scholarly journals Variability of OH reactivity in the Landes maritime Pine forest: Results from the LANDEX campaign 2017

2019 ◽  
Author(s):  
Sandy Bsaibes ◽  
Mohamad Al Ajami ◽  
Kenneth Mermet ◽  
François Truong ◽  
Sébastien Batut ◽  
...  
Keyword(s):  
Atmospheric Stability ◽  
Secondary Products ◽  
Temperature Dependent ◽  
Night Time ◽  
Strong Concentration ◽  
Oxygenated Compounds ◽  
Volatile Organic ◽  
Photolysis Laser ◽  
Primary Emissions ◽  
Comparative Reactivity

Abstract. Total OH reactivity measurements were conducted during the LANDEX intensive field campaign in a coniferous temperate forest located in the Landes area, south-western France, during July 2017. In order to investigate inter-canopy and intra-canopy variability, measurements were performed inside (6 m) and above the canopy level (12 m), as well as at two different locations within the canopy, using a Comparative Reactivity Method (CRM) and a Laser Photolysis-Laser Induced Fluorescence (LP-LIF) instrument. The two techniques were intercompared at the end of the campaign by performing measurements at the same location. Volatile organic compounds were also monitored at both levels with a proton transfer-time of flight mass spectrometer and online gas Chromatography instruments to evaluate their contribution to total OH reactivity, with monoterpenes being the main reactive species emitted in this Pinus pinaster Aiton dominated forest. Total OH reactivity varied diurnally, following the trend of BVOCs of which emissions and concentrations were dependent on meteorological parameters. Highest levels of total OH reactivity were observed during nights with a low turbulence (u* ≤ 0.2 m/s) leading to lower mixing of emitted species within the canopy and thus an important vertical stratification, characterized by a strong concentration gradient. By comparing the calculated OH reactivity from contributions of individually measured compounds to the measured OH reactivity, a discrepancy was seen at both heights mainly related to ambient temperature during day-time. It highlights that missing OH sinks could be due to temperature-dependent missing primary emissions or secondary products linked to a temperature-enhanced photochemistry. During night-time hours, atmospheric stability and relative humidity played a key role in the missing reactivity. Lower turbulence showed to be favourable for night-time chemistry, inducing a higher missing OH reactivity. Humid surfaces may have represented an additional sink for oxygenated compounds, escaping de facto total OH reactivity, and leading to lower or no missing OH reactivity.

scholarly journals Variability of hydroxyl radical (OH) reactivity in the Landes maritime pine forest: results from the LANDEX campaign 2017

2020 ◽  
Vol 20 (3) ◽  
pp. 1277-1300 ◽  
Author(s):  
Sandy Bsaibes ◽  
Mohamad Al Ajami ◽  
Kenneth Mermet ◽  
François Truong ◽  
Sébastien Batut ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Hydroxyl Radical ◽  
Organic Compounds ◽  
Secondary Products ◽  
Strong Concentration ◽  
Volatile Organic ◽  
Warm Night ◽  
Photolysis Laser ◽  
Primary Emissions ◽  
Comparative Reactivity

Abstract. Total hydroxyl radical (OH) reactivity measurements were conducted during the LANDEX intensive field campaign in a coniferous temperate forest located in the Landes area, southwestern France, during July 2017. In order to investigate inter-canopy and intra-canopy variability, measurements were performed inside (6 m) and above the canopy level (12 m), as well as at two different locations within the canopy, using a comparative reactivity method (CRM) and a laser photolysis–laser-induced fluorescence (LP-LIF) instrument. The two techniques were intercompared at the end of the campaign by performing measurements at the same location. Volatile organic compounds were also monitored at both levels with a proton transfer time-of-flight mass spectrometer and online gas chromatography instruments to evaluate their contribution to total OH reactivity, with monoterpenes being the main reactive species emitted in this forest dominated by Pinus pinaster Aiton. Total OH reactivity varied diurnally, following the trend of biogenic volatile organic compounds (BVOCs), the emissions and concentrations of which were dependent on meteorological parameters. Average OH reactivity was around 19.2 and 16.5 s−1 inside and above the canopy, respectively. The highest levels of total OH reactivity were observed during nights with a low turbulence (u*≤0.2 m s−1), leading to lower mixing of emitted species within the canopy and thus an important vertical stratification characterized by a strong concentration gradient. Comparing the measured and the calculated OH reactivity highlighted an average missing OH reactivity of 22 % and 33 % inside and above the canopy, respectively. A day–night variability was observed on missing OH reactivity at both heights. Investigations showed that during daytime, missing OH sinks could be due to primary emissions and secondary products linked to a temperature-enhanced photochemistry. Regarding nighttime missing OH reactivity, higher levels were seen for the stable and warm night of 4–5 July, showing that these conditions could have been favorable for the accumulation of long-lived species (primary and secondary species) during the transport of the air mass from nearby forests.

