Chemical Components Of PM2 Research Articles

Synergic effects and possible mechanism of emodin and stilbene glycosides on colorectal cancer

BackgroundPolygonum multiflorum (PM) is a core herb that enhances immunity. It can also detoxify, reduce swelling, and intercept malaria. Its main components, emodin (EMD) and 2,3,5,4'-Tetrahydroxy stilbene-2-O-β-D-glucoside (stilbene glycoside, TSG), have good anti-cancer potential. PurposeThe study aims to investigate synergic effects of EMD and TSG on CRC and its possible mechanism. MethodsNetwork pharmacology and bioinformatics were used to identify targets. HPLC was used to analyze the effective ingredients in PM and to determine the content of the main ingredients. HT-29 cells were used for in vitro experiments. Cell Counting Kit-8 (CCK8) and scratch test were used to detect the effects of various chemical components of PM on the proliferation and migration of HT-29 cells, and Western Bolt (WB) test was used to evaluate the effects of EMD and TSG on P53 pathway. In vivo experiments, the effects of EMD and TSG were evaluated by measuring tumor weight and tumor volume in CRC mice model and histological analysis were carried out with HE staining. The expressions of HSP90, P53, COX2, and ROS were detected by quantitative reverse transcription polymerase chain reaction (PCR), and IL-1β, IL-4, IL-6, IL-10, TGF-β and IFN-γ were detected by enzyme linked immunosorbent assay (ELISA). WB and Immunohistochemistry (IHC) were used to detect the expression of P53 related proteins. ResultsNetwork pharmacology showed PM closely related to colorectal cancer pathway and the core targets included STAT3 and P53; bioinformatics indicated P53 played an important role in the development and prognosis of CRC; chemical analysis showed identified and quantified gallic acid (GA), cis-TSG, trans-TSG, Emodin glucoside(EMDG), physcion glucoside (PHYG), EMD in PM; EMD induced apoptosis and TSG inhibited migration of HT-29 cells; EMD and TSG could coordinately shrink tumor size of CRC mice, elevate expressions of F4/80, decrease the content of IL-6 and TGF-β, promote tumor oxidized and reduce expression of P53 and STAT3 in the tumor. ConclusionsIn vitro experiments showed that TSG inhibited cancer cell migration and EMD induced apoptosis. EMD and TSG had synergic effects on CRC, whose possible mechanism might be to regulate the expression of cytokines and inhibit P53 pathway.

Composition, sources and potential source regions of aerosols under contrasting environment conditions of Lanzhou, a valley city of western China: Observations by means of topographic relief

Chemical composition in PM2.5 (particulate matter with a diameter less than 2.5 μm) is essential information for evaluating their climate, environment and health effects. Concentrations of carbonaceous components and water-soluble ions in PM2.5 and the differences under varying environmental conditions in western China are poorly understood. During the period from July 2021 to July 2022, we conducted synchronous offline sampling of PM2.5 by deploying four identical sampling devices at altitudes ranging from 1500 m to 3600 m along the unique topography of the Lanzhou River Valley in western China. The major chemical components in PM2.5 are carbonaceous aerosols, NO3− and SO42− with the average concentrations of 28.07, 8.66 and 6.01 μg m−3 for the urban and surrounding rural areas, and 9.94, 2.45 and 3.11 μg m−3 for background site of Lanzhou. The concentrations of OC (organic carbon) and EC (elemental carbon) gradually decrease from urban area to suburban sites with increasing elevation. Coal combustion, vehicle emissions, secondary formation, salted aerosols and surface dust resuspension are found to be the primary sources of PM2.5 in both urban and rural areas of Lanzhou. The contribution of vehicle emissions decreases from urban areas to mountainous rural areas, contrary to the coal combustion and biomass burning. The study is significant for taking targeted measures to solve air pollution problem at different environmental conditions (urban, rural and background) over complex terrain.

An association between PM2.5 components and respiratory infectious diseases: A China's mainland-based study

