scholarly journals Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O<sub>3</sub>, NO<sub>2</sub>, and H<sub>2</sub>O on soot coated with benzo[a]pyrene

2009 ◽  
Vol 9 (19) ◽  
pp. 7461-7479 ◽  
Author(s):  
M. Springmann ◽  
D. A. Knopf ◽  
N. Riemer
Keyword(s):  
Gas Phase ◽  
Co Adsorption ◽  
Particle Surface ◽  
Chemical Oxidation ◽  
Box Model ◽  
Heterogeneous Chemistry ◽  
Heterogeneous Kinetics ◽  
Urban Plume ◽  
Uptake Coefficients ◽  
Conceptual Study

Abstract. This study assesses in detail the effects of heterogeneous chemistry on the particle surface and gas-phase composition by modeling the reversible co-adsorption of O3, NO2, and H2O on soot coated with benzo[a]pyrene (BaP) for an urban plume scenario over a period of five days. By coupling the Pöschl-Rudich-Ammann (PRA) kinetic framework for aerosols (Pöschl et al., 2007) to a box model version of the gas phase mechanism RADM2, we are able to track individual concentrations of gas-phase and surface species over the course of several days. The flux-based PRA formulation takes into account changes in the uptake kinetics due to changes in the chemical gas-phase and particle surface compositions. This dynamic uptake coefficient approach is employed for the first time in a broader atmospheric context of an urban plume scenario. Our model scenarios include one to three adsorbents and three to five coupled surface reactions. The results show a variation of the O3 and NO2 uptake coefficients of more than five orders of magnitude over the course of the simulation time and a decrease in the uptake coefficients in the various scenarios by more than three orders of magnitude within the first six hours. Thereafter, periodic peaks of the uptake coefficients follow the diurnal cycle of gas-phase O3-NOx reactions. Physisorption of water vapor reduces the half-life of the coating substance BaP by up to a factor of seven by permanently occupying ~75% of the soot surface. Soot emissions modeled by replenishing reactive surface sites lead to maximum gas-phase O3 depletions of 41 ppbv and 7.8 ppbv for an hourly and six-hourly replenishment cycle, respectively. This conceptual study highlights the interdependence of co-adsorbing species and their non-linear gas-phase feedback. It yields further insight into the atmospheric importance of the chemical oxidation of particles and emphasizes the necessity to implement detailed heterogeneous kinetics in future modeling studies.

scholarly journals Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O<sub>3</sub>, NO<sub>2</sub>, and H<sub>2</sub>O on soot coated with benzo[a]pyrene

2009 ◽  
Vol 9 (2) ◽  
pp. 10055-10099 ◽  
Author(s):  
M. Springmann ◽  
D. A. Knopf ◽  
N. Riemer
Keyword(s):  
Gas Phase ◽  
Co Adsorption ◽  
Particle Surface ◽  
Chemical Oxidation ◽  
Box Model ◽  
Experimental Investigations ◽  
Heterogeneous Chemistry ◽  
Urban Plume ◽  
Uptake Coefficients ◽  
Conceptual Study

Abstract. This study assesses in detail the effects of heterogeneous chemistry on the particle surface and gas-phase composition by modeling the reversible co-adsorption of O3, NO2, and H2O on soot coated with benzo[a]pyrene (BaP) for an urban plume scenario over a period of five days. By coupling the Pöschl-Rudich-Ammann (PRA) kinetic framework for aerosols (Pöschl et al., 2007) to a box model version of the gas phase mechanism RADM2, we are able to track individual concentrations of gas-phase and surface species over the course of several days. The flux-based PRA formulation takes into account changes in the uptake kinetics due to changes in the chemical gas-phase and particle surface compositions. This dynamic uptake coefficient approach is employed for the first time in a broader atmospheric context of an urban plume scenario. Our model scenarios include one to three adsorbents and three to five coupled surface reactions. The results show a variation of the O3 and NO2 uptake coefficients of more than five orders of magnitude over the course of simulation time and a decrease in the uptake coefficients in the various scenarios by more than three orders of magnitude within the first six hours. Thereafter, periodic peaks of the uptake coefficients follow the diurnal cycle of gas-phase O3-NOx reactions. Physisorption of water vapor delays the half-life of the coating substance BaP by up to a factor of seven by permanently occupying ~75% of the soot surface. Soot emissions modeled by replenishing reactive surface sites lead to maximum gas-phase O3 depletions of 41 ppbv for an hourly and 7.8 ppbv for a six-hourly replenishment cycle. This conceptual study highlights the interdependence of co-adsorbing species and their non-linear gas-phase feedback. It yields further insight into the atmospheric importance of the chemical oxidation of particles and guides future modeling and experimental investigations of the heterogeneous chemistry and chemical aging of aerosols.

