Abstract:Abstract. Multifunctional organic nitrates, including carbonyl nitrates, are important
species formed in NOx-rich atmospheres by the degradation of volatile organic compounds (VOCs). These
compounds have been shown to play a key role in the transport of reactive
nitrogen and, consequently, in the ozone budget; they are also known to be important
components of the total organic aerosol. However, very little is known about
their reactivity in both the gas and condensed phases. Following a previous
study that we … Show more
“…It is also expected that organic nitrates adsorb on the stainlesssteel walls. Indeed, the loss rates of several multifunctional organic nitrates (in particular carbonyl nitrates) have been observed in previous studies (Suarez-Bertoa et al, 2012;Picquet-Varrault et al, 2020) and were found to range between 0.5 and 2 × 10 −5 s −1 . However, as yields of organic nitrates in the gas phase were calculated during a relatively short period (less than 1 h), these wall losses are expected to be low (less than 10 %), and this is confirmed by the good linearity of the plots.…”
Section: Organic Nitrate Yieldssupporting
confidence: 57%
“…Since the early 1980s and the discovery of the nitrate radical (NO 3 ) in the nocturnal troposphere (Noxon et al, 1980;Platt et al, 1980) and stratosphere (Naudet et al, 1981;Noxon et al, 1978), nighttime chemistry has been known to be active. NO 3 is mainly formed by the reaction of nitrogen dioxide (NO 2 ) with ozone and has two very efficient sinks during the day, its photolysis and its reaction with NO (Brown and Stutz, 2012).…”
Section: Introductionmentioning
confidence: 99%
“…They therefore significantly influence the nitrogenous species (NO y ) and ozone budgets in these regions (Ito et al, 2007). Furthermore, some (multifunctional) organic nitrates are low-volatile and highly soluble in both the aqueous phase and organic aerosols (Picquet-Varrault et al, 2020) and are thus capable of strongly partitioning into the atmospheric condensed phases (droplets, aerosols). Recent field observations of the aerosol chemical composition have shown that organic nitrates range from 10 % to 75 % of total organic aerosol (OA) mass (Kiendler-Scharr et al, 2016;Lee et al, 2016;Xu et al, 2015), suggesting that these species are important components of OAs.…”
Abstract. Biogenic volatile organic compounds (BVOCs) are intensely
emitted by forests and crops into the atmosphere. During the night, they
react very rapidly with the nitrate radical (NO3), leading to the
formation of a variety of functionalized products including organic nitrates
and to large amounts of secondary organic aerosols (SOAs). Organic nitrates
(ONs) have been shown not only to play a key role in the transport of reactive
nitrogen and consequently in the ozone budget but also to be important
components of the total organic-aerosol mass, while SOAs are known to play a direct
and indirect role in the climate. However, the reactivity of BVOCs with
NO3 remains poorly studied. The aim of this work is to provide new
kinetic and mechanistic data for two monoterpenes (C10H16),
α- and γ-terpinene, through experiments in simulation
chambers. These two compounds, which have very similar chemical structures,
have been chosen in order not only to overcome the lack of experimental data but also to
highlight the influence of the chemical structure on the reactivity. Rate constants have been measured using both relative and absolute methods.
They were found to be (1.2±0.5)×10-10 and (2.9±1.1)×10-11 cm3 molecule−1 s−1 for α- and γ-terpinene respectively. Mechanistic studies have
also been conducted in order to identify and quantify the main reaction
products. Total organic nitrate and SOA yields have been determined. While
organic nitrate formation yields appear to be similar, SOA yields exhibit
large differences with γ-terpinene being a much more efficient
precursor of aerosols. In order to provide explanations for this difference, chemical analysis of the gas-phase products was performed at the molecular scale. Detected products allowed for proposing chemical mechanisms and providing explanations through peroxy and alkoxy reaction pathways.
“…It is also expected that organic nitrates adsorb on the stainlesssteel walls. Indeed, the loss rates of several multifunctional organic nitrates (in particular carbonyl nitrates) have been observed in previous studies (Suarez-Bertoa et al, 2012;Picquet-Varrault et al, 2020) and were found to range between 0.5 and 2 × 10 −5 s −1 . However, as yields of organic nitrates in the gas phase were calculated during a relatively short period (less than 1 h), these wall losses are expected to be low (less than 10 %), and this is confirmed by the good linearity of the plots.…”
Section: Organic Nitrate Yieldssupporting
confidence: 57%
“…Since the early 1980s and the discovery of the nitrate radical (NO 3 ) in the nocturnal troposphere (Noxon et al, 1980;Platt et al, 1980) and stratosphere (Naudet et al, 1981;Noxon et al, 1978), nighttime chemistry has been known to be active. NO 3 is mainly formed by the reaction of nitrogen dioxide (NO 2 ) with ozone and has two very efficient sinks during the day, its photolysis and its reaction with NO (Brown and Stutz, 2012).…”
Section: Introductionmentioning
confidence: 99%
“…They therefore significantly influence the nitrogenous species (NO y ) and ozone budgets in these regions (Ito et al, 2007). Furthermore, some (multifunctional) organic nitrates are low-volatile and highly soluble in both the aqueous phase and organic aerosols (Picquet-Varrault et al, 2020) and are thus capable of strongly partitioning into the atmospheric condensed phases (droplets, aerosols). Recent field observations of the aerosol chemical composition have shown that organic nitrates range from 10 % to 75 % of total organic aerosol (OA) mass (Kiendler-Scharr et al, 2016;Lee et al, 2016;Xu et al, 2015), suggesting that these species are important components of OAs.…”
Abstract. Biogenic volatile organic compounds (BVOCs) are intensely
emitted by forests and crops into the atmosphere. During the night, they
react very rapidly with the nitrate radical (NO3), leading to the
formation of a variety of functionalized products including organic nitrates
and to large amounts of secondary organic aerosols (SOAs). Organic nitrates
(ONs) have been shown not only to play a key role in the transport of reactive
nitrogen and consequently in the ozone budget but also to be important
components of the total organic-aerosol mass, while SOAs are known to play a direct
and indirect role in the climate. However, the reactivity of BVOCs with
NO3 remains poorly studied. The aim of this work is to provide new
kinetic and mechanistic data for two monoterpenes (C10H16),
α- and γ-terpinene, through experiments in simulation
chambers. These two compounds, which have very similar chemical structures,
have been chosen in order not only to overcome the lack of experimental data but also to
highlight the influence of the chemical structure on the reactivity. Rate constants have been measured using both relative and absolute methods.
