Revisiting the dynamics of gaseous ammonia and ammonium aerosols during the COVID-19 lockdown in urban Beijing using machine learning models

Article Engineering, Environmental

Vehicular Emissions Enhanced Ammonia Concentrations in Winter Mornings: Insights from Diurnal Nitrogen Isotopic Signatures

Mengna Gu et al.

Summary: NH3 concentrations in winter mornings in urban Beijing are enhanced by vehicle emissions, which is a common phenomenon with significant diurnal variations.

ENVIRONMENTAL SCIENCE & TECHNOLOGY (2022)

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Article Engineering, Environmental

Revealing Drivers of Haze Pollution by Explainable Machine Learning

Linlu Hou et al.

Summary: This study used machine learning methods to investigate the roles of meteorological factors, emissions, and chemistry in five severe haze episodes that occurred before or during the COVID-19 lockdown in China. The study found that in addition to high levels of primary emissions, meteorological factors played a dominant role in PM2.5 pollution in these episodes, followed by chemistry.

ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS (2022)

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Article Engineering, Environmental

COVID-19 Lockdowns Afford the First Satellite-Based Confirmation That Vehicles Are an Under-recognized Source of Urban NH3 Pollution in Los Angeles

Hansen Cao et al.

Summary: In situ measurements have suggested that vehicle emissions may be a major source of NH3 in urban areas, surpassing agricultural sources. A study conducted during the COVID-19 lockdowns used satellite data to constrain vehicle NH3 emissions in western Los Angeles, finding that they make up 60-95% of total NH3 emissions, significantly higher than previous estimates. This highlights the importance of considering and controlling vehicle NH3 emissions, which have been overlooked in the past.

ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS (2022)

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Editorial Material Multidisciplinary Sciences

Increasing importance of ammonia emission abatement in PM2.5 pollution control

Wen Xu et al.

SCIENCE BULLETIN (2022)

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Article Environmental Sciences

Nonlinear response of nitrate to NOx reduction in China during the COVID-19 pandemic

Chuanhua Ren et al.

Summary: This study demonstrates that despite reductions in NOx emissions, nitrate formation can still increase during the COVID-19 lockdown period due to factors such as increased O3 levels and ammonia concentrations. The findings highlight the complexity of nitrate pollution control and emphasize the importance of a coordinated and targeted approach to mitigate its impacts.

ATMOSPHERIC ENVIRONMENT (2021)

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Article Multidisciplinary Sciences

Abrupt but smaller than expected changes in surface air quality attributable to COVID-19 lockdowns

Zongbo Shi et al.

Summary: The COVID-19 lockdowns resulted in decreased NO2 concentrations and increased O-3 concentrations in most cities, with reductions in PM2.5 concentrations as well. However, the actual air quality improvements were likely more limited than previously believed based on some earlier reports or observational data.

SCIENCE ADVANCES (2021)

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Article Meteorology & Atmospheric Sciences

Changes of ammonia concentrations in wintertime on the North China Plain from 2018 to 2020

Yuexin He et al.

Summary: A study using machine learning techniques found that ammonia concentrations in Chinese urban and rural areas significantly decreased during the 2020 Spring Festival, with a more obvious reduction in urban areas compared to rural areas. Future ammonia emission control strategies should focus on emissions from the transportation, industrial, and residential sectors.

ATMOSPHERIC RESEARCH (2021)

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Article Engineering, Environmental

Atmospheric Ammonia in Beijing during the COVID-19 Outbreak: Concentrations, Sources, and Implications

Yangyang Zhang et al.

Summary: This study found higher NH3 concentrations and lower delta N-15-NH3 values in Beijing in 2020 compared to 2017. NH3 concentrations did not significantly increase after the lockdown ended, but delta N-15-NH3 values increased. Non-agricultural sources contributed a significant portion of NH3, slightly increasing after the lockdown, highlighting the importance of meteorological conditions in NH3 concentration variations.

ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS (2021)

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Article Engineering, Environmental