Photochemical conversion of toluene in simulated atmospheric matrix and characterization of large molecular weight products by +APPI FT-ICR MS

Comparative analysis of organic chemical compositions in airborne particulate matter from Ulaanbaatar, Beijing, and Seoul using UPLC-FT-ICR-MS and artificial neural network

This paper presents comparative study on the composition and sources of PM2.5 in Ulaanbaatar, Beijing, and Seoul. Ultrahigh performance liquid chromatography (UPLC) combined with ultrahigh resolution mass spectrometry (UHR-MS) were employed to analyze 85 samples collected in winter. The obtained 340 spectra were interpreted with artificial neural network (ANN). PM2.5 mass concentrations in Ulaanbaatar were significantly higher than those in Beijing and Seoul. ANN based interpretation of UPLC UHR-MS data showed that aliphatic/lipid derived organo‑sulfur compounds, polycyclic aromatic and organo‑oxygen compounds were characteristic to Ulaanbaatar. Whereas, aliphatic/lipid-derived organo‑oxygen compounds were major components in Beijing and Seoul. Aromatic organo‑nitrogen compounds were the main contributors to differentiating the spectra obtained from Beijing from the other cities. Based on two-dimensional gas chromatography/high resolution mass spectrometric (GCxGC/HRMS) data, it was determined that the concentrations of the polycyclic aromatic hydrocarbon (PAH) and polycyclic aromatic sulfur heterocycle (PASH) containing sulfur were highest in Ulaanbaatar, followed by Beijing and Seoul. Coal/biomass combustion was identified as the primary source of contamination in Ulaanbaatar, while petroleum combustion was the main contributor to PM2.5 in Beijing and Seoul. The conclusion that diesel-powered heavy-duty trucks and buses are the main contributors to NOx emissions in Beijing is consistent with previous reports. This study provides a more comprehensive understanding of the composition and sources of PM2.5 in the three cities, with a focus on the differences in their atmospheric pollution profiles based on the UPLC UHR-MS and ANN analysis. It is notable that this study is the first to utilize this method on a large-scale sample set, providing a more detailed and molecular-level understanding of the compositional differences among PM2.5. Overall, the study contributes to a better understanding of the sources and composition of PM2.5 in Northeast Asia, which is essential for developing effective strategies to reduce air pollution and improve public health.

Compilation of reaction kinetics parameters determined in the Key Development Project for Air Pollution Formation Mechanism and Control Technologies in China

A compilation of new advances made in the research field of laboratory reaction kinetics in China's Key Development Project for Air Pollution Formation Mechanism and Control Technologies was presented. These advances are grouped into six broad, interrelated categories, including volatile organic compound (VOC) oxidation, secondary organic aerosol (SOA) formation, new particle formation (NPF) and gas-particle partitioning, ozone chemistry, model parameters, and secondary inorganic aerosol (SIA) formation, highlighting the laboratory work done by Chinese researchers. For smog chamber applications, the current knowledge gained from laboratory studies is reviewed, with emphasis on summarizing the oxidation mechanisms of long-chain alkanes, aromatics, alkenes, aldehydes/ketones in the atmosphere, SOA formation from anthropogenic emission sources, and oxidation of aromatics, isoprene, and limonene, as well as SIA formation. For flow tube applications, atmospheric oxidation mechanisms of toluene and methacrolein, SOA formation from limonene oxidation by ozone, gas-particle partitioning of peroxides, and sulfuric acid-water (H₂SO₄-H₂O) binary nucleation, methanesulfonic acid-water (MSA-H₂O) binary nucleation, and sulfuric acid-ammonia-water (H₂SO₄-NH₃-H₂O) ternary nucleation are discussed.

