scholarly journals Boreal forest soil is a significant and diverse source of volatile organic compounds

2019 ◽  
Vol 441 (1-2) ◽  
pp. 89-110 ◽  
Author(s):  
Mari Mäki ◽  
Hermanni Aaltonen ◽  
Jussi Heinonsalo ◽  
Heidi Hellén ◽  
Jukka Pumpanen ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Boreal Forest ◽  
Forest Soil ◽  
Organic Compounds ◽  
Volatile Organic ◽  
Diverse Source

scholarly journals Measurement report: Molecular composition and volatility of gaseous organic compounds in a boreal forest: from volatile organic compounds to highly oxygenated organic molecules

2020 ◽  
Author(s):  
Wei Huang ◽  
Haiyan Li ◽  
Nina Sarnela ◽  
Liine Heikkinen ◽  
Yee Jun Tham ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Boreal Forest ◽  
Organic Compounds ◽  
Mass Spectrometer ◽  
Organic Molecules ◽  
Measurement Techniques ◽  
Time Of Flight ◽  
Molecular Composition ◽  
Flight Mass Spectrometer ◽  
Volatile Organic

Abstract. The molecular composition and volatility of gaseous organic compounds were investigated during April–July 2019 at the Station for Measuring Ecosystem – Atmosphere Relations (SMEAR) II situated in a boreal forest in Hyytiälä, southern Finland. A Vocus proton-transfer-reaction time-of-flight mass spectrometer (Vocus PTR-ToF; hereafter Vocus) was deployed to measure volatile organic compounds (VOC) and less oxygenated VOC (i.e., OVOC). In addition, a multi-scheme chemical ionization inlet coupled to an atmospheric pressure interface time-of-flight mass spectrometer (MION APi-ToF) was used to detect less oxygenated VOC (using Br− as the reagent ion; hereafter MION-Br) and more oxygenated VOC (including highly oxygenated organic molecules, HOM; using NO3− as the reagent ion; hereafter MION-NO3). The comparison among different measurement techniques revealed that the highest elemental oxygen-to-carbon ratios (O : C) of organic compounds were observed by the MION-NO3 (0.9 ± 0.1, average ± 1 standard deviation), followed by the MION-Br (0.8 ± 0.1); and lowest by Vocus (0.2 ± 0.1). Diurnal patterns of the measured organic compounds were found to vary among different measurement techniques, even for compounds with the same molecular formula, suggesting contributions of different isomers detected by the different techniques and/or fragmentation from different parent compounds inside the instruments. Based on the complementary molecular information obtained from Vocus, MION-Br, and MION-NO3, a more complete picture of the bulk volatility of all measured organic compounds in this boreal forest was obtained. As expected, the VOC class was the most abundant (about 49.4 %), followed by intermediate-volatility organic compounds (IVOC, about 48.9 %). Although condensable organic compounds (low-volatility organic compounds, LVOC; extremely low-volatility organic compounds, ELVOC; and ultralow-volatility organic compounds, ULVOC) only comprised about 0.3 % of the total gaseous organic compounds, they play an important role in new particle formation as shown in previous studies in this boreal forest. Our study shows the full characterization of the gaseous organic compounds in the boreal forest and the advantages of combining Vocus and MION APi-ToF for measuring ambient organic compounds with different oxidation extent (from VOC to HOM). The results therefore provide a more comprehensive understanding of the molecular composition and volatility of atmospheric organic compounds as well as new insights in interpreting ambient measurements or testing/improving parameterizations in transport and climate models.

scholarly journals Simulations of atmospheric OH, O<sub>3</sub> and NO<sub>3</sub> reactivities within and above the boreal forest

2015 ◽  
Vol 15 (7) ◽  
pp. 3909-3932 ◽  
Author(s):  
D. Mogensen ◽  
R. Gierens ◽  
J. N. Crowley ◽  
P. Keronen ◽  
S. Smolander ◽  
...  
Keyword(s):  
Steady State ◽  
Volatile Organic Compounds ◽  
Boreal Forest ◽  
Organic Compounds ◽  
Atmospheric Chemistry ◽  
Inorganic Compounds ◽  
Spectral Irradiance ◽  
Biogenic Volatile Organic Compounds ◽  
Short Period ◽  
Volatile Organic

