scholarly journals A New Portable Instrument for Continuous Measurement of Formaldehyde in Ambient Air

2006 ◽  
Vol 23 (1) ◽  
pp. 38-45 ◽  
Author(s):  
W. Junkermann ◽  
J. M. Burger
Keyword(s):  
Continuous Measurement ◽  
Ambient Air ◽  
Fluorimetric Detection ◽  
Portable Instrument ◽  
Po Valley ◽  
Mixing Ratios ◽  
Aircraft Flight ◽  
New Instrument ◽  
Field Campaigns

Abstract A new instrument for the in situ measurement of formaldehyde with online concentration output was built on the base of the Hantzsch chemistry fluorimetric detection of formaldehyde in liquid phase. The instrument was specially designed for applications in a fast-changing environment, for example, in airborne research. Individual instrument components were optimized to reduce size, weight, and power consumption and to improve response time. The small size, battery-operated system was shown to reach good performance, stable sensitivity, and detection limits of <100 ppt for temperatures between 0° and 35°C during aircraft flight missions in field campaigns in the Italian Po Valley. The instrument proved its performance with formaldehyde mixing ratios ranging from 0.5 to 25 ppb.

scholarly journals In situ measurements of isoprene and monoterpenes within a south-east Asian tropical rainforest

2011 ◽  
Vol 11 (14) ◽  
pp. 6971-6984 ◽  
Author(s):  
C. E. Jones ◽  
J. R. Hopkins ◽  
A. C. Lewis
Keyword(s):  
Tropical Rainforest ◽  
East Asian ◽  
Ground Level ◽  
Ambient Air ◽  
Tropical Rainforests ◽  
Light Conditions ◽  
Mixing Ratios ◽  
Volatile Carbon ◽  
Malaysian Borneo

Abstract. Biogenic volatile organic compounds (BVOCs) emitted from tropical rainforests comprise a substantial fraction of global atmospheric VOC emissions, however there are only relatively limited measurements of these species in tropical rainforest regions. We present observations of isoprene, α-pinene, camphene, Δ-3-carene, γ-terpinene and limonene, as well as oxygenated VOCs (OVOCs) of biogenic origin such as methacrolein, in ambient air above a tropical rainforest in Malaysian Borneo during the Oxidant and Particle Photochemical Processes above a south-east Asian tropical rainforest (OP3) project in 2008. Daytime composition was dominated by isoprene, with an average mixing ratio of the order of ~1 ppb. γ-terpinene, limonene and camphene were the most abundant monoterpenes, with average daytime mixing ratios of 102, 71 and 66 ppt respectively, and with an average monoterpene toisoprene ratio of 0.3 during sunlit hours, compared to 2.0 at night. Limonene and camphene abundances were seen to be related to both temperature and light conditions. In contrast, γ-terpinene emission continued into the late afternoon/evening, under relatively low temperature and light conditions. The contributions of isoprene, monoterpenes and other classes of VOC to the volatile carbon budget and OH reactivity have been summarised for this rainforest location. We observe good agreement between surface and aircraft measurements of boundary layer isoprene and methacrolein above the natural rainforest, suggesting that the ground-level observations are broadly representative of isoprene emissions from this region.

scholarly journals Measurement of ambient NO<sub>3</sub> reactivity: design, characterization and first deployment of a new instrument

2017 ◽  
Vol 10 (3) ◽  
pp. 1241-1258 ◽  
Author(s):  
Jonathan M. Liebmann ◽  
Gerhard Schuster ◽  
Jan B. Schuladen ◽  
Nicolas Sobanski ◽  
Jos Lelieveld ◽  
...  
Keyword(s):  
Rate Constant ◽  
Loss Rate ◽  
Dynamic Range ◽  
Ambient Air ◽  
Total Uncertainty ◽  
Reactivity Measurement ◽  
Mixing Ratios ◽  
Tube Reactor ◽  
New Instrument ◽  
The Stability

