科研成果

The variations of non-refractory submicron aerosol (NR-PM1) were characterized using an high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and other online instruments measurements sampled at an urban site in Shanghai from 2016 to 2017. Spring (from 18 May to 4 June 2017), summer (from 23 August to 10 September 2017) and winter (from 28 November 2016 to 23 January 2017) seasons were chosen for detail investigating the seasonal variations in the aerosol chemical characteristics. The average PM1 (NR-PM1 + BC) mass concentration showed little difference in the three seasons in Shanghai. The average mass concentrations of total PM1 during spring, summer, and winter observations in Shanghai were 23.9 ± 20.7 μg/m3, 28.5 ± 17.6 μg/m3, and 31.9 ± 22.7 μg/m3, respectively. The seasonal difference on chemical compositions was more significant between them. Organic aerosol (OA) and sulfate were dominant contributor of PM1 in summer, whereas OA and nitrate primarily contribution to the increase of PM1 mass loading in spring and winter. As an abundant component in PM1 (accounting for 39%–49%), OA were resolved into two primary organic aerosol (POA) factors and two secondary aerosol (SOA) factors by using positive matrix factorization (PMF), of which OA was overwhelmingly dominated by the SOA (50–60%) across the three seasons in Shanghai. Correlation analysis with relative humidity and odd oxygen indicated that aqueous-phase processing and played an important role in more aged SOA formation in summer and winter. In spring, both aqueous-phase and photochemical processing contributed significantly to fresh SOA formation. Our results suggest the significant role of secondary particles in PM pollution in Shanghai and highlight the importance of control measures for reducing emissions of gaseous precursors, especially need to consider seasonal characteristics. © 2021 Elsevier B.V.

Severe haze pollution occurs frequently in the winter over the Beijing-Tianjin-Hebei (BTH) region (China), exerting profound impacts on air quality, visibility, and human health. The Chinese Government has taken strict mitigation actions since 2013 and has achieved a significant reduction in the annual mean PM2.5 concentration over this region. However, the level of secondary aerosols during heavy haze episodes showed little decrease during this period. During heavy haze episodes, the concentrations of secondary aerosol components, including sulfate, nitrate and secondary organics, in aerosol particles increase sharply, acting as the main contributors to aerosol pollution. To achieve effective control of particle pollution in the BTH region, the precise and complete secondary aerosol formation mechanisms have been investigated, and advances have been made about the mechanisms of gas phase reaction, nucleation and heterogeneous reactions in forming secondary aerosols. This paper reviews the research progress in aerosol chemistry during haze pollution episodes in the BTH region, lays out the challenges in haze formation studies, and provides implications and directions for future research. [Figure not available: see fulltext.]. © 2020, Higher Education Press.

Severe haze pollution occurs frequently in the winter over the Beijing-Tianjin-Hebei (BTH) region (China), exerting profound impacts on air quality, visibility, and human health. The Chinese Government has taken strict mitigation actions since 2013 and has achieved a significant reduction in the annual mean PM2.5 concentration over this region. However, the level of secondary aerosols during heavy haze episodes showed little decrease during this period. During heavy haze episodes, the concentrations of secondary aerosol components, including sulfate, nitrate and secondary organics, in aerosol particles increase sharply, acting as the main contributors to aerosol pollution. To achieve effective control of particle pollution in the BTH region, the precise and complete secondary aerosol formation mechanisms have been investigated, and advances have been made about the mechanisms of gas phase reaction, nucleation and heterogeneous reactions in forming secondary aerosols. This paper reviews the research progress in aerosol chemistry during haze pollution episodes in the BTH region, lays out the challenges in haze formation studies, and provides implications and directions for future research. [Figure not available: see fulltext.]. © 2020, Higher Education Press.

