scholarly journals Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

2011 ◽  
Vol 11 (15) ◽  
pp. 7875-7891 ◽  
Author(s):  
G. M. Wolfe ◽  
J. A. Thornton ◽  
M. McKay ◽  
A. H. Goldstein
Keyword(s):  
Vertical Mixing ◽  
Trace Gas ◽  
Reaction Products ◽  
Ozone Flux ◽  
Aerosol Mass ◽  
Ozone Sensitivity ◽  
Biogenic Voc ◽  
Volatile Organic ◽  
Urban Rural ◽  
Ozone Reactivity

Abstract. Understanding the fate of ozone within and above forested environments is vital to assessing the anthropogenic impact on ecosystems and air quality at the urban-rural interface. Observed forest-atmosphere exchange of ozone is often much faster than explicable by stomatal uptake alone, suggesting the presence of additional ozone sinks within the canopy. Using the Chemistry of Atmosphere-Forest Exchange (CAFE) model in conjunction with summer noontime observations from the 2007 Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX-2007), we explore the viability and implications of the hypothesis that ozonolysis of very reactive but yet unidentified biogenic volatile organic compounds (BVOC) can influence the forest-atmosphere exchange of ozone. Non-stomatal processes typically generate 67 % of the observed ozone flux, but reactions of ozone with measured BVOC, including monoterpenes and sesquiterpenes, can account for only 2 % of this flux during the selected timeframe. By incorporating additional emissions and chemistry of a proxy for very reactive VOC (VRVOC) that undergo rapid ozonolysis, we demonstrate that an in-canopy chemical ozone sink of ~2 × 108 molec cm−3 s−1 can close the ozone flux budget. Even in such a case, the 65 min chemical lifetime of ozone is much longer than the canopy residence time of ~2 min, highlighting that chemistry can influence reactive trace gas exchange even when it is "slow" relative to vertical mixing. This level of VRVOC ozonolysis could enhance OH and RO2 production by as much as 1 pptv s−1 and substantially alter their respective vertical profiles depending on the actual product yields. Reaction products would also contribute significantly to the oxidized VOC budget and, by extension, secondary organic aerosol mass. Given the potentially significant ramifications of a chemical ozone flux for both in-canopy chemistry and estimates of ozone deposition, future efforts should focus on quantifying both ozone reactivity and non-stomatal (e.g. cuticular) deposition within the forest.

scholarly journals Forest-atmosphere exchange of ozone: sensitivity to very reactive biogenic VOC emissions and implications for in-canopy photochemistry

2011 ◽  
Vol 11 (5) ◽  
pp. 13381-13424 ◽  
Author(s):  
G. M. Wolfe ◽  
J. A. Thornton ◽  
M. McKay ◽  
A. H. Goldstein
Keyword(s):  
Vertical Mixing ◽  
Trace Gas ◽  
Reaction Products ◽  
Ozone Flux ◽  
Aerosol Mass ◽  
Ozone Sensitivity ◽  
Biogenic Voc ◽  
Volatile Organic ◽  
Urban Rural ◽  
Ozone Reactivity

Abstract. Understanding the fate of ozone within and above forested environments is vital to assessing the anthropogenic impact on ecosystems and air quality at the urban-rural interface. Observed forest-atmosphere exchange of ozone is often much faster than explicable by stomatal uptake alone, suggesting the presence of additional ozone sinks within the canopy. Using the Chemistry of Atmosphere-Forest Exchange (CAFE) model in conjunction with summer noontime observations from the 2007 Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX-2007), we explore the viability and implications of the hypothesis that ozonolysis of very reactive but yet unidentified biogenic volatile organic compounds (BVOC) can influence the forest-atmosphere exchange of ozone. Non-stomatal processes typically generate 67% of the observed ozone flux, but reactions of ozone with measured BVOC, including monoterpenes and sesquiterpenes, can account for only 2% of this flux during the selected timeframe. By incorporating additional emissions and chemistry of a proxy for very reactive VOC (VRVOC) that undergo rapid ozonolysis, we demonstrate that an in-canopy chemical ozone sink of ~2×108 molecules cm−3 s−1 can close the ozone flux budget. Even in such a case, the 65 min chemical lifetime of ozone is much longer than the canopy residence time of ~2 min, highlighting that chemistry can influence reactive trace gas exchange even when it is "slow" relative to vertical mixing. This level of VRVOC ozonolysis could enhance OH and RO2 production by as much as 1 pptv s−1 and substantially alter their respective vertical profiles depending on the actual product yields. Reaction products would also contribute significantly to the oxidized VOC budget and, by extension, secondary organic aerosol mass. Given the potentially significant ramifications of a chemical ozone flux for both in-canopy chemistry and estimates of ozone deposition, future efforts should focus on quantifying both ozone reactivity and non-stomatal (e.g. cuticular) deposition within the forest.

