scholarly journals Monoterpene chemical speciation in the Amazon tropical rainforest: variation with season, height, and time of day at the Amazon Tall Tower Observatory (ATTO)

2017 ◽  
Author(s):  
Ana María Yañez-Serrano ◽  
Anke Christine Nölscher ◽  
Efstratios Bourtsoukidis ◽  
Eliane Gomes Alves ◽  
Laurens Ganzeveld ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Tropical Rainforest ◽  
Proton Transfer Reaction ◽  
Time Of Day ◽  
Dry Season ◽  
Canopy Exchange ◽  
Mixing Ratios ◽  
Flame Ionization ◽  
Sampling Systems ◽  
Tall Tower

Abstract. Speciated monoterpene measurements in the Amazon rainforest air are scarce, but important in order to understand their contribution to the overall reactivity of volatile organic compound (VOCs) emissions towards the main atmospheric oxidants, such as hydroxyl radical (OH), ozone (O3) and nitrate radical (NO3). In this study, we present the chemical speciation of gas phase monoterpenes measured in the tropical rainforest at the Amazon Tall Tower Observatory (ATTO, Amazonas, Brazil). Samples of VOCs were collected by two automatic sampling systems positioned on a tower at 12 and 24 m height and analysed using Gas Chromatography Flame Ionization Detection (GC-FID). The samples were collected in October 2015, representing the dry season, and compared with previous wet and dry season studies at the site. In addition, vertical profile measurements (at 12 and 24 m) of total monoterpene mixing ratios were made using Proton-Transfer Reaction Mass Spectrometry (PTR-MS). The results showed a distinctly different chemical speciation between day and night. For instance, α-pinene was more abundant during the day, whereas limonene was more abundant at night. Reactivity calculations showed that the most abundant compounds may not be the most atmospheric chemically relevant compounds. Furthermore, inter- and intra-annual results demonstrate similar chemodiversity during the dry seasons analysed. Simulations with a canopy exchange modelling system compare relatively well with the observed temporal variability in speciated monoterpene mixing ratios, but also indicate the necessity of more experiments to enhance our understanding of in-canopy sinks of these monoterpenes.

scholarly journals Monoterpene chemical speciation in a tropical rainforest:variation with season, height, and time of dayat the Amazon Tall Tower Observatory (ATTO)

2018 ◽  
Vol 18 (5) ◽  
pp. 3403-3418 ◽  
Author(s):  
Ana María Yáñez-Serrano ◽  
Anke Christine Nölscher ◽  
Efstratios Bourtsoukidis ◽  
Eliane Gomes Alves ◽  
Laurens Ganzeveld ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Proton Transfer Reaction ◽  
Dry Season ◽  
Canopy Exchange ◽  
Mixing Ratios ◽  
Flame Ionization ◽  
Nitrate Radicals ◽  
Sampling Systems ◽  
Dry Seasons ◽  
Tall Tower

Abstract. Speciated monoterpene measurements in rainforest air are scarce, but they are essential for understanding the contribution of these compounds to the overall reactivity of volatile organic compound (VOC) emissions towards the main atmospheric oxidants, such as hydroxyl radicals (OH), ozone (O3) and nitrate radicals (NO3). In this study, we present the chemical speciation of gas-phase monoterpenes measured in the tropical rainforest at the Amazon Tall Tower Observatory (ATTO, Amazonas, Brazil). Samples of VOCs were collected by two automated sampling systems positioned on a tower at 12 and 24 m height and analysed using gas chromatography–flame ionization detection. The samples were collected in October 2015, representing the dry season, and compared with previous wet and dry season studies at the site. In addition, vertical profile measurements (at 12 and 24 m) of total monoterpene mixing ratios were made using proton-transfer-reaction mass spectrometry. The results showed a distinctly different chemical speciation between day and night. For instance, α-pinene was more abundant during the day, whereas limonene was more abundant at night. Reactivity calculations showed that higher abundance does not generally imply higher reactivity. Furthermore, inter- and intra-annual results demonstrate similar chemodiversity during the dry seasons analysed. Simulations with a canopy exchange modelling system show simulated monoterpene mixing ratios that compare relatively well with the observed mixing ratios but also indicate the necessity of more experiments to enhance our understanding of in-canopy sinks of these compounds.

