Formation mechanisms of atmospheric nitrate and sulfate during the winter haze pollution periods in Beijing: gas-phase, heterogeneous and aqueous-phase chemistry

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(7), P. 4153 - 4165

Published: April 7, 2020

Abstract. A vast area in China is currently going through severe haze episodes with drastically elevated concentrations of PM2.5 winter. Nitrate and sulfate are the main constituents PM2.5, but their formations via NO2 SO2 oxidation still not comprehensively understood, especially under different pollution or atmospheric relative humidity (RH) conditions. To elucidate formation pathways nitrate polluted cases, hourly samples were collected continuously Beijing during wintertime 2016. Three serious cases identified reasonably sampling period, secondary found to make a dominant contribution relatively high RH condition. The significant correlation between NOR, NOR = NO3-/(NO3-+NO2), [NO2]2 × [O3] nighttime RH≥60 % condition indicated that heterogeneous hydrolysis N2O5 involving aerosol liquid water was responsible for nocturnal at extremely levels. more often coincident trend [HONO] [DR] (direct radiation) [NO2] compared its occurrence [Dust] daytime 30 < 60 provided convincing evidence gas-phase reaction OH played pivotal role diurnal moderate mean values SOR, SOR SO42-/(SO42-+SO2), whole day could be ascribed evident aqueous-phase episodes. Based on parameters measured this study known production rate calculation method, pathway H2O2 rather than contribute greatly sulfate.

Language: Английский

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The formation of nitro-aromatic compounds under high NO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; and anthropogenic VOC conditions in urban Beijing, China

Atmospheric chemistry and physics, Journal Year: 2019, Volume and Issue: 19(11), P. 7649 - 7665

Published: June 7, 2019

Abstract. Nitro-aromatic compounds (NACs), as important contributors to the light absorption by brown carbon, have been widely observed in various ambient atmospheres; however, their formation urban atmosphere was little studied. In this work, we report an intensive field study of NACs summer 2016 at Beijing site, characterized both high-NOx and anthropogenic VOC dominated conditions. We investigated factors that influence NAC (e.g., NO2, precursors, RH photolysis) through quantification eight NACs, along with major components fine particulate matter, selected volatile organic compounds, gases. The average total concentration quantified 6.63 ng m−3, higher than those reported other summertime studies (0.14–6.44 m−3). 4-Nitrophenol (4NP, 32.4 %) 4-nitrocatechol (4NC, 28.5 were top two most abundant followed methyl-nitrocatechol (MNC), methyl-nitrophenol (MNP), dimethyl-nitrophenol (DMNP). oxidation toluene benzene presence NOx found be a more dominant source primary biomass burning emissions. NO2 level factor influencing secondary NACs. A transition from low- regimes coincided shift organic- inorganic-dominated products. thresholds ∼ 20 ppb for daytime NO2∼25 nighttime Under low-NOx conditions, increased while NO3- concentrations (NO3-)/NACs ratios lower, implying organic-dominated did not further increase showed increasing trends, signaling Nighttime enhancements 3M4NC 4M5NC, noted 4NP, 2M4NP, DMNP, indicating different pathways these groups Our analysis suggested aqueous-phase likely pathway 4M5NC 3M5NC, photo-oxidation could nitrophenol its derivatives. Using (3M4NC+4M5NC) ∕ 4NP indicator relative contribution gas-phase formation, elevated remained constant > 30 %. also precursors benzene) aerosol surface area acted promoting photolysis loss nitrophenols.

Language: Английский

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Field Determination of Nitrate Formation Pathway in Winter Beijing

Environmental Science & Technology, Journal Year: 2020, Volume and Issue: 54(15), P. 9243 - 9253

Published: June 26, 2020

Particulate nitrate (pNO3–) has often been found to be the major component of fine particles in urban air-sheds China, United States, and Europe during winter haze episodes recent years. However, there is a lack knowledge regarding experimentally determined contribution different chemical pathways formation pNO3–. Here, for first time, we combine ground tall-tower observations quantify pNO3– using observationally constrained model approach based on direct OH N2O5 air-shed. We find that gas-phase oxidation pathway (OH+NO2) daytime dominant channel over nocturnal uptake pollution episodes, with percentages 74% areas 76% suburban areas. This quite from previous studies some regions US, which was concluded account larger winter. These results indicate driving factor Beijing US different, as are mitigation strategies particulate nitrate.