The Sichuan Basin is one of the regions suffering from severe haze pollution in southwest China. However, the secondary aerosol formation in this region is poorly understood. In this study, the chemical compositions of PM2.5 and molecular compositions of water-soluble organics in wintertime Sichuan were measured to investigate the aerosol sources and formation under typical high relative humidity (RH) conditions. Strong correlations between PM2.5, carbonaceous aerosols and K+ suggested the influence of biomass burning. The impacts of biomass burning were also supported by the dominance of primarily emitted reduced/less oxidized nitrogen-containing organics as well as the high peak intensities of secondarily formed nitrocatechols and methyl-nitrocatechols. High humidity (average RH = 80%) and aerosol liquid water (ALW) in Sichuan facilitated the secondary formation of sulfate, nitrate, and secondary organic aerosols (SOA). The average sulfate oxidation ratio and nitrogen oxidation ratio in Sichuan were 2.5 and 3.1 times of those in winter Beijing (average RH = 27%). This suggested higher potentials of SO2 and NOx to form sulfate and nitrate under high-RH conditions. The abundant aqueous-SOA formation in Sichuan was supported by the dominance of organosulfates (OSs) and nitrooxy-OSs in mass spectra of water-soluble organics, while the OSs in winter Beijing were quite limited. The more abundant OS formation in Sichuan was attributed to the much higher RH, ALW, aerosol acidity, and sulfate, which favored the acidic sulfate-catalyzed aqueous-phase reactions for OS formation. Higher concentrations of biogenic volatile organic compounds were additional reasons for the more abundant OSs in Sichuan than in Beijing. © 2021. American Geophysical Union. All Rights Reserved.

Cooking has been proven to be a significant source of primary organic aerosol, especially in megacities. However, the formation of secondary organic aerosol (SOA) derived from cooking emissions is still poorly understood. In this work, four prevalent Chinese domestic cooking types involving complicated cuisines and various cooking methods were chosen to conduct a lab simulation for SOA formation using a Gothenburg potential aerosol mass reactor (Go: PAM). After samples had been aged under OH exposures of 4.3–27.1 × 1010 molecules cm–3 s, the domestic cooking SOA was characterized by mass growth potentialities (1.81–3.16), elemental ratios (O/C = 0.29–0.41), and mass spectra. Compared with other organic aerosol (OA), domestic cooking SOA is a kind of less oxidized oxygenated OA (LO-OOA) with a unique oxidation pathway (alcohol/peroxide pathway) and mass spectra (characteristic peaks at m/z 28, 29, 41, 43, 44, 55, and 57). This study is expected to identify the cooking SOA under actual cooking conditions, which could contribute to the formulation of pollution source control as well as the health risk assessment of exposure to cooking fumes.

Cooking has been proven to be a significant source of primary organic aerosol, especially in megacities. However, the formation of secondary organic aerosol (SOA) derived from cooking emissions is still poorly understood. In this work, four prevalent Chinese domestic cooking types involving complicated cuisines and various cooking methods were chosen to conduct a lab simulation for SOA formation using a Gothenburg potential aerosol mass reactor (Go: PAM). After samples had been aged under OH exposures of 4.3-27.1 × 1010 molecules cm-3 s, the domestic cooking SOA was characterized by mass growth potentialities (1.81-3.16), elemental ratios (O/C = 0.29-0.41), and mass spectra. Compared with other organic aerosol (OA), domestic cooking SOA is a kind of less oxidized oxygenated OA (LO-OOA) with a unique oxidation pathway (alcohol/peroxide pathway) and mass spectra (characteristic peaks at m/z 28, 29, 41, 43, 44, 55, and 57). This study is expected to identify the cooking SOA under actual cooking conditions, which could contribute to the formulation of pollution source control as well as the health risk assessment of exposure to cooking fumes. ©

Membrane separation has enjoyed tremendous advances in relevant material and engineering sciences, making it the fastest growing technology in water treatment. Although membranes as a broad-spectrum physical barrier have great advantages over conventional treatment processes in a myriad of applications, the need for higher selectivity and specificity in membrane separation is rising as we move to target contaminants at trace concentrations and to recover valuable chemicals from wastewater with low energy consumption. In this review, we discuss the drivers, fundamental science, and potential enabling materials for high selectivity membranes, as well as their applications in different water treatment processes. Membrane materials and processes that show promise to achieve high selectivity for water, ions, and small molecules—as well as the mechanisms involved—are highlighted. We further identify practical needs, knowledge gaps, and technological barriers in both material development and process design for high selectivity membrane processes. Finally, we discuss research priorities in the context of existing and future water supply paradigms.