scholarly journals Observations of nonmethane organic compounds during ARCTAS − Part 1: Biomass burning emissions and plume enhancements

2011 ◽  
Vol 11 (21) ◽  
pp. 11103-11130 ◽  
Author(s):  
R. S. Hornbrook ◽  
D. R. Blake ◽  
G. S. Diskin ◽  
A. Fried ◽  
H. E. Fuelberg ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Biomass Burning ◽  
Source Region ◽  
Measurement Techniques ◽  
Proton Transfer Reaction ◽  
Time Of Day ◽  
The Arctic ◽  
Mixing Ratios ◽  
Order Of Magnitude ◽  
Good Agreement

Abstract. Mixing ratios of a large number of nonmethane organic compounds (NMOCs) were observed by the Trace Organic Gas Analyzer (TOGA) on board the NASA DC-8 as part of the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field campaign. Many of these NMOCs were observed concurrently by one or both of two other NMOC measurement techniques on board the DC-8: proton-transfer-reaction mass spectrometry (PTR-MS) and whole air canister sampling (WAS). A comparison of these measurements to the data from TOGA indicates good agreement for the majority of co-measured NMOCs. The ARCTAS study, which included both spring and summer deployments, provided opportunities to sample a large number of biomass burning (BB) plumes with origins in Asia, California and central Canada, ranging from very recent emissions to plumes aged one week or more. For this analysis, BB smoke interceptions were grouped by flight, source region and, in some cases, time of day, generating 40 identified BB plumes for analysis. Normalized excess mixing ratios (NEMRs) to CO were determined for each of the 40 plumes for up to 19 different NMOCs or NMOC groups. Although the majority of observed NEMRs for individual NMOCs or NMOC groups were in agreement with previously-reported values, the observed NEMRs to CO for ethanol, a rarely quantified gas-phase trace gas, ranged from values similar to those previously reported, to up to an order of magnitude greater. Notably, though variable between plumes, observed NEMRs of individual light alkanes are highly correlated within BB emissions, independent of estimated plume ages. BB emissions of oxygenated NMOC were also found to be often well-correlated. Using the NCAR Master Mechanism chemical box model initialized with concentrations based on two observed scenarios, fresh Canadian BB and fresh Californian BB, decreases are predicted for the low molecular weight carbonyls (i.e. formaldehyde, acetaldehyde, acetone and methyl ethyl ketone, MEK) and alcohols (i.e. methanol and ethanol) as the plumes evolve in time, i.e. the production of these compounds is less than the chemical loss. Comparisons of the modeled NEMRs to the observed NEMRs from BB plumes estimated to be three days in age or less indicate overall good agreement.

scholarly journals An intercomparison of GC-FID and PTR-MS toluene measurements in ambient air under conditions of enhanced monoterpene loading

2010 ◽  
Vol 3 (1) ◽  
pp. 1-54
Author(s):  
J. L. Ambrose ◽  
K. Haase ◽  
R. S. Russo ◽  
Y. Zhou ◽  
M. L. White ◽  
...  
Keyword(s):  
Drift Tube ◽  
Ambient Air ◽  
Proton Transfer Reaction ◽  
Quantitative Agreement ◽  
Operating Conditions ◽  
Oxidation Products ◽  
Maximum Enhancement ◽  
Mixing Ratios ◽  
Flame Ionization ◽  
Two Systems

