Reduction In PM2 Research Articles

City street landscape strategy with the consideration of urban wind corridors for mitigating traffic-generated PM2.5 effect in pedestrian spaces

ABSTRACT Urban wind corridors are proven to improve outdoor thermal environments and have been gradually applied to urban planning recently. However, they may also lead to pollutants flowing throughout cities. Additionally, traffic-related air pollution remains a significant issue in Taiwan. Therefore, this study proposes to create microscale air quality zoning by street landscape. A series of CFD simulations is executed to evaluate the impact of trees and shrubs on the traffic-generated fine particles (PM2.5) distribution in roadside pedestrian areas. The results show that strategic tree placement with denser spacing can control PM2.5 to be concentrated in roadway areas while simultaneously forming air quality zoning. Shrubs are effective at blocking pollution from roadways and retaining cleaner air within pedestrian spaces. In this study, optimally spaced trees achieved an impressive 88% reduction in PM2.5 concertation in pedestrian spaces, while shrubs improved by 30% compared to scenarios without green planting.

From molecules to droplets: The Fog and Aerosol InteRAction Research Italy (FAIRARI) 2021/22 campaign

Abstract The Italian Po Valley is one of the most polluted regions in Europe. During winter, meteorological conditions favor long and dense fogs, which strongly affect visibility and human health. In spring, the frequency of nighttime fogs reduces while daytime new particle formation events become more common. This transition is likely caused by a reduction in PM2.5, leading to a decrease in the relevant condensation sink. The physics and chemistry of fog and aerosol have been studied at the San Pietro Capofiume site since the 1980s, but the detailed processes driving the observed trends are not fully understood. Hence, during winter and spring 2021/22, the Fog and Aerosol InteRAction Research Italy (FAIRARI) campaign was carried out, using a wide spectrum of approaches, including in-situ measurements, outdoor chamber experiments, and remote sensing. Atmospheric constituents and their properties were measured ranging from gas molecules and molecular clusters to fog droplets. One unique aspect of this study is the direct measurement of the aerosol composition in- and outside of fog, showing a slightly greater dominance of organic compounds in the interstitial compared to the droplet phase. Satellite observations of fog provided a spatial context and agreed well with in-situ measurements of droplet size. They were complemented with in-situ chamber experiments, providing insights into oxidative processes and revealing a large secondary organic aerosol forming potential of ambient air upon chemical aging. The oxidative potential of aerosol and fog water inferred the impact of aerosol-fog interactions on particle toxicity.

Projected health benefits of air pollution reductions in a Swedish population.

A large part of the Swedish population is exposed to higher levels of air pollution than the health-centered air quality guidelines recommended by the World Health Organization (WHO). The aim of the study was to illustrate the potential health benefits of cleaner air in Sweden by conducting a comprehensive health impact assessment, using a population sample of 100,000 individuals representing the country's demographics. Exposure-response functions for various health outcomes were derived from epidemiological literature, mainly from systematic reviews and low-exposure settings. Two hypothetical scenarios were studied: a 1 µg/m3 decrease in particulate matter with an aerodynamic diameter <2.5µm (PM2.5) and nitrogen dioxide (NO2), and a reduction in PM2.5 or NO2 from average exposure corresponding to Sweden's Clean Air objectives to WHO's air quality guidelines. The findings demonstrated that even a modest decrease in air pollution concentrations can yield significant health benefits. For example, reducing PM2.5 by 1 µg/m3 was projected to correspond to a 1% to 2% decrease in mortality, a 2% reduction in myocardial infarction cases, a 4% decrease in stroke incidence, a 2% decline in chronic obstructive pulmonary disease, and a 1% decreases in lung cancer and type 2 diabetes annually. Moreover, this reduction is estimated to lower childhood asthma cases, incidences of hypertension during pregnancy, and premature births by 3%, 3% and 2%, respectively, each year. The results highlighted that even minor enhancements in air quality would lead to substantial improvements in public health.

