Revealing Drivers of Haze Pollution by Explainable Machine Learning

Environmental Science & Technology Letters, Год журнала: 2022, Номер 9(2), С. 112 - 119

Опубликована: Янв. 4, 2022

Many places on earth still suffer from a high level of atmospheric fine particulate matter (PM2.5) pollution. Formation pollution event or haze episode (HE) involves many factors, including meteorology, emissions, and chemistry. Understanding the direct causes key drivers behind HE is thus essential. Traditionally, this done via chemical transport models. However, substantial uncertainties are introduced into model estimation when there significant changes in emissions inventory due to interventions (e.g., COVID-19 lockdown). Here we applied Random Forest coupled with Shapley additive explanation algorithm, post hoc technique, investigate roles major meteorological primary chemistry five severe HEs that occurred before during lockdown China. We discovered that, addition PM2.5 these episodes was largely driven by effects (with average contributions 30–65 μg m–3 for HEs), followed (∼15–30 m–3). Photochemistry likely pathway formation nitrate, while air humidity predominant factor forming sulfate. Our results highlight machine learning data has potential be complementary tool predicting interpreting

Язык: Английский

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The formation and mitigation of nitrate pollution: comparison between urban and suburban environments

Atmospheric chemistry and physics, Год журнала: 2022, Номер 22(7), С. 4539 - 4556

Опубликована: Апрель 8, 2022

Abstract. Ambient nitrate has been of increasing concern in PM2.5, while there are still large uncertainties quantifying the formation aerosol. The pathways aerosol at an urban site and a suburban Pearl River Delta (PRD) investigated using observation-constrained box model. Throughout campaigns, pollution episodes were constantly accompanied with increase concentrations fractions both sites. simulations demonstrate that chemical reactions daytime night contributed significantly to boundary layer two However, nighttime predominantly occurred aloft residual site, downward transport from morning is important source (53 %) for surface whereas similar amounts produced nocturnal which results little ground site. We show was volatile-organic-compound-limited (VOC-limited) regime transition identical response ozone reduction VOC emissions can be efficient approach mitigate areas through influencing hydroxyl radical (OH) N2O5 production, will also beneficial synergistic control regional pollution. highlight relative importance site-specific, quantitative understanding various provide insights developing mitigation strategies.

Язык: Английский

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Synergistic Effect of Co(III) and Co(II) in a 3D Structured Co₃O₄/Carbon Felt Electrode for Enhanced Electrochemical Nitrate Reduction Reaction

ACS Applied Materials & Interfaces, Год журнала: 2021, Номер 13(24), С. 28348 - 28358

Опубликована: Июнь 14, 2021

As nitrate contamination causes serious environmental problems, it is necessary to develop stable and efficient electrocatalysts for electrochemical reduction reaction (ENRR). Here, a nonprecious Co3O4/carbon felt (CF) electrode with 3D structure was prepared by integrating electrodeposition calcination methods. This structured Co3O4/CF exhibits high-rate constant of 1.18 × 10–4 s–1 cm–2 the ENRR, surpassing other Co3O4 electrodes in previous literature. Moreover, also has an excellent stability decrease 6.4% after 10 cycles. Density functional theory calculations, electron spin resonance analysis, cyclic voltammetry were performed study mechanism ENRR on electrode, proving that atomic H* (indirect pathway) plays prominent role NO3– clarifying synergistic effect Co(III) Co(II) Co(II)–Co(III)–Co(II) redox cycle ENRR: prefers adsorption favors production H*. Based this synergy, relatively large amounts surface (1.3 Co(II)/Co(III) ratio) maintained controlling temperature 200 °C lower energy barrier formation 0.46 eV than ratios, which beneficial forming enhancing performance ENRR. Thus, suggests building optimizing ratio are important designing electrocatalyst

Язык: Английский

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Important Role of NO₃ Radical to Nitrate Formation Aloft in Urban Beijing: Insights from Triple Oxygen Isotopes Measured at the Tower

Environmental Science & Technology, Год журнала: 2021, Номер 56(11), С. 6870 - 6879

Опубликована: Авг. 25, 2021

Until now, there has been a lack of knowledge regarding the vertical profiles nitrate formation in urban boundary layer (BL) based on triple oxygen isotopes. Here, we conducted measurements anomaly (Δ17O-NO3–) 325 m meteorological tower Beijing during winter and summer. The simultaneous suggested different mechanisms aerosols at ground level 120 260 due to less efficient mixing under stable atmospheric conditions. Particularly, chemical processes three heights were found between clean days polluted winter. On days, nocturnal chemistry (NO3 + HC N2O5 uptake) contributed production equally with OH/H2O NO2 level, while it dominated aloft (contributing 80% m), higher aerosol liquid water content O3 concentration there. reactions heights. contribution pathway increased from might be attributed hydrolysis HONO then further photolysis OH radicals day. In contrast, proportion H2O decreased m, likely low relative humidity that inhibited residual layer. Our results highlighted differences meteorology gaseous precursors could largely affect particulate within BL.