scholarly journals A comparative and experimental study of the reactivity with nitrate radical of two terpenes: <i>α</i>-terpinene and <i>γ</i>-terpinene

2020 ◽  
Vol 20 (23) ◽  
pp. 15167-15189
Author(s):  
Axel Fouqueau ◽  
Manuela Cirtog ◽  
Mathieu Cazaunau ◽  
Edouard Pangui ◽  
Jean-François Doussin ◽  
...  
Keyword(s):  
Main Reaction ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Nitrate Radical ◽  
Reaction Products ◽  
Chemical Mechanisms ◽  
Chemical Structures ◽  
Aerosol Mass ◽  
Similar Chemical ◽  
Volatile Organic

Abstract. Biogenic volatile organic compounds (BVOCs) are intensely emitted by forests and crops into the atmosphere. During the night, they react very rapidly with the nitrate radical (NO3), leading to the formation of a variety of functionalized products including organic nitrates and to large amounts of secondary organic aerosols (SOAs). Organic nitrates (ONs) have been shown not only to play a key role in the transport of reactive nitrogen and consequently in the ozone budget but also to be important components of the total organic-aerosol mass, while SOAs are known to play a direct and indirect role in the climate. However, the reactivity of BVOCs with NO3 remains poorly studied. The aim of this work is to provide new kinetic and mechanistic data for two monoterpenes (C10H16), α- and γ-terpinene, through experiments in simulation chambers. These two compounds, which have very similar chemical structures, have been chosen in order not only to overcome the lack of experimental data but also to highlight the influence of the chemical structure on the reactivity. Rate constants have been measured using both relative and absolute methods. They were found to be (1.2±0.5)×10-10 and (2.9±1.1)×10-11 cm3 molecule−1 s−1 for α- and γ-terpinene respectively. Mechanistic studies have also been conducted in order to identify and quantify the main reaction products. Total organic nitrate and SOA yields have been determined. While organic nitrate formation yields appear to be similar, SOA yields exhibit large differences with γ-terpinene being a much more efficient precursor of aerosols. In order to provide explanations for this difference, chemical analysis of the gas-phase products was performed at the molecular scale. Detected products allowed for proposing chemical mechanisms and providing explanations through peroxy and alkoxy reaction pathways.

scholarly journals Anthropogenic enhancements to production of highly oxygenated molecules from autoxidation

2019 ◽  
Vol 116 (14) ◽  
pp. 6641-6646 ◽  
Author(s):  
Havala O. T. Pye ◽  
Emma L. D’Ambro ◽  
Ben H. Lee ◽  
Siegfried Schobesberger ◽  
Masayuki Takeuchi ◽  
...  
Keyword(s):  
Fine Particulate Matter ◽  
Peroxy Radicals ◽  
Dominant Component ◽  
Fine Particulate ◽  
Biogenic Voc ◽  
Aircraft Observations ◽  
Volatile Organic ◽  
Climate Interactions ◽  
Urban Plume

Atmospheric oxidation of natural and anthropogenic volatile organic compounds (VOCs) leads to secondary organic aerosol (SOA), which constitutes a major and often dominant component of atmospheric fine particulate matter (PM2.5). Recent work demonstrates that rapid autoxidation of organic peroxy radicals (RO2) formed during VOC oxidation results in highly oxygenated organic molecules (HOM) that efficiently form SOA. As NOxemissions decrease, the chemical regime of the atmosphere changes to one in which RO2autoxidation becomes increasingly important, potentially increasing PM2.5, while oxidant availability driving RO2formation rates simultaneously declines, possibly slowing regional PM2.5formation. Using a suite of in situ aircraft observations and laboratory studies of HOM, together with a detailed molecular mechanism, we show that although autoxidation in an archetypal biogenic VOC system becomes more competitive as NOxdecreases, absolute HOM production rates decrease due to oxidant reductions, leading to an overall positive coupling between anthropogenic NOxand localized biogenic SOA from autoxidation. This effect is observed in the Atlanta, Georgia, urban plume where HOM is enhanced in the presence of elevated NO, and predictions for Guangzhou, China, where increasing HOM-RO2production coincides with increases in NO from 1990 to 2010. These results suggest added benefits to PM2.5abatement strategies come with NOxemission reductions and have implications for aerosol–climate interactions due to changes in global SOA resulting from NOxinteractions since the preindustrial era.