Language: Английский

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Photochemical Aqueous-Phase Reactions Induce Rapid Daytime Formation of Oxygenated Organic Aerosol on the North China Plain

Environmental Science & Technology, Journal Year: 2020, Volume and Issue: 54(7), P. 3849 - 3860

Published: March 4, 2020

Secondary organic aerosol (SOA) constitutes a large fraction of worldwide, however, the formation mechanisms in polluted environments remain poorly understood. Here we observed fast daytime growth oxygenated (OOA) (with rates up to 10 μg m–3 h–1) during low relative humidity (RH, average 38 ± 19%), high RH (53 and fog periods (77 13%, occurring nighttime with reaching 100%). Evidence showed that photochemical aqueous-phase SOA (aqSOA) dominantly contributed OOA fog, while both aqSOA gas-phase (gasSOA) were important other former contributing more under latter conditions, respectively. Compared production, dark was only period negligibly increase concentrations due scavenging processes. The rapid aging, as indicated by decrease m,p-xylene/ethylbenzene ratios, promoted precursors for formation, e.g., carbonyls such methylglyoxal. Photooxidants related OH radical H2O2 also bear features even solar radiative conditions. simultaneous increases ultraviolet radiation, photooxidant, precursor levels worked together promote formation. We found biomass burning emissions can adding photooxidants precursors. Therefore, future mitigation air pollution environment would benefit from stricter control on especially

Language: Английский

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The formation and mitigation of nitrate pollution: comparison between urban and suburban environments

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(7), P. 4539 - 4556

Published: April 8, 2022

Abstract. Ambient nitrate has been of increasing concern in PM2.5, while there are still large uncertainties quantifying the formation aerosol. The pathways aerosol at an urban site and a suburban Pearl River Delta (PRD) investigated using observation-constrained box model. Throughout campaigns, pollution episodes were constantly accompanied with increase concentrations fractions both sites. simulations demonstrate that chemical reactions daytime night contributed significantly to boundary layer two However, nighttime predominantly occurred aloft residual site, downward transport from morning is important source (53 %) for surface whereas similar amounts produced nocturnal which results little ground site. We show was volatile-organic-compound-limited (VOC-limited) regime transition identical response ozone reduction VOC emissions can be efficient approach mitigate areas through influencing hydroxyl radical (OH) N2O5 production, will also beneficial synergistic control regional pollution. highlight relative importance site-specific, quantitative understanding various provide insights developing mitigation strategies.

Language: Английский

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Fast particulate nitrate formation via N&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; uptake aloft in winter in Beijing

Atmospheric chemistry and physics, Journal Year: 2018, Volume and Issue: 18(14), P. 10483 - 10495

Published: July 23, 2018

Abstract. Particulate nitrate (pNO3-) is an important component of secondary aerosols in urban areas. Therefore, it critical to explore its formation mechanism assist with the planning haze abatement strategies. Here we report vertical measurements NOx and O3 by situ instruments on a movable carriage tower during winter heavy-haze episode (18 20 December 2016) Beijing, China. Based box model simulation at different heights, found that pNO3- via N2O5 heterogeneous uptake was negligible ground level due concentrations near zero controlled high NO emissions concentration. In contrast, contribution from large altitudes (e.g., > 150 m), which supported lower total oxidant (NO2 + O3) than level. Modeling results show specific case nighttime integrated production for high-altitude air mass above Beijing estimated be 50 µg m−3 enhanced surface-layer next morning 28 through mixing. Sensitivity tests suggested nocturnal loss NO3–N2O5 chemistry maximized once coefficient over 2 × 10−3 polluted days Sa 3000 µm2 cm−3 wintertime. The study provided chance highlight fact hydrolysis may source particulate airshed

Language: Английский

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The secondary formation of organosulfates under interactions between biogenic emissions and anthropogenic pollutants in summer in Beijing

Atmospheric chemistry and physics, Journal Year: 2018, Volume and Issue: 18(14), P. 10693 - 10713

Published: July 26, 2018

Abstract. Organosulfates (OSs) with ambiguous formation mechanisms are a potential source of missing secondary organic aerosol (SOA) in current atmospheric models. In this study, we chemically characterized OSs and nitrooxy-OSs (NOSs) formed under the influence biogenic emissions anthropogenic pollutants (e.g., NOx, SO42−) summer Beijing. An ultrahigh-resolution mass spectrometer equipped an electrospray ionization was applied to examine overall molecular composition S-containing organics. The number intensities organics, majority which could be assigned as NOSs, increased significantly during pollution episodes, indicated their importance for SOA accumulation. To further investigate distribution high-performance liquid chromatography coupled spectrometry employed quantify 10 3 NOS species. total concentrations quantified NOSs were 41.4 13.8 ng m−3, respectively. Glycolic acid sulfate most abundant species among all species, followed by monoterpene (C10H16NO7S−). concentration three isoprene 14.8 m−3 via HO2 channel higher than those NO ∕ NO2 channel. OS coincided increase acidic aerosols, acidity, water content (LWC), indicating acid-catalyzed aqueous-phase presence aerosols. When dominated accumulation inorganic aerosols (SIAs; sulfate, nitrate, ammonium; SO42− SIA > 0.5), would obviously promoted increasing LWC, acidity (pH < 2.8). Otherwise, limited lower when nitrate nighttime enhancement suggested NO3-initiated oxidation high-NOx conditions. However, presumed form chemistry or reactive uptake products isoprene. This study provides direct observational evidence highlights interaction between precursors (NOx, SO2, SO42−). results imply that future reduction can help reduce burden Beijing other areas impacted both pollutants.