scholarly journals Detailed heterogeneous oxidation of soot surfaces in a particle-resolved aerosol model

2011 ◽  
Vol 11 (9) ◽  
pp. 4505-4520 ◽  
Author(s):  
J. C. Kaiser ◽  
N. Riemer ◽  
D. A. Knopf
Keyword(s):  
Atmospheric Chemistry ◽  
Co Adsorption ◽  
Heterogeneous Reactions ◽  
Urban Atmosphere ◽  
Heterogeneous Chemistry ◽  
Heterogeneous Oxidation ◽  
Soot Particles ◽  
Aerosol Model ◽  
Particle Population ◽  
Uptake Coefficients

Abstract. Using the particle-resolved aerosol model PartMC-MOSAIC, we simulate the heterogeneous oxidation of a monolayer of polycyclic aromatic hydrocarbons (PAHs) on soot particles in an urban atmosphere. We focus on the interaction of the major atmospheric oxidants (O3, NO2, OH, and NO3) with PAHs and include competitive co-adsorption of water vapour for a range of atmospheric conditions. For the first time detailed heterogeneous chemistry based on the Pöschl-Rudich-Ammann (PRA) framework is modelled on soot particles with a realistic size distribution and a continuous range of chemical ages. We find PAHs half-lives, τ1/2, on the order of seconds during the night, when the PAHs are rapidly oxidised by the gas-surface reaction with NO3. During the day, τ1/2 is on the order of minutes and determined mostly by the surface layer reaction of PAHs with adsorbed O3. Such short half-lives of surface-bound PAHs may lead to efficient conversion of hydrophobic soot into more hygroscopic particles, thus increasing the particles' aerosol-cloud interaction potential. Despite its high reactivity OH appears to have a negligible effect on PAH degradation which can be explained by its very low concentration in the atmosphere. An increase of relative humidity (RH) from 30 % to 80 % increases PAH half-lives by up to 50 % for daytime degradation and by up to 100 % or more for nighttime degradation. Uptake coefficients, averaged over the particle population, are found to be relatively constant over time for O3 (∼2 × 10−7 to ∼2 × 10−6) and NO2 (∼5 × 10−6 to ∼10−5) at the different levels of NOx emissions and RH considered in this study. In contrast, those for OH and NO3 depend strongly on the surface concentration of PAHs. We do not find a significant influence of heterogeneous reactions on soot particles on the gas phase composition. The derived half-lives of surface-bound PAHs and the time and particle population averaged uptake coefficients for O3 and NO2 presented in this paper can be used as parameterisations for the treatment of heterogeneous chemistry in large-scale atmospheric chemistry models.

scholarly journals Exploration of oxidative chemistry and secondary organic aerosol formation in the Amazon during the wet season: explicit modeling of the Manaus urban plume with GECKO-A

2020 ◽  
Vol 20 (10) ◽  
pp. 5995-6014 ◽  
Author(s):  
Camille Mouchel-Vallon ◽  
Julia Lee-Taylor ◽  
Alma Hodzic ◽  
Paulo Artaxo ◽  
Bernard Aumont ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Background Level ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Box Model ◽  
Basis Set ◽  
Aerosol Formation ◽  
Wet Season ◽  
Urban Plume ◽  
The Impact

