The gas-phase degradation of chlorpyrifos and chlorpyrifos-oxon towards OH radical under atmospheric conditions

Chemosphere ◽  
2014 ◽  
Vol 111 ◽  
pp. 522-528 ◽  
Author(s):  
Amalia Muñoz ◽  
Milagros Ródenas ◽  
Esther Borrás ◽  
Mónica Vázquez ◽  
Teresa Vera
Keyword(s):  
Gas Phase ◽  
Oh Radical ◽  
Atmospheric Conditions

scholarly journals Investigation of the reaction of ozone with isoprene, methacrolein and methyl vinyl ketone using the HELIOS chamber

2017 ◽  
Vol 200 ◽  
pp. 289-311 ◽  
Author(s):  
Yangang Ren ◽  
Benoit Grosselin ◽  
Véronique Daële ◽  
Abdelwahid Mellouki
Keyword(s):  
Gas Phase ◽  
Organic Aerosol ◽  
Vinyl Ketone ◽  
Methyl Vinyl Ketone ◽  
Radical Scavenger ◽  
Oh Radical ◽  
Atmospheric Conditions ◽  
Experimental Conditions ◽  
Methyl Vinyl ◽  
Analytical Equipment

The rate constants for the ozonolysis of isoprene (ISO), methacrolein (MACR) and methyl vinyl ketone (MVK) have been measured using the newly built large volume atmospheric simulation chamber at CNRS-Orleans (France), HELIOS (Chambre de simulation atmosphérique à irradiation naturelle d’Orléans). The OH radical yields from the ozonolysis of isoprene, MACR and MVK have also been determined, as well as the gas phase stable products and their yields. The secondary organic aerosol yield for the ozonolysis of isoprene has been tentatively measured in the presence and absence of an OH radical scavenger. The measurements were performed under different experimental conditions with and without adding cyclohexane (cHX) as an OH radical scavenger. All experiments have been conducted at 760 torr of purified dry air (RH < 1%) and ambient temperature (T = 281–295 K). The data obtained are discussed and compared with those from the literature. The use of the HELIOS facility and its associated analytical equipment enables the derivation of kinetic parameters as well as mechanistic information under near realistic atmospheric conditions.

scholarly journals Secondary Organic Aerosol Formation from Nitrophenols Photolysis under Atmospheric Conditions

Atmosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1346
Author(s):  
Iustinian Gabriel Bejan ◽  
Romeo-Iulian Olariu ◽  
Peter Wiesen
Keyword(s):  
Gas Phase ◽  
Secondary Organic Aerosol ◽  
Degradation Mechanism ◽  
Organic Aerosol ◽  
Radical Scavenger ◽  
Oh Radical ◽  
Atmospheric Conditions ◽  
Aerosol Formation ◽  
Chemical Models ◽  
Secondary Organic Aerosol Formation

Nitrophenols are important products of the aromatic compounds photooxidation and play a considerable role in urban chemistry. Nitrophenols are important components of agricultural biomass burning that could influence the climate. The formation of secondary organic aerosol from the direct photolysis of nitrophenols was investigated for the first time in a quartz glass simulation chamber under simulated solar radiation. The results from these experiments indicate rapid SOA formation. The proposed mechanism for the gas-phase degradation of nitrophenols through photolysis shows the formation of biradicals that could react further in the presence of oxygen to form low volatile highly oxygenated compounds responsible for secondary organic aerosol formation. The inhibiting effect of NOx and the presence of an OH radical scavenger on the aerosol formation were also studied. For 2-nitrophenol, significant aerosol formation yields were observed in the absence of an OH radical scavenger and NOx, varying in the range of 18%–24%. A gas-phase/aerosol partitioning model was applied assuming the presence of only one compound in both phases. A degradation mechanism is proposed to explain the aerosol formation observed in the photolysis of nitrophenols. The atmospheric impact of nitrophenol photolysis is discussed and the importance for atmospheric chemical models is assessed.