The effect of the ultra-low emission zone on PM2.5 concentration in Seoul, South Korea

As studies regarding the positive effect of Low Emission Zones (LEZs) and people's risk perception about air pollution have increased, more powerful and specific traffic regulation policies have been required. London is the first city in the world to implement an Ultra-low Emission Zone (ULEZ) in addition to the existing LEZ. Benchmarking London's ULEZ, a ULEZ policy was implemented in Seoul, South Korea on December 1, 2019. The goal of the policy is to improve air quality by prohibiting entry of vehicles registered nationwide into Seoul's ULEZ that do not meet a specific emission standard including diesel, gasoline, and LPG fuel-based vehicles. This study analyzed the effect of Seoul's ULEZ policy on the five major atmospheric pollutants (PM2.5, PM10, NO2, CO, SO2, O3) concentration in the zone, particularly focusing on PM2.5 concentration. The analysis employs Difference-in-Differences (DD) approach, comparing data from one year before and after the policy's implementation on December 1, 2019. The findings indicate that Seoul's ULEZ policy resulted in a 9.8% increase in PM2.5 concentrations. Conversely, the policy led to reductions in PM10, NO2, CO, and SO2 concentrations by 12.0%, 17.3%, 5.9%, and 10.8%, respectively, while the effect on O3 was statistically insignificant. These empirical results suggest that the ULEZ may need to incorporate more stringent emission standards, expand its coverage, or introduce additional measures to address the unintended increase in PM2.5 concentration.

Clearing the Air to Address Pollution's Cardiovascular Health Crisis.

Air pollution is a critical global health issue that significantly impacts cardiovascular health. The air pollutant PM2.5 (particulate matter with a diameter of 2.5 micrometres or less) has been positioned as a leading environmental risk factor for morbidity and mortality, especially from cardiovascular diseases (CVDs). Using data from the World Health Organization (WHO), Global Health Observatory, and the United Nations Environment Programme, we explored global trends in air pollution, with a focus on PM2.5 levels, the implications for cardiovascular health, and the policy measures aimed at reducing their impact. Despite progress in reducing pollution levels in high-income countries, global trends show a limited annual reduction in PM2.5 concentration. The analysis highlights disparities between regions, with low- and middle-income countries bearing the brunt of air pollution-related CVDs. In 2019 alone, ambient air pollution was responsible for approximately 4.2 million deaths worldwide. Of these, 70% were caused by CVDs, with approximately 1.9 million deaths from ischemic heart disease and 900,000 deaths from stroke. Policy gaps remain a challenge, with many countries lacking adequate legally binding air quality standards. We recommend the adoption of WHO air quality guidelines, enhanced monitoring of air pollution levels, and increased investment in interdisciplinary research to understand the full scope of air pollution's effects on cardiovascular health. Addressing the global cardiovascular crisis linked to air pollution will require coordinated efforts from policymakers, healthcare systems, and global health organisations.

A Study on Ambient Air Quality and Management inCommercial Areas of Gorakhpur City

The current study evaluates the city of Gorakhpur's ambient air quality using an air quality index. For the period January 2018 to November 2022, the 24-hour average concentration of the three primary pollutants SO2, NO2, andPM10 in a commercial area close to Jalkal Bhawan in Gorakhpur city was measured. Pollutant measurements were made between January 2018 and November 2022. The IND-AQI technique was implemented to calculate the Air Quality Index. In July, the highest monthly average concentrations of PM10, SO2, and NO2 were recorded at 401.13, 36.41, and 54.02, respectively. The yearly average SO2 concentration was found to be within the CPCB- recommended limit, while NO2 was found to be slightly above the maximum allowable level. However, PM10 wasconsistently found to be above the CPCB-recommended limit. The average monthly concentration of NO2 is higherthan SO2, and the overall AQI rating was determined to be moderate. The global experiences clearly demonstratedthat international action had been city specific rather than country oriented, and as a result, statistics show a reductionin PM2.5 of 35%–40% in five years for cities like Beijing and Seoul, whereas cities like Santiago and Mexico Cityhave shown reductions in PM2.5 and PM10 concentration of 73% and 61% in 20 to 25 years, respectively. Recent research published in the Lancet found that over the past five years, CO and Sulphur dioxide levels decreased by 28.2% and 54.1%, respectively, while NO2 and O3 concertation showed no considerable improvement. The August2018 TERI and ARAI report examined several interventions and predicted their possible effects. PM2.5 and PM10 levelsin Delhi and the NCR are above average. A different scenario has been developed in light of the intervention that can improve air quality the most. The NCAP produces an estimated national level target of 20%-30% decreasesin PM2.5 and PM10 concentration by 2024 after taking into consideration the existing international and national studies. This keeps 2018 as the baseline year for concentration comparisons. Gorakhpur City has recently experienced an increase in development activity, which has led to particulate matter.

