scholarly journals 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

2019 ◽  
Vol 19 (20) ◽  
pp. 12857-12874 ◽  
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 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.

scholarly journals 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

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.

Understanding Aerosol Vertical Transport During Heavy Aerosol Pollution Episodes in the North China

2020 ◽  
Author(s):  
Renmin Yuan
Keyword(s):  
Surface Layer ◽  
Mass Flux ◽  
North China ◽  
Similarity Theory ◽  
Rural Site ◽  
Urban Site ◽  
The North ◽  
Aerosol Pollution ◽  
The Mean ◽  
Pollution Episodes

<p>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 PM<sub>2.5</sub> and PM<sub>10</sub> 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 January 2017 to January 31, 2017, in Beijing, the mean mass flux decreased by 51% from 0.0049 mg m<sup>-2</sup>s<sup>-1</sup> in RSs to 0.0024 mg m<sup>-2</sup>s<sup>-1</sup> in the TSs. During the ASs, the mean mass flux decreased further to 0.00087 mg m<sup>-2</sup>s<sup>-1</sup>, 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 16 December 2016 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 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.</p>

scholarly journals Organic aerosol volatility and viscosity in the North China Plain: contrast between summer and winter

2021 ◽  
Vol 21 (7) ◽  
pp. 5463-5476
Author(s):  
Weiqi Xu ◽  
Chun Chen ◽  
Yanmei Qiu ◽  
Ying Li ◽  
Zhiqiang Zhang ◽  
...  
Keyword(s):  
Coal Combustion ◽  
North China Plain ◽  
North China ◽  
Organic Aerosol ◽  
Rural Site ◽  
Urban Site ◽  
The North ◽  
Aerosol Mass ◽  
The North China Plain ◽  
Primary Emissions

Abstract. Volatility and viscosity have substantial impacts on gas–particle partitioning, formation and evolution of aerosol and hence the predictions of aerosol-related air quality and climate effects. Here aerosol volatility and viscosity at a rural site (Gucheng) and an urban site (Beijing) in the North China Plain (NCP) in summer and winter were investigated by using a thermodenuder coupled with a high-resolution aerosol mass spectrometer. The effective saturation concentration (C*) of organic aerosol (OA) in summer was smaller than that in winter (0.55 µg m−3 vs. 0.71–0.75 µg m−3), indicating that OA in winter in the NCP is more volatile due to enhanced primary emissions from coal combustion and biomass burning. The volatility distributions varied and were largely different among different OA factors. In particular, we found that hydrocarbon-like OA (HOA) contained more nonvolatile compounds compared to coal-combustion-related OA. The more oxidized oxygenated OA (MO-OOA) showed overall lower volatility than less oxidized OOA (LO-OOA) in both summer and winter, yet the volatility of MO-OOA was found to be relative humidity (RH) dependent showing more volatile properties at higher RH. Our results demonstrated the different composition and chemical formation pathways of MO-OOA under different RH levels. The glass transition temperature (Tg) and viscosity of OA in summer and winter are estimated using the recently developed parameterization formula. Our results showed that the Tg of OA in summer in Beijing (291.5 K) was higher than that in winter (289.7–290.0 K), while it varied greatly among different OA factors. The viscosity suggested that OA existed mainly as solid in winter in Beijing (RH = 29 ± 17 %), but as semisolids in Beijing in summer (RH = 48 ± 25 %) and Gucheng in winter (RH = 68 ± 24 %). These results have the important implication that kinetically limited gas–particle partitioning may need to be considered when simulating secondary OA formation in the NCP.

scholarly journals Summertime fine particulate nitrate pollution in the North China Plain: increasing trends, formation mechanisms and implications for control policy

2018 ◽  
Vol 18 (15) ◽  
pp. 11261-11275 ◽  
Author(s):  
Liang Wen ◽  
Likun Xue ◽  
Xinfeng Wang ◽  
Caihong Xu ◽  
Tianshu Chen ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Nitrate Pollution ◽  
Rural Site ◽  
Effective Control ◽  
Urban Site ◽  
Formation Mechanisms ◽  
The North ◽  
The North China Plain ◽  
Nitrate Aerosol

