Pattern, sources and toxic potential of PAHs in the agricultural soils of Delhi, India

Surface soil (0-5 cm) from various agricultural sites in Delhi was analyzed to discern the contents of 16 priority polycyclic aromatic hydrocarbons (PAHs). Reference and deuterated standards were used for identification and quantification of PAHs by high performance liquid chromatography (HPLC) with UV detection. ∑16PAHs ranged from 830 to 3880 μg kg−1 (dry wt.) with an arithmetic mean of 1910 ± 1020 μg kg−1 ∑16PAHs values at the urban sites were 2-5 times higher as compared to the rural sites. In general, low molecular weight PAHs were predominant. Total organic carbon (TOC) was found to be significantly correlated with ∑16PAHs. Isomer pair ratios and Principal component analysis (PCA) suggested biomass and fossil fuel combustion as the main sources of PAHs. The toxic equivalency factors (TEFs) were used to estimate benzo[a]pyrene-equivalent concentration (B[a]Peq). Therewith, PAH content of urban agricultural soil was found to have more carcinogenic potential.