Formation mechanisms of atmospheric nitrate and sulfate during the winter haze pollution periods in Beijing: gas-phase, heterogeneous and aqueous-phase chemistry

Liu, Pengfei; Ye, Can; Xue, Chaoyang; Zhang, Chenglong; Mu, Yujing; Sun, Xingming

doi:10.5194/acp-20-4153-2020

Cited by 118 publications

(70 citation statements)

References 65 publications

(97 reference statements)

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“…The definitions and values of these ratios are shown in Table S4. Our simulated SOR, NOR, and NHR values were in the range of values previously reported in wintertime observation studies over the NCP (Liu et al, 2020). Using the model emissions and the values in Table S4, we estimated the third term on the right-hand side of Eq.…”

Section: Cause Of the Ineffectiveness Of The Erms During The Severe Hmentioning

confidence: 73%

Emergency Response Measures to Alleviate a Severe Haze Pollution Event in Northern China during December 2015: Assessment of Effectiveness

Huang

et al. 2020

Aerosol Air Qual. Res.

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Using the WRF-Chem model, we simulated the surface PM 2.5 concentrations on the North China Plain (NCP) during a severe winter haze episode (December 6-10, 2015) with the goal of assessing the effectiveness of the implemented emergency response measures (ERMs) in alleviating the pollution. We estimated that the ERMs decreased the anthropogenic pollutant emissions, with the exception of NH 3 , by 8-48% during this event. Inputting these reduced emission estimates, our simulations reproduced the observed PM 2.5 concentrations and compositions. Stagnant regional meteorological conditions increased the lifetime of the PM 2.5 in the NCP boundary layer from 1 day during the clean period to 5 days during the haze episode. Additionally, local emissions accounted for approximately only 20% of the surface PM 2.5 in Beijing but more than 62% over the rest of the NCP. We found that the ERMs achieved a modest reduction in the mean surface PM 2.5 concentrations during the event, decreasing them by 7% and 4% in Beijing and across the rest of the NCP, respectively. The limited effect was due to the duration of the ERMs being much shorter than the lifetime of the PM 2.5 , which prevented the concentrations of the latter from fully reflecting the reduction in emissions. We conclude that anthropogenic emissions on the NCP during severe winter haze episodes must be reduced by a much larger percentage to substantially abate the PM 2.5 concentrations.

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Section: Cause Of the Ineffectiveness Of The Erms During The Severe Hmentioning

confidence: 73%

Emergency Response Measures to Alleviate a Severe Haze Pollution Event in Northern China during December 2015: Assessment of Effectiveness

Huang

et al. 2020

Aerosol Air Qual. Res.

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“…This is consistent with the increased wintertime oxidants in Figure 3a. More discussion about oxidation pathways in different phases is included in Text S8 (Liu & Wang, 2020; Liu et al, 2020; Tao et al, 2020; Wang, Chen, et al, 2019; Wang, Jacob, et al, 2019; Xue, Liu, et al, 2019; Xue, et al, 2019).…”

Section: Resultsmentioning

confidence: 99%

Wintertime Particulate Matter Decrease Buffered by Unfavorable Chemical Processes Despite Emissions Reductions in China

Leung

Shi

Zhao

et al. 2020

Geophysical Research Letters

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Extreme and persistent haze events frequently occur during wintertime China. While recent emissions reductions reduced annual mean fine particulate matter (PM2.5) concentrations over eastern China, their effectiveness on wintertime PM2.5 trend remains uncertain. We use observations and model simulations to quantify seasonal differences in PM2.5 trends and investigate the underlying chemical mechanisms driving such differences. We find a much slower decrease in observed wintertime PM2.5 (−3.2% yr−1) since 2014, in contrast to a drastic summertime decrease (−10.3% yr−1). Simulations show two previously underappreciated mechanisms buffering wintertime PM2.5 decrease, including an increase in oxidation capacity due to nitrogen oxides (NOx) reductions under wintertime volatile organic compound (VOC)‐limited chemistry, and an enhanced conversion of nitric acid to nitrate by ammonia due to sulfur dioxide reductions. Our findings suggest that control policies targeting VOC and deep NOx reductions are needed to improve wintertime PM2.5 air quality over China.