Elucidating the impacts of aerosol radiative effects for mitigating surface O3 and PM2.5 in Delhi, India during crop residue burning period

Atmospheric aerosol radiative effects regulate surface air pollution (O3 and PM2.5) via both the aerosol–photolysis effect (APE) and the aerosol–radiation feedback (ARF) on meteorology. Here, we elucidate the roles of APE and ARF on surface O3 and PM2.5 in the heavily polluted megacity, Delhi, India by using a regional model (WRF-Chem) with constraints from limited surface observations. While APE reduces surface O3 (by 6.1%) and PM2.5 concentrations (by 2.4% via impeding the secondary aerosol formations), ARF contributes to a 2.5% and 17.5% increase in surface O3 and PM2.5, respectively. The ARF from smoke enhances PM2.5 (by 8%), black carbon (by 10%), and primary organic aerosol (by 18%) during late autumn when crop residue burning is significant. The synergistic APE and ARF have a negligible impact on the total concentrations of O3 and PM2.5. Hence, the reduction of PM2.5 may lead to O3 escalation due to weakened APE. Sensitivity experiments indicate the need and effectiveness of reducing VOC emission for the co-benefits of mitigating both O3 and PM2.5 concentrations in Delhi.

Quantifying the impact of COVID-19 restrictions on air pollution in Ahvaz: a comparative dual-approach assessment of observed against baseline and forecasted criteria air pollutants.

In response to the COVID-19 pandemic, the Iranian government swiftly implemented immediate and decisive measures to control the spread of the infection. This study aims to demonstrate the impact of restriction measure on air pollution, also to highlight the potential variability in results that can arias from different methodological approach. A comprehensive dual-approach assessment was conducted to evaluate the effect of the lockdown measures on criteria air pollutants. Firstly, a traditional approach compared air quality during the pandemic period with baseline conditions from 2013 to 2019. Secondly, observed air pollution values during different periods with varying restrictions in 2020 were compared with expected values. This comprehensive analysis allows for a robust comparison and quantification of the impact of different lockdown measures in Ahvaz. The study revealed significant changes in air pollutant concentrations in Ahvaz during 2020, with variations observed across different pollutants. Notable reductions were observed in O3 levels, particularly in November (-54.44% compared to the baseline) and December (-63.58% compared to expected values). Decreases in CO levels were observed in multiple months, while substantial reductions in PM10 and PM2.5 were observed during various periods. Inconsistencies in the magnitudes and directions of changes were found when comparing baseline and forecasted values. The overall stringency index showed an inverse association with changes in O3, NO2, and CO, with international travel controls and restrictions on internal movement having significant impacts. This study provides valuable insights into the impact of COVID-19 lockdown measures on air pollution in Ahvaz, Iran, using a comprehensive dual-approach assessment. The findings highlight the effectiveness of these measures in reducing specific criteria air pollutants and emphasize the importance of implementing appropriate strategies for air quality management during similar public health emergencies.

Major air pollution and climate policies in NYC and trends in NYC air quality 1998-2021.

