scholarly journals Laboratory studies of H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O binary homogeneous nucleation from the SO<sub>2</sub>+OH reaction: evaluation of the experimental setup and preliminary results

2008 ◽  
Vol 8 (2) ◽  
pp. 6903-6947 ◽  
Author(s):  
L.-H. Young ◽  
D. R. Benson ◽  
F. R. Kameel ◽  
S.-H. Lee
Keyword(s):  
Homogeneous Nucleation ◽  
Particle Growth ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Experimental Setup ◽  
Field Observations ◽  
Laboratory Studies ◽  
Preliminary Results ◽  
Laboratory Setup ◽  
Fast Flow

Abstract. We have developed a new laboratory nucleation setup to study binary homogeneous nucleation (BHN) of sulphuric acid and water (H2SO4/H2O). Here we provide a detailed evaluation of this new experimental setup and also discuss our preliminary results by comparing with other laboratory studies. H2SO4 is produced from the SO2+OH →HSO3 reaction and OH radicals are produced from water vapor UV absorption. The residual H2SO4 concentrations ([H2SO4]) are measured at the end of the fast flow nucleation reactor with a chemical ionization mass spectrometer. The measured BHN rates (J) ranged from 0.02 and 550 cm−3 s−1 at the residual [H2SO4] from 108 to 1010 cm−3, a temperature of 288 K and relative humidity (RH) from 6 to 23%; J increased with increasing [H2SO4] and RH. J also showed a power dependence on [H2SO4] with the exponential power of 3 to 8. These results are consistent with other laboratory studies under similar [H2SO4] and RH, but different from atmospheric field observations which showed that particle number concentrations are often linearly dependent on [H2SO4]. Both particle sizes and number concentrations increased with increasing [H2SO4], RH, and nucleation time, consistent with the predictions from nucleation theories. Particle growth rates were estimated between 28 to 127 nm h−1, much higher than those seen from atmospheric field observations, because of the higher [H2SO4] used in our study. While these experimental results demonstrate a validation of our laboratory setup, there are also technical difficulties associated with nucleation studies, including wall loss and H2SO4 measurements.

scholarly journals Laboratory studies of H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O binary homogeneous nucleation from the SO<sub>2</sub>+OH reaction: evaluation of the experimental setup and preliminary results

2008 ◽  
Vol 8 (16) ◽  
pp. 4997-5016 ◽  
Author(s):  
L. H. Young ◽  
D. R. Benson ◽  
F. R. Kameel ◽  
J. R. Pierce ◽  
H. Junninen ◽  
...  
Keyword(s):  
Homogeneous Nucleation ◽  
Particle Diameter ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Field Observations ◽  
Atmospheric Conditions ◽  
Laboratory Studies ◽  
Aerosol Formation ◽  
H2so4 Concentration ◽  
Wall Loss

Abstract. Binary homogeneous nucleation (BHN) of sulphuric acid and water (H2SO4/H2O) is one of the most important atmospheric nucleation processes, but laboratory observations of this nucleation process are very limited and there are also large discrepancies between different laboratory studies. The difficulties associated with these experiments include wall loss of H2SO4 and uncertainties in estimation of H2SO4 concentration ([H2SO4]) involved in nucleation. We have developed a new laboratory nucleation setup to study H2SO4/H2O BHN kinetics and provide relatively constrained [H2SO4] needed for nucleation. H2SO4 is produced from the SO2+OH→HSO3 reaction and OH radicals are produced from water vapor UV absorption. The residual [H2SO4] were measured at the end of the nucleation reactor with a chemical ionization mass spectrometer (CIMS). Wall loss factors (WLFs) of H2SO4 were estimated by assuming that wall loss is diffusion limited and these calculated WLFs were in good agreement with simultaneous measurements of the initial and residual [H2SO4] with two CIMSs. The nucleation zone was estimated from numerical simulations based on the measured aerosol sizes (particle diameter, Dp) and [H2SO4]. The measured BHN rates (J) ranged from 0.01–220 cm−3 s−1 at the initial and residual [H2SO4] from 108−1010 cm−3, a temperature of 288 K and relative humidity (RH) from 11–23%; J increased with increasing [H2SO4] and RH. J also showed a power dependence on [H2SO4] with the exponential power of 3–8. These power dependences are consistent with other laboratory studies under similar [H2SO4] and RH, but different from atmospheric field observations which showed that particle number concentrations are often linearly dependent on [H2SO4]. These results, together with a higher [H2SO4] threshold (108–109 cm−3) needed to produce the unit J measured from the laboratory studies compared to the atmospheric conditions (106–107 cm−3), imply that H2SO4/H2O BHN alone is insufficient to explain atmospheric aerosol formation and growth. Particle growth rates estimated from the measured aerosol size distributions, residence times (tr), and [H2SO4] were 100–500 nm h−1, much higher than those seen from atmospheric field observations, because of the higher [H2SO4] used in our study.