The particulate matter with diameter of less than 2.5 µm (PM2.5) is an important risk factor for respiratory infectious diseases, such as scarlet fever, tuberculosis, and similar diseases. However, it is not clear which component of PM2.5 is more important for respiratory infectious diseases. Based on data from 31 provinces in mainland China obtained between 2013 and 2019, this study investigated the effects of different PM2.5 components, i.e., sulfate (SO42−), nitrate (NO3−), ammonium (NH4+), and organic matter (OM), and black carbon (BC), on respiratory infectious diseases incidence [pulmonary tuberculosis (PTB), scarlet fever (SF), influenza, hand, foot, and mouth disease (HFMD), and mumps]. Geographical probes and the Bayesian kernel machine regression (BKMR) model were used to investigate correlations, single-component effects, joint effects, and interactions between components, and subgroup analysis was used to assess regional and temporal heterogeneity. The results of geographical probes showed that the chemical components of PM2.5 were associated with the incidence of respiratory infectious diseases. BKMR results showed that the five components of PM2.5 were the main factors affecting the incidence of respiratory infectious diseases (PIP>0.5). The joint effect of influenza and mumps by co-exposure to the components showed a significant positive correlation, and the exposure-response curve for a single component was approximately linear. And single-component modelling revealed that OM and BC may be the most important factors influencing the incidence of respiratory infections. Moreover, respiratory infectious diseases in southern and southwestern China may be less affected by the PM2.5 component. This study is the first to explore the relationship between different components of PM2.5 and the incidence of five common respiratory infectious diseases in 31 provinces of mainland China, which provides a certain theoretical basis for future research.

Chemical composition, sources and formation mechanism of urban PM2.5 in Southwest China: a case study at the beginning of 2023

Abstract. Despite significant improvements in air quality in recent years, the Sichuan Basin (SCB) is still facing frequent haze pollution in winter, and the causes of severe haze formation have not yet been fully investigated. In this study, the chemical components of PM2.5 (i.e., particulate matter with an aerodynamic diameter of less than 2.5 µm) in a typical pollution period at the beginning of 2023 in Chengdu, a megacity in the SCB, were characterized by bulk-chemical and single-particle analysis, and the PM2.5 sources and formation mechanism of pollution were analyzed. The average mass concentration of PM2.5 during the study period was 95.6 ± 28.7 µg m−3. Organic matter (OM) was the most abundant component (35.3 %), followed by nitrate (22.0 %), sulfate (9.2 %) and ammonium (7.8 %). The individual aerosol particles were classified into five categories, i.e., mineral, OM, secondary inorganic aerosol (SIA), soot and fly ash/metal particles, and most of them were in the state of being internally mixed. The entire observation period could be divided into two non-pollution periods (NP-1 and NP-2) and two haze periods (Haze-1 and Haze-2). With the evolution of pollution, the bulk-chemical and single-particle analysis exhibited similar characteristics, suggesting that Haze-1 was mainly caused by pollutants related to fossil fuel combustion, especially local mobile sources, while Haze-2 was triggered by the rapidly increasing secondary pollutants, which mainly came from regional transmission. The PM2.5 sources included dust (8.5 %), biomass burning (3.5 %), coal combustion (15.4 %), industrial processes (6.5 %), vehicular emissions (25.6 %) and secondary sources (40.5 %). Analysis of Weather Research and Forecasting model with Chemistry (WRF-Chem) model results showed that the average contributions of local sources and regional transmission to pollution in Chengdu were the same (50 % vs. 50 %). In addition, the source composition and WRF-Chem simulation results in different periods confirmed our analysis of the formation mechanisms of the two haze events. This study confirms that further significant reductions in PM2.5 in Chengdu are still needed, and more effective policies for local emission reduction or joint prevention and control of regional air pollution will be necessary in the future.

Case Analysis of Heavy Air Pollution Process in Xi'an Using Multi-source Data

Air pollution continues to be a serious problem in Xi'an. A heavy pollution process and formation mechanism were investigated in Xi'an in January 2019 using multi-source methods (such as material balance and sulfur/nitrogen oxidation rate (SOR/NOR)). The multi-source data included the concentrations of PM2.5, PM10, SO2, NO2, CO, and O3; the chemical components of PM2.5; the meteorological records of ground and vertical observations; the atmospheric reanalysis data. Three phases were obtained including the accumulation phase (P1), maintenance phase (P2), and dispersion phase (P3) during the pollution period. The pollution event was primarily attributed to the superposition of adverse weather conditions and feedback effects. During the periods of P1 and P2, the area of Xi'an was affected by blocking and zonal westerly airflow at 500 hPa (with flat westerly airflow) and uniform-distribution pressure at sea level with a limited pressure gradient and stable weather conditions, and the easterly wind was dominant at 925 hPa; not all of these factors were conducive to the pollutant diffusion. An interaction feedback mechanism between meteorological conditions and heavy pollution could be studied using the ground-based microwave radiometer. The correlations between PM2.5 and inversions of water vapor density, relative humidity, air temperature, and temperature inversion were significant with coefficients of 0.86, 0.62, 0.53, and 0.38, respectively. The feedback mechanism was primarily manifested as follows:with the pollutant accumulation, the radiative cooling effect could lead to or strengthen the occurrence and intensity of temperature inversion, decrease the mixed layer height, and cause moisture accumulation. High humidity could further maintain the pollution by accelerating the secondary formation and promoting the hygroscopic growth of aerosol particles. Therefore, the dominant chemical components to PM2.5were secondary inorganic ions (SO42-+NO3-+NH4+, SNA) and "other" components during the period of P2, with contributions of 43.2% and 23.1%, respectively. In addition, the peak values of PM2.5, SOR, NOR, and the light extinction coefficients all occurred on the same days (January 3 and 6), indicating that the effect of secondary formation was important for both heavy pollution events and visibility. The total contribution of NH4NO3, organic matter (OM), (NH4)2SO4, and EC to the light extinction coefficient was more than 85%. Limited variations in the proportion for components were observed in three phases. During the period of P3, the strong cold air in the mid-lower atmosphere was conducive to the dry and clean air sinking and the pressure gradient at sea level increasing. These were beneficial to the diffusion of air pollutants and water vapor.

