scholarly journals Two years of online measurement of fine particulate nitrate in the western Yangtze River Delta: influences of thermodynamics and N<sub>2</sub>O<sub>5</sub> hydrolysis

2018 ◽  
Vol 18 (23) ◽  
pp. 17177-17190 ◽  
Author(s):  
Peng Sun ◽  
Wei Nie ◽  
Xuguang Chi ◽  
Yuning Xie ◽  
Xin Huang ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Yangtze River ◽  
Nitrate Concentration ◽  
Yangtze River Delta ◽  
River Delta ◽  
Water Soluble ◽  
Online Measurement ◽  
High Concentration ◽  
Soluble Ions ◽  
Water Soluble Ions

Abstract. Particulate nitrate contributes a large fraction of secondary aerosols. Despite understanding of its important role in regional air quality and global climate, long-term continuous measurements are rather limited in China. In this study, we conducted online measurement of PM2.5 (particulate matter with diameters less than 2.5 µm) nitrate for 2 years from March 2014 to February 2016 using the Monitor for AeRosols and Gases in ambient Air (MARGA) in the western Yangtze River Delta (YRD), eastern China, and investigate the main factors that influenced its temporal variations and formation pathways. Compared to other sites in China, an overall high concentration of particulate nitrate was observed, with a mean value of 15.8 µg m−3 (0.5 to 92.6 µg m−3). Nitrate on average accounted for 32 % of the total mass of water-soluble ions and the proportion increased with PM loading, indicating that nitrate is a major driver of haze pollution episodes in this region. Sufficient ammonia drove most nitrate into the particle phase in the form of ammonium nitrate. A typical seasonal cycle of nitrate was observed, with the concentrations in winter on average 2 times higher than those in summer mainly due to different meteorological conditions. In summer, the diurnal variation of particulate nitrate was determined by thermodynamic equilibrium, resulting in a much lower concentration during daytime despite a considerable photochemical production. Air masses from the polluted YRD and biomass burning region contributed to the high nitrate concentration during summer. In winter, particulate nitrate did not reveal an evident diurnal variation. Regional transport from northern China played an important role in enhancing nitrate concentration. A total of 18 nitrate episodes were selected to understand the processes that drive the formation of high concentration of nitrate. Rapid nitrate formation was observed during the pre-episode (the day before nitrate episode day) nights, and dominated the increase of total water-soluble ions. Calculated nitrate from N2O5 hydrolysis was highly correlated to and accounted for 80 % of the observed nitrate, suggesting that N2O5 hydrolysis was a major contributor to the nitrate episodes. Our results suggested that rapid formation of nitrate could be a main cause for extreme aerosol pollution events in the YRD during winter, and illustrated the urgent need to control NOx emission.

scholarly journals Two years online measurement of fine particulate nitrate in western Yangtze River Delta: Influences of thermodynamics and N<sub>2</sub>O<sub>5</sub> hydrolysis

2018 ◽  
Author(s):  
Peng Sun ◽  
Wei Nie ◽  
Xuguang Chi ◽  
Yuning Xie ◽  
Xin Huang ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Yangtze River ◽  
Nitrate Concentration ◽  
Yangtze River Delta ◽  
River Delta ◽  
Water Soluble ◽  
Online Measurement ◽  
High Concentration ◽  
Soluble Ions ◽  
Water Soluble Ions

Abstract. Particulate nitrate contributes a large fraction of secondary aerosols. Despite understanding of its important role in regional air quality and global climate, long-term continuous measurements are rather limited in China. In this study, we conducted online measurement of PM2.5 nitrate for two years from March 2014 to February 2016 using the Monitor for Aerosols and Gases in ambient Air (MARGA) in the western Yangtze River Delta (YRD), eastern China, and investigate the main factors that influenced its temporal variations and formation pathways. Compared to other sites in China, an overall high concentration of particulate nitrate was observed with a mean value of 15.8 µg m−3 (0.5 to 92.6 µg m−3). Nitrate on average accounted for 32 % of the total mass of water-soluble ions and the proportion increased with PM loading, indicating that nitrate is a major driver of haze pollution episodes in this region. Sufficient ammonia drove most nitrate into the particle phase in the form of ammonium nitrate. A typical seasonal cycle of nitrate was observed with the concentrations in winter on average two times higher than those in summer mainly due to different meteorological conditions. In summer, the diurnal variation of particulate nitrate was determined by the thermodynamic equilibrium, resulting in a much lower concentration during daytime despite of a considerable photochemical production. Air masses from polluted YRD and biomass burning region contributed to the high nitrate concentration during summer. In winter, particulate nitrate didn’t reveal an evident diurnal variation. Regional transport from northern China played an important role in enhancing nitrate concentration. Eighteen nitrate episodes were selected to understand the processes that drive the formation of high concentration of nitrate. Rapid nitrate formation was observed during the pre-episode (the day before nitrate episode day) nights, and dominated the increase of total water-soluble ions. Calculated nitrate from N2O5 hydrolysis was highly correlated to and accounted for 80 percent of the observed nitrate, suggesting that N2O5 hydrolysis was a major contributor to the nitrate episodes. Our results suggested that rapid formation of nitrate could be a main cause for extreme aerosol pollution events in YRD during winter, and illustrated the urgent needs to control the NOx emission.

