Variations in characteristics and transport pathways of PM2.5 during heavy pollution episodes in 2013–2019 in Jinan, a central city in the north China Plain

Abstract. Due to excessive anthropogenic emissions, heavy aerosol pollution episodes (HPEs) often occur during winter in the Beijing–Tianjin–Hebei (BTH) area of the North China Plain. Extensive observational studies have been carried out to understand the causes of HPEs; however, few measurements of vertical aerosol fluxes exist, despite them being the key to understanding vertical aerosol mixing, specifically during weak turbulence stages in HPEs. In the winter of 2016 and the spring of 2017 aerosol vertical mass fluxes were measured by combining large aperture scintillometer (LAS) observations, surface PM2.5 and PM10 mass concentrations, and meteorological observations, including temperature, relative humidity (RH), and visibility, at a rural site in Gucheng (GC), Hebei Province, and an urban site at the Chinese Academy of Meteorological Sciences (CAMS) in Beijing located 100 km to the northeast. These are based on the light propagation theory and surface-layer similarity theory. The near-ground aerosol mass flux was generally lower in winter than in spring and weaker in rural GC than in urban Beijing. This finding provides direct observational evidence for a weakened turbulence intensity and low vertical aerosol fluxes in winter and polluted areas such as GC. The HPEs included a transport stage (TS), an accumulative stage (AS), and a removal stage (RS). During the HPEs from 25 to 31 January 2017, in Beijing, the mean mass flux decreased by 51 % from 0.0049 mg m−2 s−1 in RSs to 0.0024 mg m−2 s−1 in the TSs. During the ASs, the mean mass flux decreased further to 0.00087 mg m−2 s−1, accounting for approximately one-third of the flux in the TSs. A similar reduction from the TSs to ASs was observed in the HPE from 16 to 22 December 2016 in GC. It can be seen that from the TS to the AS, the aerosol vertical turbulent flux decreased, but the aerosol particle concentration within the surface layer increased, and it is inferred that in addition to the contribution of regional transport from upwind areas during the TS, suppression of vertical turbulence mixing confining aerosols to a shallow boundary layer increased accumulation.

Download Full-text

Different roles of nitrate and sulfate in air pollution episodes in the North China Plain

Atmospheric Environment ◽

10.1016/j.atmosenv.2020.117325 ◽

2020 ◽

Vol 224 ◽

pp. 117325 ◽

Cited By ~ 5

Author(s):

Yinghong Wang ◽

Guiqian Tang ◽

Wei Zhao ◽

Yang Yang ◽

Lili Wang ◽

...

Keyword(s):

Air Pollution ◽

North China Plain ◽

North China ◽

The North ◽

The North China Plain ◽

Air Pollution Episodes ◽

Pollution Episodes

Download Full-text

Aerosol Vertical Mass Flux Measurements During Heavy Aerosol Pollution Episodes at a Rural Site and an Urban Site in the Beijing Area of the North China Plain

10.5194/acp-2018-1265 ◽

2019 ◽

Author(s):

Renmin Yuan ◽

Xiaoye Zhang ◽

Hao Liu ◽

Yu Gui ◽

Bohao Shao ◽

...

Keyword(s):