Chemical characteristics of fine tire wear particles generated on a tire simulator

Tire wear is one of the major sources of traffic-related particle emissions, however, laboratory data on the components of tire wear particles (TWPs) is scarce. In this study, ten brands of tires, including two types and four-speed grades, were chosen for wear tests using a tire simulator in a closed chamber. The chemical components of PM2.5 were characterized in detail, including inorganic elements, water-soluble ions (WSIs), organic carbon (OC), elemental carbon (EC), and polycyclic aromatic hydrocarbons (PAHs). Inorganic elements, WSIs, OC, and EC accounted for 8.7 ± 2.1%, 3.1 ± 0.7%, 44.0 ± 0.9%, and 9.6 ± 2.3% of the mass of PM2.5, respectively. The OC/EC ratio ranged from 2.8 to 7.6. The inorganic elements were dominated by Si and Zn. The primary ions were SO42− and NO3−, and TWPs were proven to be acidic by applying an ionic balance. The total PAHs content was 113 ± 45.0 μg g−1, with pyrene being dominant. In addition, the relationship between the chemical components and tire parameters was analyzed. Inorganic elements and WSIs in TWPs were more abundant in all-season tires than those in winter tires, whereas the content of PAHs was the opposite. The mass fractions of OC, Si, and Al in the TWPs all showed increasing trends with increasing tire speed grade, but the PAHs levels showed a decreasing trend. Ultimately, to provide more data for further research, a TWPs source profile was constructed considering the tire weighting factor.

Association between air pollutants, sources, and components of PM2.5 and pediatric outpatient visits for respiratory diseases in Shanghai, China

BackgroundAlthough exposure to ambient air pollution has been associated with outpatient visits for respiratory diseases, there have been few recent studies investigating the effect of the chemical components of ambient particulate matter with an aerodynamic diameter of <2.5 μm (PM2.5) on pediatric outpatient visits for respiratory diseases. In addition, there remains scarce evidence regarding PM2.5 components and sources that are most relevant to pediatric outpatient visits for respiratory diseases. This study aimed to determine the association between four ambient pollutants (SO2, NO2, PM10, and PM2.5), sources and chemical components of PM2.5, and pediatric outpatient visits for respiratory diseases. MethodsThis time-series study was conducted between January 1, 2018 and December 31, 2019 in Shanghai, China. A positive matrix factorization model was used to determine the source apportionment of PM2.5, and a generalized additive model was employed to evaluate the effect of air pollutants and the components and sources of PM2.5 on pediatric outpatient visits for respiratory diseases. In addition, a two-pollutant model was used to investigate the potential confounding effects of the copollutants. ResultsThe study revealed that a 10 μg/m3 increase in SO2, NO2, PM10, and PM2.5 concentrations corresponded to increases of 3.4% (95% CI: 2.3%–4.6%), 1.9% (95% CI: 1.7%–2.2%), 0.5% (95% CI: 0.4%–0.7%), and 0.5% (95% CI: 0.4%–0.7%), respectively, in pediatric outpatient visits for respiratory diseases on the day with the most significant lag effect. Notably, Ni exposure more strongly correlated with increased pediatric outpatient visits for respiratory diseases, with the percent of increase by 10 ng/m3 ranging from 7.6% to 16.5%. Moreover, among the PM2.5 sources researched in this study, oil and coal combustion were the most important for increasing pediatric outpatient visits for respiratory diseases. ConclusionThis study demonstrates that ambient pollutants and the chemical components and sources of PM2.5 were significantly associated with an elevated risk of pediatric outpatient visits for respiratory diseases and provides insights into the differential health risks of PM2.5 components.