Язык: Английский

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High atmospheric oxidation capacity drives wintertime nitrate pollution in the eastern Yangtze River Delta of China

Atmospheric chemistry and physics, Год журнала: 2022, Номер 22(7), С. 4355 - 4374

Опубликована: Апрель 5, 2022

Abstract. Nitrate aerosol plays an increasingly important role in wintertime haze pollution China. Despite intensive research on nitrate chemistry recent years, quantitative constraints the formation mechanisms of Yangtze River Delta (YRD), one most developed and densely populated regions eastern China, remain inadequate. In this study, we identify major pathways their key controlling factors during winter period YRD using 2-year (2018–2019) field observations detailed observation-constrained model simulations. We find that high atmospheric oxidation capacity, coupled with liquid water content (ALWC), made both heterogeneous hydrolysis dinitrogen pentoxide (N2O5) gas-phase OH nitrogen dioxide (NO2) for region, contribution percentages 69 % 29 urban areas 63 35 suburban episodes, respectively. further gas-to-particle partitioning nitric acid (HNO3) was very efficient so rate-determining step overall process NOx to HNO3 through processes. The capacity (i.e., availability O3 radicals) factor production rate from During COVID-19 lockdown (January–February 2020), enhanced greatly promoted hence weakened response emission reductions areas. Our study sheds light highlights demand synergetic regulation emissions mitigate

Язык: Английский

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Unexpected Increases of Severe Haze Pollution During the Post COVID‐19 Period: Effects of Emissions, Meteorology, and Secondary Production

Journal of Geophysical Research Atmospheres, Год журнала: 2022, Номер 127(3)

Опубликована: Янв. 28, 2022

Abstract Unexpectedly frequent severe haze episodes were observed in Beijing during February–March 2021 after two phases of clean air action plan (2013–2020), yet the causes remained unclear. Here, we conducted real‐time fine particle (PM2.5) composition measurements January–March using a time‐of‐flight aerosol chemical speciation monitor and an aethalometer compared with those coronavirus disease (COVID‐19) period 2020. Our results showed ubiquitously elevated concentrations chloride, black carbon (BC), primary organic (POA) 2021, suggesting increased emissions post‐COVID‐19 period. By machine learning‐based random forest (RF) algorithm, found largely different responses changes to meteorology months. After decoupling effects meteorology, PM2.5 from 2020 reduced −35.6% −29.0% January, −24.1% −4.5% February, +92.6% +34.2% March, respectively. demonstrate dominant roles stagnant secondary production formation March 2021. In particular, that compositions deweathered fairly similar between ratios OA inorganic aerosols close. study indicates influence meteorological conditions is great importance for better evaluation mitigating strategies pollution due large impact on species particularly short

Язык: Английский

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Decade-long trends in chemical component properties of PM2.5 in Beijing, China (2011−2020)

The Science of The Total Environment, Год журнала: 2022, Номер 832, С. 154664 - 154664

Опубликована: Март 18, 2022

Язык: Английский

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Recent Progress in Atmospheric Chemistry Research in China: Establishing a Theoretical Framework for the “Air Pollution Complex”

Advances in Atmospheric Sciences, Год журнала: 2023, Номер 40(8), С. 1339 - 1361

Опубликована: Апрель 28, 2023

Atmospheric chemistry research has been growing rapidly in China the last 25 years since concept of "air pollution complex" was first proposed by Professor Xiaoyan TANG 1997. For papers published 2021 on air (only included Web Science Core Collection database were considered), more than 24 000 authored or co-authored scientists working China. In this paper, we review a limited number representative and significant studies atmospheric few years, including (1) sources emission inventories, (2) chemical processes, (3) interactions with meteorology, weather climate, (4) between biosphere atmosphere, (5) data assimilation. The intention not to provide complete all progress made but rather serve as starting point for learning about advances reviewed paper have enabled theoretical framework complex be established, provided robust scientific support highly successful control policies China, created great opportunities education, training, career development many graduate students young scientists. This further highlights that developing low-income countries are heavily affected can benefit from these advances, whilst at same time acknowledging challenges still remain hopefully addressed over next decades.

Язык: Английский

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Increasing contribution of nighttime nitrogen chemistry to wintertime haze formation in Beijing observed during COVID-19 lockdowns

Nature Geoscience, Год журнала: 2023, Номер 16(11), С. 975 - 981

Опубликована: Окт. 12, 2023

Язык: Английский

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Transport Pathways of Nitrate Formed from Nocturnal N₂O₅ Hydrolysis Aloft to the Ground Level in Winter North China Plain

Environmental Science & Technology, Год журнала: 2023, Номер 57(7), С. 2715 - 2725

Опубликована: Фев. 1, 2023

Particulate nitrate (NO3–) has currently become the major component of fine particles in North China Plain (NCP) during winter haze episodes. However, contributions formation pathways to ground NO3– NCP are not fully understood. Herein, were comprehensively investigated based on model simulations combined with two-month field measurements at a rural site NCP. The results indicated that nocturnal chemistry N2O5 hydrolysis aloft could contribute evidently pollution episodes high aerosol water contents, achieving contribution percentages 25.2–30.4% total. In addition commonly proposed vertical mixing breaking boundary layer early morning, two additional transport (frontal downdrafts and downslope mountain breezes) nighttime found make higher NO3–. Considering dominant role (69.6–74.8%) diurnal formation, reduction NOx emissions daytime may be an effective control measure for reducing regional

Язык: Английский

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