Abstract. Using the 1-D atmospheric chemistry transport model SOSAA, we have investigated the atmospheric reactivity of a boreal forest ecosystem during the HUMPPA-COPEC-10 campaign (summer 2010, at SMEAR~II in southern Finland). For the very first time, we present vertically resolved model simulations of the NO3 and O3 reactivity (R) together with the modelled and measured reactivity of OH. We find that OH is the most reactive oxidant (R ∼ 3 s-1) followed by NO3 (R ∼ 0.07 s-1) and O3 (R ∼ 2 × 10-5s-1). The missing OH reactivity was found to be large in accordance with measurements (∼ 65%) as would be expected from the chemical subset described in the model. The accounted OH radical sinks were inorganic compounds (∼ 41%, mainly due to reaction with CO), emitted monoterpenes (∼ 14%) and oxidised biogenic volatile organic compounds (∼ 44%). The missing reactivity is expected to be due to unknown biogenic volatile organic compounds and their photoproducts, indicating that the true main sink of OH is not expected to be inorganic compounds. The NO3 radical was found to react mainly with primary emitted monoterpenes (∼ 60%) and inorganic compounds (∼ 37%, including NO2). NO2 is, however, only a temporary sink of NO3 under the conditions of the campaign (with typical temperatures of 20–25 °C) and does not affect the NO3 concentration. We discuss the difference between instantaneous and steady-state reactivity and present the first boreal forest steady-state lifetime of NO3 (113 s). O3 almost exclusively reacts with inorganic compounds (∼ 91%, mainly NO, but also NO2 during night) and less with primary emitted sesquiterpenes (∼ 6%) and monoterpenes (∼ 3%). When considering the concentration of the oxidants investigated, we find that OH is the oxidant that is capable of removing organic compounds at a faster rate during daytime, whereas NO3 can remove organic molecules at a faster rate during night-time. O3 competes with OH and NO3 during a short period of time in the early morning (around 5 a.m. local time) and in the evening (around 7–8 p.m.). As part of this study, we developed a simple empirical parameterisation for conversion of measured spectral irradiance into actinic flux. Further, the meteorological conditions were evaluated using radiosonde observations and ground-based measurements. The overall vertical structure of the boundary layer is discussed, together with validation of the surface energy balance and turbulent fluxes. The sensible heat and momentum fluxes above the canopy were on average overestimated, while the latent heat flux was underestimated.

Volatile organic compound fluxes across the soils of a rainforest ecosystem during a simulated drought experiment

2020 ◽  
Author(s):  
Gemma Purser ◽  
Jürgen Kreuzwieser ◽  
Johannes Ingrisch ◽  
Kathiravan Meeran ◽  
Juliana Gil Loaiza ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Forest Soil ◽  
Organic Compounds ◽  
Leaf Litter ◽  
Forest Floor ◽  
Ambient Air ◽  
Emission Source ◽  
Biosphere 2 ◽  
Volatile Organic ◽  
Drought Conditions