Mass Flux ◽

North China Plain ◽

North China ◽

Rural Site ◽

Urban Site ◽

The North ◽

The North China Plain ◽

Aerosol Pollution ◽

The Mean ◽

Pollution Episodes

Abstract. Due to excessive anthropogenic emissions, heavy aerosol pollution episodes (HPEs) often occur during winter in the Beijing-Tianjin-Hebei (BTH) area of the North China Plain. Extensive observational studies have been carried out to understand the causes of HPEs; however, few measurements of aerosol vertical fluxes exist, despite them being the key to understanding vertical aerosol mixing, specifically during weak turbulence stages in HPEs. In the winter of 2016 and the spring of 2017, based on the light propagation theory and surface-layer similarity theory, aerosol vertical mass fluxes were measured by combining large aperture scintillometer (LAS) observations, surface PM2.5 and PM10 mass concentrations, and meteorological observations, including temperature, relative humidity (RH), and visibility, at a rural site in Gucheng (GC), Hebei Province, and an urban site at the Chinese Academy of Meteorological Sciences (CAMS) in Beijing located 100 km to the northeast. The near-ground aerosol mass flux was generally lower in winter than in spring and weaker in rural GC than in urban Beijing. This finding provides direct observational evidence from the perspective of vertical aerosol fluxes for a weakened turbulence intensity in winter and in polluted areas such as GC. The HPEs included a transport stage (TS), an accumulative stage (AS), and a removal stage (RS). During the HPEs from January 25, 2017 to January 31, 2017, in Beijing, the mean mass flux decreased by 51 % from 0.0049 mg m−2 s−1 in RSs to 0.0024 mg m−2 s−1 in the TSs. During the ASs, the mean mass flux decreased further to 0.00087 mg m−2 s−1, accounting for approximately 1/3 of the flux in the TSs. A similar reduction from the TSs to ASs was observed in the HPE from December 16, 2016 to December 22, 2016 in GC. The weakened mass flux indicates that the already weak turbulence would be further weakened by aerosol pollution to a certain extent, which would further facilitate aerosol accumulation.

Download Full-text

Uplifting of carbon monoxide from biomass burning and anthropogenic sources to the free troposphere in East Asia

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-2843-2015 ◽

2015 ◽

Vol 15 (5) ◽

pp. 2843-2866 ◽

Cited By ~ 21

Author(s):

K. Ding ◽

J. Liu ◽

A. Ding ◽

Q. Liu ◽

T. L. Zhao ◽

...

Keyword(s):

East Asia ◽

Forest Fires ◽

North China Plain ◽

North China ◽

Anthropogenic Sources ◽

Free Troposphere ◽

Transport Pathways ◽

Upper Troposphere ◽

The North ◽

The North China Plain

Abstract. East Asia has experienced rapid development with increasing carbon monoxide (CO) emission in the past decades. Therefore, uplifting CO from the boundary layer to the free troposphere in East Asia can have great implications on regional air quality around the world. It can also influence global climate due to the longer lifetime of CO at higher altitudes. In this study, three cases of high CO episodes in the East China Sea and the Sea of Japan from 2003 to 2005 are examined with spaceborne Measurements of Pollution in the Troposphere (MOPITT) data, in combination with aircraft measurements from the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) program. High CO abundances of 300–550 ppbv are observed in MOZAIC data in the free troposphere during these episodes. These are among the highest CO abundances documented at these altitudes. On average, such episodes with CO over 400 ppbv (in the 2003 and 2004 cases) and between 200 and 300 ppbv (in the 2005 case) may occur 2–5 and 10–20% in time, respectively, in the respective altitudes over the region. Correspondingly, elevated CO is shown in MOPITT daytime data in the middle to upper troposphere in the 2003 case, in the lower to middle troposphere in the 2004 case, and in the upper troposphere in the 2005 case. Through analyses of the simulations from a chemical transport model GEOS-Chem and a trajectory dispersion model FLEXPART, we found different CO signatures in the elevated CO and distinct transport pathways and mechanisms for these cases. In the 2003 case, emissions from large forest fires near Lake Baikal dominated the elevated CO, which had been rapidly transported upward by a frontal system from the fire plumes. In the 2004 case, anthropogenic CO from the North China Plain experienced frontal lifting and mostly reached ~ 700 hPa near the East China Sea, while CO from biomass burning over Indochina experienced orographic lifting, lee-side-trough-induced convection, and frontal lifting through two separate transport pathways, leading to two distinct CO enhancements around 700 and 300 hPa. In the 2005 case, the observed CO of ~ 300 ppbv around 300 hPa originated from anthropogenic sources over the Sichuan Basin and the North China Plain and from forest fires over Indochina. The high CO was transported to such altitudes through strong frontal lifting, interacting with convection and orographic lifting. These cases show that topography affects vertical transport of CO in East Asia via different ways, including orographic uplifting over the Hengduan Mountains, assisting frontal lifting in the North China Plain, and facilitating convection in the Sichuan Basin. In particular, topography-induced lee-side troughs over Indochina led to strong convection that assisted CO uplifting to the upper troposphere. This study shows that the new daytime MOPITT near-infrared (NIR) and thermal-infrared (TIR) data (version 5 or above) have enhanced vertical sensitivity in the free troposphere and may help qualitative diagnosis of vertical transport processes in East Asia.

