Abstract
ABSTRACT This study investigated atmospheric particulate matter (PM) with an aerodynamic diameter of < 2.5 µm (PM2.5) observed at the Prince of Songkla University (Phuket Campus) in southern Thailand. All samples (n = 75) were collected using MiniVol™ portable air samplers from March 2017 to February 2018. Carbonaceous aerosol compositions, i.e., organic carbon (OC) and elemental carbon (EC), water-soluble ionic species (WSIS), and polycyclic aromatic hydrocarbons (PAHs) in the PM2.5 samples were identified and quantified. We found that the average PM2.5 concentration was 42.26 ± 13.45 µg m–3, while the average concentrations of OC and EC were 3.05 ± 1.70 and 0.63 ± 0.58 µg m–3, respectively. The OC/EC ratio was in the range of 2.69–16.9 (mean: 6.05 ± 2.70), and the average concentration of 10 selected ions was 6.91 ± 3.54 µg m–3. The average concentration of SO42– was the highest throughout the entire study period (2.33 ± 1.73 µg m–3); the average contribution of SO42– to the major ionic components was 34%. Surprisingly, the average concentrations of NO3– and NH4+ were relatively low. The mean ratio of [NO3–]/[SO42–] was 0.33 ± 0.24. Strong positive correlation was found between K+ and both OC and EC (r = 0.90 and r = 0.93, respectively). It is also precious to highlight that biomass burning (BB) is the major source of OC, EC and K+, which multiple studies have confirmed that the role of K+ as a biomass marker. Results showed that BB episodes might play a major role in producing the observed high levels of OC. The relatively high abundance of both B[g,h,i]P and Ind suggests that motor vehicles, petroleum/oil combustion, and industrial waste burning are the primary emission sources of PAHs in the ambient air of Phuket. Interestingly, principal component analysis (PCA) indicated that vehicular exhausts are the main source of carbonaceous aerosol compositions found in the ambient air of Phuket, whereas the contributions of biomass burning, diesel emissions, sea salt aerosols and industrial emissions were also important.
Highlights
Air pollution is primarily an urban phenomenon, it is an important problem globally
In characterizing the chemical composition of aerosols in northern Indochina in March and April 2010, Chuang et al (2013) found OC3 to be a reasonable tracer of biomass burning (BB), whereas OC2 is known as a tracer of both coal combustion (Chow et al, 2004) and vehicular exhausts (Cheng et al, 2015)
The application of diagnostic binary ratios of OC/elemental carbon (EC) and estimations of secondary organic carbon (SOC) in this study highlighted that the enhanced impacts of incomplete combustion emissions, such as motor vehicle exhaust, fuel burning, and biomass burning, which can be remained in the atmosphere for several days (Wu et al, 2019; Kaskaoutis et al, 2020)
Summary
Air pollution is primarily an urban phenomenon, it is an important problem globally. Several studies have investigated the presence of carcinogenic and/or mutagenic substances in the atmosphere, derived via gas-particle partitioning, e.g., polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls, the origin of which is incomplete combustion attributable to both natural and anthropogenic sources (Zhang et al, 2014; Achten and Andersson, 2015; Wincent et al, 2016; Bocchi et al, 2017; Idowu et al, 2019) These substances, which are classified as semi-volatile compounds, can be released as solid material or vapour that can adhere to the surface of other particles (Smith and Harrison, 1998; Jones and Voogt, 1999; Dachs and Eisenreich, 2000; Schummer et al, 2010; Lawal, 2017). Measurement of the concentration of these carbonaceous aerosols is highly important
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