scholarly journals Detection of Outflow of Formaldehyde and Glyoxal from the African continent to the Atlantic Ocean with a MAX-DOAS Instrument

2019 ◽  
Author(s):  
Lisa K. Behrens ◽  
Andreas Hilboll ◽  
Andreas Richter ◽  
Enno Peters ◽  
Leonardo M. A. Alvarado ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Cape Verde ◽  
Trace Gas ◽  
Biogenic Emissions ◽  
African Continent ◽  
Satellite Measurements ◽  
Model Simulations ◽  
Spatial Gradients ◽  
Volatile Organic ◽  
Continental Outflow

Abstract. Trace gas maps retrieved from satellite measurements show enhanced levels of the atmospheric volatile organic compounds formaldehyde (HCHO) and glyoxal (CHOCHO) over the Atlantic Ocean. To validate the spatial distribution of this continental outflow, ship-based measurements were taken during the project Continental Outflow of Pollutants towards the MArine tRoposphere (COPMAR). A Multi-AXis Differential Optical Absorption Spectrometer (MAX-DOAS) was operated on board the research vessel (RV) Maria S. Merian during the cruise MSM58/2. This cruise was conducted in October 2016 from Ponta Delgada (Azores) to Cape Town (South Africa), crossing between Cape Verde and the African continent. The instrument was continuously scanning the horizon looking towards the African continent. Enhanced levels of HCHO and CHOCHO were found in the area of expected outflow during this cruise. The observed spatial gradients of HCHO and CHOCHO along the cruise track agree with the spatial distributions from satellite measurements and MOZART-4 model simulations. The continental outflow from the African continent is observed in an elevated layer, higher than 1000 m, and probably originates from biogenic emissions or biomass burning according to FLEXPART emission sensitivities.

scholarly journals Abiotic stress impact on aerosol mass spectra over a forest site in Lithuania

2019 ◽  
Vol 59 (3) ◽  
Author(s):  
Julija Pauraitė ◽  
Steigvilė Byčenkienė ◽  
Kristina Plauškaitė ◽  
Algirdas Augustaitis ◽  
Vitas Marozas ◽  
...  
Keyword(s):  
Abiotic Stress ◽  
Mass Spectra ◽  
Organic Aerosol ◽  
Response Analysis ◽  
Forest Site ◽  
Tree Trunk ◽  
Integrated Monitoring ◽  
Aerosol Mass ◽  
Volatile Organic ◽  
Normal Increase

Volatile organic compounds (VOCs) emitted by trees in response to abiotic stress evoke high levels of secondary organic aerosol (SOA) compounds. Few techniques exist to provide chemically-resolved submicron (PM1) particle mass concentrations and source apportionment of stress-induced emissions from trees and SOA formation. The chemical composition of atmospheric aerosol particles was characterized using an aerosol chemical speciation monitor (ACSM) at a mixed-mature forest site – the Aukštaitija Integrated Monitoring Station in the eastern part of Lithuania. The organic fraction of PM1 consisted of SOA (76%) and of anthropogenic combustion related primary organic aerosol (POA) (24%). The analysis of tree trunk circumference revealed three shrinkage and three normal increase episodes. During the episodes of tree trunk circumference shrinkage, several m/z signal (m/z 42, 43, 45, 48, 50) intensities were found to be magnified together with the daily SOA concentration. The stress response analysis confirm that tree trunk circumference shrinkage may be observed through the enhancement of selected m/z signals and result in increased SOA levels.

scholarly journals Measurement report: Biogenic VOC emissions profiles of Rapeseed leaf litter and their SOA formation potential

2021 ◽  
Author(s):  
Letizia Abis ◽  
Carmen Kalalian ◽  
Bastien Lunardelli ◽  
Tao Wang ◽  
Liwu Zhang ◽  
...  
Keyword(s):  
Uv Light ◽  
Organic Aerosols ◽  
Light Irradiation ◽  
Large Contribution ◽  
Biogenic Volatile Organic Compounds ◽  
Voc Emissions ◽  
Uv Light Irradiation ◽  
Biogenic Voc ◽  
Volatile Organic ◽  
First Time