Emissions and chemistry of volatile organic compounds (VOCs) in urban air: important contributions from oxygenated compounds

2020 ◽  
Author(s):  
Bin Yuan ◽  
Caihong Wu ◽  
Chaomin Wang ◽  
Sihang Wang ◽  
Wenjie Wang ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Mass Spectrometer ◽  
Proton Transfer Reaction ◽  
Urban Site ◽  
Oxygenated Compounds ◽  
Secondary Formation ◽  
Volatile Organic ◽  
Particle Pollution ◽  
Comparative Reactivity

<p>Volatile organic compounds (VOCs) play central roles in formation of ozone and secondary particles. However, emissions and evolution of VOCs remain uncertain in different environments, including urban regions. A field campaign was conducted at an urban site of Guangzhou in September-November of 2018 to study ozone and particle pollution in this region. VOCs species were measured by both a gas chromatography mass spectrometer (GC-MS/FID) and a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS). Another PTR-MS associated with comparative reactivity method (CRM) was used for quantifing OH reactivity in the atmosphere. In total, around 1700 ions were detected in mass spectra of PTR-TOF during this campaign, among of which 438 ions are with noticeable concentrations in the atmosphere. For all of the measured VOCs species, the total average concentrations of oxygenated VOCs was 28.2 ppb, which are significantly higher than other VOCs classes, namely alkanes (19.6 ppb), aromatics (4.4 ppb) and alkenes (2.9 ppb). These oxygenated VOCs contribute large fractions (campaign-average: 28%) of the total measured OH reactivity, which leaves only a small fraction of measured reactivity as “missing”. We will show that primary emission and secondary formation both contribute to the measured OVOCs. These results indicate important roles of OVOCs in emissions and evolution budget of VOCs in the atmosphere.</p>

scholarly journals Selectivity of Tungsten Oxide Synthesized by Sol-Gel Method Towards Some Volatile Organic Compounds and Gaseous Materials in a Broad Range of Temperatures

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 523 ◽  
Author(s):  
Simonas Ramanavičius ◽  
Milda Petrulevičienė ◽  
Jurga Juodkazytė ◽  
Asta Grigucevičienė ◽  
Arūnas Ramanavičius
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Sol Gel ◽  
Temperature Dependent ◽  
Sensing Systems ◽  
Sensing Material ◽  
Operational Temperature ◽  
Volatile Organic ◽  
Different Gases

In this research, the investigation of sensing properties of non-stoichiometric WO3 (WO3−x) film towards some volatile organic compounds (VOC) (namely: Methanol, ethanol, isopropanol, acetone) and ammonia gas are reported. Sensors were tested at several temperatures within the interval ranging from a relatively low temperature of 60 up to 270 °C. Significant variation of selectivity, which depended on the operational temperature of sensor, was observed. Here, the reported WO3/WO3–x-based sensing material opens an avenue for the design of sensors with temperature-dependent sensitivity, which can be applied in the design of new gas- and/or VOC-sensing systems that are dedicated for the determination of particular gas- and/or VOC-based analyte concentration in the mixture of different gases and/or VOCs, using multivariate analysis of variance (MANOVA).

scholarly journals Characteristics of marine shipping emissions at berth: profiles for particulate matter and volatile organic compounds

2018 ◽  
Vol 18 (13) ◽  
pp. 9527-9545 ◽  
Author(s):  
Qian Xiao ◽  
Mei Li ◽  
Huan Liu ◽  
Mingliang Fu ◽  
Fanyuan Deng ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Mass Spectrometer ◽  
Elemental Carbon ◽  
Atmospheric Stability ◽  
Diesel Oil ◽  
Human Populations ◽  
Volatile Organic ◽  
Before And After ◽  
The Impact