Abstract. The GoAmazon 2014/5 field campaign took place in Manaus, Brazil, and allowed the investigation of the interaction between background-level biogenic air masses and anthropogenic plumes. We present in this work a box model built to simulate the impact of urban chemistry on biogenic secondary organic aerosol (SOA) formation and composition. An organic chemistry mechanism is generated with the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to simulate the explicit oxidation of biogenic and anthropogenic compounds. A parameterization is also included to account for the reactive uptake of isoprene oxidation products on aqueous particles. The biogenic emissions estimated from existing emission inventories had to be reduced to match measurements. The model is able to reproduce ozone and NOx for clean and polluted situations. The explicit model is able to reproduce background case SOA mass concentrations but does not capture the enhancement observed in the urban plume. The oxidation of biogenic compounds is the major contributor to SOA mass. A volatility basis set (VBS) parameterization applied to the same cases obtains better results than GECKO-A for predicting SOA mass in the box model. The explicit mechanism may be missing SOA-formation processes related to the oxidation of monoterpenes that could be implicitly accounted for in the VBS parameterization.

scholarly journals Secondary formation of nitrated phenols: insights from observations during the Uintah Basin Winter Ozone Study (UBWOS) 2014

2015 ◽  
Vol 15 (20) ◽  
pp. 28659-28697 ◽  
Author(s):  
B. Yuan ◽  
J. Liggio ◽  
J. Wentzell ◽  
S.-M. Li ◽  
H. Stark ◽  
...  
Keyword(s):  
Gas Phase ◽  
Oil And Gas ◽  
Gas Production ◽  
Heterogeneous Reactions ◽  
Box Model ◽  
Ionization Mass ◽  
Oil And Gas Production ◽  
Production Region ◽  
Secondary Formation ◽  
Online Measurements

Abstract. We describe the results from online measurements of nitrated phenols using a time of flight chemical ionization mass spectrometer (ToF-CIMS) with acetate as reagent ion in an oil and gas production region in January and February of 2014. Strong diurnal profiles were observed for nitrated phenols, with concentration maxima at night. Based on known markers (CH4, NOx, CO2), primary emissions of nitrated phenols were not important in this study. A box model was used to simulate secondary formation of phenol, nitrophenol (NP) and dinitrophenols (DNP). The box model results indicate that oxidation of aromatics in the gas phase can explain the observed concentrations of NP and DNP in this study. Photolysis was the most efficient loss pathway for NP in the gas phase. We show that aqueous-phase reactions and heterogeneous reactions were minor sources of nitrated phenols in our study. This study demonstrates that the emergence of new ToF-CIMS (including PTR-TOF) techniques allows for the measurement of intermediate oxygenates at low levels and these measurements improve our understanding of the evolution of primary VOCs in the atmosphere.

scholarly journals Dissolved organic carbon (DOC) and select aldehydes in cloud and fog water: the role of the aqueous phase in impacting trace gas budgets

2013 ◽  
Vol 13 (10) ◽  
pp. 5117-5135 ◽  
Author(s):  
B. Ervens ◽  
Y. Wang ◽  
J. Eagar ◽  
W. R. Leaitch ◽  
A. M. Macdonald ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Water Soluble ◽  
Box Model ◽  
High Solubility ◽  
Fog Water ◽  
Air Masses ◽  
Order Of Magnitude