PM2.5-mediated photochemical reaction of typical toluene in real air matrix with identification of products by isotopic tracing and FT-ICR MS

The sight into photoconversion of toluene, a ubiquitous typical pollutant, attentively by the involvement of PM2.5 in the real air environment is crucial for controlling haze pollution. Compared with the large-size PM2.5 on normal day (PM2.5-ND), the PM2.5 on haze day (PM2.5-HD) formed of small particle agglomerates featured greater oxidation capability, evidenced by the valence distribution of sulfur species. Notably, PM2.5-HD had abundant O₂^-• and •OH and participated in the photochemical reaction of toluene, giving it a greater toluene conversion with a first-order kinetic rate constant of 0.4 d^-1 on haze day than on normal day (0.2 d^-1). During the toluene photoconversion, isotopic labelling traced small molecules including benzene and newfound pentane, ethylbenzene, 1,3,8-p-menthatriene and 4-methyl-1-pentanone benzene that could be formed by methyl breakage, ring opening, fragmentation reforming and addition reaction of toluene. Given ADMET properties, 1,3,8-p-menthatriene was assigned high priority since it had poor metabolism, low excretion and severe toxicity, while benzene and 4-methyl-1-pentanone benzene should also be noticeable. FT-ICR MS results indicated that toluene could create multiple macromolecular products that are more sensitive to SOA generation in haze air matrix with broader carbon number and O/C, more oxygenated substitution with CHO/CHON occupying by 81.4%, lower DBE_average at 4.66 and higher OS_C‾ at -1.60 than normal air matrix. Accordingly, a photochemical reaction mechanism for toluene in real air atmosphere was proposed. The stronger oxidation property of PM2.5 not only facilitated toluene to generate small molecules but also boosted the conversion of intermediates to oxygenated macromolecular products, contributing to the formation of SOA.

Determination of anthropogenic organics in dichlomethane extracts of aerosol particulate matter collected from four different locations in China and Republic of Korea by GC-MS and FTICR-MS

In this study, the hypothesis that particulate matter in east of Korea peninsula would be significantly influenced by particulate matter originated from east of China was evaluated. To test the hypothesis, water-insoluble compounds in particulate matter samples collected from three different locations in Korea and one in China were characterized by atmospheric pressure photoionization (APPI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and gas chromatography mass spectrometry (GC-MS). Each sample was collected twice, in winter and in spring. The GC-MS data revealed the presence of high levels of polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]anthracene in the samples from Tianjin, China. The sample collected in the winter from Baengnyeong Island, which is the location in Korea that is geographically closest to the east coast of China was also rich in aromatic compounds. Meanwhile, the APPI FTICR-MS data showed that polycondensed PAHs and two- to four-ring PAHs with long alkyl chains were abundant in the winter samples from Tianjin and Baengnyeong Island which stems most likely from coal combustion in the eastern China. In contrast, nonaromatic compounds with a biogenic origin were mostly observed in samples collected from islands located in eastern (Ulleung Island) and southern (Jeju Island) Korea. A principal component analysis by FTICR-MS and GC-MS also showed that the samples from Tianjin and those collected from Baengnyeong Island in the winter are strongly associated with coal combustion, whereas the other samples are mainly influenced by vehicle emissions. Therefore, it is concluded that the atmosphere from east of China has significant influence over atmosphere in west of Korea peninsula.

Photochemical reactions of 1,3-butadiene with nitrogen oxide in different matrices: Kinetic behavior, humidity effect, product and mechanisms

Understanding the photochemical reaction process between VOCs and co-pollutants in the troposphere is crucial for controlling the haze. The photochemical reactions of 1,3-butadiene (1,3-BD) with NO were carried out at 308 K for up to 96 h in clean air with various relative humidity (RH) values, and actual haze atmosphere. In the haze, the representative pseudo-first-order kinetic rate constants of the 1,3-BD-NO system was 1.53 time higher than those in dry clean air. The effect of the RH (0%-80%) on the conversion behavior of the 1,3-BD-NO system in clean air was studied, revealing that increasing RH promoted the photochemical reaction in the low range of 0%-40% but retarded it in the high range of 40%-80%. Interestingly, OH radicals were directly detected under different RH values, and the strongest OH signal was obtained at an RH of 40%. Multiple macromolecular products with carbon numbers of 10-36 were identified. Unexpectedly, richer products and extended unsaturation range were detected at an RH of 40% than 0%. The photochemical products were also analyzed using ion chromatography. A reaction mechanism was proposed from the detected NO₂, O₃, OH, HNO₂, HNO₃, organic acids and macromolecular products.