scholarly journals Investigations on the gas-phase photolysis and OH radical kinetics of nitrocatechols: Implications of intramolecular interactions on their atmospheric behavior

2021 ◽  
Author(s):  
Claudiu Roman ◽  
Cecilia Arsene ◽  
Iustinian Gabriel Bejan ◽  
Romeo-Iulian Olariu
Keyword(s):  
Gas Phase ◽  
Rate Coefficient ◽  
Relative Rate ◽  
Structural Features ◽  
Intramolecular Interactions ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Phase Reaction ◽  
Oh Radical ◽  
Atmospheric Conditions

Abstract. The Environmental Simulation Chamber made of Quartz from the University “Alexandru Ioan Cuza” from Iasi (ESC-Q-UAIC), Romania, was used to investigate for the first time the gas-phase reaction rate coefficients for four nitrocatechols towards OH radicals under simulated atmospheric conditions. Employing relative rate technique at a temperature of 298 ± 2 K and total air pressure of 1 atm, the obtained rate coefficients (in 10−12 cm3×s−1) were as followed: k3NCAT = (3.41 ± 0.37) for 3-nitrocatechol, k4NCAT = (1.27 ± 0.19) for 4-nitrocatechol, k5M3NCAT = (5.55 ± 0.45) for 5-methyl-3-nitrocatechol and k4M5NCAT = (0.92 ± 0.14) for 4-methyl-5-nitrocatechol. For the investigated compounds the photolysis rates in the actinic region, scaled to atmospheric relevant conditions, were evaluated as well. In this case the photolysis rate coefficient values were obtained only for 3-nitrocatechol and 5-methyl-3-nitrocatechol: J3NCAT = (3.06 ± 0.16) × 10−4 s−1 and J5M3NCAT = (2.14 ± 0.18) × 10−4 s−1, respectively. Considering the obtained results our study suggests that photolysis may be the main degradation process for 3-nitrocatechol and 5-methyl-3-nitrocatechol in the atmosphere. Results are discussed in terms of the reactivity of the investigated four nitrocatechols towards OH-radical initiated oxidation and their structural features. The rate coefficient values are also compared with those estimated from the structure-activity relationship for monocyclic aromatic hydrocarbons. Additional comparison with similar compounds is also presented underlining the implications towards possible degradation pathways and atmospheric behavior.

2-Deoxyribose Radicals in the Gas Phase and Aqueous Solution. Transient Intermediates of Hydrogen Atom Abstraction from 2-Deoxyribofuranose

2005 ◽  
Vol 70 (11) ◽  
pp. 1769-1786 ◽  
Author(s):  
Luc A. Vannier ◽  
Chunxiang Yao ◽  
František Tureček
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Computational Study ◽  
Hydrogen Atom Abstraction ◽  
Oh Radical ◽  
Free Energies ◽  
Intramolecular Hydrogen ◽  
Solvation Free Energies ◽  
Transient Intermediates

A computational study at correlated levels of theory is reported to address the structures and energetics of transient radicals produced by hydrogen atom abstraction from C-1, C-2, C-3, C-4, C-5, O-1, O-3, and O-5 positions in 2-deoxyribofuranose in the gas phase and in aqueous solution. In general, the carbon-centered radicals are found to be thermodynamically and kinetically more stable than the oxygen-centered ones. The most stable gas-phase radical, 2-deoxyribofuranos-5-yl (5), is produced by H-atom abstraction from C-5 and stabilized by an intramolecular hydrogen bond between the O-5 hydroxy group and O-1. The order of radical stabilities is altered in aqueous solution due to different solvation free energies. These prefer conformers that lack intramolecular hydrogen bonds and expose O-H bonds to the solvent. Carbon-centered deoxyribose radicals can undergo competitive dissociations by loss of H atoms, OH radical, or by ring cleavages that all require threshold dissociation or transition state energies >100 kJ mol-1. This points to largely non-specific dissociations of 2-deoxyribose radicals when produced by exothermic hydrogen atom abstraction from the saccharide molecule. Oxygen-centered 2-deoxyribose radicals show only marginal thermodynamic and kinetic stability and are expected to readily fragment upon formation.