Abstract. We analysed the biogenic volatile organic compounds (BVOC) emissions from rapeseed leaves litter and their potential to create secondary organic aerosols (SOA) under three different conditions i.e., (i) in presence of UV light irradiation; (ii) in presence of ozone, and (iii) with both ozone and UV light. These experiments have been performed in a controlled atmospheric simulation chamber containing leaves litter samples, where BVOC and aerosol number concentrations have been measured for 6 days. Our results show that BVOC emission profiles were affected by UV light irradiation, which increased the summed BVOC emissions compared to the experiment with solely O3. Furthermore, the diversity of emitted VOCs from the rapeseed litter increased also in presence of UV light irradiation. SOA formation was observed when leaves litter were exposed to both UV light and O3, indicating a potentially large contribution to particle formation or growth at local scales. To our knowledge, this study investigates for the first time the effect of UV irradiation and O3 exposure on both VOC emissions and SOA formation for leaves litter samples. A detailed discussion about the processes behind the biological production of the most important VOC is proposed.

scholarly journals Application of the Statistical Oxidation Model (SOM) to Secondary Organic Aerosol formation from photooxidation of C<sub>12</sub> alkanes

2013 ◽  
Vol 13 (3) ◽  
pp. 1591-1606 ◽  
Author(s):  
C. D. Cappa ◽  
X. Zhang ◽  
C. L. Loza ◽  
J. S. Craven ◽  
L. D. Yee ◽  
...  
Keyword(s):  
Formation Process ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Atomic Ratio ◽  
Model Parameters ◽  
Reaction Products ◽  
Aerosol Formation ◽  
Volatile Organic ◽  
Oxidation Model ◽  
Mechanism Of Oxidation

Abstract. Laboratory chamber experiments are the main source of data on the mechanism of oxidation and the secondary organic aerosol (SOA) forming potential of volatile organic compounds. Traditional methods of representing the SOA formation potential of an organic do not fully capture the dynamic, multi-generational nature of the SOA formation process. We apply the Statistical Oxidation Model (SOM) of Cappa and Wilson (2012) to model the formation of SOA from the formation of the four C12 alkanes, dodecane, 2-methyl undecane, cyclododecane and hexylcyclohexane, under both high- and low-NOx conditions, based upon data from the Caltech chambers. In the SOM, the evolution of reaction products is defined by the number of carbon (NC) and oxygen (NO) atoms, and the model parameters are (1) the number of oxygen atoms added per reaction, (2) the decrease in volatility upon addition of an oxygen atom and (3) the probability that a given reaction leads to fragmentation of the molecules. Optimal fitting of the model to chamber data is carried out using the measured SOA mass concentration and the aerosol O:C atomic ratio. The use of the kinetic, multi-generational SOM is shown to provide insights into the SOA formation process and to offer promise for application to the extensive library of existing SOA chamber experiments that is available.

scholarly journals Simultaneous factor analysis of organic particle and gas mass spectra: AMS and PTR-MS measurements at an urban site

2010 ◽  
Vol 10 (4) ◽  
pp. 1969-1988 ◽  
Author(s):  
J. G. Slowik ◽  
A. Vlasenko ◽  
M. McGuire ◽  
G. J. Evans ◽  
J. P. D. Abbatt
Keyword(s):  
Mass Spectrometer ◽  
Mass Spectra ◽  
Relative Weight ◽  
Proton Transfer Reaction ◽  
Urban Site ◽  
Emission Sources ◽  
Reaction Products ◽  
Aerosol Mass ◽  
Direct Emission ◽  
The Individual

Abstract. During the winter component of the SPORT (Seasonal Particle Observations in the Region of Toronto) field campaign, particulate non-refractory chemical composition and concentration of selected volatile organic compounds (VOCs) were measured by an Aerodyne time-of-flight aerosol mass spectrometer (AMS) and a proton transfer reaction-mass spectrometer (PTR-MS), respectively. Sampling was performed in downtown Toronto ~15 m from a major road. The mass spectra from the AMS and PTR-MS were combined into a unified dataset, which was analysed using positive matrix factorization (PMF). The two instruments were given balanced weight in the PMF analysis by the application of a scaling factor to the uncertainties of each instrument. A residual based metric, Δesc, was used to evaluate the instrument relative weight within each solution. The PMF analysis yielded a 6-factor solution that included factors characteristic of regional transport, local traffic emissions, charbroiling and oxidative processing. The unified dataset provides information on emission sources (particle and VOC) and atmospheric processing that cannot be obtained from the datasets of the individual instruments: (1) apportionment of oxygenated VOCs to either direct emission sources or secondary reaction products; (2) improved correlation of oxygenated aerosol factors with photochemical age; and (3) increased detail regarding the composition of oxygenated organic aerosol factors. This analysis represents the first application of PMF to a unified AMS/PTR-MS dataset.