Air pollution poses serious health risks to humans, with particular harm to children. To address the gap in understanding the efficacy of policies to reduce exposure to air pollution, we sought to assess the temporal relationship between the enactment of major air pollution and climate policies in NYC and trends in air quality during the period 1998-2021. We used previously available data from citywide monitoring and new data from the Columbia Center for Children's Environmental Health (CCCEH) longitudinal cohort studies of mothers and children living in communities in Northern Manhattan and the South Bronx. We utilized publicly available citywide air monitoring data for particulate matter (PM2.5) and nitrogen dioxide (NO2) from 2009 to 2021 from the New York City Community Air Survey (NYCCAS) database and CCCEH cohort data on residential exposure to PM2.5 and NO2 and personal exposure to polycyclic aromatic hydrocarbons (PAH) during pregnancies occurring from 1998-2016 and 1998-2021, respectively. We compared annual and overall reductions in PM2.5 and NO2 citywide and reductions in PAH concentrations in the cohort studies. As previously reported, annual average concentrations of pollutants in NYC dropped significantly over time. Between 1998 and 2021, PM2.5 and NO2 concentrations were reduced citywide by 37 and 31%, respectively. In our CCCEH cohorts, between 1998 and 2016, the annual average PM2.5 and NO2 concentrations also decreased significantly by 51 and 48%, respectively. Between 1998 and 2020, PAH concentrations decreased significantly by 66%. While it is not possible to link improved air quality to a single policy, our analysis provides evidence of a cumulative beneficial effect of clean air and climate policies enacted between 1998 and 2021 both city-wide and in our cohorts residing in communities that have been disproportionately affected by air pollution. There are important implications for health benefits, particularly for children, who are known to be especially vulnerable to these exposures. The results support further environmental and social policy changes to prevent the serious health impacts of air pollution from fossil fuel emissions.

Economic and environmental benefits of optimized waste transportation routes in Khulna

Urban transportation is a big source of pollution and greenhouse gas emissions. Khulna City handles the waste of 1.23 million people daily, using Heavy Duty Diesel Vehicles (HDDV) that release major environmental pollutants. The current waste transportation routes lack proper planning, leading to extra fuel consumption and pollutant emissions. This study aims to reduce fuel consumption and socio-environmental costs by improving waste transportation routes. Present collection routes, collecting points, and the speed of 30 waste collector vehicles were tracked using GPS devices for ten months between July 2023 and April 2024. The network dataset was modified according to four types of waste collector vehicles. ArcGIS Pro was used to find the optimal paths and their lengths. Fuel usage and prices were estimated using simple fuel consumption rate calculations. The lengths of current and optimal routes were used in COPERT to measure pollutant emissions. The results show that improved routes lower fuel consumption costs by approximately USD 55.39 per day and CO2 emissions by about 38.242 tonnes per year. Reductions in CO, CH4, NMVOC, NO2, PM10, and PM2.5 were roughly 9.3%, 9.53%, 9.21%, 9.29%, 9.35%, and 9.3%, respectively. This study demonstrates a comprehensive approach for improving solid waste management covering both financial efficiency and environmental effects.

Analysis of the impact of growing green walls based on the reduction of PM2.5 particles in the resilient central urban fabric

Analysis of the impact of growing green walls based on the reduction of PM2.5 particles in the resilient central urban fabric

Impact of green infrastructure on PM10 in port-adjacent residential complexes: A finite volume method-based computational fluid dynamics study

This study examines the effects of PM10 reduction by introducing green infrastructure (GI) in residential areas adjacent to ports, where significant pollutant emissions from ships are prevalent. Using finite volume method (FVM)-based computational fluid dynamics (CFD) simulations, we evaluated 30 scenarios based on various GI types and spacings and validated these simulations using observational data. The assessed GI types included trees and shrubs (hedges). Planting configurations were categorized into single (T for trees, H for hedges) and mixed (TH for both trees and hedges) plantings, with one or two rows and spacings of trees from 6 m to 14 m at 2 m intervals. We also considered both aerodynamic and depositional effects as mechanisms for PM10 reduction by GI. Our results revealed the following: 1) Plant spacing significantly influenced PM10 reduction, with both excessively narrow and wide spacings being suboptimal. (2) Trees proved to be more effective, whereas combining them with shrubs offers limited advantages. 3) Among the shrubs, the adsorption effect was more influential on PM10 reduction than the aerodynamic effects. These insights are not limited to port regions but also offer foundational knowledge for enhancing urban air quality, setting the groundwork for subsequent studies.