Abstract. Toluene was measured using both a gas chromatographic system (GC), with a flame ionization detector (FID), and a proton transfer reaction-mass spectrometer (PTR-MS) at the AIRMAP atmospheric monitoring station Thompson Farm (THF) in rural Durham, NH during the summer of 2004. Simultaneous measurements of monoterpenes, including α- and β-pinene, camphene, Δ3-carene, and d-limonene, by GC-FID demonstrated large enhancements in monoterpene mixing ratios relative to toluene, with median and maximum enhancement ratios of ~2 and ~30, respectively. A detailed intercomparison among the GC-FID and PTR-MS toluene measurements was conducted to test the specificity of PTR-MS for atmospheric toluene measurements under conditions often dominated by biogenic emissions. We derived quantitative estimates of potential interferences in the PTR-MS toluene measurements related to sampling and analysis of monoterpenes, including fragmentation of the monoterpenes and some of their primary carbonyl oxidation products via reactions with H3O+, O2+ and NO+ in the PTR-MS drift tube. The PTR-MS and GC-FID toluene measurements were in good quantitative agreement and the two systems tracked one another well from the instrumental limits of detection to maximum mixing ratios of ~0.5 ppbv. Discrepancies in the measured mixing ratios were not well correlated with enhancements in the monoterpenes. Better quantitative agreement between the two systems was obtained by correcting the PTR-MS measurements for contributions from monoterpene fragmentation in the PTR-MS drift tube; however, the improvement was minor. Interferences in the PTR-MS measurements from fragmentation of the monoterpene oxidation products pinonaldehyde, caronaldehyde and α-pinene oxide were also likely negligible. The results from THF suggest that toluene can be reliably quantified by PTR-MS using our operating conditions under the ambient compositions probed. This work extends the range of field conditions under which PTR-MS validation studies have been conducted.

scholarly journals Measurements of OVOC fluxes by eddy covariance using a proton-transfer-reaction mass spectrometer – method development at a coastal site

2013 ◽  
Vol 13 (13) ◽  
pp. 6165-6184 ◽  
Author(s):  
M. Yang ◽  
R. Beale ◽  
T. Smyth ◽  
B. Blomquist
Keyword(s):  
Proton Transfer ◽  
Eddy Covariance ◽  
Mass Spectrometer ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Time Of Day ◽  
Reaction Mass ◽  
Mixing Ratio ◽  
Mixing Ratios ◽  
Vertical Fluxes

Abstract. We present here vertical fluxes of oxygenated volatile organic compounds (OVOCs) measured with eddy covariance (EC) during the period of March to July 2012 near the southwest coast of the United Kingdom. The performance of the proton-transfer-reaction mass spectrometer (PTR-MS) for flux measurement is characterized, with additional considerations given to the homogeneity and stationarity assumptions required by EC. Observed mixing ratios and fluxes of OVOCs (specifically methanol, acetaldehyde, and acetone) vary significantly with time of day and wind direction. Higher mixing ratios and fluxes of acetaldehyde and acetone are found in the daytime and from the direction of a forested park, most likely due to light-driven emissions from terrestrial plants. Methanol mixing ratio and flux do not demonstrate consistent diel variability, suggesting sources in addition to plants. We estimate air–sea exchange and photochemical rates of these compounds, which are compared to measured vertical fluxes. For acetaldehyde, the mean (1σ) mixing ratio of 0.13 (0.02) ppb at night may be maintained by oceanic emission, while photochemical destruction outpaces production during the day. Air–sea exchange and photochemistry are probably net sinks of methanol and acetone in this region. Their nighttime mixing ratios of 0.46 (0.20) and 0.39 (0.08) ppb appear to be affected more by terrestrial emissions and long-distance transport, respectively.

scholarly journals A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux

2005 ◽  
Vol 5 (2) ◽  
pp. 505-513 ◽  
Author(s):  
A. Lee ◽  
G. W. Schade ◽  
R. Holzinger ◽  
A. H. Goldstein
Keyword(s):  
Ponderosa Pine ◽  
Proton Transfer Reaction ◽  
Mixing Ratio ◽  
Mixing Ratios ◽  
Flame Ionization ◽  
Ratio Difference ◽  
Accumulation System ◽  
The Common ◽  
Ionization Detectors

Abstract. Many monoterpenes have been identified in forest emissions using gas chromatography (GC). Until now, it has been impossible to determine whether all monoterpenes are appropriately measured using GC techniques. We used a proton transfer reaction mass spectrometer (PTR-MS) coupled with the eddy covariance (EC) technique to measure mixing ratios and fluxes of total monoterpenes above a ponderosa pine plantation. We compared PTR-MS-EC results with simultaneous measurements of eight speciated monoterpenes, β-pinene, α-pinene, 3-carene, d-limonene, β-phellandrene, α-terpinene, camphene, and terpinolene, made with an automated, in situ gas chromatograph with flame ionization detectors (GC-FID), coupled to a relaxed eddy accumulation system (REA). Monoterpene mixing ratios and fluxes measured by PTR-MS averaged 30±2.3% and 31±9.2% larger than by GC-FID, with larger mixing ratio discrepancies between the two techniques at night than during the day. Two unidentified peaks that correlated with β-pinene were resolved in the chromatograms and completely accounted for the daytime difference and reduced the nighttime mixing ratio difference to 20±2.9%. Measurements of total monoterpenes by PTR-MS-EC indicated that GC-FID-REA measured the common, longer-lived monoterpenes well, but that additional terpenes were emitted from the ecosystem that represented an important contribution to the total mixing ratio above the forest at night.

