Unexpected seasonality in quantity and composition of Amazon rainforest air reactivity

Nölscher, A. C.; Yáñez‐Serrano, Ana María; Wolff, Stefan; Araújo, Alessandro; Lavrič, Jošt V.; Kesselmeier, J.; Williams, Jonathan

doi:10.1038/ncomms10383

Cited by 106 publications

(150 citation statements)

References 58 publications

(92 reference statements)

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“…The inlet lines were made of PTFE (9.5 mm OD), insulated and heated to 50 • C, and had PTFE particle inlet filters. More information about the gradient system and PTR-MS operation at ATTO can be found elsewhere (Nölscher et al, 2016;. The limit of detection (LOD) and uncertainty in the PTR-MS were 0.05 ppb and 34 %, respectively.…”

Section: Sites and Methodologymentioning

confidence: 99%

“…Several studies report that the mixing ratio of MEK in the free troposphere is roughly one-quarter of that of acetone (Moore et al, 2012;Singh et al, 2004). However, MEK is about an order of magnitude more reactive than acetone with respect to the hydroxyl radical (OH) (Atkinson, 2000), which makes it a compound of interest in ongoing discussions about the inability to fully account for the reactivity of OH (Nölscher et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

et al. 2016

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Abstract. Methyl ethyl ketone (MEK) enters the atmosphere following direct emission from vegetation and anthropogenic activities, as well as being produced by the gas-phase oxidation of volatile organic compounds (VOCs) such as nbutane. This study presents the first overview of ambient MEK measurements at six different locations, characteristic of forested, urban and marine environments. In order to understand better the occurrence and behaviour of MEK in the atmosphere, we analyse diel cycles of MEK mixing ratios, vertical profiles, ecosystem flux data, and HYSPLIT back trajectories, and compare with co-measured VOCs. MEK measurements were primarily conducted with protontransfer-reaction mass spectrometer (PTR-MS) instruments. Results from the sites under biogenic influence demonstrate that vegetation is an important source of MEK. The diel cycle of MEK follows that of ambient temperature and the forest structure plays an important role in air mixing. At such sites, a high correlation of MEK with acetone was observed (e.g. r 2 = 0.96 for the SMEAR Estonia site in a remote hemiboreal forest in Tartumaa, Estonia, and r 2 = 0.89 at the ATTO pristine tropical rainforest site in central Amazonia). Under polluted conditions, we observed strongly enhanced MEK mixing ratios. Overall, the MEK mixing ratios and flux data presented here indicate that both biogenic and anthropogenic sources contribute to its occurrence in the global atmosphere.

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Section: Sites and Methodologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

et al. 2016

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“…Therefore, a lower abundance of a certain monoterpene species could not necessarily be related to a lower vegetation emission but also to a higher reactivity with atmospheric oxidants. Despite the small amount of α-terpinene present in the atmosphere, it can profoundly affect reactivity due to its fast reaction rate (its lifetime, according to the oxidant mixing ratios stated above, can be 103, 2 and 11 min to OH, O 3 and NO 3 , respectively; Neeb et al, 1997). In terms of total OH reactivity accounted for by the monoterpenes, the values of this study are very low compared to the total OH reactivity measurements by , with a mean total OH reactivity for the dry season of 32 s −1 , mostly dominated by isoprene chemistry.…”

Section: Reactivitymentioning

confidence: 99%

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

et al. 2018

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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 (O 3 ) and nitrate radicals (NO 3 ). 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.

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“…In forested environments, the measured reactivity has generally been found to be significantly higher than that calculated from summing up reactivity due to individual reactive trace gases, 5 Nölscher et al, 2012;Nolscher et al, 2016) resulting in an apparent "missing reactivity". In a similar vein, O 3 flux measurements in Californian pine forests required monoterpene emissions that were 10 times higher than measured in order to explain the O 3 losses (Goldstein et al, 2004).…”

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Direct measurement of NO<sub>3</sub> reactivity in a boreal forest

Liebmann

Karu

Sobanski

et al. 2017

Preprint

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Abstract. We present the first direct measurements of NO 3 reactivity (or inverse lifetime, s -1 ) in the Finnish boreal forest.The data were obtained during the IBAIRN campaign (Influence of Biosphere-Atmosphere Interactions on the Reactive 15 Nitrogen budget) which took place in Hyytiälä, Finland during the summer / autumn transition in September 2016. The NO 3 reactivity was generally very high with a maximum value of 0.94 s -1 and displayed a strong diel variation with a campaignaveraged nighttime mean value of 0.11 s -1 compared to a daytime value of 0.04 s -1 . The highest nighttime NO 3 -reactivity was accompanied by major depletion of canopy level ozone and was associated with strong temperature inversions and high levels of monoterpenes. The daytime reactivity was sufficiently large that reactions of NO 3 with organic trace gases could 20 compete with photolysis and reaction with NO. There was no significant reduction in the measured NO 3 reactivity between the beginning and end of the campaign indicating that any seasonal reduction in canopy emissions of reactive biogenic trace gases was offset by emissions from the forest floor. Observations of biogenic hydrocarbons (BVOC) suggested a dominant role for monoterpenes in determining the NO 3 reactivity. Reactivity not accounted for by in-situ measurement of NO and BVOCs was variable across the diel cycle with, on average, ≈ 30% "missing" during nighttime and ≈ 60% missing during 25 the day. Measurement of the NO 3 reactivity at various heights (8.5 to 25 m) both above and below the canopy, revealed a strong nighttime, vertical gradient with maximum values closest to the ground. The gradient disappeared during daytime due to efficient vertical mixing.

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Unexpected seasonality in quantity and composition of Amazon rainforest air reactivity

Cited by 106 publications

References 58 publications

Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

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

Direct measurement of NO<sub>3</sub> reactivity in a boreal forest

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Unexpected seasonality in quantity and composition of Amazon rainforest air reactivity

Cited by 106 publications

References 58 publications

Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

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

Direct measurement of NO&lt;sub&gt;3&lt;/sub&gt; reactivity in a boreal forest

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Direct measurement of NO<sub>3</sub> reactivity in a boreal forest