A detailed look at monoterpene oxidation reactions: results from the CERVOLAND field campaign and MCM modelling

2021 ◽  
Author(s):  
Nina Reijrink ◽  
Ahmad Lahib ◽  
Hichem Bouzidi ◽  
Marius Duncianu ◽  
Emilie Perraudin ◽  
...  
Keyword(s):  
Field Experiments ◽  
Uv Light ◽  
Ambient Air ◽  
Measurement Model ◽  
Oxidation Products ◽  
Peroxy Radicals ◽  
Oxidation Reactions ◽  
Field Campaign ◽  
Oxidation Processes ◽  
Artificial Uv

<p>Atmospheric oxidation reactions can be studied in the field, in the lab and by modelling, with each methodic approach having advantages and issues. The main drawback for field experiments is that both chemical and non-chemical processes (emission, advection, vertical dilution, etc.) can simultaneously impact the chemical composition of ambient air, making it difficult to assess their respective contributions. For this purpose, a mobile atmospheric chamber (DouAir) has been developed to trap ambient air at a measurement site and to investigate the chemistry taking place in this isolated air mass. Since the environment within the chamber is controllable, oxidation processes can be measured and modelled with relative ease, so that the underlying chemistry can be better understood.</p><p>During July 2018 the DouAir chamber was brought to the Landes Forest in the southwest of France for the CERVOLAND field campaign (Characterisation of Emissions and Reactivity of Volatile Organic compounds in the LANDes forest). The reactor was used to trap real air masses coming from the surrounding forest - consisting mainly of Pinus pinaster trees - and the captured air was subsequently oxidised within the chamber. Different oxidation regimes were studied: dark oxidation, light oxidation by natural sunlight and light oxidation by artificial UV light with a known spectrum. Oxidation processes within the chamber were monitored by a variety of online instruments, including PTR-ToF-MS (for VOCs), PERCA (for peroxy radicals), O3 and NOx analysers, and CPC (for particles).</p><p>Here, we present the experimental results from the CERVOLAND field campaign under different oxidation conditions and the results from the 0-D modelling of these experiments using MCM. The focus is on measured and modelled monoterpene oxidation products and possible explanations for measurement-model discrepancies.</p>

Photooxidation and ozonolysis of Δ3-carene and its oxidation product caronaldehyde in the atmospheric simulation chamber SAPHIR

2021 ◽  
Author(s):  
Luisa Hantschke ◽  
Anna Novelli ◽  
Birger Bohn ◽  
Changmin Cho ◽  
David Reimer ◽  
...  
Keyword(s):  
Oxidation Product ◽  
Boreal Forests ◽  
Oxidation Products ◽  
Organic Nitrate ◽  
Organic Nitrates ◽  
Peroxy Radicals ◽  
Atmospheric Conditions ◽  
Oxidation Reactions ◽  
Reaction Rate Constants ◽  
Simulation Chamber

<p>Of the total global annual monoterpene emissions, Δ<sup>3</sup>-carene contributes 4.5 %, making it the 7<sup>th</sup> most abundant monoterpene worldwide. As it is primarily emitted by pine trees, Δ<sup>3</sup>-carene can regionally gain in importance, for example in boreal forests and Mediterranean regions.  Oxidation products of monoterpenes such as organic nitrates and aldehydes are known to impact the formation of secondary pollutants such as ozone and particles, so understanding their atmospheric formation and fate is crucial.</p><p>The photooxidation and ozonolysis of Δ<sup>3</sup>-carene and the photooxidation and photolysis of its main daytime photooxidation product caronaldehyde were investigated in the atmospheric simulation chamber SAPHIR. Oxidation reactions were studied under atmospheric conditions with high (> 8 ppbv) and low (< 2 ppbv) NOx concentrations. Reaction rate constants of the reaction of Δ<sup>3</sup>-carene with OH and O<sub>3</sub>, and of the reaction of caronaldehyde with OH as well as photolysis frequencies of caronaldehyde were determined. Production and destruction rates of the sum of hydroxyl and peroxy radicals (ROx = OH+HO2+RO2) were analysed to determine if there were unaccounted production and loss processes of radicals in the oxidation of Δ<sup>3</sup>-carene. The yield of Δ<sup>3</sup>-carene’s oxidation product caronaldehyde was determined from measured timeseries from OH photooxidation and ozonolysis experiments. Additionally, the OH yield from ozonolysis of Δ<sup>3</sup>-carene was determined.</p><p>Organic nitrate (RONO<sub>2</sub>) yields of the reaction of RO<sub>2</sub> + NO, from RO<sub>2</sub> produced from the reactions of Δ<sup>3</sup>-carene and caronaldehyde with OH were determined by analyzing the reactive nitrogen species (NOy) in the chamber.</p>