&lt;p&gt;Rainforests have important role in global carbon cycle. They act as an important sink for carbon dioxide and are a net source of volatile organic compounds (VOCs), which are emitted predominately from trees. However, the functioning of rainforest ecosystems are particularly vulnerable to changes in climate and extreme weather events such as drought, which are expected to become more frequent as global temperatures rise.&lt;/p&gt;&lt;p&gt;The forest floor acts as an interface between the biosphere and atmosphere within a forest ecosystem. Both emission (source) and deposition (sink) of atmospheric volatile organic compounds (VOCs) occur at this interface. Organic matter such as leaf litter in particular is a well characterised source of VOCs which are released through both biotic and abiotic degradation processes. Other emission sources of VOCs include those emitted from roots within the soil and also from soil microbial communities. Typically leaf litter or vegetation is the dominant emission source of VOCs from the forest floor, which has previously been reported to contribute up to 5% of the total ecosystem emission of forests. It is predicted that leaf litter will begin to accumulate on the forest floor as trees become drought stressed increasing the contribution of this source to the atmosphere. However the response of the soils within the rainforest ecosystem under drought conditions is less well understood.&lt;/p&gt;&lt;p&gt;We investigated changes in the direction of VOC fluxes across the forest floor before, during, and after a 7-week artificial drought as part of the Biosphere 2 Water, Atmosphere, and Life Dynamics campaign (B2 WALD). Initial results from the campaign showed that the forest floor soils act as an important sink for atmospheric concentrations of VOCs such as isoprene. The unique setting of an enclosed ecosystem in Biosphere 2 leads to elevated concentrations of VOCs including monoterpenes in the atmosphere which have allowed for the uptake rates of different VOCs by forest soil to be assessed.&lt;/p&gt;&lt;p&gt;A dynamic flow through system was used to collect VOC samples from both ambient air and chambers situated on the forest soil at a flow rate of 0.2 L/min for approximately 2 hours onto glass cartridges filled with Tenax&amp;#174;. The samples were analysed using a thermal desorption-Gas chromatrography-Ion Ratio-Mass spectrometry instrument. Fluxes were calculated using the difference between the concentration of monoterpenes in the ambient air and chamber samples. Here we will discuss further the variability in fluxes of monoterpenes across the rainforest floor interface under both ambient and severe drought conditions alongside the environmental drivers that have an impact on this ecosystem process.&amp;#160;&lt;/p&gt;

scholarly journals Alkyl nitrates in the boreal forest: formation via the NO<sub>3</sub>-, OH- and O<sub>3</sub>-induced oxidation of biogenic volatile organic compounds and ambient lifetimes

2019 ◽  
Vol 19 (15) ◽  
pp. 10391-10403 ◽  
Author(s):  
Jonathan Liebmann ◽  
Nicolas Sobanski ◽  
Jan Schuladen ◽  
Einar Karu ◽  
Heidi Hellén ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Boreal Forest ◽  
Organic Compounds ◽  
High Reactivity ◽  
Anthropogenic Sources ◽  
Reactive Nitrogen ◽  
Biogenic Volatile Organic Compounds ◽  
Night Time ◽  
Alkyl Nitrates ◽  
Volatile Organic

Abstract. The formation of alkyl nitrates in various oxidation processes taking place throughout the diel cycle can represent an important sink of reactive nitrogen and mechanism for chain termination in atmospheric photo-oxidation cycles. The low-volatility alkyl nitrates (ANs) formed from biogenic volatile organic compounds (BVOCs), especially terpenoids, enhance rates of production and growth of secondary organic aerosol. Measurements of the NO3 reactivity and the mixing ratio of total alkyl nitrates (ΣANs) in the Finnish boreal forest enabled assessment of the relative importance of NO3-, O3- and OH-initiated formation of alkyl nitrates from BVOCs in this environment. The high reactivity of the forest air towards NO3 resulted in reactions of the nitrate radical, with terpenes contributing substantially to formation of ANs not only during the night but also during daytime. Overall, night-time reactions of NO3 accounted for 49 % of the local production rate of ANs, with contributions of 21 %, 18 % and 12 % for NO3, OH and O3 during the day. The lifetimes of the gas-phase ANs formed in this environment were on the order of 2 h due to efficient uptake to aerosol (and dry deposition), resulting in the transfer of reactive nitrogen from anthropogenic sources to the forest ecosystem.

scholarly journals The oxidation capacity of the boreal forest: first simulated reactivities of O<sub>3</sub> and NO<sub>3</sub>

2014 ◽  
Vol 14 (22) ◽  
pp. 30947-31007 ◽  
Author(s):  
D. Mogensen ◽  
R. Gierens ◽  
J. N. Crowley ◽  
P. Keronen ◽  
S. Smolander ◽  
...  
Keyword(s):  
Steady State ◽  
Volatile Organic Compounds ◽  
Boreal Forest ◽  
Organic Compounds ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Inorganic Compounds ◽  
Spectral Irradiance ◽  
Biogenic Volatile Organic Compounds ◽  
Volatile Organic