Abstract. We describe the first instrument for measurement of the rate constant (s−1) for reactive loss (i.e., the total reactivity) of NO3 in ambient air. Cavity-ring-down spectroscopy is used to monitor the mixing ratio of synthetically generated NO3 ( ≈  30–50 pptv) after passing through a flow-tube reactor with variable residence time (generally 10.5 s). The change in concentration of NO3 upon modulation of the bath gas between zero air and ambient air is used to derive its loss rate constant, which is then corrected for formation and decomposition of N2O5 via numerical simulation. The instrument is calibrated and characterized using known amounts of NO and NO2 and tested in the laboratory with an isoprene standard. The lowest reactivity that can be detected (defined by the stability of the NO3 source, instrumental parameters and NO2 mixing ratios) is 0.005 s−1. An automated dilution procedure enables measurement of NO3 reactivities up to 45 s−1, this upper limit being defined mainly by the dilution accuracy. The typical total uncertainty associated with the reactivity measurement at the center of its dynamic range is 16 %, though this is dependent on ambient NO2 levels. Results from the first successful deployment of the instrument at a forested mountain site with urban influence are shown and future developments outlined.

scholarly journals Evidence for heterogeneous chlorine activation in the tropical UTLS

2010 ◽  
Vol 10 (7) ◽  
pp. 18063-18099
Author(s):  
M. von Hobe ◽  
J.-U. Grooß ◽  
G. Günther ◽  
P. Konopka ◽  
I. Gensch ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Gas Phase Chemistry ◽  
In Situ Observations ◽  
Field Campaigns ◽  
Phase Chemistry ◽  
The Tropics

Abstract. Airborne in-situ observations of ClO in the tropics were made during the TROCCINOX (Aracatuba, Brasil, February 2005) and SCOUT-O3 (Darwin, Australia, November/December 2005) field campaigns. While during most flights significant amounts of ClO (≈10–20 parts per trillion, ppt) were present only in aged stratospheric air, instances of enhanced ClO mixing ratios of up to 40 ppt – significantly exceeding those expected from gas phase chemistry – were observed in air masses of a more tropospheric character. Most of these observations concur with low temperatures or with the presence of cirrus clouds (often both), suggesting that cirrus ice particles and/or liquid aerosol at low temperatures may promote significant heterogeneous chlorine activation in the tropical upper troposphere lower stratosphere (UTLS). In two case studies, particularly high levels of ClO observed were reproduced by chemistry simulations only under the assumption that significant denoxification had occurred in the observed air. At least for one of these flights, a significant denoxification is in contrast to the observed NO levels suggesting that the coupling of chlorine and nitrogen compounds in the tropical UTLS may not be completely understood.

scholarly journals In situ measurements of isoprene and monoterpenes within a South-East Asian tropical rainforest

2011 ◽  
Vol 11 (1) ◽  
pp. 1189-1218 ◽  
Author(s):  
C. E. Jones ◽  
J. R. Hopkins ◽  
A. C. Lewis
Keyword(s):  
Tropical Rainforest ◽  
Ground Level ◽  
Ambient Air ◽  
Tropical Rainforests ◽  
Light Conditions ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Malaysian Borneo ◽  
Good Agreement

Abstract. Biogenic volatile organic compounds (BVOCs) emitted from tropical rainforests comprise a substantial fraction of global atmospheric VOC emissions, however there are only relatively limited measurements of these species in tropical rainforest regions. We present observations of isoprene, α-pinene, camphene, Δ-3-carene, γ-terpinene and limonene, and oxygenated VOCs (OVOCs) of biogenic origin such as methacrolein, in ambient air above a~tropical rainforest in Malaysian Borneo. Daytime composition was dominated by isoprene, with an average mixing ratio of the order of ~1 ppb. γ-terpinene, limonene and camphene were the most abundant monoterpenes, with average daytime mixing ratios of 102, 71 and 66 ppt, respectively, and with an average monoterpene to isoprene ratio of 0.3 during sunlight hours, compared to 2.0 at night. Limonene and camphene abundances were seen to be related to both temperature and light conditions. In contrast, γ-terpinene emission occurred into the late afternoon/evening, under relatively low temperature and light conditions. We observe good agreement between surface and aircraft measurements of boundary layer isoprene and methacrolein above the natural rainforest, suggesting that the ground-level observations are broadly representative of isoprene emissions from this region.

scholarly journals Evidence for heterogeneous chlorine activation in the tropical UTLS

2011 ◽  
Vol 11 (1) ◽  
pp. 241-256 ◽  
Author(s):  
M. von Hobe ◽  
J.-U. Grooß ◽  
G. Günther ◽  
P. Konopka ◽  
I. Gensch ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Air Masses ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Gas Phase Chemistry ◽  
In Situ Observations ◽  
Field Campaigns ◽  
Phase Chemistry ◽  
The Tropics