Language: Английский

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Nitrate formation from heterogeneous uptake of dinitrogen pentoxide during a severe winter haze in southern China

Atmospheric chemistry and physics, Journal Year: 2018, Volume and Issue: 18(23), P. 17515 - 17527

Published: Dec. 11, 2018

Abstract. Nitrate (NO3-) has become a major component of fine particulate matter (PM2.5) during hazy days in China. However, the role heterogeneous reactions dinitrogen pentoxide (N2O5) nitrate formation is not well constrained. In January 2017, severe haze event occurred Pearl River Delta (PRD) southern China which high levels PM2.5 (∼400 µg m−3) and O3 (∼160 ppbv) were observed at semi-rural site (Heshan) western PRD. concentrations reached 108 m−3 (1 h time resolution), contribution to was nearly 40 %. Concurrent increases NO3- ClNO2 (with maximum value 8.3 ppbv 1 min resolution) first several hours after sunset, indicating an intense N2O5 uptake by aerosols. The potential via estimated be between 29.0 77.3 early (2 6 h) sunset based on measurement data, could completely explain measured increase concentration same period. Daytime production nitric acid from gas-phase reaction OH+NO2 calculated with chemical box model built using Master Chemical Mechanism (MCM v3.3.1) constrained data. integrated nocturnal formed chemistry comparable or even higher than day. This study confirms that significant source aerosol

Language: Английский

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Heterogeneous N&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; uptake coefficient and production yield of ClNO&lt;sub&gt;2&lt;/sub&gt; in polluted northern China: roles of aerosol water content and chemical composition

Atmospheric chemistry and physics, Journal Year: 2018, Volume and Issue: 18(17), P. 13155 - 13171

Published: Sept. 12, 2018

Abstract. Heterogeneous uptake of dinitrogen pentoxide (N2O5) and production nitryl chloride (ClNO2) are important nocturnal atmospheric processes that have significant implications for the secondary pollutants. However, understanding N2O5 ClNO2 remains limited, especially in China. This study presents a field investigation heterogeneous coefficient (γ(N2O5)) yield (ϕ) polluted area northern China during summer 2014. The were estimated by using simultaneously measured total nitrate 10 selected cases, which concurrent increases concentrations relatively stable environmental conditions. determined γ(N2O5) ϕ values varied greatly, with an average 0.022 (±0.012, standard deviation) 0.34 (±0.28, deviation). variations could not be fully explained previously derived parameterizations consider nitrate, chloride, organic coating. was found to strong positive dependence on relative humidity aerosol water content. result suggests Wangdu is governed mainly amount aerosol, strongly different from most observations US Europe. parameterization also overestimated comparing observation. observation-derived showed decreasing trend increasing ratio acetonitrile carbon monoxide, indicator biomass burning emissions, possible suppressive effect plumes influenced this region. findings illustrate need improve our parameterize key factors accurately assess photochemical haze pollution.

Language: Английский

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Atmospheric Δ&lt;sup&gt;17&lt;/sup&gt;O(NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt;) reveals nocturnal chemistry dominates nitrate production in Beijing haze

Atmospheric chemistry and physics, Journal Year: 2018, Volume and Issue: 18(19), P. 14465 - 14476

Published: Oct. 10, 2018

Abstract. The rapid mass increase of atmospheric nitrate is a critical driving force for the occurrence fine-particle pollution (referred to as haze hereafter) in Beijing. However, exact mechanisms this have not been well constrained from field observations. Here we present first observations oxygen-17 excess (Δ17O(NO3-)) collected Beijing reveal relative importance different formation pathways, and also simultaneously observed δ15N(NO3-). During our sampling period, 12 h averaged concentrations PM2.5 varied 16 323 µg m−3 with mean (141±88(1SD)) m−3, ranging 0.3 106.7 m−3. Δ17O(NO3-) ranged 27.5 ‰ 33.9 (30.6±1.8) ‰, while δ15N(NO3-) −2.5 19.2 (7.4±6.8) ‰. Δ17O(NO3-)-constrained calculations suggest nocturnal pathways (N2O5+H2O/Cl- NO3+HC) dominated production during polluted days (PM2.5≥75 m−3), possible fraction 56–97 %. Our results illustrate potentiality Δ17O tracing pathways; future modeling work constraint isotope data reported here may further improve understanding nitrogen cycle haze.

Language: Английский

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