Emerging investigator series: heterogeneous OH oxidation of primary brown carbon aerosol: effects of relative humidity and volatility

2020 ◽  
Author(s):  
Elijah G. Schnitzler ◽  
Tengyu Liu ◽  
Rachel F. Hems ◽  
Jonathan P. D. Abbatt
Keyword(s):  
Relative Humidity ◽  
Hydroxyl Radical ◽  
Reaction Chamber ◽  
Brown Carbon ◽  
Aerosol Effects

Changes in the composition and absorptivity of primary brown carbon aerosol generated from smoldering pine were measured during exposure to hydroxyl radical in a photo-reaction chamber.

Effect of Relative Humidity on Secondary Brown Carbon Formation in Aqueous Droplets

2020 ◽  
Vol 54 (20) ◽  
pp. 13207-13216
Author(s):  
Nethmi Y. Kasthuriarachchi ◽  
Laura-Hélèna Rivellini ◽  
Xi Chen ◽  
Yong Jie Li ◽  
Alex K. Y. Lee
Keyword(s):  
Relative Humidity ◽  
Carbon Formation ◽  
Brown Carbon

scholarly journals Glyoxal's impact on dry ammonium salts: fast and reversible surface aerosol browning

2020 ◽  
Author(s):  
David O. De Haan ◽  
Lelia N. Hawkins ◽  
Kevin Jansen ◽  
Hannah G. Welsh ◽  
Raunak Pednekar ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Gas Phase ◽  
Ammonium Sulfate ◽  
Aerosol Particles ◽  
Ammonium Salts ◽  
Carbon Formation ◽  
Cloud Droplets ◽  
Brown Carbon ◽  
Dicarbonyl Compounds ◽  
Dry Conditions

Abstract. Alpha-dicarbonyl compounds are believed to form brown carbon in the atmosphere via reactions with ammonium sulfate (AS) in cloud droplets and aqueous aerosol particles. In this work, brown carbon formation in AS and other aerosol particles was quantified as a function of relative humidity (RH) during exposure to gas-phase glyoxal (GX) in chamber experiments. Under dry conditions (RH 

scholarly journals Determination of α-pinene-derived organic nitrate yields: particle phase partitioning and hydrolysis

2014 ◽  
Vol 14 (3) ◽  
pp. 3301-3335 ◽  
Author(s):  
J. D. Rindelaub ◽  
K. M. McAvey ◽  
P. B. Shepson
Keyword(s):  
Relative Humidity ◽  
Reaction Chamber ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Particle Phase ◽  
Radical Oxidation ◽  
Phase Partitioning ◽  
Aerosol Acidity ◽  
Phase Loss ◽  
Regional Air Quality

Abstract. The hydroxyl radical oxidation of α-pinene under high NOx conditions was studied in a photochemical reaction chamber to investigate organic nitrate (RONO2) production and partitioning between the gas and particle phases. We report an organic nitrate yield of 26 ± 7% from the oxidation of this monoterpene in the presence of nitric oxide (NO). However, the organic nitrate yield was found to be highly dependent on both chamber relative humidity (RH) and seed aerosol acidity, likely as a result of particle phase hydrolysis. The particle phase loss of organic nitrates perturbs the gas-particle equilibrium within the system, leading to decreased RONO2 yields in both the gas and particle phases at elevated RH and an apparent non-equilibrium partitioning mechanism. This resulted in smaller apparent partition coefficients of the total organic nitrate species under high chamber RH. The hydrolysis of particle phase organic nitrates at low chamber relative humidity in this study implies that aerosol partitioning of organic nitrates may be an important sink for atmospheric NOx and may have a significant impact on regional air quality.

Influence of Ammonia and Relative Humidity on the Formation and Composition of Secondary Brown Carbon from Oxidation of 1-Methylnaphthalene and Longifolene

2021 ◽  
Author(s):  
Yumeng Cui ◽  
Alexander L. Frie ◽  
Justin H. Dingle ◽  
Stephen Zimmerman ◽  
Isis Frausto-Vicencio ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Brown Carbon

scholarly journals Satellite observed indications of aerosol effects on warm cloud properties over Yangtze River Delta of China

2016 ◽  
Author(s):  
Yuqin Liu ◽  
Gerrit de Leeuw ◽  
Veli-Matti Kerminen ◽  
Jiahua Zhang ◽  
Putian Zhou ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Yangtze River ◽  
Yangtze River Delta ◽  
Absorption Efficiency ◽  
Meteorological Conditions ◽  
River Delta ◽  
Smoke Aerosol ◽  
Cloud Properties ◽  
Aerosol Effects ◽  
The Impact

