Comments on “Attributions of meteorological and emission factors to the 2015 winter severe haze pollution episodes in Northern China” by T. Liu et al.

2016 ◽  
Author(s):  
Anonymous
Keyword(s):  
Northern China ◽  
Emission Factors ◽  
Haze Pollution ◽  
Pollution Episodes

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

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

<p>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 (PM<sub>2.5</sub>) in suburban Shanghai and Nanjing during the winter of 2017 and the summer of 2018. The average PM<sub>2.5</sub> mass concentrations were 53.9 (65.7) µg m<sup>-3</sup> and 32.8 (37.3) µg m<sup>-3 </sup>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.</p>

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

2016 ◽  
Vol 16 (7) ◽  
pp. 1625-1637 ◽  
Author(s):  
Mengfei Zhao ◽  
Guangli Xiu ◽  
Ting Qiao ◽  
Yulan Li ◽  
Jianzhen Yu
Keyword(s):  
Haze Pollution ◽  
Pollution Episodes

Formation process of the widespread extreme haze pollution over northern China in January 2013: Implications for regional air quality and climate

2014 ◽  
Vol 98 ◽  
pp. 417-425 ◽  
Author(s):  
Minghui Tao ◽  
Liangfu Chen ◽  
Xiaozhen Xiong ◽  
Meigen Zhang ◽  
Pengfei Ma ◽  
...  
Keyword(s):  
Air Quality ◽  
Formation Process ◽  
Northern China ◽  
Haze Pollution ◽  
Regional Air Quality

scholarly journals Spatiotemporal Associations between PM2.5 and SO2 as well as NO2 in China from 2015 to 2018

2019 ◽  
Vol 16 (13) ◽  
pp. 2352 ◽  
Author(s):  
Ke Li ◽  
Kaixu Bai
Keyword(s):  
Statistical Modeling ◽  
Fine Particulate Matter ◽  
Monitoring Network ◽  
Northern China ◽  
Coupled Modes ◽  
Maximum Covariance Analysis ◽  
Relative Contribution ◽  
Haze Pollution ◽  
Pollution Events

Given the critical roles of nitrates and sulfates in fine particulate matter (PM2.5) formation, we examined spatiotemporal associations between PM2.5 and sulfur dioxide (SO2) as well as nitrogen dioxide (NO2) in China by taking advantage of the in situ observations of these three pollutants measured from the China national air quality monitoring network for the period from 2015 to 2018. Maximum covariance analysis (MCA) was applied to explore their possible coupled modes in space and time. The relative contribution of SO2 and NO2 to PM2.5 was then quantified via a statistical modeling scheme. The linear trends derived from the stratified data show that both PM2.5 and SO2 decreased significantly in northern China in terms of large values, indicating a fast reduction of high PM2.5 and SO2 loadings therein. The statistically significant coupled MCA mode between PM2.5 and SO2 indicated a possible spatiotemporal linkage between them in northern China, especially over the Beijing–Tianjin–Hebei region. Further statistical modeling practices revealed that the observed PM2.5 variations in northern China could be explained largely by SO2 rather than NO2 therein, given the estimated relatively high importance of SO2. In general, the evidence-based results in this study indicate a strong linkage between PM2.5 and SO2 in northern China in the past few years, which may help to better investigate the mechanisms behind severe haze pollution events in northern China.

scholarly journals Heterogeneous N<sub>2</sub>O<sub>5</sub> uptake coefficient and production yield of ClNO<sub>2</sub> in polluted northern China: roles of aerosol water content and chemical composition

2018 ◽  
Vol 18 (17) ◽  
pp. 13155-13171 ◽  
Author(s):  
Yee Jun Tham ◽  
Zhe Wang ◽  
Qinyi Li ◽  
Weihao Wang ◽  
Xinfeng Wang ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Water Content ◽  
Biomass Burning ◽  
Northern China ◽  
Field Investigation ◽  
Organic Coating ◽  
Production Yield ◽  
Uptake Coefficient ◽  
Positive Dependence ◽  
Haze Pollution

