Aqueous aging of secondary organic aerosol coating onto black carbon: Insights from simultaneous L-ToF-AMS and SP-AMS measurements at an urban site in southern China

2021 ◽  
pp. 129888
Author(s):  
Li-Ming Cao ◽  
Jing Wei ◽  
Ling-Yan He ◽  
Hui Zeng ◽  
Meng-Lin Li ◽  
...  
Keyword(s):  
Black Carbon ◽  
Secondary Organic Aerosol ◽  
Southern China ◽  
Organic Aerosol ◽  
Urban Site ◽  
Aerosol Coating

scholarly journals Formation of secondary organic aerosol coating on black carbon particles near vehicular emissions

2017 ◽  
Author(s):  
Alex K. Y. Lee ◽  
Chia-Li Chen ◽  
Jun Liu ◽  
Derek J. Price ◽  
Raghu Betha ◽  
...  
Keyword(s):  
Black Carbon ◽  
Mass Spectrometer ◽  
Secondary Organic Aerosol ◽  
Spectral Characteristics ◽  
Organic Aerosol ◽  
Vehicular Emissions ◽  
Aerosol Mass Spectrometer ◽  
Diurnal Cycles ◽  
Aerosol Mass ◽  
Inorganic Species

Abstract. Black carbon (BC) emitted from incomplete combustion can result in significant impacts on air quality and climate. Understanding the mixing state of ambient BC and the chemical characteristics of its associated coatings are particularly important to evaluate BC fate and environmental impacts. In this study, we investigate the formation of organic coatings on BC particles in an urban environment (Fontana, California) under hot and dry conditions using a Soot-Particle Aerosol Mass Spectrometer (SP-AMS). The SP-AMS was operated in a configuration that can detect refractory BC (rBC) particles and their coatings exclusively. Using the −log(NOx/NOy) ratio as a proxy for photochemical age of air masses, substantial formation of secondary organic aerosol (SOA) coatings on rBC particles was observed due to active photochemistry in the afternoon, whereas primary organic aerosol (POA) components were strongly associated with rBC from fresh vehicular missions in the morning rush hours. There is also evidence that cooking related organic aerosols were externally mixed from rBC. Positive matrix factorization and elemental analysis illustrate that most of the observed SOA coatings were freshly formed, providing an opportunity to examine SOA coating formation on rBC near vehicular emissions. Approximately 7–20 wt % of secondary organic and inorganic species were estimated to be internally mixed with rBC on average, implying that rBC is unlikely the major condensation sinks of SOA in this study. Diurnal cycles of oxygenated organic aerosol (OOA) observed by a co-located standard high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-MS) correlated well with that of SOA coatings on rBC, but their mass spectral characteristics were different from each other. Our results suggest that at least a portion of SOA materials condensed on rBC surface were chemically different from OOA particles that were externally mixed with rBC, although they are both generated from local photochemistry.

scholarly journals Origin and transformation of ambient volatile organic compounds during a dust-to-haze episode in northwest China

2020 ◽  
Vol 20 (9) ◽  
pp. 5425-5436 ◽  
Author(s):  
Yonggang Xue ◽  
Yu Huang ◽  
Steven Sai Hang Ho ◽  
Long Chen ◽  
Liqin Wang ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Sharp Decrease ◽  
Fold Increase ◽  
Organic Aerosol ◽  
Northwest China ◽  
Photochemical Reactions ◽  
Urban Site ◽  
Vehicle Exhaust ◽  
Haze Pollution ◽  
Volatile Organic