A new species of Hypatima Hübner (Lepidoptera: Gelechiidae) injurious to mango trees in East Africa

1989 ◽  
Vol 79 (3) ◽  
pp. 411-420 ◽  
Author(s):  
K. Sattler ◽  
A. B. Stride
Keyword(s):  
Life History ◽  
New Species ◽  
East Africa ◽  
Female Genitalia ◽  
Field Observations ◽  
Laboratory Studies ◽  
Male And Female ◽  
Extensive Field ◽  
A New Species

AbstractHypatima mangiferae Sattler sp. n. is described from Kenya, where its larva is injurious to commercial mango trees. A description of its life-history, based on extensive field observations and laboratory studies, is also provided. The moth, its male and female genitalia and the damage caused by the larva are illustrated.

scholarly journals Heterogeneous oxidation of saturated organic aerosols by hydroxyl radicals: Uptake kinetics and condensed-phase products

2007 ◽  
Vol 7 (3) ◽  
pp. 6803-6842 ◽  
Author(s):  
I. J. George ◽  
A. Vlasenko ◽  
J. G. Slowik ◽  
J. P. D. Abbatt
Keyword(s):  
Hydroxyl Radicals ◽  
Particle Density ◽  
Organic Aerosols ◽  
Oxidation Products ◽  
Photochemical Oxidation ◽  
Mass Spectrometry Analysis ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Phase Reaction ◽  
Heterogeneous Oxidation

Abstract. The kinetics and reaction mechanism for the heterogeneous oxidation of saturated organic aerosols by gas-phase OH radicals were investigated under NOx-free conditions. The reaction of 150 nm diameter Bis(2-ethylhexyl) sebacate (BES) particles with OH was studied as a proxy for chemical aging of atmospheric aerosols containing saturated organic matter. An aerosol reactor flow tube combined with an Aerodyne time-of-flight aerosol mass spectrometer (ToF-AMS) and scanning mobility particle sizer (SMPS) was used to study this system. Hydroxyl radicals were produced by 254 nm photolysis of O3 in the presence of water vapour. The kinetics of the heterogeneous oxidation of the BES particles was studied by monitoring the loss of a mass fragment of BES with the ToF-AMS as a function of OH exposure. We measured an initial OH uptake coefficient of γ0 = 1.26 (±0.04), confirming that this reaction is highly efficient. The density of BES particles increased by up to 20% of the original BES particle density at the highest OH exposure studied, consistent with the particle becoming more oxidized. Electrospray ionization mass spectrometry analysis showed that the major particle-phase reaction products are multifunctional carbonyls and alcohols with higher molecular weights than the starting material. Volatilization of oxidation products accounted for a maximum of 17% decrease of the particle volume at the highest OH exposure studied. Tropospheric organic aerosols will become more oxidized from heterogeneous photochemical oxidation, which may affect not only their physical and chemical properties, but also their hygroscopicity and cloud nucleation activity.

scholarly journals Laboratory study on new particle formation from the reaction OH + SO<sub>2</sub>: influence of experimental conditions, H<sub>2</sub>O vapour, NH<sub>3</sub> and the amine tert-butylamine on the overall process

2010 ◽  
Vol 10 (3) ◽  
pp. 6447-6484 ◽  
Author(s):  
T. Berndt ◽  
F. Stratmann ◽  
M. Sipilä ◽  
J. Vanhanen ◽  
T. Petäjä ◽  
...  
Keyword(s):  
Relative Humidity ◽  
High Sensitivity ◽  
Particle Growth ◽  
Counting Efficiency ◽  
Oh Radicals ◽  
Atmospheric Conditions ◽  
Promoting Effect ◽  
Experimental Conditions ◽  
H2so4 Concentration ◽  
Tert Butylamine

Abstract. Nucleation experiments starting from the reaction of OH radicals with SO2 have been performed in the IfT-LFT flow tube under atmospheric conditions at 293±0.5 K for a relative humidity of 13–61%. The presence of different additives (H2, CO, 1,3,5-trimethylbenzene) for adjusting the OH radical concentration and resulting OH levels in the range (4–300)·105 molecule cm−3 did not influence the nucleation process itself. The number of detected particles as well as the threshold H2SO4 concentration needed for nucleation was found to be strongly dependent on the counting efficiency of the used counting devices. High-sensitivity particle counters allowed the measurement of freshly nucleated particles with diameters down to about 1.5 nm. A parameterization of the experimental data was developed using power law equations for H2SO4 and H2O vapour. The exponent for H2SO4 from different measurement series was in the range of 1.7–2.1 being in good agreement with those arising from analysis of nucleation events in the atmosphere. For increasing relative humidity, an increase of the particle number was observed. The exponent for H2O vapour was found to be 3.1 representing a first estimate. Addition of 1.2·1011 molecule cm−3 or 1.2·1012 molecule cm−3 of NH3 (range of atmospheric NH3 peak concentrations) revealed that NH3 has a measureable, promoting effect on the nucleation rate under these conditions. The promoting effect was found to be more pronounced for relatively dry conditions. NH3 showed a contribution to particle growth. Adding the amine tert-butylamine instead of NH3, the enhancing impact for nucleation and particle growth appears to be stronger.