Characteristics of Water Soluble Ions in Atmospheric Aerosol on Clear and Hazy Days at Lin’an Regional Background Station, China

2011 ◽  
Vol 356-360 ◽  
pp. 2233-2238
Author(s):  
Hong Hui Xu ◽  
Jie Liu ◽  
Min Juan Mao ◽  
Jie Yao
Keyword(s):  
Atmospheric Aerosol ◽  
Yangtze River ◽  
Fine Particles ◽  
Yangtze River Delta ◽  
River Delta ◽  
Water Soluble ◽  
Coarse Particles ◽  
Regional Background ◽  
Soluble Ions ◽  
Water Soluble Ions

To investigate the characteristics of size distributions and water-soluble ions compositions of atmospheric aerosol in different weather conditions in the area of Yangtze River delta in China, aerosol samples were collected with Andersen cascade sampler on typical clear and hazy days at Lin’an regional background station. The water-soluble ionic concentrations were analyzed by the ion chromatography (IC). Results showed the concentrations of SO42-, NO3-, NH4+ and K+ on hazy days were 20.14, 17.45, 10.30, and 1.27µg m-3 in fine particles, respectively, and the concentrations of NO3-, NH4+ and K+ were 14.50, 2.35 and 0.50µg m-3 in coarse particles, respectively. This was 1.1-2.9 times higher than on clear days. The concentrations of Ca2+, Na+, Mg2+ and Cl- on hazy days were 2.67, 1.33, 0.37, and 1.03µg m-3 in fine particles, respectively, and the concentrations of Ca2+, Na+, Mg2+, Cl- and SO42- were 4.34, 1.27, 0.41, 0.89 and 2.08µg m-3 in coarse particles, respectively. This was 0.6-0.9 times lower than on clear days. K+ and secondary particles including sulfate, nitrate and ammonium came from the long-range transport which mainly from the area of Yangtze River delta, which was the main cause of formation of haze.

scholarly journals Seasonal variations of water-soluble ions in PM10 at a WMO/GAW station in the Yangtze River Delta, China

2020 ◽  
Vol 194 ◽  
pp. 04058
Author(s):  
Dongqing Fang ◽  
Junli Jin ◽  
Wei Huang ◽  
Yong Zhang ◽  
Wanqi Sun ◽  
...  
Keyword(s):  
Yangtze River ◽  
Inorganic Ions ◽  
Yangtze River Delta ◽  
Water Soluble ◽  
The Yangtze River ◽  
Soluble Ions ◽  
Water Soluble Ions ◽  
Water Soluble Inorganic Ions ◽  
Oxidation Ratio ◽  
The Yangtze River Delta

In order to understand the seasonal levels, formation mechanism and atmospheric chemical behaviours of water-soluble ions of PM10 in the Yangtze River Delta (YRD) region, aerosol samples were collected from January 2nd to December 28th, 2017 at a WMO/GAW regional background station in Lin’an. The concentrations of PM mass and nine water-soluble inorganic ions were obtained. The annual average concentration of PM10 was 59.9±33.9 μg m−3, lower than those reported in previous studies, indicating air quality of YRD region was improved. Nine water-soluble inorganic ions was accounted for 30.2-45.1% of the total PM mass, while ammonium (NH4+), sulfate (SO42+), as well as nitrate (NO3-) were the major ions which contributed 86.3% to total ions. The NO3- concentration was lowest in summer but highest in winter, suggesting it was likely influenced by thermodynamics. The levels of SO42- in spring and winter were related to photochemical reaction and regional transportation. Except for the SNA, Ca2+ was highest in four seasons likely due to sand storm and road fugitive dust. The annual mean ratio of [NO3-]/[SO42-] was nearly to 1, indicating mobile and stationary sources were equally important in Lin’an. The mean nitrogen oxidation ratio (NOR) and sulfur oxidation ratio (SOR) were 0.22±0.13 and 0.41±0.13, respectively, suggesting secondary formation was significant in the atmosphere at the background station of YRD region.