Abstract. Airborne in-situ observations of ClO in the tropics were made during the TROCCINOX (Aracatuba, Brazil, February 2005) and SCOUT-O3 (Darwin, Australia, November/December 2005) field campaigns. While during most flights significant amounts of ClO (≈10–20 parts per trillion, ppt) were present only in aged stratospheric air, instances of enhanced ClO mixing ratios of up to 40 ppt – significantly exceeding those expected from gas phase chemistry – were observed in air masses of a more tropospheric character. Most of these observations are associated with low temperatures or with the presence of cirrus clouds (often both), suggesting that cirrus ice particles and/or liquid aerosol at low temperatures may promote significant heterogeneous chlorine activation in the tropical upper troposphere lower stratosphere (UTLS). In two case studies, particularly high levels of ClO observed were reproduced by chemistry simulations only under the assumption that significant denoxification had occurred in the observed air. However, to reproduce the ClO observations in these simulations, O3 mixing ratios higher than observed had to be assumed, and at least for one of these flights, a significant denoxification is in contrast to the observed NO levels, suggesting that the coupling of chlorine and nitrogen compounds in the tropical UTLS may not be completely understood.

scholarly journals Using in situ GC-MS for analysis of C<sub>2</sub>–C<sub>7</sub> volatile organic acids in ambient air of a boreal forest site

2017 ◽  
Vol 10 (1) ◽  
pp. 281-289 ◽  
Author(s):  
Heidi Hellén ◽  
Simon Schallhart ◽  
Arnaud P. Praplan ◽  
Tuukka Petäjä ◽  
Hannele Hakola
Keyword(s):  
Organic Acids ◽  
Boreal Forest ◽  
Mass Spectrometer ◽  
Detection Limits ◽  
Ambient Air ◽  
Cold Trap ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Volatile Organic Acids

Abstract. An in situ method for studying gas-phase C2–C7 monocarboxylic volatile organic acids (VOAs) in ambient air was developed and evaluated. Samples were collected directly into the cold trap of the thermal desorption unit (TD) and analysed in situ using a gas chromatograph (GC) coupled to a mass spectrometer (MS). A polyethylene glycol column was used for separating the acids. The method was validated in the laboratory and tested on the ambient air of a boreal forest in June 2015. Recoveries of VOAs from fluorinated ethylene propylene (FEP) and heated stainless steel inlets ranged from 83 to 123 %. Different VOAs were fully desorbed from the cold trap and well separated in the chromatograms. Detection limits varied between 1 and 130 pptv and total uncertainty of the method at mean ambient mixing ratios was between 16 and 76 %. All straight chain VOAs except heptanoic acid in the ambient air measurements were found with mixing ratios above the detection limits. The highest mixing ratios were found for acetic acid and the highest relative variations for hexanoic acid. In addition, mixing ratios of acetic and propanoic acids measured by the novel GC-MS method were compared with proton-mass-transfer time-of-flight mass spectrometer (PTR-TOFMS) data. Both instruments showed similar variations, but differences in the mixing ratio levels were significant.

scholarly journals MAX-DOAS measurements of formaldehyde in the Po-Valley

2005 ◽  
Vol 5 (4) ◽  
pp. 909-918 ◽  
Author(s):  
A. Heckel ◽  
A. Richter ◽  
T. Tarsu ◽  
F. Wittrock ◽  
C. Hak ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Scattered Light ◽  
Optical Absorption Spectroscopy ◽  
Data Set ◽  
Po Valley ◽  
Mixing Ratios ◽  
Aerosol Parameters ◽  
First Time ◽  
The Eu

