OH Reactivity Measurements within a Boreal Forest: Evidence for Unknown Reactive Emissions

Sinha, Vinayak; Williams, Jonathan; Lelieveld, Jos; Ruuskanen, T. M.; Kajos, M. K.; Patokoski, J.; Hellén, Heidi; Hakola, Hannele; Mogensen, D.; Boy, Michael; Rinne, Janne; Kulmala, Markku

doi:10.1021/es101780b

Cited by 142 publications

(185 citation statements)

References 36 publications

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“…The limited observations of OH reactivity in BVOC dominant environments show consistent unaccounted OH chemical loss with observational data sets (Di Carlo et al, 2004;Edwards et al, 2013;Lou et al, 2010;Nölscher et al, 2012;Nakashima et al, 2014;Sinha et al, 2010). Two different processes are speculated to cause unaccounted OH loss known as missing OH reactivity: (1) primary emissions of unmeasured or unknown compounds and (2) oxidation products of well-known BVOCs, especially isoprene.…”

Section: Implications Of the Uncertainty In Ho X Estimations In Assesmentioning

confidence: 74%

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

Kim

Lee³

et al. 2015

Atmos. Chem. Phys.

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Abstract. Rapid urbanization and economic development in East Asia in past decades has led to photochemical air pollution problems such as excess photochemical ozone and aerosol formation. Asian megacities such as Seoul, Tokyo, Shanghai, Guangzhou, and Beijing are surrounded by densely forested areas, and recent research has consistently demonstrated the importance of biogenic volatile organic compounds (VOCs) from vegetation in determining oxidation capacity in the suburban Asian megacity regions. Uncertainties in constraining tropospheric oxidation capacity, dominated by hydroxyl radical, undermine our ability to assess regional photochemical air pollution problems. We present an observational data set of CO, NO x , SO 2 , ozone, HONO, and VOCs (anthropogenic and biogenic) from Taehwa research forest (TRF) near the Seoul metropolitan area in early June 2012. The data show that TRF is influenced both by aged pollution and fresh biogenic volatile organic compound emissions. With the data set, we diagnose HO x (OH, HO 2 , and RO 2 ) distributions calculated using the University of Washington chemical box model (UWCM v2.1) with nearexplicit VOC oxidation mechanisms from MCM v3.2 (Master Chemical Mechanism). Uncertainty from unconstrained HONO sources and radical recycling processes highlighted in recent studies is examined using multiple model simulations with different model constraints. The results suggest that (1) different model simulation scenarios cause systematic differences in HO x distributions, especially OH levels (up to 2.5 times), and (2) radical destruction (HO 2 + HO 2 or HO 2 + RO 2 ) could be more efficient than radical recycling (RO 2 + NO), especially in the afternoon. Implications of the uncertainties in radical chemistry are discussed with respect to ozone-VOC-NO x sensitivity and VOC oxidation product formation rates. Overall, the NO x limited regime is assessed except for the morning hours (8 a.m. to 12 p.m. local standard time), but the degree of sensitivity can significantly vary depending on the model scenarios. The model results also suggest that RO 2 levels are positively correlated with oxygenated VOCs (OVOCs) production that is not routinely constrained by observations. These unconstrained OVOCs can cause higher-than-expected OH loss rates (missing OH reactivity) and secondary organic aerosol formation. The series of modeling experiments constrained by observations strongly urge observational constraint of the radical pool to enable precise understanding of regional photochemical pollution problems in the East Asian megacity region.

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Section: Implications Of the Uncertainty In Ho X Estimations In Assesmentioning

confidence: 74%

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

Kim

Lee³

et al. 2015

Atmos. Chem. Phys.

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“…However, a substantial difference between measured and calculated or modeled OH reactivity, termed the missing reactivity, was revealed in most field campaigns. Compared to the high percentages of missing reactivity in forested areas (Sinha et al, 2010;Nölscher et al, 2012Nölscher et al, , 2016Edwards et al, 2013;Williams et al, 2016), most campaigns in urban and suburban areas gave relatively lower percentages of missing reactivity, except for the 75 % missing reactivity in Paris in MEGAPOLI under the influence of continental air masses (Dolgorouky et al, 2012).…”

Section: Introductionmentioning

confidence: 80%

How the OH reactivity affects the ozone production efficiency: case studies in Beijing and Heshan, China

et al. 2017

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Abstract. Total OH reactivity measurements were conducted on the Peking University campus (Beijing) in August 2013 and in Heshan (Guangdong province) from October to November 2014. The daily median OH reactivity was 20 ± 11 s −1 in Beijing and 31 ± 20 s −1 in Heshan, respectively. The data in Beijing showed a distinct diurnal pattern with the maxima over 27 s −1 in the early morning and minima below 16 s −1 in the afternoon. The diurnal pattern in Heshan was not as evident as in Beijing. Missing reactivity, defined as the difference between measured and calculated OH reactivity, was observed at both sites, with 21 % missing reactivity in Beijing and 32 % missing reactivity in Heshan. Unmeasured primary species, such as branched alkenes, could contribute to missing reactivity in Beijing, especially during morning rush hours. An observation-based model with the RACM2 (Regional Atmospheric Chemical Mechanism version 2) was used to understand the daytime missing reactivity in Beijing by adding unmeasured oxygenated volatile organic compounds and simulated intermediates of the degradation from primary volatile organic compounds (VOCs). However, the model could not find a convincing explanation for the missing reactivity in Heshan, where the ambient air was found to be more aged, and the missing reactivity was presumably attributed to oxidized species, such as unmeasured aldehydes, acids and dicarbonyls. The ozone production efficiency was 21 % higher in Beijing and 30 % higher in Heshan when the model was constrained by the measured reactivity, compared to the calculations with measured and modeled species included, indicating the importance of quantifying the OH reactivity for better understanding ozone chemistry.

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“…High mixing ratios of terpenoids in airmasses that have passed over the sawmill have been documented frequently (Eerdekens et al, 2009;Sinha et al, 2010;Hakola et al, 2012;Nölscher et al, 2012 on the 14 th of September from 06:30 to 08:00 UTC, HYSPLIT back-trajectories (GDAS global, 0.5°), indicating that the air mass passed over Korkeakoski ≈ 0.5 hours prior to reaching the SMEAR II site.…”

Section: Type 3 Nightsmentioning

confidence: 97%

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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OH Reactivity Measurements within a Boreal Forest: Evidence for Unknown Reactive Emissions

Cited by 142 publications

References 36 publications

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

How the OH reactivity affects the ozone production efficiency: case studies in Beijing and Heshan, China

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

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OH Reactivity Measurements within a Boreal Forest: Evidence for Unknown Reactive Emissions

Cited by 142 publications

References 36 publications

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

How the OH reactivity affects the ozone production efficiency: case studies in Beijing and Heshan, China

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