Levels, Sources, and Toxic Potential of Polycyclic Aromatic Hydrocarbons in Urban Soil of Delhi, India

ABSTRACT

This study was done to determine the concentration of PAHs in urban soil of Delhi (India). Surface top soil (up to 10 cm depth) samples were collected from four different sampling sites including industrial, roadside, residential, and agricultural areas of Delhi and 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were evaluated. Total PAH concentrations at industrial, roadside, residential, and agricultural sites were 11.46 ± 8.39, 6.96 ± 4.82, 2.12 ± 1.12, and 1.55 ± 1.07 mg/kg (dry weight), respectively, with 3–7 times greater concentrations in industrial and roadside soils than that in residential and agricultural soils. The PAH pattern was dominated by 4- and 5-ring PAHs (contributing >50% to the total PAHs) at industrial and roadside sites with greater concentration of fluoranthene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]anthracene, benzo[ghi]perylene, and pyrene, whereas, residential and agricultural sites showed a predominance of low molecular weight 2- and 3-ring PAHs (fluoranthene, acenaphthene, naphthalene, chrysene, and anthracene). Isomeric pair ratios suggested biomass combustion and fossil fuel emissions as the main sources of PAHs. The toxic equivalency factors (TEFs) showed that carcinogenic potency (benzo[a]pyrene-equivalent concentration (B[a]P_eq) of PAH load in industrial and roadside soils was ∼10 and ∼6 times greater than the agricultural soil.

Key Words:

• PAHs
• urban soils
• PAH profile
• Isomeric pair ratio
• B[a]P_eq.
• vehicular emissions

ACKNOWLEDGMENTS

The authors are grateful to Prof. D.K. Bandhopadhyay, Vice Chancellor, GGSIP University, Prof. Nupur Prakash, Principal, IGIT and Prof. R.C. Budhani, Director, National Physical Laboratory for their encouragement. Thanks are due to the Council of Scientific & Industrial Research, New Delhi, for funding the research project and for the award of Senior Research Fellowship to one of the authors (DPS) under the Project.