Evaluation of the PM2.5 concentrations in South America: Climatological patterns and trend analysis

This study assessed the concentration of particulate matter with an aerodynamic diameter of 2.5 (PM2.5) over South America (SA) based on climatological patterns and trend analysis. This study used monthly PM2.5 data from the Copernicus Atmosphere Monitoring Service (CAMS) at the European Centre for Medium-range Weather Forecasts from 2003 to 2022. The bilinear interpolation method was applied to the data resampling from 0.75° × 0.75°–0.25° × 0.25° spatial resolution, and subsequently, the climatological analysis was performed on seasonal and annual scales of PM2.5 concentrations for the 20-year series. The assessment comprised three main stages: 1) descriptive statistics, 2) seasonal and annual climatology patterns, and 3) trend analysis (Mann-Kendall - MK and Pettitt tests). Results indicated that the largest annual PM2.5 concentrations were found in the Amazon region and northern Paraguay due the El-Niño South Oscillation events (2003–2005, 2007, 2010, 2020, and 2022). The annual average PM2.5 concentrations exceeded the WHO recommended limit (5 μg m−3), ranging from 15.57 μg m−3 (1999) and 22.74 μg m−3 (2007 and 2010). The highest PM2.5 concentrations were observed in the Amazon and Chile (Santiago), reaching 160.4 μg m−3 annually and 177.8 μg m−3 seasonally (spring). Elevated seasonal PM2.5 concentrations were attributed to increased deforestation and wildfires associated with meteorological systems such as the Bolivian high and subtropical jets during dry periods (winter and spring). The MK test revealed a significant reduction in PM2.5 concentrations between 2003 and 2022, observed in Argentina (north), Brazil (arc of reforestation), Bolivia (south), and Chile (north). Reduction values varied between 0.5 and 10 μg m−3.year−1 annually and during winter, attributed to no-tillage practices in regions cultivating commodities. The Pettitt test also identified significant structural changes occurring in 2006–2008 and 2010–2011, aligning with areas highlighted in the MK test. This study provides valuable insights for air quality and environmental monitoring managers to mitigate PM2.5 pollution in SA.

Insight of effects of air quality and sustainable aviation fuel blend on energy saving and emission reduction in airport

Air quality in airport attracts a widespread attention due to the emission of GHGs and pollutants related with aircraft flight. Sustainable aviation fuel (SAF) has confirmed PM2.5 reduction due to free of aromatics and sulphur, and thus air quality improvement in airport is prospected by SAF blend. Two types of SAF were assessed the potential of energy saving and emission reduction by ZF850 jet engine. FT fuel is characterized with only paraffins without aromatics and cycloparaffins while HCHJ fuels is characterized with no aromatics. The descend of air quality and SAF blend were both investigated the effect on the engine performance and emission characteristic. The critical parameters were extracted from fuel compositions and air pollutants. Ambient air with a higher PM2.5 could lead to the rise of engine emission especially in UHC and PM2.5 despite at the low thrust setting and high thrust setting, and even couple with 3.2% rise in energy consumption and 1% reduction in combustion efficiency. CO, NO and NO2 in ambient air show less influence on engine performance and emission characteristic than PM2.5. Both types of SAF blend were observed significant reductions in PM2.5 and UHC. PM2.5 reduction obtained 37.9%—99.8% by FT blend and 0.64%-93.9% by HCHJ blend through the whole trust settings. There are almost 6.67% positive benefit in TSFC through the whole thrust setting by 7% FT blend. The effects of air quality and SAF blend on engine emission present significant changes on PM and UHC but the slight change on CO and NOx. By SAF blend, the energy saving and pollutant reduction obtained could be both benefit for air quality improvement in airport and further reduce engine emission as the feedback of less pollutants in ambient air.Graphical

Comparative Assessment of the Impact of COVID-19 Lockdown on Air Quality: A Multinational Study of SARS-CoV-2 Hotspots.

