Severe haze in northern China: A synergy of anthropogenic emissions and atmospheric processes

Proceedings of the National Academy of Sciences, Journal Year: 2019, Volume and Issue: 116(18), P. 8657 - 8666

Published: April 15, 2019

Significance Severe haze events with large temporal/spatial coverages have occurred frequently in wintertime northern China. These extremes result from a complex interplay between emissions and atmospheric processes provide unique scientific platform to gain insights into many aspects of the relevant chemistry physics. Here we synthesize recent progress understanding severe formation In particular, highlight that improved emission sources, physical/chemical during evolution, interactions meteorological/climatic changes are necessary unravel causes, mechanisms, trends for pollution. This viewpoint established on basis sound science is critical improving prediction/forecast, formulating effective regulatory policies by decision makers, raising public awareness environmental protection.

Language: Английский

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Changes in Aerosol Chemistry From 2014 to 2016 in Winter in Beijing: Insights From High‐Resolution Aerosol Mass Spectrometry

Journal of Geophysical Research Atmospheres, Journal Year: 2018, Volume and Issue: 124(2), P. 1132 - 1147

Published: Dec. 22, 2018

Abstract Air quality has been continuously improved in recent years Beijing, yet severe haze episodes still frequently occur winter. Here we deployed an Aerodyne high‐resolution aerosol mass spectrometer two winter seasons during the same period to investigate changes chemistry from 2014 2016 Beijing. Compared 2014, submicron (PM 1 ) species showed ubiquitous increases concentrations by 10–130% 2016, of which nitrate largest increase among all leading a much higher NO 3 /SO 4 ratio (1.36 ± 0.90) than (0.72 0.59). This result highlights increasing role particulate matter pollution Aerosol composition and size distributions also changed significantly. Secondary inorganic elevated contributions ~10% associated with corresponding decreases organic (OA). Positive matrix factorization OA illustrated significant both primary emissions secondary production. While cooking decreased substantially 25% 15% contribution biomass burning slightly increased instead. Although contributed similarly winters (49% vs. 53%), observed (~50%) photochemically related oxygenated oxidized OA, oxygen‐to‐carbon ratios indicating enhanced photochemical production 2016. Aqueous‐phase however was relatively similar winters. Further analysis demonstrated that varied differently across different relative humidity levels.

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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Nitrate-driven urban haze pollution during summertime over the North China Plain

Atmospheric chemistry and physics, Journal Year: 2018, Volume and Issue: 18(8), P. 5293 - 5306

Published: April 19, 2018

Abstract. Compared to the severe winter haze episodes in North China Plain (NCP), pollution during summertime has drawn little public attention. In this study, we present highly time-resolved chemical composition of submicron particles (PM1) measured Beijing and Xinxiang NCP region evaluate driving factors aerosol pollution. During campaign periods (30 June 27 July 2015, for 8 25 2017, Xinxiang), average PM1 concentrations were 35.0 64.2 µg m−3 Xinxiang. Pollution characterized with largely enhanced nitrate observed at both sites. contrast slightly decreased mass fractions sulfate, semivolatile oxygenated organic (SV-OOA), low-volatility (LV-OOA) PM1, displayed a significantly contribution aggravation pollution, highlighting importance formation as force evolution summer. Rapid production mainly occurred after midnight, higher rate than that SV-OOA, or LV-OOA. Based on observation measurements thermodynamic modeling, high ammonia emissions favored Nighttime through heterogeneous hydrolysis dinitrogen pentoxide (N2O5) development addition, air masses from surrounding polluted areas led more production. Finally, atmospheric particulate data acquired by spectrometric techniques various field campaigns Asia, Europe, America uncovered concentration fraction China. Although different years demonstrate decline recent years, still remains high. To effectively alleviate matter summer, our results suggest an urgent need initiate emission control measures further reduce nitrogen oxide over region.