Abstract. Using the 1D atmospheric chemistry–transport model SOSAA, we have investigated the atmospheric reactivity of a boreal forest ecosystem during the HUMPPA-COPEC-10 campaign (summer 2010, at SMEAR II in Southern Finland). For the very first time, we present vertically resolved model simulations of the NO3- and O3-reactivity (R) together with the modelled and measured reactivity of OH. We find that OH is the most reactive oxidant (R~3 s−1) followed by NO3 (R~0.07 s−1) and O3 (R~2 × 10−5 s−1). The missing OH-reactivity was found to be large in accordance with measurements (~65%) as would be expected from the chemical subset described in the model. The accounted OH radical sinks were inorganic compounds (~41%, mainly due to reaction with CO), emitted monoterpenes (~14%) and oxidised biogenic volatile organic compounds (~44%). The missing reactivity is expected to be due to unknown biogenic volatile organic compounds and their photoproducts, indicating that the true main sink of OH is not expected to be inorganic compounds. The NO3 radical was found to react mainly with primary emitted monoterpenes (~60%) and inorganic compounds (~37%, including NO2). NO2 is, however, only a temporary sink of NO3 under the conditions of the campaign and does not affect the NO3 concentration. We discuss the difference between instantaneous and steady state reactivity and present the first boreal forest steady state lifetime of NO3 (113 s). O3 almost exclusively reacts with inorganic compounds (~91%, mainly NO, but also NO2 during night) and less with primary emitted sesquiterpenes (~6%) and monoterpenes (~3%). When considering the concentration of the oxidants investigated, we find that O3 is the oxidant that is capable of removing pollutants fastest. As part of this study, we developed a simple empirical parameterisation for conversion of measured spectral irradiance into actinic flux. Further, the meteorological conditions were evaluated using radiosonde observations and ground based measurements. The overall vertical structure of the boundary layer is discussed, together with validation of the surface energy balance and turbulent fluxes. The sensible heat and momentum fluxes above the canopy were on average overestimated, while the latent heat flux was underestimated.

scholarly journals Modelling day-time concentrations of biogenic volatile organic compounds in a boreal forest canopy

2010 ◽  
Vol 10 (8) ◽  
pp. 20035-20068
Author(s):  
H. K. Lappalainen ◽  
S. Sevanto ◽  
M. Dal Maso ◽  
R. Taipale ◽  
M. K. Kajos ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Boreal Forest ◽  
Organic Compounds ◽  
Air Temperature ◽  
Photosynthetic Efficiency ◽  
Photon Flux ◽  
Biogenic Volatile Organic Compounds ◽  
High Concentration ◽  
Volatile Organic ◽  
S Model

Abstract. Three different models for day-time atmospheric methanol, acetaldehyde, acetone, isoprene and monoterpene concentrations were developed using measurements above a boreal forest stand in Southern Finland in 2006–2007 and tested against an independent dataset from the same forest measured in summer 2008. The models were based on the exponential relationship between air temperature and the concentration of biogenic volatile organic compounds (BVOC). Our first model for BVOC concentrations was a simple exponential function of air temperature (T-model). The T-model could explain 27–66% of the variation of all the compounds, but it failed to catch the extremely high concentration peaks observed in summer. To improve the temperature model we developed two other models. The second model, a Temperature-State of Development- model (T-S model), included two explaining variables: air temperature and the seasonal photosynthetic efficiency. This model performed slightly better compared to the T-model for both datasets and increased the fraction of variation explained to 29–69%, but it still could not explain the high concentration peaks. To explain those we modified the T-S model to include environmental triggers that could increase the concentrations momentarily. The triggers that improved the model most were high photosynthetically active photon flux density (PPDF) compared to the seasonally available radiation and high ozone concentration. The Trigger model described the peak concentrations somewhat better than T or T-S model, thus the level of explanation was improved and was 30–71%. This study shows the importance to include seasonal variations in photosynthetic efficiency when modeling BVOC concentrations and presents the idea of a trigger model for explaining high peak concentrations of BVOCs. Our study suggests that when developing a trigger type modelfurther the model and the triggers should be more compounds-specific.

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