In response to the global COVID-19 pandemic, nations implemented lockdown measures to contain the virus. This study assessed air pollution levels during and after lockdowns, focusing on the following heavily affected locations: Oulu and Helsinki in Finland, Paris in France, Madrid in Spain, Milan in Italy, and Wuhan in China. Air Quality Index (AQI) data from these locations over two years were analyzed to understand the effects of lockdowns. The study compared COVID-19 lockdowns in these six cities with SARS-CoV-2 measurements using statistical methods. Variations in outdoor pollutants were evaluated through tests, revealing significant differences. Parametric analyses and regression were employed to study the impacts of lockdown measures on pollution and their relationships. The study comprehensively analyzed the effects of COVID-19 lockdowns on air quality, identifying differences, quantifying changes, and exploring patterns in each city. Pollutant correlations varied among cities during the lockdowns. Regression analysis highlighted the impact of independent variables on pollutants. Decreases in NO2 were observed in Helsinki, Madrid, Oulu, Paris, and Milan, reflecting reduced traffic and industrial activities. Reductions in PM2.5 and PM10 were noted in these cities and in Wuhan, except for O3 levels, which increased. The reduction in human activities improved air quality, particularly for NO2 and PM10. Regional variations underscore the need for tailored interventions. The study observed a substantial decrease in both PM2.5 and NO2 levels during the COVID-19 lockdowns, indicating a direct correlation between reduced human activities, such as transportation and industrial operations, and improved air quality. This underscores the potential impact of environmental measures and suggests the need for sustainable practices to mitigate urban pollution.

Co-Benefits of Antimicrobial Resistance Mitigation from China’s PM2.5 Air Pollution Reduction Between 2014–2020

The One Health concept acknowledges the importance of multiple dimensions in controlling antimicrobial resistance (AMR). However, our understanding of how anthropological, socioeconomic, and environmental factors drive AMR at a national level remains limited. To explore associations between potential contributing factors and AMR, this study analyzed an extensive database comprising 13 major antibiotic-resistant bacteria and over 30 predictors (e.g., air pollution, antibiotic usage, economy, husbandry, public services, health services, education, diet, climate, and population) from 2014 to 2020 across China. The multivariate analysis results indicate that fine particulate matter with a diameter of 2.5 μm or less (PM2.5) is associated with AMR, accounting for 12% of the variation, followed by residents’ income (10.3%) and antibiotic usage density (5.1%). A reduction in PM2.5 of 1 µg·m−3 is linked to a 0.17% decrease in aggregate antibiotic resistance (p < 0.001, R2 = 0.74). Under different scenarios of China’s PM2.5 air-quality projections, we further estimated the premature death toll and economic burden derived from PM2.5-related antibiotic resistance in China until 2060. PM2.5-derived AMR is estimated to cause approximately 27 000 (95% confidence interval (CI): 6468–48 830) premature deaths and about 0.51 (0.12–0.92) million years of life lost annually in China, equivalent to an annual welfare loss of 8.4 (2.0–15.0) billion USD. Implementing the “Ambitious Pollution 1.5 ℃ Goals” scenario to reduce PM2.5 concentrations could prevent roughly 14 000 (3324–26 320) premature deaths—with a potential monetary value of 9.8 (2.2–17.6) billion USD—from AMR by 2060. These results suggest that reducing air pollution may offer co-benefits in the health and economic sectors by mitigating AMR.

Dynamic evolution of particulate and gaseous emissions for typical residential coal combustion

Residential coal combustion still accounts for half of the heating energy consumption in many developing countries. The dynamic variation during the combustion process importantly determines the combustion facility design and appropriate air quality assessment, which was omitted in conventional studies. This study investigated the emissions of particulate and gaseous pollutants during the combustion process for typical coal types using online monitoring. During the first pyrolysis stage with temperature climbing, the organic aerosols (OA) and gases reached peak concentration. The second fierce combustion stage had the highest temperature and produced the highest cumulative emissions, particularly a substantial amount of black carbon for coals with higher volatile content. Using higher-quality coals will undoubtedly reduce PM emissions, by a factor of 10 from bituminous to anthracite coal. However, more ultrafine particles (d < 0.1 μm) from cleaner coal may pose additional health risks. Anthracite and honeycomb coal had approximately twice the energy content and emitted more CO2 per unit mass of fuel and had more persistent SO2 emissions throughout the burnout stage. The oxygenation of OA and organic gases remained increased during combustion, suggesting the pyrolysis products underwent oxidation before being emitted. The investigation of the coal combustion process suggests the importance of reducing volatiles to control PM emissions, but the potential negative synergistic effects between PM reduction and increased carbon emissions should also be considered.