Abstract. Nitrate aerosol makes up a significant fraction of fine particles and plays a key role in regional air quality and climate. The North China Plain (NCP) is one of the most industrialized and polluted regions in China. To obtain a holistic understanding of the nitrate pollution and its formation mechanisms over the NCP region, intensive field observations were conducted at three sites during summertime in 2014–2015. The measurement sites include an urban site in downtown Jinan – the capital city of Shandong Province –, a rural site downwind of Jinan city, and a remote mountain site at Mt. Tai (1534 m a.s.l.). Elevated nitrate concentrations were observed at all three sites despite distinct temporal and spatial variations. Using historical observations, the nitrate ∕ PM2.5 and nitrate ∕ sulfate ratios have statistically significantly increased in Jinan (2005–2015) and at Mt. Tai (from 2007 to 2014), indicating the worsening situation of regional nitrate pollution. A multiphase chemical box model (RACM–CAPRAM) was deployed and constrained by observations to elucidate the nitrate formation mechanisms. The principal formation route is the partitioning of gaseous HNO3 to the aerosol phase during the day, whilst the nocturnal nitrate formation is dominated by the heterogeneous hydrolysis of N2O5. The daytime nitrate production in the NCP region is mainly limited by the availability of NO2 and to a lesser extent by O3 and NH3. In comparison, the nighttime formation is controlled by both NO2 and O3. The presence of NH3 contributes to the formation of nitrate aerosol during the day, while there is slightly decreasing nitrate formation at night. Our analyses suggest that controlling NOx and O3 is an efficient way, at the moment, to mitigate nitrate pollution in the NCP region, where NH3 is usually in excess in summer. This study provides observational evidence of a rising trend of nitrate aerosol as well as scientific support for formulating effective control strategies for regional haze in China.

scholarly journals Aerosol optical depth thresholds as a tool to assess diffuse radiation fertilization of the land carbon uptake in China

2017 ◽  
Vol 17 (2) ◽  
pp. 1329-1342 ◽  
Author(s):  
Xu Yue ◽  
Nadine Unger
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
North China Plain ◽  
North China ◽  
Carbon Uptake ◽  
The North ◽  
The North China Plain ◽  
Haze Pollution ◽  
Aerosol Pollution ◽  
Sky Conditions

Abstract. China suffers from frequent haze pollution episodes that alter the surface solar radiation and influence regional carbon uptake by the land biosphere. Here, we apply combined vegetation and radiation modeling and multiple observational datasets to assess the radiative effects of aerosol pollution in China on the regional land carbon uptake for the 2009–2011 period. First, we assess the inherent sensitivity of China's land biosphere to aerosol pollution by defining and calculating two thresholds of aerosol optical depth (AOD) at 550 nm, (i) AODt1, resulting in the maximum net primary productivity (NPP), and (ii) AODt2, such that if local AOD < AODt2, the aerosol diffuse fertilization effect (DFE) always promotes local NPP compared with aerosol-free conditions. Then, we apply the thresholds, satellite data, and interactive vegetation modeling to estimate current impacts of aerosol pollution on land ecosystems. In the northeast, observed AOD is 55 % lower than AODt1, indicating a strong aerosol DFE on local NPP. In the southeastern coastal regions, observed AOD is close to AODt1, suggesting that regional NPP is promoted by the current level of aerosol loading, but that further increases in AOD in this region will weaken the fertilization effects. The North China Plain experiences limited enhancement of NPP by aerosols because observed AOD is 77 % higher than AODt1 but 14 % lower than AODt2. Aerosols always inhibit regional NPP in the southwest because of the persistent high cloud coverage that already substantially reduces the total light availability there. Under clear-sky conditions, simulated NPP shows widespread increases of 20–60 % (35.0 ± 0.9 % on average) by aerosols. Under all-sky conditions, aerosol pollution has spatially contrasting opposite sign effects on NPP from −3 % to +6 % (1.6 ± 0.5 % on average), depending on the local AOD relative to the regional thresholds. Stringent aerosol pollution reductions motivated by public health concerns, especially in the North China Plain and the southwest, will help protect land ecosystem functioning in China and mitigate long-term global warming.

