Seasonal effect and source apportionment of polycyclic aromatic hydrocarbons in PM2.5

Abstract

This study aims to investigate distribution and sources of 16 polycyclic aromatic hydrocarbons (PAHs) bound to fine particulate matter (PM2.5) captured in a semi-urban area in Malaysia during different seasons, and to assess their health risks. PM2.5 samples were collected using a high volume air sampler on quartz filter paper at a flow rate of 1m3min−1 for 24h. PAHs on the filter paper were extracted with dichloromethane (DCM) using an ultrasonic centrifuge solid-phase extraction method and measured by gas chromatography–mass spectroscopy. The results showed that the range of PAHs concentrations in the study period was between 0.21 and 12.08ngm−3. The concentrations of PAHs were higher during the south-west monsoon (0.21–12.08ngm−3) compared to the north-east monsoon (0.68–3.80ngm−3). The high molecular weight (HMW) PAHs (≥5 ring) are significantly prominent (>70%) compared to the low molecular weight (LMW) PAHs (≤4 ring) in PM2.5. The Spearman correlation indicates that the LMW and HMW PAHs correlate strongly among themselves. The diagnostic ratios (DRs) of I[c]P/I[c]P+BgP and B[a]P/B[g]P suggest that the HMW PAHs originated from fuel combustion sources. The source apportionment analysis of PAHs was resolved using DRs-positive matrix factorization (PMF)-multiple linear regression (MLR). The main sources identified were (a) gasoline combustion (65%), (b) diesel and heavy oil combustion (19%) and (c) natural gas and coal burning (15%). The health risk evaluation, by means of the lifetime lung cancer risk (LLCR), showed no potential carcinogenic risk from the airborne BaPeq (which represents total PAHs at the present study area in Malaysia). The seasonal LLCR showed that the carcinogenic risk of total PAHs were two fold higher during south-westerly monsoon compared to north-easterly monsoon.