scholarly journals Uptake and emission of VOCs near ground level below a mixed forest at Borden, Ontario

2014 ◽  
Vol 14 (17) ◽  
pp. 9087-9097 ◽  
Author(s):  
M. Gordon ◽  
A. Vlasenko ◽  
R. M. Staebler ◽  
C. Stroud ◽  
P. A. Makar ◽  
...  
Keyword(s):  
Forest Canopy ◽  
Mixed Forest ◽  
Ground Level ◽  
Proton Transfer Reaction ◽  
Emission Rates ◽  
Surface Deposition ◽  
Canopy Exchange ◽  
Surface Emission ◽  
Mixing Ratios ◽  
Deposition Velocities

Abstract. Understanding of the atmosphere/forest canopy exchange of volatile organic compounds (VOCs) requires insight into the deposition, emission, and chemical reactions of VOCs below the canopy. Between 18 July and 9 August 2009, VOCs were measured with proton-transfer-reaction mass spectrometry (PTR-MS) at six heights between 1 and 6 m beneath a 23 m high mixed-forest canopy. Measured VOCs included methanol, isoprene, acetone, methacrolein and methyl vinyl ketone (MACR + MVK), monoterpenes, and sesquiterpenes. There are pronounced differences in the behaviour of isoprene and its by-products and that of the terpenes. Non-terpene mixing ratios increase with height, suggesting predominantly downward fluxes. In contrast, the terpene mixing ratios decrease with height, suggesting upward fluxes. A 1-D canopy model was used to compare results to measurements with and without surface deposition of isoprene and MACR + MVK and emissions of monoterpenes and sesquiterpenes. Results suggest deposition velocities of 2.7 mm s−1 for isoprene and 1.2 mm s−1 for MACR + MVK and daytime surface emission rates of 63 μg m−2 h−1 for monoterpenes. The modelled isoprene surface deposition is approximately 2% of the canopy-top isoprene emissions and the modelled emissions of monoterpenes comprise approximately 15 to 27% of the canopy-top monoterpene emissions to the atmosphere. These results suggest that surface monoterpene emissions are significant for forest canopy/atmosphere exchange for this mixed-forest location and surface uptake is relatively small for all the species measured in this study.

scholarly journals A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux

2004 ◽  
Vol 4 (6) ◽  
pp. 7819-7835
Author(s):  
A. Lee ◽  
G. W. Schade ◽  
R. Holzinger ◽  
A. H. Goldstein
Keyword(s):  
Ponderosa Pine ◽  
Forest Canopy ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Mixing Ratios ◽  
Flame Ionization ◽  
Accumulation System ◽  
The Common ◽  
Ionization Detectors

Abstract. Many monoterpenes have been identified in forest emissions using gas chromatography (GC). Until now, it has been impossible to determine whether all monoterpenes are appropriately measured using GC techniques. We used a proton transfer reaction mass spectrometer (PTR-MS) coupled with the eddy covariance (EC) technique to measure mixing ratios and fluxes of total monoterpenes above a ponderosa pine plantation. We compared PTR-MS-EC results with simultaneous measurements of eight speciated monoterpenes, β-pinene, α-pinene, 3-carene, d-limonene, β-phellandrene, α-terpinene, camphene, and terpinolene, made with an automated, in situ gas chromatograph with flame ionization detectors (GC-FID), coupled to a relaxed eddy accumulation system (REA). Monoterpene mixing ratios and fluxes measured by PTR-MS averaged 30±2.3% and 31±9.2% larger than by GC-FID, with larger differences at night than during the day. Four unidentified peaks that correlated with β-pinene were resolved in the chromatograms and completely accounted for the daytime difference and reduced the nighttime difference to 19±3.4%. Measurements of total monoterpenes by PTR-MS-EC indicated that GC-FID-REA measured the common, longer-lived monoterpenes well, but that additional monoterpenes were emitted from the ecosystem that represented an important contribution to the total mixing ratio above the forest at night, and that must have been oxidized during the day before they escaped the forest canopy.