Abstract. Cloud and fog droplets efficiently scavenge and process water-soluble compounds and, thus, modify the chemical composition of the gas and particle phases. The concentrations of dissolved organic carbon (DOC) in the aqueous phase reach concentrations on the order of ~ 10 mgC L−1 which is typically on the same order of magnitude as the sum of inorganic anions. Aldehydes and carboxylic acids typically comprise a large fraction of DOC because of their high solubility. The dissolution of species in the aqueous phase can lead to (i) the removal of species from the gas phase preventing their processing by gas phase reactions (e.g., photolysis of aldehydes) and (ii) the formation of unique products that do not have any efficient gas phase sources (e.g., dicarboxylic acids). We present measurements of DOC and select aldehydes in fog water at high elevation and intercepted clouds at a biogenically-impacted location (Whistler, Canada) and in fog water in a more polluted area (Davis, CA). Concentrations of formaldehyde, glyoxal and methylglyoxal were in the micromolar range and comprised ≤ 2% each individually of the DOC. Comparison of the DOC and aldehyde concentrations to those at other locations shows good agreement and reveals highest levels for both in anthropogenically impacted regions. Based on this overview, we conclude that the fraction of organic carbon (dissolved and insoluble inclusions) in the aqueous phase of clouds or fogs, respectively, comprises 2–~ 40% of total organic carbon. Higher values are observed to be associated with aged air masses where organics are expected to be more highly oxidised and, thus, more soluble. Accordingly, the aqueous/gas partitioning ratio expressed here as an effective Henry's law constant for DOC (KH*DOC) increases by an order of magnitude from 7 × 103 M atm−1 to 7 × 104 M atm−1 during the ageing of air masses. The measurements are accompanied by photochemical box model simulations. These simulations are used to contrast two scenarios, i.e., an anthropogenically vs. a more biogenically impacted one as being representative for Davis and Whistler, respectively. Since the simplicity of the box model prevents a fully quantitative prediction of the observed aldehyde concentrations, we rather use the model results to compare trends in aldehyde partitioning and ratios. They suggest that the scavenging of aldehydes by the aqueous phase can reduce HO2 gas phase levels significantly by two orders of magnitude due to a weaker net source of HO2 production from aldehyde photolysis in the gas phase. Despite the high solubility of dicarbonyl compounds (glyoxal, methylglyoxal), their impact on the HO2 budget by scavenging is < 10% of that of formaldehyde. The overview of DOC and aldehyde measurements presented here reveals that clouds and fogs can be efficient sinks for organics, with increasing importance in aged air masses. Even though aldehydes, specifically formaldehyde, only comprise ~ 1% of DOC, their scavenging and processing in the aqueous phase might translate into significant effects in the oxidation capacity of the atmosphere.

Heat Transfer of Polymer Particles in Gas-Phase Polymerization Reactors

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Yaghoub Behjat ◽  
Mohammad Ali Dehnavi ◽  
Shahrokh Shahhosseini ◽  
Seyed Hassan Hashemabadi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Gas Phase ◽  
Transfer Rate ◽  
Fluid Dynamic ◽  
Convective Heat Transfer Coefficient ◽  
Particle Surface ◽  
Cfd Modeling ◽  
Polymerization Reactor ◽  
Gas Phase Polymerization

In this paper the effects of particles configuration and particles distance on the heat transfer rate in a gas phase olefin polymerization reactor have been studied using the computational fluid dynamic (CFD) modeling approach. The goal was to determine the causes of particle overheating in this reactor. It has been shown that classic correlations such as Ranz-Marshall are sufficiently adequate when far away particles with no interactions are to be modeled. However, when particles are sufficiently close to having interactions, these correlations fail to satisfactorily predict the convective heat transfer coefficient. The results indicate an increase in particle distance leads to an increase in the Nusselt number on the particle surface. Therefore, for particles with a large distance and triangular or rotated square configurations, the local Nusselt number is closer to the Nusselt number for a single particle.

