Levels and sources of organic compounds in fine ambient aerosols over National Capital Region of India

Abstract

The study presents the spatial and temporal variation of fine ambient aerosols (PM_2.5) over National Capital Region (NCR), India, during January to June 2016. The investigation includes three sampling sites, one in Delhi and two in the adjoining states of Delhi (Uttar Pradesh and Haryana), across NCR, India. The average PM_2.5 concentration was highest for Delhi (128.5 ± 51.5 μg m⁻³) and lowest for Mahendragarh, Haryana (74.5 ± 28.7 μg m⁻³), during the study period. Seasonal variation was similar for all the sites with highest concentration during winter and lowest in summer. PM_2.5 samples were analysed for organic compounds using gas chromatograph (GC). The concentration of three organic compound classes, n-alkanes (C11–C35), polycyclic aromatic hydrocarbons (PAHs), and phthalates, present in PM_2.5 samples has been reported. Diagnostic ratios for n-alkanes demonstrated that biogenic emissions were dominant over Mahendragarh while major contributions were observed from petrogenic emissions over Delhi and Modinagar, Uttar Pradesh. Molecular diagnostic ratios were calculated to distinguish between different sources of PAHs, which revealed that the fossil fuel combustion (diesel and gasoline emissions), traffic emissions, and biomass burning are the major source contributors. Health risk associated with human exposure of phthalates and PAHs was also assessed as daily intake (DI, ng kg⁻¹ day⁻¹) and lung cancer risk, respectively. Backward trajectory analysis explained the local, regional, and long-range transport routes of PM_2.5 for all sites. Principal component analysis (PCA) results summarized that the vehicular emissions, biomass burning, and plastic burning were the major sources of the PAHs and phthalates over the sampling sites.