Peroxyacetyl nitrate (PAN) in the border of Beijing, Tianjin and Hebei of China: Concentration, source apportionment and photochemical pollution assessment

2020 ◽  
Vol 246 ◽  
pp. 105106 ◽  
Author(s):  
Wei Wei ◽  
Jiaxin Zang ◽  
Xiaoqi Wang ◽  
Shuiyuan Cheng
Keyword(s):  
Source Apportionment ◽  
Pollution Assessment ◽  
Peroxyacetyl Nitrate ◽  
Photochemical Pollution

scholarly journals Seasonal characteristics of atmospheric peroxyacetyl nitrate (PAN) in a coastal city of Southeast China: Explanatory factors and photochemical effects

2021 ◽  
Author(s):  
Taotao Liu ◽  
Gaojie Chen ◽  
Jinsheng Chen ◽  
Lingling Xu ◽  
Mengren Li ◽  
...  
Keyword(s):  
Influencing Factors ◽  
Formation Rate ◽  
Additive Model ◽  
Meteorological Conditions ◽  
Photochemical Reactions ◽  
Peroxyacetyl Nitrate ◽  
Photochemical Pollution ◽  
Explanatory Factors ◽  
Seasonal Characteristics ◽  
Intensive Observation

Abstract. Peroxyacetyl nitrate (PAN) acting as a typical indicator of photochemical pollution can redistribute NOx and modulate O3 production. Coupled with the observation-based model (OBM) and a generalized additive model (GAM), the intensive observation campaigns were conducted to reveal the pollution characteristics of PAN and its impact on O3, the contributions of influencing factors to PAN formation were also quantified in this paper. The F-values of GAM results reflecting the importance of the influencing factors showed that ultraviolet radiation (UV, F-value = 60.64), Ox (Ox = NO2+O3, 57.65), and air temperature (T, 17.55) were the main contributors in the PAN pollution in spring, while the significant effects of Ox (58.45), total VOCs (TVOCs, 21.63) and T (20.46) were found in autumn. The PAN formation rate in autumn was 1.58 times higher than that in spring, relating to the intense photochemical reaction and meteorological conditions. Without considering the transformation of peroxyacetyl radical (PA) and PAN, acetaldehyde contributed to the dominant production of PA (46 ± 4 %), followed by methylglyoxal (28 ± 3 %) and radical cycling (19 ± 3 %). The PAN formation was highly VOC-sensitive, and sufficient NOx (compared with VOCs abundance) would not be the limited factor for atmospheric photochemistry. PAN could promote or inhibit O3 formation under high or low ROx levels, respectively. The PAN promoting O3 formation mainly occurred during the periods of 11:00–16:00 (local time) when the favorable meteorological conditions (high UV and T) stimulated the photochemical reactions to offer ROx radicals, which accounted for 17 % of the whole monitoring periods in spring and 31 % in autumn. In this study, the formation mechanism of PAN and its effect on ozone were identified, which might be helpful to improve the scientific understanding of photochemical pollution in coastal areas.

scholarly journals Measurement report: Fast photochemical production of peroxyacetyl nitrate (PAN) over the rural North China Plain during haze events in autumn

2021 ◽  
Vol 21 (23) ◽  
pp. 17995-18010
Author(s):  
Yulu Qiu ◽  
Zhiqiang Ma ◽  
Ke Li ◽  
Mengyu Huang ◽  
Jiujiang Sheng ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Cold Season ◽  
Rural Site ◽  
Dominant Factor ◽  
Urban Region ◽  
Chemical Production ◽  
Peroxyacetyl Nitrate ◽  
Photochemical Pollution ◽  
Acetaldehyde Oxidation