scholarly journals Comparisons of observed and modeled OH and HO2concentrations during the ambient measurement period of the HOxComp field campaign

2012 ◽  
Vol 12 (5) ◽  
pp. 2567-2585 ◽  
Author(s):  
Y. Kanaya ◽  
A. Hofzumahaus ◽  
H.-P. Dorn ◽  
T. Brauers ◽  
H. Fuchs ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Chemical Mechanism ◽  
Ozone Production ◽  
High Yield ◽  
Base Case ◽  
Peroxy Radicals ◽  
Field Campaign ◽  
Mixing Ratios ◽  
Measurement Mode ◽  
Single Instrument

Abstract. A photochemical box model constrained by ancillary observations was used to simulate OH and HO2 concentrations for three days of ambient observations during the HOxComp field campaign held in Jülich, Germany in July 2005. Daytime OH levels observed by four instruments were fairly well reproduced to within 33% by a base model run (Regional Atmospheric Chemistry Mechanism with updated isoprene chemistry adapted from Master Chemical Mechanism ver. 3.1) with high R2 values (0.72–0.97) over a range of isoprene (0.3–2 ppb) and NO (0.1–10 ppb) mixing ratios. Daytime HO2(*) levels, reconstructed from the base model results taking into account the sensitivity toward speciated RO2 (organic peroxy) radicals, as recently reported from one of the participating instruments in the HO2 measurement mode, were 93% higher than the observations made by the single instrument. This also indicates an overprediction of the HO2 to OH recycling. Together with the good model-measurement agreement for OH, it implies a missing OH source in the model. Modeled OH and HO2(*) could only be matched to the observations by addition of a strong unknown loss process for HO2(*) that recycles OH at a high yield. Adding to the base model, instead, the recently proposed isomerization mechanism of isoprene peroxy radicals (Peeters and Müller, 2010) increased OH and HO2(*) by 28% and 13% on average. Although these were still only 4% higher than the OH observations made by one of the instruments, larger overestimations (42–70%) occurred with respect to the OH observations made by the other three instruments. The overestimation in OH could be diminished only when reactive alkanes (HC8) were solely introduced to the model to explain the missing fraction of observed OH reactivity. Moreover, the overprediction of HO2(*) became even larger than in the base case. These analyses imply that the rates of the isomerization are not readily supported by the ensemble of radical observations. One of the measurement days was characterized by low isoprene concentrations (∼0.5 ppb) and OH reactivity that was well explained by the observed species, especially before noon. For this selected period, as opposed to the general behavior, the model tended to underestimate HO2(*). We found that this tendency is associated with high NOx concentrations, suggesting that some HO2 production or regeneration processes under high NOx conditions were being overlooked; this might require revision of ozone production regimes.

