scholarly journals Volatile organic compound fluxes over a winter wheat field by PTR-Qi-TOF-MS and eddy covariance

2021 ◽  
Author(s):  
Benjamin Loubet ◽  
Pauline Buysse ◽  
Lais Gonzaga-Gomez ◽  
Florence Lafouge ◽  
Raluca Ciuraru ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Terrestrial Ecosystems ◽  
Global Scale ◽  
Voc Emissions ◽  
Wheat Field ◽  
Volatile Organic ◽  
Eddy Covariance Measurements ◽  
Secondary Aerosols ◽  
Mass Basis ◽  
Tof Ms

Abstract. Volatile organic compounds (VOC) contribute to air pollution through the formation of secondary aerosols and ozone and contribute to increasing the lifetime of methane in the atmosphere. Tropospheric VOC are 90 % originating from biogenic sources at the global scale. Forests are the main contributors to these emissions with isoprene and monoterpenes being the most emitted compounds. Crops are also a potentially large, yet poorly characterised, source of VOC. In particular, measurements of VOC fluxes for wheat at the ecosystem scale are scarce, although this is the most cultivated crop in Europe. Available evidence indicates that crops may contribute to 30% of the VOC emissions in Europe, especially oxygenated, low-molecular-weight VOC such as methanol, acetone and acetaldehyde. In this study, which is part of the COV3ER French national project, we investigated VOC fluxes over a wheat field in-situ by eddy covariance using a PTR-Qi-TOF-MS with an outmost sensitivity and mass resolution. We found 264 compounds to have a flux three times above the flux detection limit. Methanol was the most emitted compound, with an averaged flux of 63 µg m−2 h−1, representing around 60 % of summed VOC emissions on a molar basis (40 % on a mass basis). This finding is in line with previous measurements at canopy and plant scales. We also measured acetone, acetaldehyde and dimethyl sulphide among the five most emitted compounds. The second most emitted VOC corresponded to the ion m/z 93.037, tentatively identified as C6H4O. This compound was not reported previously as one of the most emitted compound by terrestrial ecosystems. Summed VOC emissions amounted around 150 µg m−2 h−1. Summed VOC deposition amounted to around −125 µg m−2 h−1, which represented about 70 % of the VOC emissions on a mass basis. The most depositing VOC were tentatively identified as hydroxyacetone and fragments of oxidised VOC with a flux of −16 µg m−2 h−1. Overall, our results reveal that wheat fields represent a non-negligible source and sink of VOC to be considered in regional VOC budgets, and underline the usefulness and limitations of eddy covariance measurements with PTR-Qi-TOF-MS.

scholarly journals PTR-TOF-MS eddy covariance measurements of isoprene and monoterpene fluxes from an eastern Amazonian rainforest

2020 ◽  
Vol 20 (12) ◽  
pp. 7179-7191 ◽  
Author(s):  
Chinmoy Sarkar ◽  
Alex B. Guenther ◽  
Jeong-Hoo Park ◽  
Roger Seco ◽  
Eliane Alves ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Atmospheric Chemistry ◽  
Sensible Heat Flux ◽  
Proton Transfer Reaction ◽  
Strongly Correlated ◽  
Mixing Ratios ◽  
Flux Measurements ◽  
Eddy Covariance Measurements ◽  
Emission Models ◽  
Tof Ms

Abstract. Biogenic volatile organic compounds (BVOCs) are important components of the atmosphere due to their contribution to atmospheric chemistry and biogeochemical cycles. Tropical forests are the largest source of the dominant BVOC emissions (e.g. isoprene and monoterpenes). In this study, we report isoprene and total monoterpene flux measurements with a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) using the eddy covariance (EC) method at the Tapajós National Forest (2.857∘ S, 54.959∘ W), a primary rainforest in eastern Amazonia. Measurements were carried out from 1 to 16 June 2014, during the wet-to-dry transition season. During the measurement period, the measured daytime (06:00–18:00 LT) average isoprene mixing ratios and fluxes were 1.15±0.60 ppb and 0.55±0.71 mg C m−2 h−1, respectively, whereas the measured daytime average total monoterpene mixing ratios and fluxes were 0.14±0.10 ppb and 0.20±0.25 mg C m−2 h−1, respectively. Midday (10:00–14:00 LT) average isoprene and total monoterpene mixing ratios were 1.70±0.49 and 0.24±0.05 ppb, respectively, whereas midday average isoprene and monoterpene fluxes were 1.24±0.68 and 0.46±0.22 mg C m−2 h−1, respectively. Isoprene and total monoterpene emissions in Tapajós were correlated with ambient temperature and solar radiation. Significant correlation with sensible heat flux, SHF (r2=0.77), was also observed. Measured isoprene and monoterpene fluxes were strongly correlated with each other (r2=0.93). The MEGAN2.1 (Model of Emissions of Gases and Aerosols from Nature version 2.1) model could simulate most of the observed diurnal variations (r2=0.7 to 0.8) but declined a little later in the evening for both isoprene and total monoterpene fluxes. The results also demonstrate the importance of site-specific vegetation emission factors (EFs) for accurately simulating BVOC fluxes in regional and global BVOC emission models.