Abstract. The high contribution of secondary organic aerosol to the loading of fine particle pollution in China highlights the roles of volatile organic compound (VOC) oxidation. In this respect, particulate active metallic oxides in dust, like TiO2 and Fe ions, were proposed to influence the photochemical reactions of ambient VOCs. A case study was conducted at an urban site in Xi'an, northwest China, to investigate the origin and transformation of VOCs during a windblown dust-to-haze pollution episode, and the assumption that dust would enhance the oxidation of VOCs was verified. Local vehicle exhaust (25 %) and biomass burning (18 %) were found to be the two largest contributors to ambient VOCs. In the dust pollution period, a sharp decrease in the loading of VOCs and the aging of their components were observed. Simultaneously, the secondary oxygenated VOC fraction (i.e., methylglyoxal) increased. Source strength, physical dispersion, and regional transport were eliminated as major factors for the variation of ambient VOCs. In another aspect, about a 2- to 3-fold increase in the loading of iron (Fe) and titanium (Ti) was found in the airborne particles, together with a fast decrease in trans-/cis-2-butene ratios, which demonstrated that dust can accelerate the oxidation of ambient VOCs and the formation of secondary organic aerosol (SOA) precursors.

scholarly journals Effect of secondary organic aerosol coating thickness on the real-time detection and characterization of biomass-burning soot by two particle mass spectrometers

2016 ◽  
Vol 9 (12) ◽  
pp. 6117-6137 ◽  
Author(s):  
Adam T. Ahern ◽  
Ramachandran Subramanian ◽  
Georges Saliba ◽  
Eric M. Lipsky ◽  
Neil M. Donahue ◽  
...  
Keyword(s):  
Black Carbon ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Particle Mass ◽  
Laser Vaporization ◽  
Mass Spectrometers ◽  
Ir Laser ◽  
Biomass Burning Particles

Abstract. Biomass burning is a large source of light-absorbing refractory black carbon (rBC) particles with a wide range of morphologies and sizes. The net radiative forcing from these particles is strongly dependent on the amount and composition of non-light-absorbing material internally mixed with the rBC and on the morphology of the mixed particles. Understanding how the mixing state and morphology of biomass-burning aerosol evolves in the atmosphere is critical for constraining the influence of these particles on radiative forcing and climate. We investigated the response of two commercial laser-based particle mass spectrometers, the vacuum ultraviolet (VUV) ablation LAAPTOF and the IR vaporization SP-AMS, to monodisperse biomass-burning particles as we sequentially coated the particles with secondary organic aerosol (SOA) from α-pinene ozonolysis. We studied three mobility-selected soot core sizes, each with a number of successively thicker coatings of SOA applied. Using IR laser vaporization, the SP-AMS had different changes in sensitivity to rBC compared to potassium as a function of applied SOA coatings. We show that this is due to different effective beam widths for the IR laser vaporization region of potassium versus black carbon. The SP-AMS's sensitivity to black carbon (BC) mass was not observed to plateau following successive SOA coatings, despite achieving high OA : BC mass ratios greater than 9. We also measured the ion fragmentation pattern of biomass-burning rBC and found it changed only slightly with increasing SOA mass. The average organic matter ion signal measured by the LAAPTOF demonstrated a positive correlation with the condensed SOA mass on individual particles, despite the inhomogeneity of the particle core compositions. This demonstrates that the LAAPTOF can obtain quantitative mass measurements of aged soot-particle composition from realistic biomass-burning particles with complex morphologies and composition.

scholarly journals Formation of secondary organic aerosol coating on black carbon particles near vehicular emissions

2017 ◽  
Vol 17 (24) ◽  
pp. 15055-15067 ◽  
Author(s):  
Alex K. Y. Lee ◽  
Chia-Li Chen ◽  
Jun Liu ◽  
Derek J. Price ◽  
Raghu Betha ◽  
...  
Keyword(s):  
Black Carbon ◽  
Mass Spectrometer ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Vehicular Emissions ◽  
Aerosol Mass Spectrometer ◽  
Carbon Particles ◽  
Aerosol Mass ◽  
Inorganic Species ◽  
Dry Conditions