scholarly journals Controlled nitric oxide production via O(<sup>1</sup>D)+N<sub>2</sub>O reactions for use in oxidation flow reactor studies

2017 ◽  
Author(s):  
Andrew Lambe ◽  
Paola Massoli ◽  
Xuan Zhang ◽  
Manjula Canagaratna ◽  
John Nowak ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Flow Reactor ◽  
Branching Ratio ◽  
Oxidation Products ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Flow Reactors ◽  
Oxidative Aging ◽  
Gas Phase Oxidation

Abstract. Oxidation flow reactors that use low-pressure mercury lamps to produce hydroxyl (OH) radicals are an emerging technique for studying the oxidative aging of organic aerosols. Here, ozone (O3) is photolyzed at 254 nm to produce O(1D) radicals, which react with water vapor to produce OH. However, the need to use parts-per-million levels of O3 hinders the ability of oxidation flow reactors to simulate NOx-dependent SOA formation pathways. Simple addition of nitric oxide (NO) results in fast conversion of NOx (NO + NO2) to nitric acid (HNO3), making it impossible to sustain NO at levels that are sufficient to compete with hydroperoxy (HO2) radicals as a sink for organic peroxy (RO2) radicals. We developed a new method that is well suited to the characterization of NOx-dependent SOA formation pathways in oxidation flow reactors. NO and NO2 are produced via the reaction O(1D) + N2O→ 2NO, followed by the reaction NO + O3 → NO2+ O2. Laboratory measurements coupled with photochemical model simulations suggest that O(1D) + N2O reactions can be used to systematically vary the relative branching ratio of RO2 + NO reactions relative to RO2 + HO2 and/or RO2 + RO2 reactions over a range of conditions relevant to atmospheric SOA formation. We demonstrate proof of concept using high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) measurements with nitrate (NO3−) reagent ion to detect gas-phase oxidation products of isoprene and α-pinene previously observed in NOx-influenced environments and in laboratory chamber experiments.

Nucleation rates and the kinetics of particle growth II. The birth and death process

1964 ◽  
Vol 277 (1369) ◽  
pp. 167-182 ◽  
Keyword(s):  
Steady State ◽  
Homogeneous Nucleation ◽  
Time Lag ◽  
Particle Growth ◽  
Statistical Problem ◽  
Death Process ◽  
Birth And Death Process ◽  
Growth Mechanisms ◽  
Nucleation Kinetics ◽  
Kinetics Of

The model considered in part I is generalized to include growth mechanisms in which the chemical reaction which proceeds at the particle-atm osphere interface is reversible, so that molecules may evaporate from a particle as well as condense upon it. The Becker-Döring-Zeldovich-Frenkel theory of homogeneous nucleation kinetics is then reviewed in the light of the known statistical problem of the birth -and -death process, and an improved approximation is introduced which significantly alters the calculated results. Both steady-state nucleation kinetics and the time lag problem are discussed.

scholarly journals A Parameterization of Sticking Efficiency for Collisions of Snow and Graupel with Ice Crystals: Theory and Comparison with Observations*

2015 ◽  
Vol 72 (12) ◽  
pp. 4885-4902 ◽  
Author(s):  
Vaughan T. J. Phillips ◽  
Marco Formenton ◽  
Aaron Bansemer ◽  
Innocent Kudzotsa ◽  
Barry Lienert
Keyword(s):  
Probability Distribution ◽  
Kinetic Energy ◽  
Ice Crystals ◽  
Field Observations ◽  
Laboratory Studies ◽  
Atmospheric Models ◽  
Vapor Growth ◽  
Collision Processes ◽  
Work Done ◽  
Temperature Surface

Abstract A new parameterization of sticking efficiency for aggregation of ice crystals onto snow and graupel is presented. This parameter plays a crucial role for the formation of ice precipitation and for electrification processes. The parameterization is intended to be used in atmospheric models simulating the aggregation of ice particles in glaciated clouds. It should improve the ability to forecast snow. Based on experimental results and general considerations of collision processes, dependencies of the sticking efficiency on temperature, surface area, and collision kinetic energy of impacting particles are derived. The parameters have been estimated from some laboratory observations by simulating the experiments and minimizing the squares of the errors of the prediction of observed quantities. The predictions from the new scheme are compared with other available laboratory and field observations. The comparisons show that the parameterization is able to reproduce the thermal behavior of sticking efficiency, observed in published laboratory studies, with a peak around −15°C corresponding to dendritic vapor growth of ice. Finally, a new theory of sticking efficiency is proposed. It explains the empirically derived parameterization in terms of a probability distribution of the work that would be required to separate two contacting particles colliding in all possible ways among many otherwise identical collisions of the same pair with a given initial collision kinetic energy. For each collision, if this work done would exceed the initial collision kinetic energy, then there is no separation after impact. The probability of that occurring equals the sticking efficiency.

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