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“…This is anticipated to be due to meteorological factors, such as stagnant air with little transport or vertical mixing in a low planetary boundary layer, which often occurs in winter, and high relative humidity. These meteorological factors are conducive to the formation of haze [51] and the intensification of the occurrence of haze in the NCP [52].…”

Section: Aodmentioning

confidence: 99%

The Impact of the Control Measures during the COVID-19 Outbreak on Air Pollution in China

et al. 2020

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The outbreak of the COVID-19 virus in Wuhan, China, in January 2020 just before the Spring Festival and subsequent country-wide measures to contain the virus, effectively resulted in the lock-down of the country. Most industries and businesses were closed, traffic was largely reduced, and people were restrained to their homes. This resulted in the reduction of emissions of trace gases and aerosols, the concentrations of which were strongly reduced in many cities around the country. Satellite imagery from the TROPOspheric Monitoring Instrument (TROPOMI) showed an enormous reduction of tropospheric NO2 concentrations, but aerosol optical depth (AOD), as a measure of the amount of aerosols, was less affected, likely due to the different formation mechanisms and the influence of meteorological factors. In this study, satellite data and ground-based observations were used together to estimate the separate effects of the Spring Festival and the COVID-19 containment measures on atmospheric composition in the winter of 2020. To achieve this, data were analyzed for a period from 30 days before to 60 days after the Spring Festivals in 2017–2020. This extended period of time, including similar periods in previous years, were selected to account for both the decreasing concentrations in response to air pollution control measures, and meteorological effects on concentrations of trace gases and aerosols. Satellite data from TROPOMI provided the spatial distributions over mainland China of the tropospheric vertical column density (VCD) of NO2, and VCD of SO2 and CO. The MODerate resolution Imaging Spectroradiometer (MODIS) provided the aerosol optical depth (AOD). The comparison of the satellite data for different periods showed a large reduction of, e.g., NO2 tropospheric VCDs due to the Spring Festival of up to 80% in some regions, and an additional reduction due to the COVID-19 containment measures of up to 70% in highly populated areas with intensive anthropogenic activities. In other areas, both effects are very small. Ground-based in situ observations from 26 provincial capitals provided concentrations of NO2, SO2, CO, O3, PM2.5, and PM10. The analysis of these data was focused on the situation in Wuhan, based on daily averaged concentrations. The NO2 concentrations started to decrease a few days before the Spring Festival and increased after about two weeks, except in 2020 when they continued to be low. SO2 concentrations behaved in a similar way, whereas CO, PM2.5, and PM10 also decreased during the Spring Festival but did not trace NO2 concentrations as SO2 did. As could be expected from atmospheric chemistry considerations, O3 concentrations increased. The analysis of the effects of the Spring Festival and the COVID-19 containment measures was complicated due to meteorological influences. Uncertainties contributing to the estimates of the different effects on the trace gas concentrations are discussed. The situation in Wuhan is compared with that in 26 provincial capitals based on 30-day averages for four years, showing different effects across China.

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Formation mechanisms of atmospheric nitrate and sulfate during the winter haze pollution periods in Beijing: gas-phase, heterogeneous and aqueous-phase chemistry

Cited by 118 publications

References 65 publications

Emergency Response Measures to Alleviate a Severe Haze Pollution Event in Northern China during December 2015: Assessment of Effectiveness

Emergency Response Measures to Alleviate a Severe Haze Pollution Event in Northern China during December 2015: Assessment of Effectiveness

Wintertime Particulate Matter Decrease Buffered by Unfavorable Chemical Processes Despite Emissions Reductions in China

The Impact of the Control Measures during the COVID-19 Outbreak on Air Pollution in China

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