Abstract. Aerosol effects on summertime low warm clouds over the Yangtze River Delta (YRD) are examined using co-located MODIS, CALIOP and CloudSat observations. By taking the vertical locations of aerosol and cloud layers into account, we use simultaneously observed aerosol and cloud data to investigate relationships between cloud properties and the amount of aerosol particles (using aerosol optical depth, AOD, as a proxy). Also, we investigate the impact of aerosol types on the variation of cloud properties with AOD. Finally, we explore how meteorological conditions affect these relationships using ERA Interim Reanalysis data. This study shows that the relation between cloud droplet effective radius (CDR) and AOD depends on the aerosol abundance, with a different behaviour for low and high AOD (i.e. AOD  0.3). Cloud fraction (CF) is found to be little dependent on the AOD when aerosol and cloud physically interact, but has a positive relation in case of well-separated clouds. Cloud optical Thickness (COT) is found to decrease when AOD increases, which may be due to radiative effects and retrieval artefacts caused by absorbing aerosol. Conversely, cloud top pressure (CTP) tends to increase with elevated AOD, indicating that the aerosol is not always prone to expand the vertical extension. Furthermore, separation of cases with either polluted dust or smoke aerosol shows that COT and CF are smaller for clouds mixed with smoke aerosol which is ascribed to the higher absorption efficiency of smoke than dust. The variation of cloud properties with AOD is analysed for different values of relative humidity (RH) and boundary layer thermodynamic and dynamic conditions, showing that high relative humidity and upward motion of air parcels can enhance the strength of aerosol-cloud interaction, especially pronounced in heavily polluted conditions than in moderately polluted conditions. Meteorological conditions play a weak role in the COT-AOD and CTP-AOD relationships throughout the range of AOD. Overall, the interpretation of the observed relationships between cloud properties and AOD requires that ambient environmental conditions are considered in addition to the aerosol and cloud parameters.

A tilting high temperature gas reaction chamber for the JEM 7A T.E.M.

1978 ◽  
Vol 36 (1) ◽  
pp. 70-71
Author(s):  
Brian L. Rhoades
Keyword(s):  
Cross Section ◽  
Reaction Chamber ◽  
Objective Lens ◽  
Reduced Cross Section ◽  
Cross Sectional ◽  
Structural Investigations ◽  
Transmission Electron ◽  
Dynamic Experiments ◽  
Successful Design ◽  
Thermocouple Junction

A gas reaction chamber has been designed and constructed for the JEM 7A transmission electron microscope which is based on a notably successful design by Hashimoto et. al. but which provides specimen tilting facilities of ± 15° aboutany axis in the plane of the specimen.It has been difficult to provide tilting facilities on environmental chambers for 100 kV microscopes owing to the fundamental lack of available space within the objective lens and the scope of structural investigations possible during dynamic experiments has been limited with previous specimen chambers not possessing this facility.A cross sectional diagram of the specimen chamber is shown in figure 1. The specimen is placed on a platinum ribbon which is mounted on a mica ring of the type shown in figure 2. The ribbon is heated by direct current, and a thermocouple junction spot welded to the section of the ribbon of reduced cross section enables temperature measurement at the point where localised heating occurs.

Activation of cytochrome c to a peroxidase compound I-type intermediate by H2O2: relevance to redox signalling in apoptosis

2004 ◽  
Vol 71 ◽  
pp. 97-106 ◽  
Author(s):  
Mark Burkitt ◽  
Clare Jones ◽  
Andrew Lawrence ◽  
Peter Wardman
Keyword(s):  
Cytochrome C ◽  
Hydroxyl Radical ◽  
Redox Regulation ◽  
Chemotherapeutic Agents ◽  
Tyrosyl Radical ◽  
Compound I ◽  
Definitive Evidence ◽  
Enhanced Production ◽  
Physico Chemical

The release of cytochrome c from mitochondria during apoptosis results in the enhanced production of superoxide radicals, which are converted to H2O2 by Mn-superoxide dismutase. We have been concerned with the role of cytochrome c/H2O2 in the induction of oxidative stress during apoptosis. Our initial studies showed that cytochrome c is a potent catalyst of 2′,7′-dichlorofluorescin oxidation, thereby explaining the increased rate of production of the fluorophore 2′,7′-dichlorofluorescein in apoptotic cells. Although it has been speculated that the oxidizing species may be a ferryl-haem intermediate, no definitive evidence for the formation of such a species has been reported. Alternatively, it is possible that the hydroxyl radical may be generated, as seen in the reaction of certain iron chelates with H2O2. By examining the effects of radical scavengers on 2′,7′-dichlorofluorescin oxidation by cytochrome c/H2O2, together with complementary EPR studies, we have demonstrated that the hydroxyl radical is not generated. Our findings point, instead, to the formation of a peroxidase compound I species, with one oxidizing equivalent present as an oxo-ferryl haem intermediate and the other as the tyrosyl radical identified by Barr and colleagues [Barr, Gunther, Deterding, Tomer and Mason (1996) J. Biol. Chem. 271, 15498-15503]. Studies with spin traps indicated that the oxo-ferryl haem is the active oxidant. These findings provide a physico-chemical basis for the redox changes that occur during apoptosis. Excessive changes (possibly catalysed by cytochrome c) may have implications for the redox regulation of cell death, including the sensitivity of tumour cells to chemotherapeutic agents.

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