Carbon-modified TiO2 as Photocatalysts

2010 ◽  
Vol 13 (3) ◽  
Author(s):  
Magdalena Janus ◽  
Antoni W. Morawski
Keyword(s):  
Carbon Dioxide ◽  
Titanium Dioxide ◽  
Advanced Oxidation Processes ◽  
Uv Light ◽  
Pure Titanium ◽  
Light Irradiation ◽  
Oxidation Processes ◽  
Uv Light Irradiation ◽  
Ultraviolet Light Irradiation ◽  
Long Time

AbstractPhotocatalysis belongs to one of the Advanced Oxidation Processes (AOP). These processes make possible the decomposition of organic compounds to carbon dioxide and water. The most useful photocatalyst is titanium dioxide which, to make it active, requires irradiation with suitable wavelengths. Pure titanium dioxide can be activated only by ultraviolet light irradiation (UV). For a long time, studies have been carried on modified titanium dioxide materials to obtain more effective photocatalysts with greater activity under UV light irradiation or to obtain photocatalysts which may be active also under visible light irradiation. One of the possible ways for modifying TiO

be detected specifically, which is possible for sane groups of odorants (thiols or mercaptans, sulphides, amines) with specific GC-detectors. Spe­ cific detectors are available for haloganted compounds, sulphur-, phosphor-and nitrogen compounds. Figure 4 shews the analysis of the sulphur-ccmpounds produced by the acidic decomposition of phosphate-rock and causing the typi­ cal smell of fertilizer plants. Another approach is to aim at selective concentration methods. Indeed odour problems are caused by a limited number of compounds, on rather a li­ mited number of classes of compounds, mentioned in figure 5. For most odour nuisance problems, chemical plants, refineries, live­ stock production, food processing, rendering, water purification plants etc., the compounds responsible for the odour are known. So chemical analysis of the odour can be limited to these odorants, and selective concentrating techniques can be used. Selective concentrating methods are based on speci­ fic absorption techniques, using particular chemical reactions of odorant classes. Semet imes several absorption methods have to be used in order to describe the odour problem, thus increasing the labor cost of the analysis. On the other hand absorption methods allow better quantitative results. Se­ lective absorption of odorants from air produces a far less complex mixture. We developed or are developing several of these methods for aldehydes, amines, acids, thiols etc. Carbonyl ccnpounds for instance can be trapped by absorption in a rea­ gent solution containing 2,4-dinitrcphenylhydrazine and hydrogen chloride. Details of this method are extensively described elsewhere (8). The prin­ ciple of the method is that the carbonyl ccnpounds, in case of rendering plant emission the aldehydes, react with the 2,4-dinitrophenylhydrazine and form 2,4-dinitrophenylhydrazones (2,4-DNPH's) according to the scheme. These 2,4-dinitrophenylhydrazones have seme interesting properties. It are cristalline caipounds so that after extract of the 2,4-DNPH's fran the reagens, they can be concentrated by evaporation of the solvent without losing product. Besides these caipounds shown intense absorption of UV-light (X 356 nm) and so they can easily be detected with an UV-detec-tor. These properties make the 2,4-DNPH's particularly suitable for HPDC-analyse. This methods is used since seme time. A chranatogram is given in figure 6 and results of the quantitative determination of carbonyl com­ pounds in different situations are given in table 2. For amines absorption in an acid solution, or preferably adsorption onto an acid ion exchange column (acidified divinylbenzene-styrenesulfo-nic acid copolymer) is used. 10-50 1 of ambient air is sent over*a wet 100nnix3irmI.D. column; the ion exchange polymer is put into a vial, made alkaline and the water solution is analysed on packed Carbowax-KDH GC-column with a thermionic selective detector (TSD), which is specific for nitrogen- and phosphorus-catpounds. Trimethylamine is detected easi­ ly at 1 ppb. Aibids can be absorbed specifically in an alkaline impringer, which is extracted with ether after acidification to pH 2. This method was used for rendering plant emissions, shewing a series of linear and branched

1986 ◽  
pp. 170-170
Keyword(s):  
Ion Exchange ◽  
Uv Light ◽  
Water Solution ◽  
Complex Mixture ◽  
Ambient Air ◽  
Labor Cost ◽  
Chemical Plants ◽  
Nitrogen And Phosphorus ◽  
Plant Emissions ◽  
Number Of Classes

scholarly journals The importance of sesquiterpene oxidation products for secondary organic aerosol formation in a spring-time hemi-boreal forest