Abstract. Black carbon (BC) emitted from incomplete combustion can result in significant impacts on air quality and climate. Understanding the mixing state of ambient BC and the chemical characteristics of its associated coatings is particularly important to evaluate BC fate and environmental impacts. In this study, we investigate the formation of organic coatings on BC particles in an urban environment (Fontana, California) under hot and dry conditions using a soot-particle aerosol mass spectrometer (SP-AMS). The SP-AMS was operated in a configuration that can exclusively detect refractory BC (rBC) particles and their coatings. Using the −log(NOx ∕ NOy) ratio as a proxy for photochemical age of air masses, substantial formation of secondary organic aerosol (SOA) coatings on rBC particles was observed due to active photochemistry in the afternoon, whereas primary organic aerosol (POA) components were strongly associated with rBC from fresh vehicular emissions in the morning rush hours. There is also evidence that cooking-related organic aerosols were externally mixed from rBC. Positive matrix factorization and elemental analysis illustrate that most of the observed SOA coatings were freshly formed, providing an opportunity to examine SOA coating formation on rBCs near vehicular emissions. Approximately 7–20 wt % of secondary organic and inorganic species were estimated to be internally mixed with rBC on average, implying that rBC is unlikely the major condensation sink of SOA in this study. Comparison of our results to a co-located standard high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) measurement suggests that at least a portion of SOA materials condensed on rBC surfaces were chemically different from oxygenated organic aerosol (OOA) particles that were externally mixed with rBC, although they could both be generated from local photochemistry.

scholarly journals The effects of morphology, mobility size, and secondary organic aerosol (SOA) material coating on the ice nucleation activity of black carbon in the cirrus regime

2020 ◽  
Vol 20 (22) ◽  
pp. 13957-13984
Author(s):  
Cuiqi Zhang ◽  
Yue Zhang ◽  
Martin J. Wolf ◽  
Leonid Nichman ◽  
Chuanyang Shen ◽  
...  
Keyword(s):  
Black Carbon ◽  
State Transition ◽  
Phase State ◽  
Secondary Organic Aerosol ◽  
Global Climate ◽  
Surface Oxidation ◽  
Organic Aerosol ◽  
Ice Nucleation ◽  
Supersaturation Ratio ◽  
Homogeneous Freezing

Abstract. There is evidence that black carbon (BC) particles may affect cirrus formation and, hence, global climate by acting as potential ice nucleating particles (INPs) in the troposphere. Nevertheless, the ice nucleation (IN) ability of bare BC and BC coated with secondary organic aerosol (SOA) material remains uncertain. We have systematically examined the IN ability of 100–400 nm size-selected BC particles with different morphologies and different SOA coatings representative of anthropogenic (toluene and n-dodecane) and biogenic (β-caryophyllene) sources in the cirrus regime (−46 to −38 ∘C). Several BC proxies were selected to represent different particle morphologies and oxidation levels. Atmospheric aging was further replicated with the exposure of SOA-coated BC to OH. The results demonstrate that the 400 nm hydrophobic BC types nucleate ice only at or near the homogeneous freezing threshold. Ice formation at cirrus temperatures below homogeneous freezing thresholds, as opposed to purely homogeneous freezing, was observed to occur for some BC types between 100 and 200 nm within the investigated temperature range. More fractal BC particles did not consistently act as superior INPs over more spherical ones. SOA coating generated by oxidizing β-caryophyllene with O3 did not seem to affect BC IN ability, probably due to an SOA-phase state transition. However, SOA coatings generated from OH oxidation of various organic species did exhibit higher IN-onset supersaturation ratio with respect to ice (SSi), compared with bare BC particles, with the toluene-SOA coating showing an increase in SSi of 0.1–0.15 while still below the homogeneous freezing threshold. Slightly oxidized toluene SOA coating seemed to have a stronger deactivation effect on BC IN ability than highly oxidized toluene SOA, which might be caused by oligomer formation and the phase state transition of toluene SOA under different oxidation levels. n-dodecane and β-caryophyllene-derived SOA-coated BC only froze in the homogeneous regime. We attribute the inhibition of IN ability to the filling of the pores on the BC surface by the SOA material coating. OH exposure levels of n-dodecane and β-caryophyllene SOA coating experiments, from an equivalent atmospheric exposure time from 10 to 90 d, did not render significant differences in the IN potential. Our study of selected BC types and sizes suggests that increases in diameter, compactness, and/or surface oxidation of BC particles lead to more efficient IN via the pore condensation freezing (PCF) pathway, and that coatings of common SOA materials can inhibit the formation of ice.

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