Concentration level, pattern and toxic potential of PAHs in traffic soil of Delhi, India

Present study was envisaged to examine the impact of vehicular traffic on the contamination status of urban traffic sites in Delhi with respect to Polycyclic Aromatic Hydrocarbon (PAH). Surface soil (0-5 cm) from three traffic sites and one rural site was analyzed and the content of 16 priority PAHs was determined. Total PAH concentration at traffic sites ranged from 1062 microg kg(-1) to 9652 microg kg(-1) with an average value of 4694+/-3028 microg kg(-1). At the rural site average concentration of total PAHs was found to be 886+/-303 microg kg(-1). Carcinogenic potency of PAH load in traffic soil was nearly 21 times higher as compared to the rural soil. PAH pattern was dominated by five- and six-ring PAHs (contributing >50% to the total PAHs) at all the three traffic sites. On the other hand, rural soil showed a predominance of low molecular weight two- and three-ring PAHs (contributing >50% to the total PAHs). A lack of correlation was observed between total PAH and total organic carbon (TOC) content in traffic soils but in rural soil both were positively correlated (r=0.76). In rural soil naphthalene (r=0.88, P=<0.05) displayed strongest correlation with TOC. Indeno[123-cd]pyrene/benz[ghi]perylene (IP/BgP) ratio indicated that PAH load at the traffic sites is predominated by the gasoline-driven vehicles. Principal Component Analysis (PCA) provided the fingerprints of vehicular traffic emission and coal combustion in the study area.