualitatively in this work can help in selecting the appropriate source profiles for estimating the quantitative contribution of these sources.
PM10; Molecular marker; Diagnostic ratios; CPI; Mumbai.