Effects of seasonal management programs on PM2.5 in Seoul and Beijing using DN-PMF: Collaborative efforts from the Korea-China joint research

South Korea and China have implemented increasingly stringent mitigation measures to reduce the health risks from PM2.5 exposure, jointly conducting a ground-based air quality observation study in Northeast Asia. Dispersion normalized positive matrix factorization (DN-PMF) was used to identify PM2.5 sources in Seoul and Beijing and assess the effectiveness of the seasonal management programs (SMPs) through a comparative study. Samples were collected during three periods: January-December 2019, September 2020-May 2021, and July 2021-March 2022. In Seoul, ten sources were resolved (Secondary nitrate: 8.67 μg/m3, 34 %, Secondary sulfate: 5.67 μg/m3, 22 %, Motor vehicle: 1.83 μg/m3, 7.2 %, Biomass burning: 2.30 μg/m3, 9.1 %, Residual oil combustion: 1.66 μg/m3, 6.5 %, Industry: 2.15 μg/m3, 8.5 %, Incinerator: 1.39 μg/m3, 5.5 %, Coal combustion: 0.363 μg/m3, 1.4 %, Road dust/soil: 0.941 μg/m3, 3.7 %, Aged sea salt: 0.356 μg/m3, 1.4 %). The SMP significantly decreased PM2.5 mass concentrations and source contributions of motor vehicle, residual oil combustion, industry, coal combustion, and biomass burning sources (p-value < 0.05). For Seoul, the reduction effects of the SMPs were evident even considering the influence of the natural meteorological variations and the responses to COVID-19. In Beijing, nine sources were resolved (Secondary nitrate: 12.6 μg/m3, 28 %, Sulfate: 8.27 μg/m3, 18 %, Motor vehicle: 3.77 μg/m3, 8.4 %, Biomass burning: 2.70 μg/m3, 6.0 %, Incinerator: 4.50 μg/m3, 10 %, Coal combustion: 3.52 μg/m3, 7.8 %, Industry: 5.01 μg/m3, 11 %, Road dust/soil: 2.92 μg/m3, 6.5 %, Aged sea salt: 1.63 μg/m3, 3.6 %). Significant reductions in PM2.5 mass concentrations and source contributions of industry, coal combustion, and incinerator (p-value < 0.05) were observed, attributed to the SMP and additional measures enforced before the 2022 Beijing Winter Olympics. Unlike comparing PM2.5 mass concentration variations using conventional methods, investigation of the source contribution variations of PM2.5 by using DN-PMF can provide a deeper understanding of the effectiveness of the air quality management policies.

Atmospheric reactive nitrogen conversion kicks off the co-directional and contra-directional effects on PM2.5-O3 pollution

As the two important ambient air pollutants, particulate matter (PM2.5) and ozone (O3) can both originate from gas nitrogen oxides. In this study, applied by theoretical analysis and machine learning method, we examined the effects of atmospheric reactive nitrogen on PM2.5-O3 pollution, in which nitric oxide (NO), nitrogen dioxide (NO2), gaseous nitric acid (HNO3) and particle nitrate (pNO3−) conversion process has the co-directional and contra-directional effects on PM2.5-O3 pollution. Of which, HNO3 and SO2 are the co-directional driving factors resulting in PM2.5 and O3 growing or decreasing simultaneously; while NO, NO2, and temperature represent the contra-directional factors, which can promote the growth of one pollutant and reduce another one. Our findings suggest that designing the suitable co-controlling strategies for PM2.5-O3 sustainable reduction should target at driving factors by considering the contra-directional and co-directional effects under suitable sensitivity regions. For co-directional driving factors, the design of suitable mitigation strategies will jointly achieve effective reduction in PM2.5 and O3; while for contra-directional driving factors, it should be more patient, otherwise, it is possible to reduce one item but increase another one at the same time.

Reductions in PM2.5 exposure and mortality risk following household cooking fuel interventions in Kenyan cities using a ‘synthetic population’ model

Reductions in PM2.5 exposure and mortality risk following household cooking fuel interventions in Kenyan cities using a ‘synthetic population’ model