2021 ◽  
Author(s):  
Luis M. F. Barreira ◽  
Arttu Ylisirniö ◽  
Iida Pullinen ◽  
Angela Buchholz ◽  
Zijun Li ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Boreal Forest ◽  
Organic Compounds ◽  
Field Experiments ◽  
Complex Mixture ◽  
Particle Formation ◽  
Oxidation Products ◽  
Ionization Mass ◽  
Particle Phase ◽  
Aerosol Formation

Abstract. Secondary organic aerosols (SOA) formed from biogenic volatile organic compounds (BVOCs) constitute a significant fraction of atmospheric particulate matter and have been recognized to affect significantly the climate and air quality. Many laboratory and field experiments have studied SOA particle formation and growth in the recent years. Most of them have focused on a few monoterpenes and isoprene. However, atmospheric SOA particulate mass yields and chemical composition result from a much more complex mixture of oxidation products originating from many BVOCs, including terpenes other than isoprene and monoterpenes. Thus, a large uncertainty still remains regarding the contribution of BVOCs to SOA. In particular, organic compounds formed from sesquiterpenes have not been thoroughly investigated, and their contribution to SOA remains poorly characterized. In this study, a Filter Inlet for Gases and Aerosols (FIGAERO) combined with a high-resolution time-of-flight chemical ionization mass spectrometer (CIMS), with iodide ionization, was used for the simultaneous measurement of gas and particle phase atmospheric SOA. The aim of the study was to evaluate the relative contribution of sesquiterpene oxidation products to SOA in a spring-time hemi-boreal forest environment. Our results revealed that monoterpene and sesquiterpene oxidation products were the main contributors to SOA particles. The chemical composition of SOA particles was compared for times when either monoterpene or sesquiterpene oxidation products were dominant and possible key oxidation products for SOA particle formation were identified. Surprisingly, sesquiterpene oxidation products were the predominant fraction in the particle phase at some periods, while their gas phase concentrations remained much lower than those of monoterpene products. This can be explained by quick and effective partitioning of sesquiterpene products into the particle phase or their efficient removal by dry deposition. The SOA particle volatility determined from measured thermograms increased when the concentration of sesquiterpene oxidation products in SOA particles was higher than that of monoterpenes. Overall, this study demonstrates the important role of sesquiterpenes in atmospheric chemistry and suggests that the contribution of their products to SOA particles is being underestimated in comparison to the most studied terpenes.

scholarly journals Rapid formation of isoprene photo-oxidation products observed in Amazonia

2009 ◽  
Vol 9 (3) ◽  
pp. 13629-13653 ◽  
Author(s):  
T. Karl ◽  
A. Guenther ◽  
A. Turnipseed ◽  
P. Artaxo ◽  
S. Martin
Keyword(s):  
Atmospheric Chemistry ◽  
Global Climate ◽  
Oxidative Capacity ◽  
Oxidation Products ◽  
Lower Atmosphere ◽  
Peroxy Radicals ◽  
Aerosol Formation ◽  
Photo Oxidation ◽  
Voc Oxidation ◽  
Rapid Formation

Abstract. Isoprene represents the single most important reactive hydrocarbon for atmospheric chemistry in the tropical atmosphere. It plays a central role in global and regional atmospheric chemistry and possible climate feedbacks. Photo-oxidation of primary hydrocarbons (e.g. isoprene) leads to the formation of oxygenated VOCs (OVOCs). The evolution of these intermediates affects the oxidative capacity of the atmosphere (by reacting with OH) and can contribute to secondary aerosol formation, a poorly understood process. An accurate and quantitative understanding of VOC oxidation processes is needed for model simulations of regional air quality and global climate. Based on field measurements conducted during the Amazonian aerosol characterization experiment (AMAZE-08) we show that the production of certain OVOCs (e.g. hydroxyacetone) from isoprene photo-oxidation in the lower atmosphere is significantly underpredicted by standard chemistry schemes. A recently suggested novel pathway for isoprene peroxy radicals could explain the observed discrepancy and reconcile the rapid formation of these VOCs. Furthermore, if generalized our observations suggest that prompt photochemical formation of OVOCs and other uncertainties in VOC oxidation schemes could result in substantial underestimates of modelled OH reactivity that could explain a major fraction of the missing OH sink over forests which has previously been attributed to a missing source of primary biogenic VOCs.

