Publications by authors named "Cao Junji"
Modulating the electronic structure of noble metals via electronic metal-support interaction (EMSI) has been proven effectively for facilitating molecular oxygen activation and catalytic oxidation reactions. Nevertheless, the investigation of the fundamental mechanisms underlying activity enhancement has primarily focused on metal oxides as supports, especially in the catalytic degradation of volatile organic compounds. In this study, a novel Pt catalyst supported on nitrogen-doped carbon encapsulating FeNi alloy, featuring ultrafine Pt nanoparticles, was synthesized.
View Article and Find Full Text PDFAir pollution carries different disease burdens across all age groups, with the elderly and children being the most affected. Therefore, it is of practical significance to study air pollution exposure characteristics of different age groups in the context of accelerating aging in China. In this study, we used the number of people and air pollutant concentration data at the township-level scale (the smallest administrative unit in China) to calculate population-weighted PM concentration exposure (PM PWE) values of different age groups in the Beijing-Tianjin-Hebei (BTH) region, quantified the pollution exposure disparities among different groups, and analyzed the spatiotemporal changes in such differences and their driving factors.
View Article and Find Full Text PDFAerosol light absorption alleviates particulate pollution during wintertime haze events.
Proc Natl Acad Sci U S A
January 2025
Aerosol light absorption has been widely considered as a contributing factor to the worsening of particulate pollution in large urban areas, primarily through its role in stabilizing the planetary boundary layer (PBL). Here, we report that absorption-dominated aerosol-radiation interaction can decrease near-surface fine particulate matter concentrations ([PM]) at a large-scale during wintertime haze events. A "warm bubble" effect by the significant heating rate of absorbing aerosols above the PBL top generates a secondary circulation, enhancing the upward motion (downward motion) and the convergence (divergence) in polluted (relatively clean) areas, with a net effect of lowering near-surface [PM].
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- Ambient PM pollution in China poses serious health risks, despite recent declines in overall PM concentrations; understanding of chemical constituents remains limited due to inadequate monitoring.
- A Super Learner model using satellite data and other information predicts daily organic carbon (OC) concentrations with high accuracy, revealing elevated levels in Northern China from industrial activities and contributions from forest fires in Yunnan.
- From 2003 to 2019, national OC levels declined by 1.3% annually, with regional variations, and the OC/EC ratio analysis indicated different pollution sources in urban versus rural areas, highlighting the effectiveness of air quality policies post-2013.
Exposure to fine particulate matter (PM) is recognized to induce atherosclerosis, but the underlying mechanisms are not fully understood. This study used ambient PM samples collected in one of the highly polluted regions of Guanzhong Plain in China (2017-2020) and an ApoE mouse model to investigate the association between exposure to PM and atherosclerosis. Despite a substantial decrease in the ambient concentration of PM from 266.
View Article and Find Full Text PDFAbundant residual heat from industrial emissions may provide energy resource for CO conversion, which relies on H gas and cannot be accomplished at low temperatures. Here, we report an approach to store electrons and hydrogen atoms in catalysts using sunlight and water, which can be released for CO reduction in dark at relatively low temperatures (150-300 °C), enabling on-demand CO conversion. As a proof of concept, a model catalyst is developed by loading single Cu sites on hexagonal tungsten trioxide (Cu/WO).
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- The study examines how coal-fired plants influence local environments, particularly by creating a hot and dry "heat island" effect that is 3-10 °C warmer and 30%-60% drier compared to surrounding areas.
- Measurements taken from advanced lidar technology in a coal-fired steel plant in Yuncheng, China, reveal that this heat island can affect the dispersion of pollutants by forming a mushroom-shaped cloud due to upward transport of factory emissions.
- The research indicates that pollutants from this cloud can be pushed down to ground level after sunrise, contributing to pollution peaks in urban areas and signaling a need for better air quality models that consider heat emissions from coal-fired sources.
Article Synopsis
- Shipping emissions significantly contribute to air pollution in coastal cities, prompting China to implement the Domestic Emission Control Area (DECA) policy in phases, which included stricter low-sulfur fuel mandates.
- Long-term measurements at Dian Shan Lake showed a 63% decrease in vanadium (V) concentrations after DECA 2.0 was implemented, indicating improvements in air quality.
- The study emphasizes the need for ongoing monitoring and suggests that nickel (Ni) emissions may come from sources beyond shipping, highlighting the complexity of managing air pollutants.