scholarly journals Volatility of secondary organic aerosol during OH radical induced ageing

2011 ◽  
Vol 11 (21) ◽  
pp. 11055-11067 ◽  
Author(s):  
K. Salo ◽  
M. Hallquist ◽  
Å. M. Jonsson ◽  
H. Saathoff ◽  
K.-H. Naumann ◽  
...  
Keyword(s):  
Gas Phase ◽  
Organic Aerosol ◽  
Oh Radical ◽  
High Concentration ◽  
Volatile Material ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Institute Of Technology ◽  
Set Up ◽  
Pinic Acid

Abstract. The aim of this study was to investigate oxidation of SOA formed from ozonolysis of α-pinene and limonene by hydroxyl radicals. This paper focuses on changes of particle volatility, using a Volatility Tandem DMA (VTDMA) set-up, in order to explain and elucidate the mechanism behind atmospheric ageing of the organic aerosol. The experiments were conducted at the AIDA chamber facility of Karlsruhe Institute of Technology (KIT) in Karlsruhe and at the SAPHIR chamber of Forchungzentrum Jülich (FZJ) in Jülich. A fresh SOA was produced from ozonolysis of α-pinene or limonene and then aged by enhanced OH exposure. As an OH radical source in the AIDA-chamber the ozonolysis of tetramethylethylene (TME) was used while in the SAPHIR-chamber the OH was produced by natural light photochemistry. A general feature is that SOA produced from ozonolysis of α-pinene and limonene initially was rather volatile and becomes less volatile with time in the ozonolysis part of the experiment. Inducing OH chemistry or adding a new portion of precursors made the SOA more volatile due to addition of new semi-volatile material to the aged aerosol. The effect of OH chemistry was less pronounced in high concentration and low temperature experiments when lower relative amounts of semi-volatile material were available in the gas phase. Conclusions drawn from the changes in volatility were confirmed by comparison with the measured and modelled chemical composition of the aerosol phase. Three quantified products from the α-pinene oxidation; pinonic acid, pinic acid and methylbutanetricarboxylic acid (MBTCA) were used to probe the processes influencing aerosol volatility. A major conclusion from the work is that the OH induced ageing can be attributed to gas phase oxidation of products produced in the primary SOA formation process and that there was no indication on significant bulk or surface reactions. The presented results, thus, strongly emphasise the importance of gas phase oxidation of semi- or intermediate-volatile organic compounds (SVOC and IVOC) for atmospheric aerosol ageing.

scholarly journals Quantitative estimates of the volatility of ambient organic aerosol

2010 ◽  
Vol 10 (1) ◽  
pp. 1901-1938 ◽  
Author(s):  
C. D. Cappa ◽  
J. L. Jimenez
Keyword(s):  
Los Angeles ◽  
Gas Phase ◽  
Organic Aerosol ◽  
Basis Sets ◽  
Volatile Fraction ◽  
Volatile Components ◽  
Atmospheric Conditions ◽  
Volatile Material ◽  
Evaporation Coefficient ◽  
Quantitative Estimates