scholarly journals Ozone response to emission changes: a modeling study during the MCMA-2006/MILAGRO campaign

2009 ◽  
Vol 9 (6) ◽  
pp. 23419-23463 ◽  
Author(s):  
J. Song ◽  
W. Lei ◽  
N. Bei ◽  
M. Zavala ◽  
B. de Foy ◽  
...  
Keyword(s):  
Control Strategies ◽  
Monitoring Network ◽  
Ambient Air ◽  
Ozone Production ◽  
Daily Maximum ◽  
Chemical Production ◽  
Field Campaign ◽  
Ozone Concentrations ◽  
Urban Core ◽  
Emission Changes

Abstract. The sensitivity of ozone production to precursor emissions was investigated under five different meteorological conditions in the Mexico City Metropolitan Area (MCMA) during the MCMA-2006/MILAGRO field campaign using the gridded photochemical model CAMx driven by observation-nudged WRF meteorology. Precursor emissions were constrained by the comprehensive data from the field campaign and the routine ambient air quality monitoring network. Simulated plume mixing and transport were examined by comparing with measurements from the G-1 aircraft during the campaign. The observed concentrations of ozone precursors and ozone were well reproduced by the model. The effects of reducing precursor emissions on urban ozone production were performed for three representative emission control strategies. A 50% reduction in VOC emissions led to 7 to 22 ppb decrease in daily maximum ozone concentrations, while a 50% reduction in NOx emissions leads to 4 to 21 ppb increase, and 50% reductions in both NOx and VOC emission decrease the daily maximum ozone concentrations up to 10 ppb. These results along with a chemical indicator analysis using the chemical production ratios of H2O2 to HNO3 demonstrate that the MCMA urban core region is VOC-limited for all meteorological episodes, which is consistent with the results from MCMA-2003 field campaign; however the degree of the VOC-sensitivity is higher in the MCMA-2006 due to lower VOC/NOx emission ratio and VOC reactivity. Ozone formation in the surrounding mountain/rural area is mostly NOx-limited, but can be VOC-limited, and the range of the NOx-limited or VOC-limited areas depends on meteorology.

scholarly journals In situ secondary organic aerosol formation from ambient pine forest air using an oxidation flow reactor

2015 ◽  
Vol 15 (21) ◽  
pp. 30409-30471 ◽  
Author(s):  
B. B. Palm ◽  
P. Campuzano-Jost ◽  
A. M. Ortega ◽  
D. A. Day ◽  
L. Kaser ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Flow Reactor ◽  
Secondary Organic Aerosol ◽  
Ambient Air ◽  
Organic Aerosol ◽  
Pine Forest ◽  
Oxidation Products ◽  
Oh Radicals ◽  
Aerosol Formation ◽  
Photochemical Aging