scholarly journals Variations of O<sub>3</sub> and CO in summertime at a rural site near Beijing

2008 ◽  
Vol 8 (21) ◽  
pp. 6355-6363 ◽  
Author(s):  
Y. Wang ◽  
M. B. McElroy ◽  
J. W. Munger ◽  
J. Hao ◽  
H. Ma ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Rural Site ◽  
Mixing Ratio ◽  
Efficient Manner ◽  
Strong Negative Correlation ◽  
Cloud Optical Depth ◽  
Mixing Ratios ◽  
The North ◽  
The North China Plain

Abstract. Large intra-season differences in mixing ratios of CO and O3 were detected at Miyun, a rural site north of Beijing, in summer 2006. Despite an increase in mean daytime mixing ratio of CO from 500 ppbv in June to 700 ppbv in July, mean daytime O3 dropped from 67 ppbv in June to 50 ppbv in July and August. The observed changes in CO and O3 are attributed to the influence of the summer monsoonal circulation that develops over the North China Plain in July. Photochemical production of O3 is reduced as a consequence of increased cloudiness during July and August, as indicated by the strong negative correlation observed between O3 and satellite observations of cloud optical depth, with cloudiness having little effect on CO. The analysis suggests a strategy for emission controls that could be implemented in an economically efficient manner to minimize the frequency of high levels of O3 during summer in Beijing.

Carbonaceous components in particulate matter during a haze episode at a typical industrial area in the North China Plain

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hongya Niu ◽  
Zhaoce Liu ◽  
Wei Hu ◽  
Wenjing Cheng ◽  
Mengren Li ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Organic Carbon ◽  
North China Plain ◽  
North China ◽  
Large Fraction ◽  
Industrial Emissions ◽  
Content Type ◽  
The North ◽  
The North China Plain ◽  
The Mean

Purpose Severe airborne particulate pollution frequently occurs over the North China Plain (NCP) region in recent years. To better understand the characteristics of carbonaceous components in particulate matter (PM) over the NCP region. Design/methodology/approach PM samples were collected at a typical area affected by industrial emissions in Handan, in January 2016. The concentrations of organic carbon (OC) and elemental carbon (EC) in PM of different size ranges (i.e. PM2.5, PM10 and TSP) were measured. The concentrations of secondary organic carbon (SOC) were estimated by the EC tracer method. Findings The results show that the concentration of OC ranged from 14.9 μg m−3 to 108.4 μg m−3, and that of EC ranged from 4.0 μg m−3 to 19.4μg m−3, when PM2.5 changed from 58.0μg m−3 to 251.1μg m−3 during haze days, and the carbonaceous aerosols most distributed in PM2.5 rather than large fraction. The concentrations of OC and EC PM2.5 correlated better (r = 0.7) than in PM2.5−10 and PM>10, implying that primary emissions were dominant sources of OC and EC in PM2.5. The mean ratios of OC/EC in PM2.5, PM2.5–10 and PM>10 were 4.4 ± 2.1, 3.6 ± 0.9 and 1.9 ± 0.7, respectively. Based on estimation, SOC accounted for 16.3%, 22.0% and 9.1% in PM2.5, PM2.5–10 and PM>10 respectively. Originality/value The ratio of SOC/OC (48.2%) in PM2.5 was higher in Handan than those (28%–32%) in other megacities, e.g. Beijing, Tianjin and Shijiazhuang in the NCP, suggesting that the formation of SOC contributed significantly to OC. The mean mass absorption efficiencies of EC (MACEC) in PM10 and TSP were 3.4 m2 g−1 (1.9–6.6 m2 g−1) and 2.9 m2 g−1 (1.6–5.6 m2 g−1), respectively, both of which had similar variation patterns to those of OC/EC and SOC/OC.

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

2020 ◽  
Vol 224 ◽  
pp. 117325 ◽  
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
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