Download Full-text

Sensitivity of PM2.5 and O3 pollution episodes to meteorological factors over the North China Plain

The Science of The Total Environment ◽

10.1016/j.scitotenv.2021.148474 ◽

2021 ◽

pp. 148474

Author(s):

Simeng Ma ◽

Min Shao ◽

Yufen Zhang ◽

Qili Dai ◽

Mingjie Xie

Keyword(s):

North China Plain ◽

North China ◽

Meteorological Factors ◽

The North ◽

The North China Plain ◽

Pollution Episodes

Download Full-text

Aerosol transport pathways and source attribution in China during the COVID-19 outbreak

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-15431-2021 ◽

2021 ◽

Vol 21 (20) ◽

pp. 15431-15445

Author(s):

Lili Ren ◽

Yang Yang ◽

Hailong Wang ◽

Pinya Wang ◽

Lei Chen ◽

...

Keyword(s):

Air Quality ◽

North China Plain ◽

North China ◽

Eastern China ◽

Lower Troposphere ◽

Aerosol Transport ◽

Transport Pathways ◽

The North ◽

The North China Plain ◽

Local Emissions

Abstract. Due to the coronavirus disease 2019 (COVID-19) pandemic, human activities and industrial productions were strictly restricted during January–March 2020 in China. Despite the fact that anthropogenic aerosol emissions largely decreased, haze events still occurred. Characterization of aerosol transport pathways and attribution of aerosol sources from specific regions are beneficial to air quality and pandemic control strategies. This study establishes source–receptor relationships in various regions covering all of China during the COVID-19 outbreak based on the Community Atmosphere Model version 5 with Explicit Aerosol Source Tagging (CAM5-EAST). Our analysis shows that PM2.5 burden over the North China Plain between 30 January and 19 February is mostly contributed by local emissions (40 %–66 %). For other regions in China, PM2.5 burden is largely contributed from nonlocal sources. During the most polluted days of the COVID-19 outbreak, local emissions within the North China Plain and eastern China contributed 66 % and 87 % to the increase in surface PM2.5 concentrations, respectively. This is associated with the anomalous mid-tropospheric high pressure at the location of the climatological East Asia trough and the consequently weakened winds in the lower troposphere, leading to the local aerosol accumulation. The emissions outside China, especially those from South Asia and Southeast Asia, contribute over 50 % to the increase in PM2.5 concentration in southwestern China through transboundary transport during the most polluted day. As the reduction in emissions in the near future is desirable, aerosols from long-range transport and unfavorable meteorological conditions are increasingly important to regional air quality and need to be taken into account in clean-air plans.

Download Full-text

Intra-regional transport of black carbon between the south edge of the North China Plain and central China during winter haze episodes

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-4499-2019 ◽

2019 ◽

Vol 19 (7) ◽

pp. 4499-4516 ◽

Cited By ~ 20

Author(s):

Huang Zheng ◽

Shaofei Kong ◽

Fangqi Wu ◽

Yi Cheng ◽

Zhenzhen Niu ◽

...

Keyword(s):