The molecular composition of organic aerosols in ambient PM was investigated at the northern foothills of Qinling Mountain region in central China during the summer of 2022. The molecular characteristics of organic matter were analyzed using ultrahigh performance liquid chromatography coupled with high-resolution Orbitrap mass spectrometry. The number of molecular formula assignments was dominated by organosulfur species (OrgS, on average 28-47% in total).
View Article and Find Full Text PDFBioaerosol emission and exposure risk from a wastewater treatment plant in winter and spring.
Ecotoxicol Environ Saf
November 2024
Article Synopsis
- The study investigated health risks from airborne pathogens in a wastewater treatment plant (WWTP) in Xi'an, China, focusing on bacterial concentrations and types emitted from different aeration tanks.
- The Anaerobic-Anoxic-Oxic (AAO) tank was found to release significantly more culturable bacteria, especially in spring (1.58×10^5 CFU/m³), making it the highest risk area for exposure compared to other tanks.
- A total of 139 bacterial genera, including potential human pathogens like Neisseria and Escherichia-Shigella, were identified, highlighting the need for improved bioaerosol management in WWTPs.
Article Synopsis
- * The research found higher levels of water-soluble organic carbon (WSOC) and reactive oxygen species (ROS) in the biomass fuel group, while the coal group showed greater amounts of water-soluble inorganic ions and nitrogen.
- * A strong correlation between ROS and WSOC was observed in coal PMs, particularly in smaller particles, suggesting that coal combustion produces more transition metals affecting ROS levels, while specific relationships between components varied in both fuel groups.
Spatiotemporal variations of farmland crop residue burning in China from 2013 to 2022.
Sci Total Environ
December 2024
Article Synopsis
- Farmland crop residue burning (FCRB) in China has been analyzed from 2013 to 2022, showing significant effects on air quality and highlighting variations in control measures' effectiveness over time.
- The study revealed that the initial phase (2013-2017) of the "Clean Air Action" was ineffective, resulting in a 30.9% increase in FCRB, while stricter measures from 2018-2020 led to a 41.4% reduction.
- The analysis identified notable seasonal and regional differences, with the highest decreases in autumn and significant disparities across regions, emphasizing the need for tailored control strategies that consider local conditions to improve air quality.
Article Synopsis
- Over 300 daily PM filter samples were collected in Xi'an and Chongqing from October 2019 to May 2020 to analyze organic aerosol composition using dual mass spectrometric techniques.
- Seven distinct sources of water-soluble organic aerosols were identified, including dust and solid fuel combustion-related sources, with consistent findings across both mass spectrometry methods.
- The study highlights the significance of these techniques for understanding air pollution sources, which is crucial for future research, health studies, and air quality management policies.
Article Synopsis
- - China is striving for carbon neutrality by 2060 while also improving air quality, but achieving this goal creates challenges regarding nitrogen emissions and ecosystem health.
- - Research shows that following new emission control measures, nitrogen deposition in China's land could decrease by 44-57%, leading to a significant reduction in natural ecosystem productivity by 11-20%.
- - This interplay between reducing nitrogen emissions and achieving carbon neutrality could hinder the effectiveness of natural carbon sinks, highlighting the need to carefully balance these environmental goals.
Article Synopsis
- Developing effective metal-based monolithic catalysts for treating volatile organic compound (VOC) pollution is essential, and 2D metal oxides offer a promising alternative despite challenges in traditional loading methods.
- A new molten salt-loading strategy has been introduced to create a unique catalyst called CoO/Fe-S, which features 2D CoO growing on Fe foam, resulting in significantly improved catalytic performance—reducing the reaction temperature by 44 °C for effective toluene conversion.
- The presence of abundant 2D CoO/FeO composite interfaces enhances oxygen activation and toluene chemisorption, facilitating reaction mechanisms and providing insights for developing efficient catalysts for VOC oxidation.
Article Synopsis
- Formaldehyde (HCHO) is a key factor in the formation of tropospheric ozone, with this study focusing on its effects in the Guanzhong Basin, Central China, examining both man-made and natural sources of emissions.
- A severe ozone pollution incident in summer 2017 was modeled to analyze how ambient HCHO impacted ground-level ozone, revealing that secondary HCHO mainly contributed to high pollution levels, especially in the afternoons.
- The research highlighted that biogenic emissions play a significant role in producing HCHO and that controlling nitrogen oxide emissions from industries and traffic is critical for reducing ozone pollution.
Atmospheric elemental carbon pollution and its regional health disparities in China.