The impact of particulate pollution control on aerosol hygroscopicity and CCN activity in North China

Air quality has greatly improved in China owing to the strict control policy enforced during the last decade. This study investigated the impact of particulate pollution control on aerosol hygroscopicity and cloud condensation nuclei (CCN) activity in North China based on several data sources. The mass concentration of particles with an aerodynamic diameter smaller than 2.5 µm (PM2.5) decreased by one third from the summer of 2014 to the summer of 2020 in Xinzhou (XZ). The mass fractions of aerosol chemical components in PM2.5 also clearly changed, showing an increase in hydrophilic inorganics and a decrease in hydrophobic organics and black carbon from 2014 to 2020. Measurements of the particle number size distribution in XZ indicate that the occurrence frequency of new particle formation (NPF) events decreased significantly from 2014 to 2020, leading to a reduction in the generation of daytime ultrafine particles. The weakened NPF and increasing influence of morning and evening peak emissions modified the diurnal variations of the number concentration of condensation nuclei (N CN) and CCN (N CCN). The aerosol activation ratio was always higher in the summer of 2014 than in the summer of 2020. These results demonstrate that particulate pollution control can decrease N CN and N CCN but enhance aerosol hygroscopicity and activation ability.

Quantifying the pollution characteristics of chemical components in PM2.5 in the North China Plain, China: Spatiotemporal variation and health risk

To fully grasp the features of aerosol chemical composition in North China Plain (NCP) region from winter through spring, this study chose five typical cities (Jinan, Shijiazhuang, Taiyuan, Tianjin and Zhengzhou) and analyzed their spatiotemporal variation, sources and health risk from January to March 2018. The average mass concentration of PM2.5 ranged from 65.65 μg/m3 (Tianjin)–101.23 μg/m3 (Shijiazhuang). It was high in the southwest and low in the northeast because of better diffusion conditions in coastal areas than inland. In PM2.5, organic carbon (OC) accounted for 8.28% (Jinan)–35.36% (Shijiazhuang), elemental carbon (EC) accounted for 3.75% (Tianjin)–13.31% (Shijiazhuang), water-soluble ions (WSIs) accounted for 34.8% (Shijiazhuang)–57.16% (Tianjin), and elements accounted for 3.01% (Zhengzhou)–4.74% (Taiyuan). In carbonaceous aerosols, primary OC (POC) was dominant in coastal areas while secondary OC (SOC) was dominant inland. The source of OC and EC emissions in northern and central cities was coal combustion, whereas in southern cities, both vehicles and coal combustion were involved. Although NO3−, SO42− and NH4+ accounted for 70.09% (Taiyuan)–73.02% (Jinan) of WSIs over the whole region, SO42− dominated in the west and center region, and NO3− dominated in the east and south. K, Fe, and Ca had the highest concentrations in elements, accounting for 76.77% (Tianjin)–79.80% (Taiyuan). Potential ecological risk index (RI) for 7 toxic heavy metal elements—Cd, Cr, Cu, Ni, Pb, V and Zn—more than 600 (Pb contributed 51.37%) in Taiyuan and more than 1200 (Cd contributed 87.54%–97.71%) in other cities showed severe metal pollution. Kids and adults living here faced non-carcinogenic risk by exposure pathways of dermal contact and respiratory inhalation, respectively. At the same time, kids also faced non-carcinogenic risk.

Exploring the formation mechanism of fine particles in an ex-heavily polluted Northwestern city, China

Fine particle pollution is still a severe issue in the northwestern region of China where the formation mechanism of which remains ambiguous due to the limited studies there. In this study, a comprehensive study on the chemical composition and sources of PM2.5 at an ex-heavily polluted northwestern city was conducted, based on filter sampling data obtained from three consecutive winter campaigns during 2020–2022. The average PM2.5 during the three winter campaigns were 170.9 ± 66.4, 249.0 ± 75.7, and 200.9 ± 47.6 μg/m3, respectively, with the daily maximum value of PM2.5 exceeds 400 μg/m3 under stagnant meteorological conditions charactered by high relative humidity (>60 %) and low wind speed (<1 m/s). The major chemical components in PM2.5 were found to be inorganic aerosol (55.2 %) that mainly constituted by sulfate (24.2 %), and mineral dust (14.9 %); while the carbonous species contributed a minor fraction (∼13 %). In addition, (NH4)2SO4 and NH4NO3 were the dominate contributors to appearance of low visibility (<3 km) which together accounting for over 85 % of light extinction coefficient (bext) during heavy polluted period. Source appointment of fine particles was then conducted by applying the positive matrix factorization method, and the primary sources were resolved to be coal combustion (27.7 %) and biomass burning (18.6 %), followed by industrial dust (16.2 %), residential combustion (15.3 %), traffic emissions (11.9 %) and dust aerosol (10.4 %). To explore the potential formation mechanism of fine particle pollution, the chemical evolution pattern combined with gaseous pollutants and meteorological parameters were further analyzed, which refine the important role of primary emissions in the forming of high sulfate aerosol loading, while secondary formation was largely suppressed during the winter period that totally different from those reported in the developed regions of China, thus indicating more effort should be paid on the reduction of primary particles emissions in the northwestern cities than on its gaseous percussors.

