Characteristics of Haze Pollution Episodes and Analysis of a Typical Winter Haze Process in Shanghai

Abstract Based on the simultaneous observation of fine particulate matter (PM2.5) and its chemical components in four heavy haze pollution episodes at 14 sampling sites in northeast China from 2017 to 2019, the formation and existence of sulfate (SO42-) and nitrate (NO3-) secondary contaminants under different stages of the pollution episodes, and different meteorological and emission conditions were compared. The results yielded three main findings. (1) Organic carbon (OC) was the most important component of PM2.5, followed by NO3-,SO42-,and ammonium (NH4+). Nitrate surpassed sulfate as the most important secondary inorganic component over the study period. (2) The significant increase in atmospheric OC, SO42-, and NO3-concentrations was an important reason for haze formation. Meteorological factors such as wind direction, wind speed, temperature (T), relative humidity (RH), and atmospheric oxidability played an important role in secondary pollutant formation. (3) There were two potential SO42- formation mechanisms. The first was the gas-phase reaction of the hydroxyl radical(OH·) leading to the oxidation of nitrogen dioxide (NO2) and sulfur dioxide (SO2),and high ozone (O3) concentrations. A high atmospheric oxidability and high winter Ts were very important for SO42- formation. The second mechanism occurred under neutral or weakly alkaline conditions when large amounts of SO2 could enter aerosol droplets, and NO2 was more likely to react in the aqueous phase with SO2 to increase the output of SO42-. Nitrate formation was may be mainly due to the homogeneous gas-phase reaction of OH· with NO2, SO2, and ammonia(NH3). The highest NO3 concentration was observed under mild winter Ts, high RH, high atmospheric oxidability (O3 and nitrous acid (HONO)), high NH3 concentrations, and suitable light conditions. The differences in SO42- formation between northeast China and other regions were mainly a result of the suppression of the aqueous reaction of SO42- due to the low T in winter and low-sulfur coal emissions, which resulted in the gas-phase oxidation process with the highest SO42- production capacity becoming an important process. However, the aqueous reaction process was the most common mechanism of SO42- production in northeast China.

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Mixing state of ambient aerosols during different fog-haze pollution episodes in the Yangtze River Delta, China

Atmospheric Environment ◽

10.1016/j.atmosenv.2018.01.032 ◽

2018 ◽

Vol 178 ◽

pp. 1-10 ◽

Cited By ~ 19

Author(s):

Rui Hu ◽

Honglei Wang ◽

Yan Yin ◽

Kui Chen ◽

Bin Zhu ◽

...

Keyword(s):

Yangtze River ◽

Yangtze River Delta ◽

River Delta ◽

The Yangtze River ◽

Mixing State ◽

Ambient Aerosols ◽

Haze Pollution ◽

The Yangtze River Delta ◽

Pollution Episodes

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Aerosol pollution radiative effects on land carbon uptake in China

10.5194/acp-2016-899 ◽

2016 ◽

Author(s):

Xu Yue ◽

Nadine Unger

Keyword(s):

Primary Productivity ◽

Net Primary Productivity ◽

Carbon Uptake ◽

Radiative Effects ◽

Surface Solar Radiation ◽

Haze Pollution ◽

Aerosol Pollution ◽

Radiation Modeling ◽

Regional Land ◽

Pollution Episodes

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 aerosol optical depth (AOD) at 550 nm thresholds (i) AODt1, resulting in the maximum net primary productivity (NPP), and (ii) AODt2, such that if local AOD

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Impact of air transport and secondary formation on haze pollution in the Yangtze River Delta: In situ online observations in Shanghai and Nanjing

10.5194/egusphere-egu2020-1971 ◽

2020 ◽

Author(s):

Peng Sun

Keyword(s):

Fine Particles ◽

Eastern China ◽

Northern China ◽

Organic Aerosol ◽

Photochemical Activity ◽

Air Transport ◽

Ozone Level ◽

Haze Pollution ◽

The Yrd ◽

Pollution Episodes

Despite frequent haze pollution in China in recent years, our knowledge of regional pollution episodes associated with air transport and synoptic weather systems is limited. In this study, we conducted two intensive campaigns simultaneously to measure the highly time-resolved chemical composition of fine particles (PM2.5) in suburban Shanghai and Nanjing during the winter of 2017 and the summer of 2018. The average PM2.5 mass concentrations were 53.9 (65.7) &#181;g m-3 and 32.8 (37.3) &#181;g m-3 in Shanghai (Nanjing) in winter and summer, respectively. In winter, extreme haze episodes were observed synchronously with enhanced contributions of nitrate at both sites and of low-volatile oxidized organic aerosol (LV-OOA) in Shanghai. Long-range transport from Northern China was demonstrated to play an important role in the episodes, which occurred simultaneously at both sites. Influenced by the cold fronts, Nanjing had a relatively longer pollution duration, whereas Shanghai exhibited faster PM increases. In summer, air masses passing though the city-clusters of the YRD were responsible for the pollution episodes. Low wind speeds, which favored the accumulation of primary aerosols, and strong photochemical activity indicated by high ozone level, which promoted the formation of secondary aerosols, resulted in elevated contributions of nitrate, Hydrocarbon-like organic aerosol (HOA) and semi-volatile oxidized organic aerosol (SV-OOA) to PM in Shanghai. In addition, a pollution episode dominated by increases of nitrate and organic aerosols was observed in Nanjing two days later despite the clean situation in Shanghai. Our results highlight the importance of regional or sub-regional emission control to mitigate haze pollution in city clusters, such as the YRD in Eastern China.

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Characteristics of Atmospheric Compositions in the Background Area of Yangtze River Delta during Heavy Air Pollution Episode

Advances in Meteorology ◽

10.1155/2016/7240486 ◽

2016 ◽

Vol 2016 ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

Hong-Hui Xu ◽

Jing-Jiao Pu ◽

Jun He ◽

Jie Liu ◽

Bing Qi ◽

...

Keyword(s):

Air Pollution ◽

Yangtze River ◽

Temporal Trend ◽

Yangtze River Delta ◽

River Delta ◽

Sampling Campaign ◽

Haze Pollution ◽

Formation And Evolution ◽

Pollution Episodes ◽

Background Area

In order to understand the formation and evolution of recurrent severe haze pollution episodes in Yangtze River Delta, China, a short comparative sampling campaign was conducted at the Lin’an background monitoring station from 25 November 2013 to 14 December 2013. The characteristic concentrations of PM2.5, black carbon, CO2, CO, and CH4have been systematically recorded at the abovementioned site. Coupled with detailed analysis of air backward trajectories, fire spot distribution surrounding the studied site and meteorological impacts, temporal trend, diurnal variation, and intercorrelation of the aforementioned species have also been comprehensively investigated throughout prehaze, haze, and posthaze periods.

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