Distribution and source of heavy metals in the sediments of the coastal East China sea: Geochemical controls and typhoon impact

The present study conducted a comprehensive study on the distribution and source of heavy metals (Cu, Zn, Ni, Pb, Cd) in the sediments of the coastal East China Sea (ECS), one of the most developed regions in China with very active land-sea interactions, using 119 surface sediment samples and a 2-m sediment core collected after super Typhoon Chan-hom in 2015. Heavy metals in the surface sediments exhibited metal-dependent and regional distribution patterns, showing higher levels in the southern inner shelf (SIS) than the Yangtze River estuary (YRE), and generally being evaluated as unpolluted to moderately polluted in the coastal ECS (except few sites adjacent to Xiangshan Harbor were strongly polluted by Cd). Based on the organic carbon isotope compositions (δ¹³C) data as well as the strong correlations between heavy metals and natural major elemental contents (Al₂O₃, Fe₂O₃, and SiO₂), we suggest natural weathering detritus as the major source of heavy metals in the YRE region and the spatial distributions were highly controlled by sediment grain size and organic matter. In contrast, the spatial distributions of heavy metals in the SIS region were less correlated with sediment properties, due to more complex sources and stronger hydrodynamic impacts. The vertical distribution of heavy metals in the sediment core indicated significant enrichments since 1950s, but showed unusual gradually decreasing trends in top layer (30 cm-0.5 cm), attributing to the strong disturbance of super Typhoon Chan-hom on sediment transportation and metal partitioning. Besides, we also observed that heavy metal levels in shallow water regions of Zhejiang coast were reduced due to the passage of typhoon. Such strong impacts of super Typhoon Chan-hom on heavy metal distributions in the ECS indicates that the impacts of extreme hydrodynamic events should raise more concern when assessing the distribution and potential risks of contaminants in coastal regions.

Emissions Characteristics of Hazardous Air Pollutants from the Incineration of Sacrificial Offerings

The incineration of sacrificial offerings generates numerous hazardous air pollutants, including particulate matter (PM), CO, SO2, NOx and non-methane hydrocarbons (NMHC), which has significant effects on the environment and human health. However, due to the concealment of sacrificial offerings incineration, the emission of such pollutants has not received sufficient attention. Relevant quantification of the emission, emission factors and pollution control measures for this pollution source are lacking. To address these problems, herein, we quantified the particulate matter and its chemical composition and the emission levels of gaseous pollutants, including SO2, NOx, NMHC and CO, by performing incineration experiments of four typical sacrificial offerings (Joss paper, Funeral wreath, Taoist paper art and Yuanbao paper), and obtained the emission factors and emission characteristics for the incineration of sacrificial offerings. Therefore, this study lays the foundation and provides support for establishing an emission inventory of the air pollutants from the incineration of sacrificial offerings and introducing corresponding pollution control measures. The results show that the emission concentrations of CO and total suspended particulate (TSP) from the incineration of sacrificial offerings greatly exceed the emission standard, with averages of 621.4 mg m−3 and 142.9 mg m−3 at 11% oxygen content, respectively. The average emission factors of SO2, NOx, NMHC, CO, PM10 and PM2.5 for the incineration of the four offerings are (0.47 ± 0.17) kg t−1, (2.46 ± 0.35) kg t−1, (5.78 ± 2.41) kg t−1, (32.40 ± 8.80) kg t−1, (4.23 ± 0.71) kg t−1 and (2.62 ± 0.48) kg t−1, respectively, among which the emission intensities of NMHC and CO are relatively high. Among the different types of sacrificial offerings, the overall average emission factor of air pollutants generated from the incineration of Yuanbao paper is the highest, which is mainly due to the low burning efficiency and the coating material. For the chemical composition of the particulate matters, ions, OC, EC and metal elements account for proportions of the PM2.5 at (23.55 ± 10.37) %, (29.74 ± 9.95) %, (14.83 ± 6.55) % and (13.45 ± 4.88) %, respectively, indicating that the organic pollution is severe