Abstract. Heterogeneous uptake of dinitrogen pentoxide (N2O5) and production of nitryl chloride (ClNO2) are important nocturnal atmospheric processes that have significant implications for the production of secondary pollutants. However, the understanding of N2O5 uptake processes and ClNO2 production remains limited, especially in China. This study presents a field investigation of the N2O5 heterogeneous uptake coefficient (γ(N2O5)) and ClNO2 production yield (ϕ) in a polluted area of northern China during the summer of 2014. The N2O5 uptake coefficient and ClNO2 yield were estimated by using the simultaneously measured ClNO2 and total nitrate in 10 selected cases, which have concurrent increases in the ClNO2 and nitrate concentrations and relatively stable environmental conditions. The determined γ(N2O5) and ϕ values varied greatly, with an average of 0.022 for γ(N2O5) (±0.012, standard deviation) and 0.34 for ϕ (±0.28, standard deviation). The variations in γ(N2O5) could not be fully explained by the previously derived parameterizations of N2O5 uptake that consider nitrate, chloride, and the organic coating. Heterogeneous uptake of N2O5 was found to have a strong positive dependence on the relative humidity and aerosol water content. This result suggests that the heterogeneous uptake of N2O5 in Wangdu is governed mainly by the amount of water in the aerosol, and is strongly water limited, which is different from most of the field observations in the US and Europe. The ClNO2 yield estimated from the parameterization was also overestimated comparing to that derived from the observation. The observation-derived ϕ showed a decreasing trend with an increasing ratio of acetonitrile to carbon monoxide, an indicator of biomass burning emissions, which suggests a possible suppressive effect on the production yield of ClNO2 in the plumes influenced by biomass burning in this region. The findings of this study illustrate the need to improve our understanding and to parameterize the key factors for γ(N2O5) and ϕ to accurately assess photochemical and haze pollution.

scholarly journals Possible influence of atmospheric circulations on winter haze pollution in the Beijing–Tianjin–Hebei region, northern China

2016 ◽  
Vol 16 (2) ◽  
pp. 561-571 ◽  
Author(s):  
Z. Zhang ◽  
X. Zhang ◽  
D. Gong ◽  
S.-J. Kim ◽  
R. Mao ◽  
...  
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Correlation Coefficients ◽  
Northern China ◽  
Reanalysis Data ◽  
Atmospheric Circulations ◽  
Boundary Layer Height ◽  
Haze Pollution ◽  
Atmospheric Circulation Indices ◽  
Circulation Indices

Abstract. Using the daily records derived from the synoptic weather stations and the NCEP/NCAR and ERA-Interim reanalysis data, the variability of the winter haze pollution (indicated by the mean visibility and number of hazy days) in the Beijing–Tianjin–Hebei (BTH) region during the period 1981 to 2015 and its relationship with the atmospheric circulations at middle–high latitude were analyzed in this study. The winter haze pollution in BTH had distinct inter-annual and inter-decadal variabilities without a significant long-term trend. According to the spatial distribution of correlation coefficients, six atmospheric circulation indices (I1 to I6) were defined from the key areas in sea level pressure (SLP), zonal and meridional winds at 850 hPa (U850, V850), geopotential height field at 500 hPa (H500), zonal wind at 200 hPa (U200), and air temperature at 200 hPa (T200), respectively. All of the six indices have significant and stable correlations with the winter visibility and number of hazy days in BTH. In the raw (unfiltered) correlations, the correlation coefficients between the six indices and the winter visibility (number of hazy days) varied from 0.57 (0.47) to 0.76 (0.6) with an average of 0.65 (0.54); in the high-frequency ( < 10 years) correlations, the coefficients varied from 0.62 (0.58) to 0.8 (0.69) with an average of 0.69 (0.64). The six circulation indices together can explain 77.7 % (78.7 %) and 61.7 % (69.1 %) variances of the winter visibility and the number of hazy days in the year-to-year (inter-annual) variability, respectively. The increase in Ic (a comprehensive index derived from the six individual circulation indices) can cause a shallowing of the East Asian trough at the middle troposphere and a weakening of the Siberian high-pressure field at sea level, and is then accompanied by a reduction (increase) of horizontal advection and vertical convection (relative humidity) in the lowest troposphere and a reduced boundary layer height in BTH and its neighboring areas, which are favorable for the formation of haze pollution in BTH winter, and vice versa. The high level of the prediction statistics and the reasonable mechanism suggested that the winter haze pollution in BTH can be forecasted or estimated credibly based on the optimized atmospheric circulation indices. Thus it is helpful for government decision-making departments to take action in advance in dealing with probably severe haze pollution in BTH indicated by the atmospheric circulation conditions.

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