Abstract. Emissions from ships at berth play an important role regarding the exposure of high density human populations to atmospheric pollutants in port areas; however, these emissions are not well understood. In this study, volatile organic compounds (VOCs) and particle emissions from 20 container ships at berth were sampled and analyzed during the “fuel switch” period at Jingtang Port in Hebei Province, China. VOCs and particles were analyzed using a gas chromatography-mass spectrometer (GC-MS) and a single particle aerosol mass spectrometer (SPAMS), respectively. VOC analysis showed that alkanes and aromatics, especially benzene, toluene and heavier compounds e.g., n-heptane, n-octane and n-nonane, dominated the total identified species. Secondary organic aerosol (SOA) yields and ozone (O3) forming potential were 0.017 ± 0.007 g SOA g−1 VOCs and 2.63 ± 0.37 g O3 g−1 VOCs, respectively. Both positive and negative ion mass spectra from individual ships were derived and the intensity of specific ions were quantified. Results showed that elemental carbon (35.74 %), elemental carbon–organic carbon mixtures (33.95 %) and Na-rich particles (21.12 %) were major classes, comprising 90.7 % of the particles observed. Particles from ship auxiliary engines were in the 0.2 to 2.5 µm size range, with a peak occurring at around 0.4 µm. The issue of using vanadium (V) as tracer element was examined, and it was found that V was not a proper tracer of ship emissions when using low sulfur content diesel oil. The average percentage of sulfate particles observed in shipping emissions before and after switching to marine diesel oil remained unchanged at 24 %. Under certain wind conditions, when berths were upwind of emission sources, the ratios before and after 1 January were 35 and 27 % respectively. The impact of atmospheric stability was discussed based on PM2.5 and primary pollutant (carbon monoxide) concentration. With a background of frequent haze episodes and complex mechanisms of particulate accumulation and secondary formation, the impact of atmospheric stability is believed to have been weak on the sulfate contribution from shipping emissions. The results from this study provide robust support for port area air quality assessment and source apportionment.

scholarly journals VOC reactivity in central California: comparing an air quality model to ground-based measurements

2007 ◽  
Vol 7 (5) ◽  
pp. 13077-13119 ◽  
Author(s):  
A. L. Steiner ◽  
R. C. Cohen ◽  
R. A. Harley ◽  
S. Tonse ◽  
A. H. Goldstein ◽  
...  
Keyword(s):  
Air Quality ◽  
Urban Areas ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Air Quality Model ◽  
Quality Model ◽  
Secondary Products ◽  
Central California ◽  
Primary Emissions ◽  
The Relationship

Abstract. Volatile organic compound (VOC) reactivity in central California is examined using a photochemical air quality model (the Community Multiscale Air Quality model; CMAQ) and ground-based measurements to evaluate the contribution of VOC to photochemical activity. We classify VOC into four categories: anthropogenic, biogenic, aldehyde, and other oxygenated VOC. Anthropogenic and biogenic VOC consist of primary emissions, while aldehydes and other oxygenated VOC include both primary anthropogenic emissions and secondary products from primary VOC oxidation. To evaluate the model treatment of VOC chemistry, we compare measured and modeled OH and VOC reactivities using the following metrics: 1) cumulative distribution functions of NOx concentration and VOC reactivity (ROH,VOC), 2) the relationship between ROH,VOC and NOx, 3) total OH reactivity (ROH,total) and speciated contributions, and 4) the relationship between speciated ROH,VOC and NOx. We find that the model predicts ROH,total to within 25–40% at three sites representing urban (Sacramento), suburban (Granite Bay) and rural (Blodgett Forest) chemistry. However in the urban area of Fresno, the model under predicts NOx and VOC emissions by a factor of 2–3. At all locations the model is consistent with observations of the relative contributions of total VOC. In urban areas, anthropogenic and biogenic ROH,VOC are predicted fairly well over a range of NOx conditions. In suburban and rural locations, anthropogenic and other oxygenated ROH,VOC relationships are reproduced, but measured biogenic and aldehyde ROH,VOC are often poorly characterized by measurements, making evaluation of the model with available data unreliable. In central California, 30–50% of the modeled urban VOC reactivity is due to aldehydes and other oxygenated species, and the total oxygenated ROH,VOC is nearly equivalent to anthropogenic VOC reactivity. In rural vegetated regions, biogenic and aldehyde reactivity dominates. This indicates that more attention needs to be paid to the accuracy of models and measurements of both primary emissions of oxygenated VOC and secondary production of oxygenates, especially formaldehyde and other aldehydes, and that a more comprehensive set of oxygenated VOC measurements is required to include all of the important contributions to atmospheric reactivity.

scholarly journals Temperature-dependent accumulation mode particle and cloud nuclei concentrations from biogenic sources during WACS 2010

2012 ◽  
Vol 12 (10) ◽  
pp. 27989-28031 ◽  
Author(s):  
L. Ahlm ◽  
K. M. Shakya ◽  
L. M. Russel ◽  
J. C. Schroder ◽  
J. P. S. Wong ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Number Concentration ◽  
Particle Mass ◽  
Strongly Correlated ◽  
Submicron Particle ◽  
Temperature Dependent ◽  
Volatile Organic ◽  
Mountain Site ◽  
Condensational Growth ◽  
Organic Particle

