Characterization, risk assessment, and source estimation of PM10-bound polycyclic aromatic hydrocarbons during wintertime in the ambient air of Basrah City, Iraq.

In this study, the concentration and structure of polycyclic aromatic hydrocarbons (PAHs) associated with the ambient PM10 in Basrah City, Iraq have been investigated for the first time. From December 2021 to February 2022, PM10 samples were collected on quartz fiber filters, extracted using an optimized extraction protocol, and analyzed for the sixteen US EPA priority PAHs. The results indicated that 4- and 5-ring PAHs represent 52% of the total detected PAHs. The most abundant PAHs over the study period were chrysene (1.2 ± 1.5 ng m-3), fluorene (0.9 ± 1.4 ng m-3), and benzo[b]fluoranthene (0.7 ± 0.9 ng m-3). Source identification suggested that PM10-bound PAHs primarily originated from pyrogenic and petrogenic activities in Basrah City. In addition, the cancer risk associated to PAH exposure was assessed based on benzo[a]pyrene equivalent concentration and was found ranging from 0.07 to 6.32 ng m-3; hence, it exceeded the threshold limit of 1.0 ng m-3 established by the European legislation (EU, 2014). Benzo[a]pyrene was determined to be main contributor to total carcinogenic power of the detected PAHs, accounting for 50.3%, followed by dibenz[a,h]anthracene (22.3%). Similarly, benzo[a]pyrene represented a major contributor to PAH associated mutagenicity, accounting for 43.5% of the total.

Secondary Organic Aerosols from Aromatic Hydrocarbons and their Contribution to Fine Particulate Matter in Atlanta, Georgia.

Tracers of secondary organic aerosols (SOA) from thirteen aromatic hydrocarbons were quantified in laboratory smog chamber experiments. Class-specific SOA tracers emerged, including 2,3-dihydroxy-4-oxo-pentatonic acid (DHOPA) from monoaromatic volatile organic compounds (VOCs), phthalic acid from naphthalene and 1-methylnaphthalene, and methyl-nitrocatechol isomers from o,m,p-cresol oxidation. Organic carbon mass fractions (fSOC) for these and other tracers were determined and extend the SOA tracer method widely used to apportion biogenic SOC. The extended SOA tracer model was applied to evaluate the sources of SOC in Atlanta, GA during summer 2015 and winter 2016 after modifying the chamber-derived fSOC values to reflect SOA yields and local VOC levels (fSOC'). Monoaromatic, diaromatic, and cresol SOC contributed an average of 24%, 8%, and 0.12% of organic carbon (OC) mass during summer and 17%, 5%, and 0.27% during winter, respectively. Cresol SOC peaked during winter and was highly correlated with levoglucosan (r=0.83, p<0.001), consistent with it originating from biomass burning. Together, aromatic, biogenic, and biomass burning derived SOC accounted for an average of 77% and 28% of OC in summer and winter, respectively. The new understanding of SOA composition from aromatic VOCs advances the tracer-based method by including important precursors of SOC and enables a better understanding of the sources of atmospheric aerosol.

Source apportionment of fine particulate matter organic carbon in Shenzhen, China by chemical mass balance and radiocarbon methods.

Chemical mass balance (CMB) modeling and radiocarbon measurements were combined to evaluate the sources of carbonaceous fine particulate matter (PM2.5) in Shenzhen, China during and after the 2011 summer Universiade games when air pollution control measurements were implemented to achieve air quality targets. Ambient PM2.5 filter samples were collected daily at two sampling sites (Peking University Shenzhen campus and Longgang) over 24 consecutive days, covering the controlled and uncontrolled periods. During the controlled period, the average PM2.5 concentration was less than half of what it was after the controls were lifted. Organic carbon (OC), organic molecular markers (e.g., levoglucosan, hopanes, polycyclic aromatic hydrocarbons), and secondary organic carbon (SOC) tracers were all significantly lower during the controlled period. After pollution controls ended, at Peking University, OC source contributions included gasoline and diesel engines (24%), coal combustion (6%), biomass burning (12.2%), vegetative detritus (2%), biogenic SOC (from isoprene, α-pinene, and ß-caryophyllene; 7.1%), aromatic SOC (23%), and other sources not included in the model (25%). At Longgang after the controls ended, similar source contributions were observed: gasoline and diesel engines (23%), coal combustion (7%), biomass burning (17.7%), vegetative detritus (1%), biogenic SOC (from isoprene, α-pinene, and ß-caryophyllene; 5.3%), aromatic SOC (13%), and other sources (33%). The contributions of the following sources were smaller during the pollution controls: biogenic SOC (by a factor of 10-16), aromatic SOC (4-12), coal combustion (1.5-6.8), and biomass burning (2.3-4.9). CMB model results and radiocarbon measurements both indicated that fossil carbon dominated over modern carbon, regardless of pollution controls. However, the CMB model needs further improvement to apportion contemporary carbon (i.e. biomass burning, biogenic SOC) in this region. This work defines the major contributors to carbonaceous PM2.5 in Shenzhen and demonstrates that control measures for primary emissions could significantly reduce secondary organic aerosol (SOA) formation.