scholarly journals PTR-TOF-MS eddy covariance measurements of isoprene and monoterpene fluxes from an Eastern Amazonian rainforest

2020 ◽  
Author(s):  
Chinmoy Sarkar ◽  
Alex B. Guenther ◽  
Jeong-Hoo Park ◽  
Roger Seco ◽  
Eliane Alves ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Atmospheric Chemistry ◽  
Sensible Heat Flux ◽  
Proton Transfer Reaction ◽  
Strongly Correlated ◽  
Mixing Ratios ◽  
Flux Measurements ◽  
Eddy Covariance Measurements ◽  
Emission Models ◽  
Tof Ms

Abstract. Biogenic volatile organic compounds (BVOCs) are important components of the atmosphere due to their contribution to atmospheric chemistry and biogeochemical cycles. Tropical forests are the largest source of the dominant BVOC emissions (e.g. isoprene and monoterpenes). In this study, we report isoprene and total monoterpene flux measurements with a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) using the eddy covariance (EC) method at the Tapajós National Forest (−2.857°S, −54.959°W), a primary rainforest in eastern Amazonia. Measurements were carried out from 1–16 June 2014, during the wet to dry transition season. During the measurement period, the measured daytime (06:00–18:00 LT) average isoprene mixing ratios and fluxes were 1.15 ± 0.60 ppb and 0.55 ± 0.71 mg C m−2 h−1, respectively, whereas the measured daytime average total monoterpenes mixing ratios and fluxes were 0.14 ± 0.10 ppb and 0.20 ± 0.25 mg C m−2 h−1, respectively. Midday (10:00–14:00 LT) average isoprene and total monoterpenes mixing ratios were 1.70 ± 0.49 ppb and 0.24 ± 0.05 ppb, respectively whereas midday average isoprene and monoterpene fluxes were 1.24 ± 0.68 mg C m−2 h−1 and 0.46 ± 0.22 mg C m−2 h−1, respectively. Isoprene and total monoterpene emissions in Tapajós were correlated with ambient temperature and solar radiation. Significant correlation with sensible heat flux, SHF (r2 = 0.77), was also observed. Measured isoprene and monoterpene fluxes were strongly correlated with each other (r2 = 0.93). The MEGAN2.1 model could simulate most of the observed diurnal variations (r2 = 0.7 to 0.8) but declined a little later in the evening for both isoprene and total monoterpene fluxes. The results also demonstrate the importance of site-specific vegetation emission factors (EFs) for accurately simulating BVOC fluxes in regional and global BVOC emission models.

scholarly journals First eddy covariance flux measurements of semi-volatile organic compounds with the PTR3-TOF-MS

2021 ◽  
Vol 14 (12) ◽  
pp. 8019-8039
Author(s):  
Lukas Fischer ◽  
Martin Breitenlechner ◽  
Eva Canaval ◽  
Wiebke Scholz ◽  
Marcus Striednig ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Eddy Covariance ◽  
Organic Compounds ◽  
Oxidation Products ◽  
Concentration Data ◽  
Single Digit ◽  
Volatile Organic ◽  
Flux Measurements ◽  
Flight Reaction ◽  
Tof Ms

Abstract. We present first eddy covariance flux measurements with the PTR3-TOF-MS, a novel proton transfer time of flight reaction mass spectrometer. During 3 weeks in spring 2016, the instrument recorded 10 Hz data of biogenic volatile organic compounds above a boreal forest, on top of a measurement tower at the SMEAR (Station for Measuring Ecosystem –Atmosphere Relations) II station in Hyytiälä, Finland. Flux and concentration data of isoprene, monoterpenes, and sesquiterpenes were compared to the literature. Due to the improved instrument sensitivity and a customized wall-less inlet design, we could detect fluxes of semi-volatile and low-volatility organic compounds with less than single-digit picomol per square meter per second (pmolm-2s-1) values for the first time. These compounds include sesquiterpene oxidation products and diterpenes. Daytime diterpene fluxes were in the range of 0.05 to 0.15 pmolm-2s-1, which amounts to about 0.25 % to 0.5 % of the daytime sesquiterpene flux above canopy.

scholarly journals First Eddy Covariance Flux Measurements of Semi Volatile Organic Compounds with the PTR3-TOF-MS

