Ambient peroxyacyl nitrate concentration and regional transportation in Beijing

Zhang, Boya; Zhao, Bu; Zuo, Peng; Huang, Zhiyuan; Zhang, Jianbo

doi:10.1016/j.atmosenv.2017.07.053

Cited by 21 publications

(12 citation statements)

References 25 publications

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“…Compared with recent studies in China (Table S2), the observed PAN concentration during autumn at the SDZ site is generally lower than PAN levels over the urban NCP (Zhang et al, 2017;Liu et al, 2018) and in southwestern China but comparable to those in the suburban NCP region (Qiu et al, 2019a;Zhang et al, 2019). In addition, the PAN level at the SDZ site is remarkably higher than those obtained from the southern coastal region (Zhu et al, 2018;Zeng et al, 2019a;Hu et al, 2020) and Tibet (Xu et al, 2018), implying a severe photochemical pollution level over the NCP on a regional scale.…”

Section: High Pan Levels During Haze Events In Autumncontrasting

confidence: 71%

“…As another important photochemical pollutant, PAN pollution events were also extensively recognized both in the urban (Zhang et al, 2014;Zhang et al, 2015;Zhang et al, 2017;Qiu et al, 2019a) and rural NCP regions (Qiu et al, 2020a;Wei et al, 2020) at the same time. These also confirm the severity and complexity of photochemical pollution in this highlypopulated NCP region.…”

Section: Introductionmentioning

confidence: 99%

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

Qiu

et al. 2021

Preprint

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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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Section: High Pan Levels During Haze Events In Autumncontrasting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

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

Qiu

et al. 2021

Preprint

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“…In extreme haze, the base model underestimates the mean of [NO 2 ] and [O 3 ] by 55% and 54%, respectively. The large model‐observation discrepancy in [NO 2 ] cannot be explained by the long‐known interference of NO z species (members in the NO y family that are not NO or NO 2 ) in chemiluminescence‐based measurements (Lamsal et al., 2008; Reed et al., 2016), because both our model (see Figure ) and other observations suggest that non‐NO 3 − gas‐phase NO z species’ (e.g., PAN) concentration is small in comparison with [NO x ] in wintertime in Beijing (S. Chen et al., 2020; B. Zhang et al., 2017; G. Zhang et al., 2020; H. Zhang et al., 2014). The underestimate of NO 2 leads to a modeled overestimate of NOR (0.33) in intense haze compared to the observations (0.21).…”

Section: Resultsmentioning

confidence: 54%

Heterogeneous Nitrate Production Mechanisms in Intense Haze Events in the North China Plain

Chan

Evans

et al. 2021

JGR Atmospheres

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Studies of wintertime air quality in the North China Plain (NCP) show that particulate‐nitrate pollution persists despite rapid reduction in NOx emissions. This intriguing NOx‐nitrate relationship may originate from non‐linear nitrate‐formation chemistry, but it is unclear which feedback mechanisms dominate in NCP. In this study, we re‐interpret the wintertime observations of 17O excess of nitrate (∆17O(NO3−)) in Beijing using the GEOS‐Chem (GC) chemical transport model to estimate the importance of various nitrate‐production pathways and how their contributions change with the intensity of haze events. We also analyze the relationships between other metrics of NOy chemistry and [PM2.5] in observations and model simulations. We find that the model on average has a negative bias of −0.9‰ and −36% for ∆17O(NO3−) and [Ox,major] (≡ [O3] + [NO2] + [p‐NO3−]), respectively, while overestimating the nitrogen oxidation ratio ([NO3−]/([NO3−] + [NO2])) by +0.12 in intense haze. The discrepancies become larger in more intense haze. We attribute the model biases to an overestimate of NO2‐uptake on aerosols and an underestimate in wintertime O3 concentrations. Our findings highlight a need to address uncertainties related to heterogeneous chemistry of NO2 in air‐quality models. The combined assessment of observations and model results suggest that N2O5 uptake in aerosols and clouds is the dominant nitrate‐production pathway in wintertime Beijing, but its rate is limited by ozone under high‐NOx‐high‐PM2.5 conditions. Nitrate production rates may continue to increase as long as [O3] increases despite reduction in [NOx], creating a negative feedback that reduces the effectiveness of air pollution mitigation.

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“…PAN is easily decomposed under high temperatures (Seinfeld & Pandis, 2006), while O 3 production rate increases with temperature (Sillman & Samson, 1995). In a conventional view, the winter PAN levels are low due to weak solar radiation (G. Zhang et al, 2014), and in summer, observed PAN pollution events are usually accompanied by O 3 pollution episodes (B. Zhang et al, 2017). However, recent studies in China found that PAN concentrations on winter haze days could be as high as those observed in summer photochemical smog (Liu et al, 2018; Qiu, Ma, et al, 2019; G. Zhang, Xia, et al, 2020; B. Zhang et al, 2019), suggesting potential contributions from unfavorable meteorological conditions and local photochemical reactions (Qiu, Ma, et al, 2019; J. Zhang, Guo, et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Markedly Enhanced Levels of Peroxyacetyl Nitrate (PAN) During COVID‐19 in Beijing

Qiu

et al. 2020

Geophysical Research Letters

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High levels of secondary air pollutants during COVID-19 in China have aroused great concern. In Beijing, measured daily mean peroxyacetyl nitrate (PAN) concentrations reached 4 ppb over the lockdown period (24 January to 15 February), whose averages were 2-3 times that before lockdown (1-23 January). The lockdown PAN levels also reached a high historical record based on our long-term measurements (2016-2019). Unlike ozone and PM 2.5 , PAN formation depends on less complex photochemistry between NO x and volatile organic compounds (VOCs), providing a novel approach to investigate the wintertime photochemistry during COVID-19. The GEOS-Chem simulations suggest a markedly enhanced photochemistry by a factor of 2 during the lockdown. Change of meteorology featuring with anomalous wind convergence under higher temperatures is the main reason for enhanced photochemical formation of PAN, while chemically nonlinear feedbacks also play a role. Our results suggest implementing targeted VOC emission controls in the context of increasing photochemical pollution over this complex polluted region. Plain Language Summary Outbreaks of the COVID-19 pandemic caused immediate implementation of lockdown policy in China, which drastically decreased emissions of primary air pollutants. Peroxyacetyl nitrate (PAN), as an important photochemical product, is controlled by reactions between NO x and volatile organic compounds (VOCs) that were reduced substantially due to the lockdown. However, observed PAN levels in Beijing during the lockdown were markedly enhanced and were even much higher than the concentrations during the same periods in 2016-2019. Modeling results prove that this increase in PAN is driven by enhanced photochemistry, resulting from anomalous wind convergence under higher temperature and enhanced radical level in response to NO x reduction. Our results suggest the necessity of reducing VOC emissions in controlling photochemical pollution even in the wintertime over China.

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Ambient peroxyacyl nitrate concentration and regional transportation in Beijing

Cited by 21 publications

References 25 publications

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

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

Heterogeneous Nitrate Production Mechanisms in Intense Haze Events in the North China Plain

Markedly Enhanced Levels of Peroxyacetyl Nitrate (PAN) During COVID‐19 in Beijing

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