They were found to be (1.2±0.5)×10-10 and (2.9±1.1)×10-11 cm3 molecule−1 s−1 for α- and γ-terpinene respectively. Mechanistic studies have
also been conducted in order to identify and quantify the main reaction
products. Total organic nitrate and SOA yields have been determined. While
organic nitrate formation yields appear to be similar, SOA yields exhibit
large differences with γ-terpinene being a much more efficient
precursor of aerosols. In order to provide explanations for this difference, chemical analysis of the gas-phase products was performed at the molecular scale. Detected products allowed for proposing chemical mechanisms and providing explanations through peroxy and alkoxy reaction pathways.
“…We used the developed SAR to predict the kOH rate constants of other atmospherically relevant organic nitrates to evaluate if the aqueous-phase •OH-oxidation has a significant role on their atmospheric lifetimes. Some of the evaluated organic nitrates have been detected in field campaigns (Beaver et al, 2012;Li et al, 2018); they are expected products from isoprene or monoterpenes photooxidation (Lee et al, 2014); or they are small polyfunctional nitrates that may be formed by the fragmentation of terpene nitrates or by the oxidation of alkyl nitrates (Picquet-Varrault et al, 2020;Treves and Rudich, 2003). Selecting organic nitrates potentially relevant to atmospheric chemistry, as well as those mentioned in the literature, we listed 49 compounds that were divided into 7 categories depending on their functionalization and chemical structure: 6 alkyl nitrates, 7 hydroxy nitrates, 7 ketonitrates, 5 aldehyde nitrates, 5 nitrooxy carboxylic acids, 7 other polyfunctional nitrates containing more than one oxygenated group, and 12 terpene nitrates corresponding to highly oxidized organic nitrates formed by the oxidation of terpenes, such as α-and β-pinene, limonene and myrcene.…”
Section: Atmospheric Implicationsmentioning
confidence: 99%
“…The gas-phase chemistry of organic nitrates has been studied through kinetic experiments focusing on their •OH-oxidation (Bedjanian et al, 2018;Picquet-Varrault et al, 2020;Treves and Rudich, 2003;Wängberg et al, 1996;Zhu et al, 1991) and direct photolysis (Clemitshaw et al, 1997;Picquet-Varrault et al, 2020;Suarez-Bertoa et al, 2012). These experiments provide data for different types of organic nitrates, including alkyl nitrates, ketonitrates, hydroxy nitrates, dinitrates, cyclonitrates and alkene nitrates, and provide knowledge on their gas-phase atmospheric fate.…”
Abstract. Organic nitrates are secondary species in the atmosphere. Their fate is related to the chemical transport of pollutants from polluted areas to more distant zones. While their gas-phase chemistry has been studied, their reactivity in condensed phases is far from being understood. However, these compounds represent an important fraction of organic matter in condensed phases. In particular, their partition to the aqueous-phase may be especially important for oxidized organic nitrates for which water solubility increase with functionalization. This work has studied for the first time the aqueous-phase ·OH-oxidation kinetics of 5 alkyl nitrates (isopropyl nitrate, isobutyl nitrate, 1-pentyl nitrate, isopentyl nitrate and 2-ethylhexyl nitrate) and 3 functionalized organic nitrates (α-nitrooxyacetone, 1-nitrooxy-2-propanol and isosorbide 5-mononitrate) by developing a novel and accurate competition kinetic method. Low reactivity was confirmed, with kOH (at 296 ± 2 K) ranging from 8·107 to 2.5·109 L mol−1 s−1. Using these results, the previously developed aqueous-phase Structure Activity Relationship (SAR) was extended, and the resulting parameters confirmed the extreme deactivating effect of the nitrate group, up to two adjacent carbon atoms. The achieved extended SAR was then used to determine the ·OH-oxidation rate constants of 49 organic nitrates, including hydroxy nitrates, ketonitrates, aldehyde nitrates, nitrooxy carboxylic acids and more functionalized organic nitrates such as isoprene and terpene nitrates. Their multiphase atmospheric lifetimes towards ·OH-oxidation were calculated using these rate constants, and compared to their gas-phase lifetimes. Large differences were observed, especially for polyfunctional organic nitrates: for 50 % of the proposed organic nitrates for which ·OH-reaction occurs mainly in the aqueous-phase (more than 50 % of the overall removal) their ·OH-oxidation lifetimes increased by 20 % to 155 % under cloud/fog conditions (LWC = 0.35 g m−3). In particular, for 83 % of the proposed terpene nitrates, the reactivity towards ·OH occurred mostly (> 98 %) in the aqueous-phase while for 60 % of these terpene nitrates their lifetimes increased by 25 % to 140 % compared to their gas-phase reactivity. We demonstrate that these effects are of importance under cloud/fog conditions, but also under wet aerosol conditions, especially for the terpene nitrates. These results suggest that taking into account aqueous-phase ·OH-oxidation reactivity of biogenic nitrates is necessary to improve the predictions of their atmospheric fate.
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