2021 ◽  
Author(s):  
Lukas Fischer ◽  
Martin Breitenlechner ◽  
Eva Canaval ◽  
Wiebke Scholz ◽  
Marcus Striednig ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Eddy Covariance ◽  
Organic Compounds ◽  
Proton Transfer Reaction ◽  
Oxidation Products ◽  
Concentration Data ◽  
Single Digit ◽  
Volatile Organic ◽  
Flux Measurements ◽  
Tof Ms

Abstract. We present first eddy covariance flux measurements with the PTR3-TOF-MS, a novel proton-transfer-reaction mass-spectrometer (PTR-MS). During three weeks in spring 2016 the instrument recorded 10 Hz BVOC data on top of the SMEAR II tower in Hyytiälä, Finland. Flux and concentration data of isoprene, monoterpenes and sesquiterpenes were compared to the literature. Due to the improved instrument sensitivity and a customized “wall less” inlet design we could detect a number of fluxes of semi-volatile and low volatile organic compounds (SVOC and LVOC) with less than single digit picomol/m2/s values for the first time. These compounds include sesquiterpene oxidation products and diterpenes. Daytime diterpene fluxes were in the range of 0.05 to 0.15 picomol/m2/s, which amounts to about 0.25 % to 0.5 % of the daytime sesquiterpene flux above canopy.

First eddy covariance flux measurements of gaseous elemental mercury over a grassland

2020 ◽  
Author(s):  
Stefan Osterwalder ◽  
Werner Eugster ◽  
Iris Feigenwinter ◽  
Martin Jiskra
Keyword(s):  
Detection Limit ◽  
Eddy Covariance ◽  
Net Ecosystem Exchange ◽  
Elemental Mercury ◽  
Terrestrial Ecosystems ◽  
Global Scale ◽  
Gaseous Elemental Mercury ◽  
Direct Measurements ◽  
The Us ◽  
Flux Measurements

<p>Direct measurements of the net ecosystem exchange (NEE) of gaseous elemental mercury (Hg<sup>0</sup>) are crucial to improve our understanding of global Hg cycling and ultimately Hg exposure in humans and wildlife. The lack of long-term, ecosystem-scale measurements causes large uncertainties in Hg<sup>0</sup> flux estimates. Today it remains unclear whether terrestrial ecosystems are net sinks or sources of atmospheric Hg<sup>0</sup>. Here, we present the first successful eddy covariance NEE measurements of Hg<sup>0</sup> over natural, low-Hg soils (41 - 75 ng Hg g<sup>-1</sup> topsoil [0-10 cm]) at a managed grassland site in Chamau, Switzerland. We present a detailed validation of the eddy covariance technique for Hg<sup>0</sup> based on a Lumex mercury monitor RA-915AM. The flux detection limit derived from a zero-flux experiment in the laboratory was 0.22 ng m<sup>-2</sup> h<sup>-1</sup> (maximum) with a 50 % cut-off at 0.074 ng m<sup>-2</sup> h<sup>-1</sup>. The statistical estimate of the Hg<sup>0</sup> flux detection limit under real-world outdoor conditions at the site was 5.9 ng m<sup>-2</sup> h<sup>-1</sup> (50 % cut-off). Based on our analysis we give suggestions to further improve the precision of the system and pinpoint challenges and interferences that occurred during the 34-day pilot campaign in summer 2018. The data were obtained during extremely hot and dry meteorological conditions. We estimated a net summertime grassland-atmosphere Hg<sup>0</sup> flux from -0.6 to 7.4 ng m<sup>-2</sup> h<sup>-1</sup> (range between 25<sup>th</sup> and 75<sup>th</sup> percentiles). The measurements revealed a distinct diel pattern with lower nighttime fluxes (1.0 ng m<sup>-2</sup> h<sup>-1</sup>) compared to daytime fluxes (8.4 ng m<sup>-2</sup> h<sup>-1</sup>). Drought stress during the campaign induced partial stomata closure of vegetation leading to a midday depression in CO<sub>2</sub> uptake, which did not recover during the afternoon. We suggest that partial stomata closure dampened Hg<sup>0</sup> uptake by vegetation as well, resulting in a NEE of Hg<sup>0</sup> dominated by soil emission. The new Eddy Mercury system seems suitable to complement existing research infrastructures such as ICOS RI in Europe or NOAA Observing Systems in the US built to calculate greenhouse gas balances with direct Hg<sup>0</sup> deposition and emission measurements. We anticipate our Eddy Mercury system to improve knowledge about Hg cycling between ecosystems and the atmosphere and to challenge model simulations on a regional and global scale.</p>

Sign in / Sign up

Export Citation Format

Share Document