Molecular characterisation of ambient aerosols by sequential solvent extractions and high-resolution mass spectrometry

2018 ◽  
Vol 15 (3) ◽  
pp. 150 ◽  
Author(s):  
Jingyi Zhang ◽  
Bin Jiang ◽  
Zhiheng Wang ◽  
Yongmei Liang ◽  
Yahe Zhang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Organic Carbon ◽  
Organic Compounds ◽  
Atmospheric Chemistry ◽  
Fine Particles ◽  
High Resolution Mass Spectrometry ◽  
Water Soluble ◽  
Aerosol Sample ◽  
Large Contribution ◽  
Nitrogen Containing Compounds

Environmental contextOrganic compounds generally make a large contribution to ambient aerosol fine particles, and can influence atmospheric chemistry. Solvent extraction before mass spectrometry is widely used for the determination of organic compounds in aerosols, but the molecular selectivity of different solvents is unclear. We extracted an aerosol sample with various solvents and show how the organic compound profile obtained by mass spectrometry changes depending on the extracting solvent. AbstractFor a comprehensive characterisation of organic compounds in aerosols, samples collected on a hazy day from Beijing were sequentially extracted with various solvents and analysed by Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Electrospray ionisation (ESI) was used for the MS analysis. Aerosol samples were extracted in an apolar-to-polar solvent order of n-hexane (n-C6), dichloromethane (DCM), acetonitrile (ACN) and water, and also extracted in reverse sequence. The separated fractions were defined as non-polar, low-polarity, mid-polarity and high-polarity organic compounds respectively. Approximately 70 % of the total organic carbon (TOC) was extractable, of which the water-soluble organic carbon (WSOC) and non-polar organic carbon accounted for 30 and 25 % of the TOC respectively. Non-polar and low-polarity compounds with a high degree of molecular condensation such as oxidised polycyclic aromatic hydrocarbons (PAHs) and nitrogen-containing compounds (CHN) were extracted by n-C6 and DCM. Water-soluble organic matter (WSOM) was predominant with aliphatic and aromatic organosulfates (CHOS) and nitrooxy-organosulfates (CHONS). Most oxygen-containing compounds (CHO) and oxygen- and nitrogen-containing compounds (CHON) with high double-bond equivalents (DBEs) and long carbon chains tended to be extracted into organic solvents.

scholarly journals Molecular Composition and Photochemical Evolution of Water Soluble Organic Carbon (WSOC) Extracted from Field Biomass Burning Aerosols using High Resolution Mass Spectrometry

2019 ◽  
Author(s):  
Jing Cai ◽  
Xiangying Zeng ◽  
Guorui Zhi ◽  
Sasho Gligorovski ◽  
Guoying Sheng ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Organic Carbon ◽  
Biomass Burning ◽  
High Resolution Mass Spectrometry ◽  
Water Soluble ◽  
Oxygenated Compounds ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Resolution Mass

Abstract. Photochemistry plays an important role in the evolution of atmospheric water soluble organic carbon (WSOC), which dissolves into clouds, fogs and aerosol liquid water. In this study, we examined the molecular composition and evolution of a WSOC mixture extracted from fresh biomass burning aerosols upon photolysis, using direct infusion electrospray ionization high-resolution mass spectrometry (ESI-HRMS) and liquid chromatography coupled with mass spectrometry (LC/ESI-HRMS). For comparison, two typical phenolic compounds (i.e., phenol and guaiacol) emitted from lignin pyrolysis in combination with hydrogen peroxide (H2O2) as a typical OH radical precursor, were exposed to simulated sunlight irradiation. The photochemistry of both, the phenols (photo-oxidation) and WSOC mixture (direct photolysis) can produce a series of highly oxygenated compounds which in turn increases the degree of oxidation of organic composition and acidity of the bulk solution. In particular, the LC/ESI-HRMS technique revealed significant photochemical evolution on the WSOC composition, e.g., the photodegradation of low oxygenated species and the formation of highly oxygenated products. We also tentatively compared the mass spectra of photolytic time-profile extract with each other for a more comprehensive description of the photolytic evolution. The calculated average oxygen-to-carbon (O / C) ratios of oxygenated compounds in bulk extract increases from 0.38 ± 0.02 to 0.44 ± 0.02 (mean±standard deviation) while the intensity (S / N)-weighted average O / C (O / Cw) increases from 0.45 ± 0.03 to 0.53 ± 0.06 as the time of irradiation extends from 0 to 12 h. These findings indicate that the water soluble organic fraction of fresh combustion-derived aerosols have the potential to form more oxidized organic matter, accounting for the highly oxygenated nature of atmospheric organic aerosols.