Abstract. Ambient air was oxidized by OH radicals in an oxidation flow reactor (OFR) located in a montane pine forest during the BEACHON-RoMBAS campaign to study biogenic secondary organic aerosol (SOA) formation and aging. High OH concentrations and short residence times allowed for semi-continuous cycling through a large range of OH exposures ranging from hours to weeks of equivalent (eq.) atmospheric aging. A simple model is derived and used to account for the relative time scales of condensation of low volatility organic compounds (LVOCs) onto particles, condensational loss to the walls, and further reaction to produce volatile, non-condensing fragmentation products. More SOA production was observed in the OFR at nighttime (average 4 μg m-3 when LVOC fate corrected) compared to daytime (average 1 μg m-3 when LVOC fate corrected), with maximum formation observed at 0.4–1.5 eq. days of photochemical aging. SOA formation followed a similar diurnal pattern to monoterpenes, sesquiterpenes, and toluene + p-cymene concentrations, including a substantial increase just after sunrise at 07:00 LT. Higher photochemical aging (> 10 eq. days) led to a decrease in new SOA formation and a loss of preexisting OA due to heterogeneous oxidation followed by fragmentation and volatilization. When comparing two different commonly used methods of OH production in OFRs (OFR185 and OFR254), similar amounts of SOA formation were observed. We recommend the OFR185 mode for future forest studies. Concurrent gas-phase measurements of air after OH oxidation illustrate the decay of primary VOCs, production of small oxidized organic compounds, and net production at lower ages followed by net consumption of terpenoid oxidation products as photochemical age increased. New particle formation was observed in the reactor after oxidation, especially during times when precursor gas concentrations and SOA formation were largest. Approximately 6 times more SOA was formed in the reactor from OH oxidation than could be explained by the VOCs measured in ambient air. Several recently-developed instruments quantified ambient semi- and intermediate-volatility organic compounds (S/IVOCs) that were not detected by a PTR-TOF-MS. An SOA yield of 24–80 % from those compounds can explain the observed SOA, suggesting that these typically unmeasured S/IVOCs play a substantial role in ambient SOA formation. Our results allow ruling out condensation sticking coefficients much lower than 1. Our measurements help clarify the magnitude of SOA formation in forested environments, and demonstrate methods for interpretation of ambient OFR measurements.

Effects of drought conditions on VOC soil fluxes within the rainforest mesocosm of Biosphere 2

2021 ◽  
Author(s):  
Giovanni Pugliese ◽  
Johannes Ingrisch ◽  
Thomas Klüpfel ◽  
Kathiravan Meeran ◽  
Gemma Purser ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Uv Light ◽  
Soil Microbial Activity ◽  
Oxidation Products ◽  
Severe Drought ◽  
Molecular Formula ◽  
Drought Period ◽  
Biosphere 2 ◽  
Drought Conditions ◽  
Mild Drought

<p>Volatile organic compounds (VOC) play an important role in determining atmospheric processes that control air quality and climate. Although atmospheric VOC concentrations are mostly affected by plants, soils are significant contributors as they are simultaneously a source, a sink and a storage of atmospheric VOCs. The aim of the present study was to assess the effects of a prolonged drought condition on VOC soil fluxes in the tropical rainforest mesocosm of Biosphere 2 (B2; Tucson, Arizona, USA). The absence of atmospheric chemistry due to UV light filtering by the glass and the possibility to control and manipulate the conditions of the ecosystem make the B2 an ideal set-up to study the rainforest VOC dynamics.</p><p>The experiments were conducted over the 4 months B2WALD campaign during which the rainforest was subjected to a controlled drought period of about 10 weeks followed by a rewetting period. Soil VOCs fluxes were measured continuously by means of a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) that was connected to 12 automated soil chambers (LI 8100-104 Long-Term Chambers, Licor Inc.) placed in 4 different locations within the B2 rainforest.</p><p>The B2 rainforest soil acted as a strong sink for all isoprenoid species. The isoprene sink steadily weakened during drought period, but increased sharply back to the pre-drought levels after the rain rewet. In contrast, the monoterpene soil sink became slightly stronger during the mild drought period (up to 5 weeks after the last rainfall) but weakened during the severe drought period (up to 10 weeks after rainfall). A huge increase in monoterpene uptake was observed after the rain rewet. The oxidation products of isoprene (methacrolein, methyl vinyl ketone and isoprene peroxides) showed a similar trend to the monoterpenes, even in absence of atmospheric chemistry. The species with molecular formula C5H8O was taken up by the soil during predrought, which was reduced during mild drought period but increased again during the severe drought period.Sulfur-containing compounds including DMS and methanethiol all showed a significant emission peak immediately after the rain rewet.Oxygenated VOCs such as methanol and acetone were taken up by the soil in wet conditions. The uptake of both compounds strongly decreased with the drought and in severe drought conditions they were even emitted by the soil.</p><p>In summary, soil VOC fluxes changed markedly with the onset and development drought stages (pre, mild and severe drought) of the B2 rainforest, mirroring atmospheric VOC concentrations and soil microbial activity changes related to overall ecosystem response to drought and recovery.</p>

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