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 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 (r = 0.69-0.98, p < 0.001) for log Kvs. 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 in its logarithmic form correlated with 1/T (r = 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.

A comparison of PM&lt;sub&gt;2.5&lt;/sub&gt;-bound polycyclic aromatic hydrocarbons in summer Beijing (China) and Delhi (India)

“…The distribution of highly volatile PAHs (e.g. 2-3 ring) are known to be influenced by temperature (Tsapakis and Stephanou., 2005;Gaga and Ari., 2011;Verma et al, 2017), while the low volatile PAHs and PAHs-derivatives (e.g. oxygenated and nitrated-PAHs) are mostly associated to the particle phase (Albinet et al, 2008;Liu et al, 2017, Zhang et al, 2018.…”

“…6). Ambient temperature highly affects the gas/particle partitioning of 2-3 ring PAH (Tsapakis and Stephanou., 2005;Gaga and Ari., 2011;Verma et al, 2017). Therefore, higher contributions from 2, 3 and 4 rings in winter Beijing are likely due to lower temperature and to the use of coal and wood combustion for residential heating.…”

A comparison of PM&lt;sub&gt;2.5&lt;/sub&gt;-bound polycyclic aromatic hydrocarbons in summer Beijing (China) and Delhi (India)

“…The distribution of highly volatile PAHs (e.g. two to three rings) is known to be influenced by temperature (Tsapakis and Stephanou, 2005;Gaga and Ari., 2011;Verma et al, 2017), while the low volatility PAHs and PAH derivatives (e.g. oxygenated and nitrated PAHs) are mostly associated with the particle phase (Albinet et al, 2008;Liu et al, 2017, Zhang et al, 2018.…”

“…The sampling site in both Beijing and Delhi was at a short distance from busy roads with significant vehicle exhaust emissions. BaP lifetime is affected by light and oxidants in the atmosphere; BaP is far more reactive than its isomer BeP (Butler and Crossley, 1981;Ringuet et al, 2012b); thus the decline of the ratio BaP / (BaP + BeP) can be regarded as an indicator of particle ageing (Liu et al, 2013;Watson et al, 2016). Considering the above, BaP / (BaP + BeP) has been used in this study to assess the contribution of local sources to particle composition.…”

“…Generally, there is no defined threshold value for BaP / (BaP + BeP) which can distinguish aged particles from freshly emitted ones. However, Watson et al (2016) suggested that similar amounts of BaP and BeP (ratio = 0.5) indicate that particles are freshly emitted and mostly affected by local emissions rather than long-range atmospheric transport. Moreover, Liu et al (2013) compared BaP and BeP ratios at remote sites and emission source regions and reported that BaP / BeP lower than 0.4 means aged aerosol type, while a value higher than 0.4 indicates local emission source.…”