Abstract. Measurements of the sensitivity of organic aerosol (OA, and its components) mass to changes in temperature were recently reported by Huffman et al. (2009) using a tandem thermodenuder-aerosol mass spectrometer (TD-AMS) system in Mexico City and the Los Angeles area. Here, we use these measurements to derive quantitative estimates of aerosol volatility within the framework of absorptive partitioning theory using a kinetic model of aerosol evaporation in the TD. OA volatility distributions (or "basis-sets") are determined using several assumptions as to the enthalpy of vaporization (ΔHvap). We present two definitions of "non-volatile OA," one being a global and one a local definition. Based on these definitions, our analysis indicates that a substantial fraction of the organic aerosol is comprised of non-volatile components that will not evaporate under any atmospheric conditions, on the order of 50–80% when the most realistic ΔHvap assumptions are considered. The sensitivity of the total OA mass to dilution and ambient changes in temperature has been assessed for the various ΔHvap assumptions. The temperature sensitivity is relatively independent of the particular ΔHvap assumptions whereas dilution sensitivity is found to be greatest for the low (ΔHvap = 50 kJ/mol) and lowest for the high (ΔHvap = 150 kJ/mol) assumptions. This difference arises from the high ΔHvap assumptions yielding volatility distributions with a greater fraction of non-volatile material than the low ΔHvap assumptions. If the observations are fit using a 1 or 2-component model the sensitivity of the OA to dilution is unrealistically high. An empirical method introduced by Faulhaber et al. (2009) has also been used to independently estimate a volatility distribution for the ambient OA and is found to give results consistent with the high and variable ΔHvap assumptions. Our results also show that the amount of semivolatile gas-phase organics in equilibrium with the OA could range from ~20% to 400% of the OA mass, with smaller values generally corresponding to the higher ΔHvap assumptions. The volatility of various OA components determined from factor analysis of AMS spectra has also been assessed. In general, it is found that the fraction of non-volatile material follows the pattern: biomass burning OA < hydrocarbon-like OA < semivolatile oxygenated OA < low-volatility oxygenated OA. Correspondingly, the sensitivity to dilution and the estimated amount of semivolatile gas-phase material for the OA factors follows the reverse order. Primary OA has a substantial semivolatile fraction, in agreement with previous results, while the non-volatile fraction appears to be dominated by oxygenated OA produced by atmospheric aging. The overall OA volatility is thus controlled by the relative contribution of each aerosol type to the total OA burden. Finally, the model/measurement comparison appears to require OA having an evaporation coefficient (γe) substantially greater than 10−2; at this point it is not possible to place firmer constraints on γe based on the observations.

Mechanism and kinetic study on the gas-phase reactions of OH radical with carbamate insecticide isoprocarb

2012 ◽  
Vol 60 ◽  
pp. 460-466 ◽  
Author(s):  
Chenxi Zhang ◽  
Wenbo Yang ◽  
Jing Bai ◽  
Yuyang Zhao ◽  
Chen Gong ◽  
...  
Keyword(s):  
Kinetic Study ◽  
Gas Phase ◽  
Oh Radical ◽  
Gas Phase Reactions ◽  
Carbamate Insecticide

scholarly journals Evaluation of the SOA Formation in the Reaction of Furfural with Atmospheric Oxidants

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 927
Author(s):  
Inmaculada Colmenar ◽  
Pilar Martín ◽  
Beatriz Cabañas ◽  
Sagrario Salgado ◽  
Florentina Villanueva ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ultrafine Particles ◽  
Analytical Techniques ◽  
Organic Aerosol ◽  
Nitrate Radical ◽  
Atmospheric Conditions ◽  
Severe Damage ◽  
Infrared Spectrophotometer ◽  
Cl Atoms ◽  
Product Study

An experimental product study of the reactions of furfural with the main tropospheric oxidants (Cl, OH and NO3) has been carried out using a Fourier Transform Infrared spectrophotometer (FTIR) and a gas chromatograph–mass spectrometer with a time of flight detector (GC–TOFMS). The main gas-phase products detected were 5-chloro-2(5H)-furanone, maleic anhydride, 2-nitrofuran and CO. Molar yields were quantified for the detected products in these reactions, thus suggesting the existence of nongaseous products that could not be observed with the analytical techniques employed. The formation of Secondary Organic Aerosol (SOA) from the oxidation of furfural with Cl atoms, OH, NO3 and ozone was investigated in a smog chamber in the absence of inorganic seed aerosols. The experimental results show the formation of ultrafine particles (less than 1 µm in diameter) for all of the studied reactions except for the nitrate radical. Given their small size, these ultrafine particles (<1 µm) can easily penetrate into the respiratory tract and reach the alveolar region. These particles, therefore, have the potential to cause severe damage to the respiratory system. The aerosol yield obtained, Y, was low (<0.04) in all cases, which means that the aerosols generated from furfural, under atmospheric conditions, could have little impact.

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