Persistent Heavy Winter Nitrate Pollution Driven by Increased Photochemical Oxidants in Northern China

Environmental Science & Technology, Journal Year: 2020, Volume and Issue: 54(7), P. 3881 - 3889

Published: March 3, 2020

Nitrate is an increasingly important component of fine particulate matter (PM2.5) during winter in northern China. Past emission control has been ineffective reducing nitrate. Here, we use extensive observations and a model with state-of-the-art nitrogen chemistry to identify the key factors that nitrate formation heavily polluted North China Plain (NCP). In contrast previous view weak photochemistry, show O3 OH productions are sufficiently high facilitate fast gas-phase heterogeneous conversion NOX over NCP. Increasing from higher precursor levels ROX cycling accelerate generation heavy pollution. We find 31.8% reduction emissions 2010 2017 NCP lowers surface by only 0.2% even increases some areas. This mainly due increase (by ∼30%), which subsequently increased efficiency HNO3 38.7%). Future strategies for haze should also aim lower photochemical oxidants, via larger synchronized VOCs reduction, overcome effects nonlinear photochemistry aerosol chemical feedback.

Language: Английский

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Control of particulate nitrate air pollution in China

Nature Geoscience, Journal Year: 2021, Volume and Issue: 14(6), P. 389 - 395

Published: April 26, 2021

Language: Английский

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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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Explosive Secondary Aerosol Formation during Severe Haze in the North China Plain

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(4), P. 2189 - 2207

Published: Feb. 4, 2021

Severe haze events with exceedingly high-levels of fine aerosols occur frequently over the past decades in North China Plain (NCP), exerting profound impacts on human health, weather, and climate. The development effective mitigation policies requires a comprehensive understanding formation mechanisms, including identification quantification sources, formation, transformation aerosol species. Haze evolution this region exhibits distinct physical chemical characteristics from clean to polluted periods, as evident increasing stagnation relative humidity, but decreasing solar radiation well explosive secondary formation. latter is attributed highly elevated concentrations precursor gases reflected by rapid increases particle number mass concentrations, both corresponding nonequilibrium processes. Considerable new knowledge has been acquired understand processes regulating particularly light progress elucidating mechanisms. This review synthesizes recent advances highlighting several critical chemical/physical processes, that is, growth driven photochemistry aqueous chemistry interaction between atmospheric stability. Current challenges future research priorities are also discussed.

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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Interaction Between Planetary Boundary Layer and PM2.5 Pollution in Megacities in China: a Review

Current Pollution Reports, Journal Year: 2019, Volume and Issue: 5(4), P. 261 - 271

Published: Sept. 9, 2019

Abstract Purpose of Review During the past decades, number and size megacities have been growing dramatically in China. Most Chinese are suffering from heavy PM 2.5 pollution. In pollution formation, planetary boundary layer (PBL) plays an important role. This review is aimed at presenting current state understanding PBL-PM interaction megacities, as well to identify main gaps knowledge further research needs. Recent Findings The PBL critical formation urban multiple temporal scales, ranging diurnal change seasonal variation. For essential structure/process pollution, coastal different concerns mountainous or land-locked megacities. cities, recirculation induced by sea-land breeze can accumulate pollutants, whereas valley/basin, blocking effects terrains lead stagnant conditions thermal inversion. Within a megacity, although urbanization-induced land use cause thermodynamic perturbations facilitate development PBL, increases emissions outweigh this impact, resulting net increase aerosol concentration. Moreover, radiative modify heating upper layers reducing surface heat flux, suppressing exacerbating Summary presented 13 with various geographic elucidated influencing processes. To understand complicated interactions, long-term observations meteorology properties multi-layers need be implemented.

Language: Английский

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Air pollution scenario over Pakistan: Characterization and ranking of extremely polluted cities using long-term concentrations of aerosols and trace gases

Remote Sensing of Environment, Journal Year: 2021, Volume and Issue: 264, P. 112617 - 112617

Published: July 27, 2021

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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Introduction to the special issue “In-depth study of air pollution sources and processes within Beijing and its surrounding region (APHH-Beijing)”

Atmospheric chemistry and physics, Journal Year: 2019, Volume and Issue: 19(11), P. 7519 - 7546

Published: June 5, 2019

Abstract. The Atmospheric Pollution and Human Health in a Chinese Megacity (APHH-Beijing) programme is an international collaborative project focusing on understanding the sources, processes health effects of air pollution Beijing megacity. APHH-Beijing brings together leading China UK research groups, state-of-the-art infrastructure quality models to work four themes: (1) sources emissions pollutants; (2) atmospheric affecting urban pollution; (3) exposure impacts; (4) interventions solutions. Themes 1 2 are closely integrated support Theme 3, while 1–3 provide scientific data for 4 develop cost-effective mitigation This paper provides introduction (i) rationale (ii) measurement modelling activities performed as part it. In addition, this introduces meteorology conditions during two joint intensive field campaigns – core integration activity APHH-Beijing. coordinated provided observations chemistry physics at sites: Institute Physics central Pinggu rural 10 November–10 December 2016 (winter) 21 May–22 June 2017 (summer). were complemented by numerical automatic low-cost sensor summary, background information sets scene more focused papers addressing specific aspects, Beijing.

Language: Английский

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An Odd Oxygen Framework for Wintertime Ammonium Nitrate Aerosol Pollution in Urban Areas: NO_x and VOC Control as Mitigation Strategies

Geophysical Research Letters, Journal Year: 2019, Volume and Issue: 46(9), P. 4971 - 4979

Published: April 8, 2019

Abstract Wintertime ammonium nitrate aerosol pollution is a severe air quality issue affecting both developed and rapidly urbanizing regions from Europe to East Asia. In the United States, it acute in western basins subject inversions that confine pollutants near surface. Measurements modeling of wintertime episode Salt Lake Valley, Utah, demonstrate closely related photochemical ozone through common parameter, total odd oxygen, O x,total . We show traditional nitrogen oxide volatile organic compound (NOx‐VOC) framework for evaluating mitigation strategies also applies nitrate. Despite being nitrate‐limited, Valley responsive VOCs control and, counterintuitively, not initially NO x control. simultaneous limitation saturation suggest this phenomenon may be general. This finding identify an unrecognized strategy address global public health with winter pollution.

Language: Английский

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