Study of the co-adsorption of hexane from the gas phase at the surface of aqueous C10EO8 drops

Soft Matter ◽  
2011 ◽  
Vol 7 (17) ◽  
pp. 7860 ◽  
Author(s):  
V. B. Fainerman ◽  
E. V. Aksenenko ◽  
V. I. Kovalchuk ◽  
A. Javadi ◽  
R. Miller
Keyword(s):  
Gas Phase ◽  
Co Adsorption

scholarly journals Modeling reactive ammonia uptake by secondary organic aerosol in CMAQ: application to the continental US

2018 ◽  
Vol 18 (5) ◽  
pp. 3641-3657 ◽  
Author(s):  
Shupeng Zhu ◽  
Jeremy R. Horne ◽  
Julia Montoya-Aguilera ◽  
Mallory L. Hinks ◽  
Sergey A. Nizkorodov ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Air Quality ◽  
Ammonium Nitrate ◽  
Gas Phase ◽  
Ammonium Sulfate ◽  
Fine Particulate Matter ◽  
Considerable Uncertainty ◽  
Ammonia Uptake ◽  
Different Seasons ◽  
Uptake Coefficients

Abstract. Ammonium salts such as ammonium nitrate and ammonium sulfate constitute an important fraction of the total fine particulate matter (PM2.5) mass. While the conversion of inorganic gases into particulate-phase sulfate, nitrate, and ammonium is now well understood, there is considerable uncertainty over interactions between gas-phase ammonia and secondary organic aerosols (SOAs). Observations have confirmed that ammonia can react with carbonyl compounds in SOA, forming nitrogen-containing organic compounds (NOCs). This chemistry consumes gas-phase NH3 and may therefore affect the amount of ammonium nitrate and ammonium sulfate in particulate matter (PM) as well as particle acidity. In order to investigate the importance of such reactions, a first-order loss rate for ammonia onto SOA was implemented into the Community Multiscale Air Quality (CMAQ) model based on the ammonia uptake coefficients reported in the literature. Simulations over the continental US were performed for the winter and summer of 2011 with a range of uptake coefficients (10−3–10−5). Simulation results indicate that a significant reduction in gas-phase ammonia may be possible due to its uptake onto SOA; domain-averaged ammonia concentrations decrease by 31.3 % in the winter and 67.0 % in the summer with the highest uptake coefficient (10−3). As a result, the concentration of particulate matter is also significantly affected, with a distinct spatial pattern over different seasons. PM concentrations decreased during the winter, largely due to the reduction in ammonium nitrate concentrations. On the other hand, PM concentrations increased during the summer due to increased biogenic SOA (BIOSOA) production resulting from enhanced acid-catalyzed uptake of isoprene-derived epoxides. Since ammonia emissions are expected to increase in the future, it is important to include NH3 + SOA chemistry in air quality models.

scholarly journals Uptake of HO<sub>2</sub> radicals onto Arizona Test Dust aerosols

2014 ◽  
Vol 14 (4) ◽  
pp. 4229-4261 ◽  
Author(s):  
P. S. J. Matthews ◽  
M. T. Baeza-Romero ◽  
L. K. Whalley ◽  
D. E. Heard
Keyword(s):  
Time Dependence ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Reaction Times ◽  
Box Model ◽  
Partial Saturation ◽  
Flow Tube ◽  
Uptake Coefficients ◽  
Gas Expansion ◽  
Dust Surface

Abstract. Uptake coefficients for HO2 radicals onto Arizona Test Dust (ATD) aerosols were measured at room temperature and atmospheric pressure using an aerosol flow tube and the sensitive Fluorescence Assay by Gas Expansion (FAGE) technique, enabling HO2 concentrations in the range 3–10 × 108 molecule cm−3 to be investigated. The uptake coefficients were measured as 0.031 ± 0.008 and 0.018 ± 0.006 for the lower and higher HO2 concentrations, respectively, over a range of relative humidities (5–76%). A time dependence for the HO2 uptake onto the ATD aerosols was observed, with larger uptake coefficients observed at shorter reaction times. The combination of time and HO2 concentration dependencies suggest either the partial saturation of the dust surface or that a chemical component of the dust is partially consumed whilst the aerosols are exposed to HO2. A constrained box model is used to show that HO2 uptake to dust surfaces may be an important loss pathway of HO2 in the atmosphere.

Sign in / Sign up

Export Citation Format

Share Document