Abstract. Submicron aerosol particles collected simultaneously at the mountain peak (2182 m a.s.l.) and at a forested mid-mountain site (1300 m a.s.l.) on Whistler Mountain, British Columbia, Canada, during June and July 2010 were analyzed by Fourier transform infrared (FTIR) spectroscopy for quantification of organic functional groups. Positive matrix factorization (PMF) was applied to the FTIR spectra. Three PMF factors associated with (1) combustion, (2) biogenics, and (3) vegetative detritus, were identified at both sites. The biogenic factor was correlated with both temperature and several volatile organic compounds (VOCs). The combustion factor dominated the submicron particle mass during the beginning of the campaign when the temperature was lower and advection was from the Vancouver area, but as the temperature started to rise in early July the biogenic factor came to dominate as a result of increased emissions of biogenic VOCs and thereby increased formation of secondary organic aerosol (SOA). On average, the biogenic factor represented 69% and 49% of the submicron organic particle mass at Whistler Peak and at the mid-mountain site, respectively. The lower fraction at the mid-mountain site was a result of more vegetative detritus there, and also higher influence from local combustion sources. The biogenic factor was strongly correlated (r ~ 0.9) to number concentration of particles with diameter (Dp)> 100 nm, whereas the combustion factor was better correlated to number concentration of particles with Dp < 100 nm (r~ 0.4). The number concentration of cloud condensation nuclei (CCN) was correlated (r ~ 0.7) to the biogenic factor for supersaturations (S) of 0.2% or higher, which indicates that particle condensational growth from biogenic vapors was an important factor in controlling the CCN concentration for clouds where S≥0.2%. Both the number concentration of particles with Dp > 100 nm and numbers of CCN for S≥0.2% were correlated to temperature. Considering the biogenic influence, these results indicate that temperature was a primary factor controlling these CCN concentrations at 0.2% supersaturation.

scholarly journals An empirical method to correct for temperature-dependent variations in the overlap function of CHM15k ceilometers

2016 ◽  
Vol 9 (7) ◽  
pp. 2947-2959 ◽  
Author(s):  
Maxime Hervo ◽  
Yann Poltera ◽  
Alexander Haefele
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Correction Method ◽  
Empirical Method ◽  
Cloud Base ◽  
Atmospheric Conditions ◽  
Cloud Detection ◽  
Temperature Dependent ◽  
Night Time ◽  
Gradient Based

Abstract. Imperfections in a lidar's overlap function lead to artefacts in the background, range and overlap-corrected lidar signals. These artefacts can erroneously be interpreted as an aerosol gradient or, in extreme cases, as a cloud base leading to false cloud detection. A correct specification of the overlap function is hence crucial in the use of automatic elastic lidars (ceilometers) for the detection of the planetary boundary layer or of low cloud. In this study, an algorithm is presented to correct such artefacts. It is based on the assumption of a homogeneous boundary layer and a correct specification of the overlap function down to a minimum range, which must be situated within the boundary layer. The strength of the algorithm lies in a sophisticated quality-check scheme which allows the reliable identification of favourable atmospheric conditions. The algorithm was applied to 2 years of data from a CHM15k ceilometer from the company Lufft. Backscatter signals corrected for background, range and overlap were compared using the overlap function provided by the manufacturer and the one corrected with the presented algorithm. Differences between corrected and uncorrected signals reached up to 45 % in the first 300 m above ground. The amplitude of the correction turned out to be temperature dependent and was larger for higher temperatures. A linear model of the correction as a function of the instrument's internal temperature was derived from the experimental data. Case studies and a statistical analysis of the strongest gradient derived from corrected signals reveal that the temperature model is capable of a high-quality correction of overlap artefacts, in particular those due to diurnal variations. The presented correction method has the potential to significantly improve the detection of the boundary layer with gradient-based methods because it removes false candidates and hence simplifies the attribution of the detected gradients to the planetary boundary layer. A particularly significant benefit can be expected for the detection of shallow stable layers typical of night-time situations. The algorithm is completely automatic and does not require any on-site intervention but requires the definition of an adequate instrument-specific configuration. It is therefore suited for use in large ceilometer networks.

