Atmospheric concentrations and gas–particle partitioning of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs at Indo-Gangetic sites

Abstract

Aerosol samples in the dual-phase (gaseous and particulate) were collected simultaneously for the first time in Agra at a rural and a traffic dominated site during post-monsoon and winter seasons to investigate the gas–particle partitioning of polycyclic aromatic hydrocarbons (PAHs). The samples were collected using a high volume sampler on quartz micro-fiber filter papers and polyurethane foam plugs for particulate and gas phases respectively. The samples were extracted in a mixture of DCM and n-hexane. 16 priority PAHs and two nitro-PAHs were analyzed using gas chromatograph-mass spectrometry. The total concentration of PAHs (gas + particulate) was 4015 and 624 ng m⁻³ at the traffic and rural sites respectively. Two and three ring PAHs were dominant in the gas phase while four, five and six ring PAHs were abundant in the particle phase. A statistically significant correlation (r² = 0.69–0.98, p < 0.001) for log K_pvs. was obtained for individual PAHs at both sites where slopes varied between −2.83 and −0.04 at the traffic site and from −3.15 to −0.06 at the rural site. Regression statistics of Clausius–Clapeyron plots suggest that the concentration of highly volatile PAHs in the atmosphere is influenced by temperature. The gas–particle partitioning coefficient K_p in its logarithmic form correlated with 1/T (r² = 0.5–0.95, p < 0.001) and a positive slope for individual PAHs was found. In health risk assessment DbA was found to be the most carcinogenic and mutagenic as compared to other PAHs followed by BaP. 1-NPyr had a larger contribution to BaP-TEQ than 3-NFla.