scholarly journals How much is particulate matter near the ground influenced by upper-level processes within and above the PBL? A summertime case study in Milan (Italy) evidences the distinctive role of nitrate

2015 ◽  
Vol 15 (5) ◽  
pp. 2629-2649 ◽  
Author(s):  
G. Curci ◽  
L. Ferrero ◽  
P. Tuccella ◽  
F. Barnaba ◽  
F. Angelini ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Vertical Mixing ◽  
Ground Level ◽  
Lower Atmosphere ◽  
Aerosol Layer ◽  
Dynamical Processes ◽  
Aerosol Mass ◽  
Short Period ◽  
Important Player ◽  
Upper Level

Abstract. Chemical and dynamical processes lead to the formation of aerosol layers in the upper planetary boundary layer (PBL) and above it. Through vertical mixing and entrainment into the PBL these layers may contribute to the ground-level particulate matter (PM); however, to date a quantitative assessment of such a contribution has not been carried out. This study investigates this aspect by combining chemical and physical aerosol measurements with WRF/Chem (Weather Research and Forecasting with Chemistry) model simulations. The observations were collected in the Milan urban area (northern Italy) during the summer of 2007. The period coincided with the passage of a meteorological perturbation that cleansed the lower atmosphere, followed by a high-pressure period favouring pollutant accumulation. Lidar observations revealed the formation of elevated aerosol layers and evidence of their entrainment into the PBL. We analysed the budget of ground-level PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 μm) with the help of the online meteorology–chemistry WRF/Chem model, focusing in particular on the contribution of upper-level processes. Our findings show that an important player in determining the upper-PBL aerosol layer is particulate nitrate, which may reach higher values in the upper PBL (up to 30% of the aerosol mass) than in the lower PBL. The nitrate formation process is predicted to be largely driven by the relative-humidity vertical profile, which may trigger efficient aqueous nitrate formation when exceeding the ammonium nitrate deliquescence point. Secondary PM2.5 produced in the upper half of the PBL may contribute up to 7–8 μg m−3 (or 25%) to ground-level concentrations on an hourly basis. The residual aerosol layer above the PBL is also found to potentially play a large role, which may occasionally contribute up to 10–12 μg m−3 (or 40%) to hourly ground-level PM2.5 concentrations during the morning hours. Although the results presented here refer to one relatively short period in one location, this study highlights the importance of considering the interplay between chemical and dynamical processes occurring within and above the PBL when interpreting ground-level aerosol observations.

scholarly journals Development and characterisation of a state-of-the-art GOME-2 formaldehyde air-mass factor algorithm

2015 ◽  
Vol 8 (1) ◽  
pp. 1109-1150 ◽  
Author(s):  
W. Hewson ◽  
M. P. Barkley ◽  
G. Gonzalez Abad ◽  
H. Bösch ◽  
T. Kurosu ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Vertical Profile ◽  
Trace Gas ◽  
Satellite Line ◽  
Air Mass ◽  
Volatile Organic ◽  
Weight Calculation ◽  
Transfer Error ◽  
Mass Factor ◽  
The University

Abstract. Space-borne observations of formaldehyde (HCHO) are frequently used to derive surface emissions of isoprene, an important biogenic volatile organic compound. The conversion of retrieved HCHO slant column concentrations from satellite line of sight measurements to vertical columns is determined through application of an air mass factor (AMF), accounting for instrument viewing geometry, radiative transfer, and vertical profile of the absorber in the atmosphere. This step in the trace gas retrieval is subject to large errors. This work presents the AMF algorithm in use at the University of Leicester (UoL), which introduces scene specific variables into a per-observation full radiative transfer AMF calculation, including increasing spatial resolution of key environmental parameter databases, input variable area weighting, instrument specific scattering weight calculation, and inclusion of an ozone vertical profile climatology. Application of these updates to HCHO slant columns from the GOME-2 instrument is shown to typically adjust the AMF by ±10%, compared to a~reference algorithm without these advanced parameterisations. Furthermore, the new UoL algorithm also incorporates a full radiative transfer error calculation for each scene to help characterise AMF uncertainties. Global median AMF errors are typically 50–60%, and are dominated by uncertainties in the HCHO profile shape and its corresponding seasonal variation.

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