Language: Английский

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Mutual promotion between aerosol particle liquid water and particulate nitrate enhancement leads to severe nitrate-dominated particulate matter pollution and low visibility

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(4), P. 2161 - 2175

Published: Feb. 26, 2020

Abstract. As has been the case in North America and western Europe, SO2 emissions have substantially reduced China Plain (NCP) recent years. Differential rates of reduction NOx concentrations result frequent occurrence particulate matter pollution dominated by nitrate (pNO3-) over NCP. In this study, we observed a polluted episode with mass fraction nonrefractory PM1 (NR-PM1) being up to 44 % during wintertime Beijing. Based on typical pNO3--dominated haze event, linkage between aerosol water uptake pNO3- enhancement, further impacting visibility degradation, investigated based field observations theoretical calculations. During development, as ambient relative humidity (RH) increased from ∼10 70 %, particle liquid ∼1 µg m−3 at beginning ∼75 fully developed period. The surface area volume, enhancing condensational loss N2O5 particles. From haze, factor 20 when only considering volume dry particles, while increasing 25 extra due uptake. Furthermore, favored thermodynamic equilibrium HNO3 phase under supersaturated NH3 atmosphere. All above results demonstrated that is enhanced elevated RH turn facilitating take-up hygroscopicity salt. Such mutual promotion enhancement can rapidly degrade air quality halve within 1 d. Reduction nitrogen-containing gaseous precursors, e.g., control traffic emissions, essential mitigating severe events

Language: Английский

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A review of aerosol chemistry in Asia: insights from aerosol mass spectrometer measurements

Environmental Science Processes & Impacts, Journal Year: 2020, Volume and Issue: 22(8), P. 1616 - 1653

Published: Jan. 1, 2020

Aerosol mass spectrometer has been widely deployed in Asia for real-time characterization of aerosol chemistry, and significantly improved our understanding the sources, properties, formation processes aerosols a complex environment.

Language: Английский

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The underlying mechanisms of PM2.5 and O3 synergistic pollution in East China: Photochemical and heterogeneous interactions

The Science of The Total Environment, Journal Year: 2023, Volume and Issue: 873, P. 162434 - 162434

Published: Feb. 24, 2023

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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Nitrate-dominated PM&lt;sub&gt;2.5&lt;/sub&gt; and elevation of particle pH observed in urban Beijing during the winter of 2017

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(8), P. 5019 - 5033

Published: April 28, 2020

Abstract. The Chinese government has exerted strict emission controls to mitigate air pollution since 2013, which resulted in significant decreases the concentrations of pollutants such as SO2. Strict control actions also reduced average PM2.5 concentration low level 39.7 µg m−3 urban Beijing during winter 2017. To investigate impact changes on physiochemical properties atmospheric aerosols China, we conducted a comprehensive observation focusing Compared with historical record (2014–2017), SO2 decreased 3.2 ppbv 2017, but NO2 was still high (21.4 2017). Accordingly, contribution nitrate (23.0 m−3) far exceeded that sulfate (13.1 episodes, resulting increase nitrate-to-sulfate molar ratio. thermodynamic model (ISORROPIA II) calculation results showed episodes particle pH increased from 4.4 (moderate acidic) 5.4 (more neutralized) when ratio 1 5, indicating were more neutralized content elevated. Controlled variable tests elevation should be attributed fraction other than crustal ion and ammonia increases. Based sensitivity tests, future prediction for acidity change discussed. We found nitrate-rich particles at moderate humid conditions (RH: 20 %–50 %) can absorb twice amount water sulfate-rich can, higher levels have synergetic effects, rapidly elevating merely neutral (above 5.6). As haze events might occur frequently under abundant nitrate-dominated conditions, major chemical processes target re-evaluated obtain most effective strategy.

Language: Английский

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Characterization of black carbon-containing fine particles in Beijing during wintertime

Atmospheric chemistry and physics, Journal Year: 2019, Volume and Issue: 19(1), P. 447 - 458

Published: Jan. 11, 2019

Abstract. Refractory black carbon (BC) is a product of incomplete combustion fossil fuel, biomass and biofuel, etc. By mixing with other species, BC can play significant roles in climate change, visibility impairment human health. Such BC-containing particles densely populated megacities like Beijing may have specific sources properties that are important to haze formation air quality. In this work, we exclusively characterized the urban by using laser-only Aerodyne soot particle aerosol mass spectrometer (SP-AMS), as part Atmospheric Pollution &amp; Human Health (APHH) 2016 winter campaign. The average ratio coating core (RBC) was found be ∼5.0. Positive matrix factorization shows presence primary fuel biomass-burning organics (64 % total organics). Yet secondary including sulfate, nitrate oxygenated organic (OA) could impacts on particles, especially for ones larger sizes thicker coatings. Analyses diurnal cycles reveal afternoon photochemical production OA (SOA), well nighttime aqueous portion highly OA. Besides SOA, nitrate, not appeared important. Further investigations during different periods show that, average, more polluted would contributions from species thickly coated tended associate indicating role chemical aging pollution wintertime. However, individual events, (fossil coal emissions) also dominant role, revealed compositions two episodes sampling period.

Language: Английский

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