Vacuum Ultraviolet Photoionization Mass Spectra and Cross-Sections for Volatile Organic Compounds at 10.5 eV

2007 ◽  
Vol 61 (8) ◽  
pp. 896-902 ◽  
Author(s):  
Nozomu Kanno ◽  
Kenichi Tonokura
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Cross Sections ◽  
Mass Spectra ◽  
Vacuum Ultraviolet ◽  
Single Photon ◽  
Photoionization Cross Section ◽  
Oxygenated Compounds ◽  
Flight Mass Spectrometry ◽  
Volatile Organic

Vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) has been applied to the detection of volatile organic compounds (VOCs), including aromatic, chlorinated, and oxygenated compounds. Photoionization mass spectra of 23 VOCs were measured using SPI-TOFMS at 10.5 eV (118 nm). The limits of detection of VOCs using SPI-TOFMS at 10.5 eV were estimated to be a few ppbv. The mass spectra of 20 VOCs exhibit only the parent ion and its isotopes' signals. The ionization processes of the VOCs were discussed on the basis of the reaction enthalpies predicted by the quantum chemical calculations. Absolute photoionization cross-sections for 23 VOCs, including 12 newly measured VOCs, at 10.5 eV were determined in comparison to the reported absolute photoionization cross-section of NO.

scholarly journals Fluxes and concentrations of volatile organic compounds above central London, UK

2009 ◽  
Vol 9 (4) ◽  
pp. 17297-17333 ◽  
Author(s):  
B. Langford ◽  
E. Nemitz ◽  
E. House ◽  
G. J. Phillips ◽  
D. Famulari ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Traffic Density ◽  
Mixing Ratios ◽  
Oxygenated Compounds ◽  
Volatile Organic ◽  
Benzene Toluene ◽  
The Uk

Abstract. Concentrations and fluxes of eight volatile organic compounds (VOCs) were measured during October 2006 from a high telecom tower above central London, as part of the CityFlux contribution to the REPARTEE I campaign. A continuous flow disjunct eddy covariance technique with analysis by proton transfer reaction mass spectrometry was used. Daily averaged VOC mixing ratios were within the range 1–19 ppb for the oxygenated compounds (methanol, acetaldehyde and acetone) and 0.2–1.3 ppb for the aromatics (benzene, toluene and ethylbenzene). Typical VOC fluxes were in the range 0.1–1.0 mg m−2 h−1. There was a non-linear relationship between VOC fluxes and traffic density for most of the measured compounds. Traffic activity was estimated to account for approximately 70% of the aromatic compound fluxes, whereas non-traffic related sources were found to be more important for methanol and isoprene fluxes. The measured fluxes were comparable to the estimates of the UK national atmospheric emission inventory for the aromatic VOCs and CO. In contrast, fluxes of the oxygenated compounds were about three times larger than inventory estimates. For isoprene and acetonitrile this difference was many times larger. At temperatures over 25°C it is estimated that more than half the isoprene observed in central London is of biogenic origin.

scholarly journals DETERMINING VERTICAL WIND SPEED PROFILE IN THE ATMOSPHERIC LIMIT LAYER ON THE OUAHIGOUYA SITE IN BURKINA FASO.

2021 ◽  
Vol 10 (1) ◽  
pp. 94-105
Keyword(s):  
Wind Speed ◽  
Burkina Faso ◽  
Power Law ◽  
Vertical Profile ◽  
Atmospheric Stability ◽  
Vertical Wind ◽  
Night Time ◽  
Wind Speed Profile ◽  
Log Linear ◽  
Annual Scale

The properties of the vertical profile of the wind speed on a monthly and annual scale at the Ouahigouya site belonging to the Sahelian climatic zone in Burkina Faso were explored in this study. To do this, wind speed and temperature data at 10 m above ground and NASA satellite data at an altitude of 50 m in the atmospheric boundary layer were used over a period of ten years. From the theory of Monin-Obukhov, the logarithmic law and the power law made it possible to develop the variation of wind speed with altitude taking into account the conditions of atmospheric stability. According to statistical performance indicators, it has been observed that the vertical profile of the wind speed adjusted according to the power law and the log-linear law corresponds to the measurements. Regarding the state of stability of the atmosphere, we note that it is generally unstable from 10:00 a.m. to 6:00 p.m. and stable during other times of the day. The annual average wind shear coefficients during the convective and night time diurnal cycle are evaluated at 0.67 and 0.7, respectively. From the power law, the values of the shear coefficients, the average vertical profile on a monthly and annual scale of the wind was obtained by extrapolation of the wind data measured at 10 m from the ground. This study is the first of its kind in this area. To assess the wind resource available on the Ouahigouya site, investors can directly use the vertical wind profile based on the power law for an altitude between 10 and 50 m.

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