scholarly journals Molecular composition and photochemical evolution of water-soluble organic carbon (WSOC) extracted from field biomass burning aerosols using high-resolution mass spectrometry

2020 ◽  
Vol 20 (10) ◽  
pp. 6115-6128
Author(s):  
Jing Cai ◽  
Xiangying Zeng ◽  
Guorui Zhi ◽  
Sasho Gligorovski ◽  
Guoying Sheng ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Organic Carbon ◽  
Biomass Burning ◽  
High Resolution Mass Spectrometry ◽  
Water Soluble ◽  
Oxygenated Compounds ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Resolution Mass

Abstract. Photochemistry plays an important role in the evolution of atmospheric water-soluble organic carbon (WSOC), which dissolves into clouds, fogs, and aerosol liquid water. In this study, we tentatively examined the molecular composition and evolution of a WSOC mixture extracted from field-collected wheat straw burning aerosol (WSBA) samples upon photolysis, using direct infusion electrospray ionisation (ESI) coupled to high-resolution mass spectrometry (HRMS) and liquid chromatography (LC) coupled with HRMS. For comparison, two typical phenolic compounds (i.e. phenol and guaiacol) emitted from lignin pyrolysis in combination with hydrogen peroxide (H2O2) as a typical OH radical precursor were simultaneously exposed to simulated sunlight irradiation. Their photochemical products such as phenolic dimers (e.g. m∕z 185.0608 for phenol dimer and m∕z 245.0823 for guaiacol dimer) or their isomers, were also observed in field-collected WSBA samples, suggesting that the aqueous-phase reactions might contribute to the formation of emitted biomass burning aerosols. The aqueous photochemistry of both the phenols (photooxidation) and WSBA extracts (direct photolysis) could produce a series of highly oxygenated compounds, which in turn increases the oxidation degree of organic composition and acidity of the bulk solution. In particular, the LC/ESI-HRMS technique revealed significant photochemical evolution of the WSOC composition in WSBA samples, e.g. the photodegradation of low oxygenated species and the formation of highly oxygenated products. We also tentatively compared the mass spectra of photolytic time-profile WSBA extracts with each other for a more comprehensive description of the photolytic evolution. The calculated average oxygen-to-carbon ratio (O∕C) of oxygenated compounds in bulk extract increases from 0.38±0.02 to 0.44±0.02 (mean ± standard deviation), while the intensity (S∕N)-weighted average O∕C (O∕Cw) increases from 0.45±0.03 to 0.53±0.06 as the time of irradiation extends from 0 to 12 h. These findings indicate that the water-soluble organic fraction of combustion-derived aerosols has the potential to form more oxidised organic matter, contributing to the highly oxygenated nature of atmospheric organic aerosols.

scholarly journals Large contribution of fossil-fuel derived secondary organic carbon to water-soluble organic aerosols in winter haze of China

2017 ◽  
Author(s):  
Yan-Lin Zhang ◽  
Imad El-Haddad ◽  
Ru-Jin Huang ◽  
Kin-Fai Ho ◽  
Jun-Ji Cao ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Source Apportionment ◽  
Atmospheric Chemistry ◽  
Coal Combustion ◽  
Large Fraction ◽  
Organic Aerosols ◽  
Water Soluble ◽  
Primary Sources ◽  
Large Contribution ◽  
Secondary Organic Carbon

Abstract. Water-soluble organic carbon (WSOC) is a large fraction of organic aerosols (OA) globally and has significant impacts on climate and human health. The sources of WSOC remain very uncertain in polluted regions. Here we present a quantitative source apportionment of WSOC isolated from aerosols in China using radiocarbon (14C) and offline high-resolution time-of-flight aerosol mass spectrometer measurements. Fossil emissions on average accounted for 32–47 % of WSOC. Secondary organic carbon (SOC) dominated both the non-fossil and fossil derived WSOC, highlighting the importance of secondary formation to WSOC in severe winter haze episodes. Contributions from fossil emissions to SOC were 61 ± 4 % and 50 ± 9 % in Shanghai and Beijing, respectively, significantly larger than those in Guangzhou (36 ± 9 %) and Xi'an (26 ± 9 %). The most important primary sources were biomass burning emissions, contributing 17–26 % of WSOC. The remaining primary sources such as coal combustion, cooking and traffic were generally very small but not negligible contributors, as coal combustion contribution could exceed 10 %. Taken together with earlier 14C source apportionment studies in urban, rural, semi-urban, and background regions in Asia, Europe and USA, we demonstrated a dominant contribution of non-fossil emissions (i.e., 75 ± 11 %) to WSOC aerosols in the North Hemisphere; however, the fossil fraction is substantially larger in aerosols from East Asia and the East Asian pollution outflow especially during winter due to increasing coal combustion. Inclusion of our findings can improve a modelling of effects of WSOC aerosols on climate, atmospheric chemistry and public health.