Abstract. Photochemical pollution over the North China Plain (NCP) is attracting much concern. We usually view peroxyacetyl nitrate (PAN) as the second most important photochemical pollutant featuring high mixing ratios during warm seasons. Our observations at a background site in the NCP identified high PAN concentrations, even during haze events in autumn. The substantial increasing ratios of PAN, by 244 % and 178 %, over the morning hours (08:00–12:00 local time) on 20 and 25 October 2020 were 10.6 and 7.7 times larger than those on clean days. Polluted days are characterized by higher temperature, higher humidity, and anomalous southerly winds compared with clean days. Enhanced local photochemistry has been identified as being the dominant factor that controls the PAN increase in the morning at the rural site, as the time when prevailing wind turns to a southerly wind is too late to promote direct transport of PAN from the polluted urban region. By removing the effect of direct transport of PAN, we provide a quantitative assessment of net PAN chemical production rate of 0.45 ppb h−1 for the mornings of polluted days, also demonstrating the strong local photochemistry. Using observations and calculated photolysis rates, we find that acetaldehyde oxidation by hydroxyl radical (OH) is the primary pathway of peroxyacetyl radical formation at the rural site. Acetaldehyde concentrations and production rates of HOx (HOx= OH + HO2) on polluted days are 2.8 and 2 times as large as those on clean days, leading to a remarkable increase in PAN in the morning. Formaldehyde (HCHO) photolysis dominates the daytime HOx production, thus contributing to fast photochemistry of PAN. Our observational results suggest the cause of a rapid increase in PAN during haze events in autumn at a rural site of the NCP and provide evidence of important role of HCHO photolysis in secondary pollutants at lower nitrogen oxide emissions. This highlights the urgency of carrying out strict volatile organic compound controls over the NCP during the cold season and not just in summer.

scholarly journals Measurement report: Fast photochemical production of peroxyacetyl nitrate (PAN) over the rural North China Plain during cold-season haze events

2021 ◽  
Author(s):  
Yulu Qiu ◽  
Zhiqiang Ma ◽  
Ke Li ◽  
Mengyu Huang ◽  
Jiujiang Sheng ◽  
...  
Keyword(s):  
North China Plain ◽  
North China ◽  
Cold Season ◽  
Rural Site ◽  
Dominant Factor ◽  
Urban Region ◽  
Chemical Production ◽  
Peroxyacetyl Nitrate ◽  
Photochemical Pollution ◽  
Mixing Ratios

Abstract. Photochemical pollution over the North China Plain (NCP) are attracting considerable concern. Peroxyacetyl nitrate (PAN) is usually viewed as the second most important photochemical pollutant featuring high mixing ratios during warm seasons. Our observations at a background site in the NCP identified high PAN concentrations even during cold-season haze events. The abrupt increasing rates of PAN by 244 % and 178 % over the morning hours (8:00–12:00) on 10/20 and 10/25, 2020 were 10.6 and 7.7 times those on clean days. The pollution days were characterized by higher temperature and humidity, accompanied by anomalous southerlies. Enhanced local photochemistry has been identified as the dominant factor that controls PAN increase in the morning at the rural site, as the time when prevailing wind turned to southerlies was too late to facilitate direct transport of PAN from the polluted urban region. By removing the effect of direct transport of PAN, we provide a quantitative assessment of net PAN chemical production rate of 0.45 ppb h−1 on the polluted morning, also demonstrating the strong local photochemistry. Using observations and calculated photolysis rates, we find that oxidation of acetaldehyde by hydroxyl radical (OH) is the primary pathway of peroxyacetyl radical formation at the rural site. Acetaldehyde concentrations and production rates of HOx (HOx = OH + HO2) radical on pollution days were 2.8 and 2 times that on clean days, respectively, leading to the abrupt increase of PAN in the morning. Formaldehyde (HCHO) photolysis dominates the daytime HOx production thus contributing to fast photochemistry of PAN. Our observational results fully explain the cause of rapid increase of PAN during cold days at a rural site of the NCP, as well as provide the evidence of important role of HCHO photolysis in secondary pollutants at lower nitrogen oxide emissions. This highlights the imperative to implement strict volatile organic compounds controls out of summer seasons over the NCP.

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