North China Plain ◽

North China ◽

Fossil Fuel ◽

Central China ◽

The South ◽

The North ◽

The North China Plain ◽

Geographic Origins ◽

Regional Air Quality ◽

Pollution Episodes

Abstract. Black carbon (BC), which is formed from the incomplete combustion of fuel sources (mainly fossil fuel, biofuel and open biomass burning), is a chemically inert optical absorber in the atmosphere. It has significant impacts on global climate, regional air quality and human health. During transportation, its physical and chemical characteristics as well as its sources change dramatically. To investigate the properties of BC (i.e., mass concentration, sources and optical properties) during intra-regional transport between the southern edge of the North China Plain (SE-NCP) and central China (CC), simultaneous BC observations were conducted in a megacity (Wuhan – WH) in CC, in three borderline cities (Xiangyang – XY, Suixian – SX and Hong'an – HA; from west to east) between the SE-NCP and CC, and in a city (Luohe – LH) in the SE-NCP during typical winter haze episodes. Using an Aethalometer, the highest equivalent BC (eBC) mass concentrations and the highest aerosol absorption coefficients (σabs) were found in LH in the SE-NCP, followed by the borderline cities (XY, SX and HA) and WH. The levels, sources, optical properties (i.e., σabs and absorption Ångström exponent, AAE) and geographic origins of eBC were different between clean and polluted periods. Compared with clean days, higher eBC levels (26.4 %–163 % higher) and σabs (18.2 %–236 % higher) were found during pollution episodes due to the increased combustion of fossil fuels (increased by 51.1 %–277 %), which was supported by the decreased AAE values (decreased by 7.40 %–12.7 %). The conditional bivariate probability function (CBPF) and concentration-weighted trajectory (CWT) results showed that the geographic origins of biomass burning (BCbb) and fossil fuel (BCff) combustion-derived BC were different. Air parcels from the south dominated for border sites during clean days, with contributions of 46.0 %–58.2 %, whereas trajectories from the northeast showed higher contributions (37.5 %–51.2 %) during pollution episodes. At the SE-NCP site (LH), transboundary influences from the south (CC) exhibited a more frequent impact (with air parcels from this direction comprising 47.8 % of all parcels) on the ambient eBC levels during pollution episodes. At WH, eBC was mainly from the northeast transport route throughout the observation period. Two transportation cases showed that the mass concentrations of eBC, BCff and σabs all increased, from upwind to downwind, whereas AAE decreased. This study highlights that intra-regional prevention and control for dominant sources at each specific site should be considered in order to improve the regional air quality.

Download Full-text

Causes of a continuous summertime O<sub>3</sub> pollution event in Jinan, a central city in the North China Plain

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-3025-2019 ◽

2019 ◽

Vol 19 (5) ◽

pp. 3025-3042 ◽

Cited By ~ 13

Author(s):

Xiaopu Lyu ◽

Nan Wang ◽

Hai Guo ◽

Likun Xue ◽

Fei Jiang ◽

...

Keyword(s):

Production Rate ◽

North China Plain ◽

North China ◽

Model Simulation ◽

Central City ◽

Source Region ◽

Urban Site ◽

The North ◽

The North China Plain ◽

Pollution Event

Abstract. In the summer of 2017, measurements of ozone (O3) and its precursors were carried out at an urban site in Jinan, a central city in the North China Plain (NCP). A continuous O3 pollution event was captured during 4–11 August, with the maximum hourly O3 mixing ratio reaching 154.1 ppbv. Model simulation indicated that local photochemical formation and regional transport contributed 14.0±2.3 and 18.7±4.0 ppbv h−1, respectively, to the increase in O3 during 09:00–15:00 LT (local time) in this event. For local O3 formation, the calculated OH reactivities of volatile organic compounds (VOCs) and carbon monoxide (CO) were comparable between O3 episodes and non-episodes (p>0.05), so was the OH reactivity of nitrogen oxides (NOx). However, the ratio of OH reactivity of VOCs and CO to that of NOx increased from 2.0±0.4 s−1 s1 during non-episodes to 3.7±0.7 s−1 s1 during O3 episodes, which resulted in the change in the O3 formation mechanism from the VOC-limited regime before the O3 pollution event to the transitional regime during the event. Correspondingly, the simulated local O3 production rate during the event (maximum: 21.3 ppbv h−1) was markedly higher than that before the event (p<0.05) (maximum: 16.9 ppbv h−1). Given that gasoline and diesel exhaust made large contributions to the abundance of O3 precursors and the O3 production rate, constraint on vehicular emissions is the most effective strategy to control O3 pollution in Jinan. The NCP has been confirmed as a source region of tropospheric O3, where the shift in regimes controlling O3 formation like the case presented in this study can be expected across the entire region, due to the substantial reductions of NOx emissions in recent years.

Download Full-text