scholarly journals Large contribution of fossil fuel derived secondary organic carbon to water soluble organic aerosols in winter haze in China

2018 ◽  
Vol 18 (6) ◽  
pp. 4005-4017 ◽  
Author(s):  
Yan-Lin Zhang ◽  
Imad El-Haddad ◽  
Ru-Jin Huang ◽  
Kin-Fai Ho ◽  
Jun-Ji Cao ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Source Apportionment ◽  
Atmospheric Chemistry ◽  
Coal Combustion ◽  
Large Fraction ◽  
Organic Aerosols ◽  
Water Soluble ◽  
Primary Sources ◽  
Large Contribution ◽  
Secondary Organic Carbon

Abstract. Water-soluble organic carbon (WSOC) is a large fraction of organic aerosols (OA) globally and has significant impacts on climate and human health. The sources of WSOC remain very uncertain in polluted regions. Here we present a quantitative source apportionment of WSOC, isolated from aerosols in China using radiocarbon (14C) and offline high-resolution time-of-flight aerosol mass spectrometer measurements. Fossil emissions on average accounted for 32–47 % of WSOC. Secondary organic carbon (SOC) dominated both the non-fossil and fossil derived WSOC, highlighting the importance of secondary formation to WSOC in severe winter haze episodes. Contributions from fossil emissions to SOC were 61 ± 4 and 50 ± 9 % in Shanghai and Beijing, respectively, significantly larger than those in Guangzhou (36 ± 9 %) and Xi'an (26 ± 9 %). The most important primary sources were biomass burning emissions, contributing 17–26 % of WSOC. The remaining primary sources such as coal combustion, cooking and traffic were generally very small but not negligible contributors, as coal combustion contribution could exceed 10 %. Taken together with earlier 14C source apportionment studies in urban, rural, semi-urban and background regions in Asia, Europe and the USA, we demonstrated a dominant contribution of non-fossil emissions (i.e., 75 ± 11 %) to WSOC aerosols in the Northern Hemisphere; however, the fossil fraction is substantially larger in aerosols from East Asia and the eastern Asian pollution outflow, especially during winter, due to increasing coal combustion. Inclusion of our findings can improve a modelling of effects of WSOC aerosols on climate, atmospheric chemistry and public health.

scholarly journals Particle size-dependent fluorescence properties of water-soluble organic compounds (WSOC) and their atmospheric implications on the aging of WSOC

2021 ◽  
Author(s):  
Juanjuan Qin ◽  
Jihua Tan ◽  
Xueming Zhou ◽  
Yanrong Yang ◽  
Yuanyuan Qin ◽  
...  
Keyword(s):  
Particle Size ◽  
Organic Compounds ◽  
Fine Particles ◽  
Stokes Shift ◽  
Bimodal Distribution ◽  
Dominant Mode ◽  
Water Soluble ◽  
Atmospheric Particle ◽  
Humification Degree ◽  
Transformation Processes

Abstract. Water-soluble organic compounds (WSOC) are essential in atmospheric particle formation, migration, and transformation processes. Size-segregated atmospheric particles were collected in a rural area of Beijing. Excitation-emission matrix (EEM) fluorescence spectroscopy was used to investigate the sources and optical properties of WSOC. Sophisticated data analysis on EEM data was performed to characteristically estimate the underlying connections among aerosol particles in different sizes. The WSOC concentrations and average fluorescence intensity (AFI) showed monomodal distribution in winter and bimodal distribution in summer, with dominant mode between 0.26 to 0.44 µm for both seasons. The EEM spectra of size-segregated WSOC were different among variant particle sizes, which could be the results of changing sources and/or chemical transformation of organics. Size distributions of fluorescence regional intensity (region Ⅲ and Ⅴ) and HIX indicate that humification degree or aromaticity of WSOC was highest between 0.26 to 0.44 µm. The Stokes shift (SS) and the harmonic mean of the excitation and emission wavelengths (WH) reflected that π-conjugated systems were high between 0.26 to 0.44 µm as well. The parallel factor analysis (PARAFAC) results showed that humic-like substances were abundant in fine particles (< 1 µm) and peaked at 0.26–0.44 µm. All evidence supported that the humification degree of WSOC increased in submicron mode (< 0.44 µm) and decreased gradually. Thus, it was conjectured that condensation of organics still goes on in submicron mode, resulting in the highest humification degree exhibit in particle size between 0.26 to 0.44 µm rather than < 0.26 µm. Synthetically analyzing 3-dimensional fluorescence data could efficiently present the secondary transformation processes of WSOC.

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