Environ Res Lett
December 2023
Article Synopsis
- * This study employs satellite remote sensing, machine learning, and atmospheric data to predict EC levels in China from 2005 to 2018, finding that while total PM has decreased, EC concentrations have remained stable over time.
- * The research reveals significant regional disparities in mortality due to long-term EC exposure, with first-tier cities benefiting from effective regulations, while areas with coal plants and industrial facilities show a need for stronger emission control measures.
Article Synopsis
- Atmospheric fine particulate matter (PM) can adversely affect various human body systems, leading to diseases in the respiratory, circulatory, endocrine, and urogenital systems.
- The study identifies specific diseases associated with PM exposure such as pulmonary emphysema, malignant thyroid neoplasm, and others, along with significant biological processes and genes involved in those conditions.
- Crucial pathways impacted by PM are linked to processes like cancer progression, cell cycle regulation, and apoptosis, highlighting PM's role in inducing disease at a molecular level.
Article Synopsis
- Solid fuel combustion in rural China emits high levels of harmful pollutants, particularly polycyclic aromatic hydrocarbons (PAHs), posing serious health risks, especially to the elderly.
- Indoor PAH concentrations are higher than outdoor levels for households using solid fuels, while biogas users see significantly lower PAH emissions (64-82% less).
- The study highlights that high molecular weight PAHs are more prevalent in solid fuel households, indicating an increased carcinogenic risk, with exposure levels for solid fuels resulting in a concerning internal health risk compared to cleaner fuel sources.
Long-term spatial distribution and implication of black and brown carbon in the Tibetan Plateau.
Sci Total Environ
October 2024
Article Synopsis
- Black carbon (BC) and brown carbon (BrC) on the Tibetan Plateau impact climate change and glacial melting, but collecting data is tough due to the region's high altitude.
- This study used a random forest algorithm to combine satellite data and ground measurements from 2018-2021, producing spatial data on BC and BrC concentrations at a fine resolution for the years 1980, 2000, and 2020.
- The results showed peak BC levels in 2000, with BC concentrations being 3-4 times higher than BrC, especially prevalent in the southeastern TP, indicating an increasing importance of BC over the decades.
Biomass burning organic aerosols (BBOA) are key components of atmospheric particulate matter, yet the effects of aging process on their chemical composition and related properties remain poorly understood. In this study, fresh smoke emissions from the combustion of three types of agricultural biomass residues (rice, maize, and wheat straws) were photochemically aged in an oxidation flow reactor. The changes in BBOA composition were characterized by offline analysis using ultrahigh performance liquid chromatography coupled with Orbitrap mass spectrometry.
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- * This review summarizes recent findings on sources, distribution, behaviors, and toxic effects of atmospheric MPs, highlighting the current methodologies for studying these aspects.
- * It advocates for the use of Machine Learning (ML) and Artificial Intelligence (AI) to enhance research on atmospheric MPs by improving data analysis and understanding their dynamics, calling for more scholarly focus in this area.
Article Synopsis
- Intermediate volatility organic compounds (IVOCs) play a vital role in forming secondary organic aerosols (SOAs) but are often overlooked in related studies.
- This study focused on IVOC emissions in the Qinghai-Tibetan Plateau, where solid fuels are used, revealing higher emission factors due to incomplete combustion in oxygen-deficient conditions.
- The research highlights that IVOCs significantly contribute to air pollution, with combined emissions leading to SOA production almost five times greater than emissions from volatile organic compounds (VOCs) alone, underscoring the need for better emission inventories and pollution strategies.
Article Synopsis
- The assessment of elemental carbon (EC) and its environmental impact is complex due to its diverse composition and morphology, particularly concerning its role in secondary aerosol formation in the troposphere.
- A study at Mt. Hua investigated the characteristics of EC particles and identified six major types, revealing that anthropogenic emissions significantly influence the lower free troposphere's chemistry.
- The research also found distinct patterns in sulfate and nitrate levels associated with different EC types, emphasizing the importance of atmospheric interactions and diurnal cycles in aerosol formation processes.
Article Synopsis
- The study examined carbon emissions from various fuels (coal, wood, biogas, and LPG) in rural villages of China to understand their impact on atmospheric pollution, especially in heavy pollution areas.
- Results showed that while biogas and LPG reduced emissions of organic carbon and elemental carbon compared to coal and wood, they still emitted more fine particulate matter than anticipated.
- The investigation indicated that coal combustion resulted in the highest concentrations of carbon monoxide and contributed significantly to regional atmospheric aerosols, posing serious health risks due to indoor air pollution from solid fuel use.