Abstract. During the first measurement campaign of the EU FORMAT project in summer 2002 near Milan, northern Italy, ground-based scattered light differential optical absorption spectroscopy (DOAS) measurements were performed using a new multi-axis instrument. From the data set of this four week measurement period, the detailed analysis results of three days, 12–14 August, are presented exemplary. Slant column densities for formaldehyde (HCHO) and the oxygen dimer (O4) have been retrieved, employing fitting windows from 335 nm to 357 nm and 350 nm to 360 nm respectively. In order to convert slant into vertical columns radiative transfer calculations were perfomred using aerosol parameters derived from the actual O4 measurements. By analysing the measurements from different viewing directions (zenith, 4x off-axis) vertical profile information, and in particular mixing ratios for the boundary layer have been derived for the first time for HCHO with a multi-axis DOAS (MAX-DOAS) instrument. HCHO vertical columns are in the range of 5 to 20·1015 molec/cm2 with an relative error of about 15%. This corresponds to HCHO mixing ratios in the boundary layer of 0.7 ppb to 4.2 ppb, which is in excellent agreement with simultaneous measurements from both a Hantzsch in-situ and a long-path DOAS instrument operated at the same place.

scholarly journals Measurement of ambient NO<sub>3</sub> reactivity: Design, characterization and first deployment of a new instrument

2016 ◽  
Author(s):  
Jonathan M. Liebmann ◽  
Gerhard Schuster ◽  
Jan B. Schuladen ◽  
Nicolas Sobanski ◽  
Jos Lelieveld ◽  
...  
Keyword(s):  
Rate Constant ◽  
Loss Rate ◽  
Dynamic Range ◽  
Ambient Air ◽  
Total Uncertainty ◽  
Reactivity Measurement ◽  
Mixing Ratios ◽  
Tube Reactor ◽  
New Instrument ◽  
The Stability

Abstract. We describe the first instrument for measurement of the rate constant (s−1) for reactive loss (i.e. the total reactivity) of NO3 in ambient air. Cavity-ring-down spectroscopy is used to monitor the mixing ratio of synthetically generated NO3 (≈ 30–50 pptv) after passing through a flow-tube reactor with variable residence time (generally 10.5 s). The change in concentration of NO3 upon modulation of the bath gas between zero-air and ambient air is used to derive its loss rate constant, which is then corrected for formation and decomposition of N2O5 via numerical simulation. The instrument is calibrated and characterized using known amounts of NO and NO2 and tested in the laboratory with an isoprene standard. The lowest reactivity that can be detected (defined by the stability of the NO3 source, instrumental parameters and NO2 mixing ratios) is 0.005 s−1. An automated dilution procedure enables measurement of NO3 reactivities up to 45 s−1, this upper limit being defined mainly by the dilution accuracy. The typical total uncertainty associated with the reactivity measurement at the centre of its dynamic range is 16 %, though this is dependent on ambient NO2 levels. Results from the first successful deployment of the instrument at a forested mountain site with urban influence are shown and future developments outlined.

scholarly journals Using in situ GC-MS for analysis of C<sub>2</sub>-C<sub>7</sub> volatile organic acids in ambient air of a boreal forest site

2016 ◽  
Author(s):  
Heidi Hellén ◽  
Simon Schallhart ◽  
Arnaud P. Praplan ◽  
Tuukka Petäjä ◽  
Hannele Hakola
Keyword(s):  
Organic Acids ◽  
Boreal Forest ◽  
Mass Spectrometer ◽  
Detection Limits ◽  
Ambient Air ◽  
Cold Trap ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Volatile Organic Acids

Abstract. Abstract. An in situ method for studying C2-C7 monocarboxylic volatile organic acids (VOAs) in ambient air was developed and evaluated. Samples were collected directly into the cold trap of the thermal desorption unit (TD) and analysed in situ using a gas chromatograph (GC) coupled to a mass spectrometer (MS). A polyethylene glycol column was used for separating the acids. The method was validated in the laboratory and tested on the ambient air of a boreal forest in June 2015. Recoveries of VOAs from fluorinated ethylene propylene (FEP) and heated stainless steel inlets were acceptable. Different VOAs were fully desorbed from the cold trap and well separated in the chromatograms. Detection limits varied between 1 and 130 pptv and total uncertainty of the method at mean ambient mixing ratios ranged between 16–76 %. All straight chain VOAs except heptanoic acid in the ambient air measurement were found with mixing ratios above the detection limits. The highest mixing ratios were found for acetic acid and the highest relative variations for hexanoic acid. In addition, mixing ratios of acetic and propanoic acids measured by the novel GC-MS method were compared with proton-mass-transfer time-of-flight mass spectrometer (PTR-TOFMS) data. Both instruments showed similar variations, but differences in the mixing ratio levels were significant.

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