scholarly journals Airborne determination of the temporo-spatial distribution of benzene, toluene, nitrogen oxides and ozone in the boundary layer across Greater London, UK

2015 ◽  
Vol 15 (9) ◽  
pp. 5083-5097 ◽  
Author(s):  
M. D. Shaw ◽  
J. D. Lee ◽  
B. Davison ◽  
A. Vaughan ◽  
R. M. Purvis ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitrogen Oxides ◽  
Linear Regression Analysis ◽  
Proton Transfer Reaction ◽  
Mixing Ratios ◽  
Spatially Resolved ◽  
Dual Channel ◽  
Benzene Toluene

Abstract. Highly spatially resolved mixing ratios of benzene and toluene, nitrogen oxides (NOx) and ozone (O3) were measured in the atmospheric boundary layer above Greater London during the period 24 June to 9 July 2013 using a Dornier 228 aircraft. Toluene and benzene were determined in situ using a proton transfer reaction mass spectrometer (PTR-MS), NOx by dual-channel NOx chemiluminescence and O3 mixing ratios by UV absorption. Average mixing ratios observed over inner London at 360 ± 10 m a.g.l. were 0.20 ± 0.05, 0.28 ± 0.07, 13.2 ± 8.6, 21.0 ± 7.3 and 34.3 ± 15.2 ppbv for benzene, toluene, NO, NO2 and NOx respectively. Linear regression analysis between NO2, benzene and toluene mixing ratios yields a strong covariance, indicating that these compounds predominantly share the same or co-located sources within the city. Average mixing ratios measured at 360 ± 10 m a.g.l. over outer London were always lower than over inner London. Where traffic densities were highest, the toluene / benzene (T / B) concentration ratios were highest (average of 1.8 ± 0.5 ppbv ppbv-1), indicative of strong local sources. Daytime maxima in NOx, benzene and toluene mixing ratios were observed in the morning (~ 40 ppbv NOx, ~ 350 pptv toluene and ~ 200 pptv benzene) and in the mid-afternoon for ozone (~ 40 ppbv O3), all at 360 ± 10 m a.g.l.

scholarly journals Ambient measurements of aromatic and oxidized VOCs by PTR-MS and GC-MS: intercomparison between four instruments in a boreal forest in Finland

2015 ◽  
Vol 8 (10) ◽  
pp. 4453-4473 ◽  
Author(s):  
M. K. Kajos ◽  
P. Rantala ◽  
M. Hill ◽  
H. Hellén ◽  
J. Aalto ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Boreal Forest ◽  
Proton Transfer Reaction ◽  
Systematic Difference ◽  
Gas Chromatography Mass Spectrometry ◽  
Forest Site ◽  
Mixing Ratios ◽  
Measurement Protocol ◽  
R Value

Abstract. Proton transfer reaction mass spectrometry (PTR-MS) and gas chromatography mass spectrometry GC-MS) are commonly used methods for automated in situ measurements of various volatile organic compounds (VOCs) in the atmosphere. In order to investigate the reliability of such measurements, we operated four automated analyzers using their normal field measurement protocol side by side at a boreal forest site. We measured methanol, acetaldehyde, acetone, benzene and toluene by two PTR-MS and two GC-MS instruments. The measurements were conducted in southern Finland between 13 April and 14 May 2012. This paper presents correlations and biases between the concentrations measured using the four instruments. A very good correlation was found for benzene and acetone measurements between all instruments (the mean R value was 0.88 for both compounds), while for acetaldehyde and toluene the correlation was weaker (with a mean R value of 0.50 and 0.62, respectively). For some compounds, notably for methanol, there were considerable systematic differences in the mixing ratios measured by the different instruments, despite the very good correlation between the instruments (mean R = 0.90). The systematic difference manifests as a difference in the linear regression slope between measurements conducted between instruments, rather than as an offset. This mismatch indicates that the systematic uncertainty in the sensitivity of a given instrument can lead to an uncertainty of 50–100 % in the methanol emissions measured by commonly used methods.

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