scholarly journals Online Measurement of PM2.5 at an Air Monitoring Supersite in Yangtze River Delta: Temporal Variation and Source Identification

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 789 ◽  
Author(s):  
Lian Duan ◽  
Lei Yan ◽  
Guangli Xiu
Keyword(s):  
Yangtze River ◽  
Chemical Species ◽  
Inorganic Ions ◽  
Ambient Air ◽  
Yangtze River Delta ◽  
River Delta ◽  
Water Soluble ◽  
Dianshan Lake ◽  
Haze Pollution ◽  
High Level

To comprehensively explore the transport of air pollutants, one-year continuous online observation of PM2.5 was conducted from 1 April 2015 to 31 March 2016 at Dianshan Lake, a suburban junction at the central of Yangtze River Delta. The chemical species of PM2.5 samples mainly focused on Organic carbon (OC), Elemental carbon (EC) and Water-Soluble Inorganic Ions (WSIIs). The annual average of PM2.5 concentration was 59.8 ± 31.7 µg·m−3, 1.7 times higher than the Chinese National Ambient Air Quality Standards (CNAAQS) (35 µg·m−3). SNA (SO42−, NO3− and NH4+) was the most dominated species of PM2.5 total WSIIs, accounting for 51% of PM2.5. PM2.5 and all of its chemical species shared the same seasonal variations with higher concentration in winter and spring, lower in autumn and summer. The higher NO3−/EC and NOR occurred in winter suggested that intensive secondary formation of nitrate contributed to the higher levels of PM2.5. Cluster analysis based on 72-h backward air trajectory showed that the air mass cluster from nearby inland cities, including Zhejiang, Anhui and Jiangxi Provinces contributed mostly to the total trajectories. Furtherly, potential source contribution function (PSCF) analysis revealed that local sources, namely the emissions in the Yangtze River, were the primary sources. During haze pollution, NO3− was the most important fraction of PM2.5 and the heterogeneous formation of nitrate became conspicuous. All the results suggested that the anthropogenic emissions (such as traffic exhaust) was responsible for the relatively high level of PM2.5 at this monitoring station.

scholarly journals Ozone affected by a succession of four landfall typhoons in the Yangtze River Delta, China: major processes and health impacts

2020 ◽  
Vol 20 (22) ◽  
pp. 13781-13799
Author(s):  
Chenchao Zhan ◽  
Min Xie ◽  
Chongwu Huang ◽  
Jane Liu ◽  
Tijian Wang ◽  
...  
Keyword(s):  
Yangtze River ◽  
Yangtze River Delta ◽  
Photochemical Reactions ◽  
River Delta ◽  
The Yangtze River ◽  
High Concentration ◽  
The Yrd ◽  
The Impact ◽  
The Yangtze River Delta ◽  
Pollution Episodes

Abstract. Landfall typhoons can significantly affect O3 in the Yangtze River Delta (YRD) region. In this study, we investigate a unique case characterized by two multiday regional O3 pollution episodes related to four successive landfall typhoons in the summer of 2018 in the YRD. The results show that O3 pollution episodes mainly occurred during the period from the end of a typhoon to the arrival of the next typhoon. The time when a typhoon reached the 24 h warning line and the time when the typhoon dies away in mainland China can be roughly regarded as time nodes. Meanwhile, the variations of O3 were related to the track, duration and landing intensity of the typhoons. The impact of typhoons on O3 was like a wave superimposed on the background of high O3 concentration in the YRD in summer. When a typhoon was near the 24 h warning line before it landed on the coastline of the YRD, the prevailing wind originally from the ocean changed to be from inland, and it transported lots of precursors from the polluted areas to the YRD. Under influences of the typhoon, the low temperature, strong upward airflows, more precipitation and wild wind hindered occurrences of high O3 episodes. After the passing of the typhoon, the air below the 700 hPa atmospheric layer was warm and dry, and the downward airflows resumed. The low troposphere was filed with high concentration of O3 due to O3-rich air transported from the low stratosphere and strong photochemical reactions. It is noteworthy that O3 was mainly generated in the middle of the boundary layer (∼ 1000 m) instead of at the surface. High O3 levels remained in the residual layer at night, and would be transported to the surface by downward airflows or turbulence by the second day. Moreover, O3 can be accumulated and trapped on the ground due to the poor diffusion conditions because the vertical diffusion and horizontal diffusion were suppressed by downward airflows and light wind, respectively. The premature deaths attributed to O3 exposure in the YRD during the study period were 194.0, more than the casualties caused directly by the typhoons. This work has enhanced our understanding of how landfall typhoons affect O3 in the YRD and thus can be useful in forecasting O3 pollution in regions strongly influenced by typhoon activities.

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