Exposure to airborne PM&lt;sub&gt;2.5&lt;/sub&gt; chemical exposome increases heart rate of middle- and old-aged populations

&lt;p&gt;Previous studies have rarely focused on the effects of industrial chemicals on heart rate. There is also a lack of epidemiological investigations to elucidate the mixture effects of complex components of fine particulate matter (PM&lt;sub&gt;2.5&lt;/sub&gt;) on cardiovascular health and identify the key toxic components. Here, a population health-oriented methodology is established to quantify mixed effects of airborne PM&lt;sub&gt;2.5&lt;/sub&gt; chemical exposome and identify key components. This methodology was applied to a cross-sectional study to elucidate the mixture effect of industrial chemical components of PM&lt;sub&gt;2.5&lt;/sub&gt; on the heart rate of middle- and old-aged populations (including 373 people from seven Chinese cities) and further identify key chemical components for the effect. Exposure to seven groups of industrial chemicals, including phthalate esters (PAEs), adipate esters (AEs), benzothiazoles and benzotriazoles (BTHs &amp; BTRs), benzophenones and benzoates (BZPs &amp; BZAs), bisphenols (BPs), alkyl organophosphate esters (alkyl-OPEs) and aryl organophosphate esters (aryl-OPEs), was observed to significantly increase the heart rate of study participants. Seven chemicals, including dimethyl isophthalate (DMiP), di-iso-nonyl adipate (DiNA), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV-328), ethyl-4-aminobenzoate (EAB), bisphenol F (BPF), triethyl phosphate (TEP) and tricresyl phosphate (TCrP), were identified as the key components driving the adverse effect on heart rate. Our study highlights the cardiovascular hazards of airborne PM&lt;sub&gt;2.5&lt;/sub&gt; chemical exposome.&lt;/p&gt;

Association between short-term exposure to fine particulate matter components and cause-specific mortality in Korea: a multi-city time-series study

Background/Aim: Many studies have reported fine particulate matter (PM2.5) has various health effects. The effects of PM2.5 have been shown to vary in space and time. One of the underlying explanations was the variability in the distribution of chemical components in PM2.5. Therefore, identifying whether the health effects of each component of PM2.5 differ can provide evidence for the heterogeneous mortality risk of PM2.5. Our study aims to estimate the associations between short-term exposure to components and cause-specific mortality across six major cities in Korea. Methods: Daily mass concentration of PM2.5 and 25 components of PM2.5 were obtained from the National Institute of Environmental Research for 2012-2019. We used six intensive air monitoring stations in each of the six major cities: Seoul, Incheon, Daejeon, Gwangju, Ulsan, and Jeju. We employed a two-stage analysis. In the first stage, we conducted generalized additive model with quasi-Poisson regression to estimate city-specific associations of mortality with PM2.5 and its components on the same day. We excluded Asian dust days and adjusted the model for temperature, relative humidity, and time trend. In the second stage, we used fixed-effects meta-analysis to pool the city-specific estimates. Results: We could not find statistically significant association of PM2.5 and all components with all-cause mortality. Potassium was associated with 2.2% increment (95% CI:0.4%, 4.0%) in cardiovascular mortality per IQR increase (0.24&amp;#x3bc;g/m3). Magnesium ion was associated with 0.7% increment (95% CI: 0.1%, 1.4%) in respiratory mortality per IQR increase (0.01&amp;#x3bc;g/m3). Conclusion: This study suggests potential adverse health effects of particles produced by dust, salt, or traffic. In contrast to previous studies, our results showed no association of elemental carbon or nitrate with any mortality. Further study would be needed to account for the joint and lagged effect of components and meteorological variables. Keyword: fine particulate matter, components, multi-city analysis, epidemiology, health

Chemical components of PM2.5 in different seasons in Harbin, China

The seasonal characteristics of fine particulate matter (PM2.5) were investigated from October 2020 to April 2021 (spreading fall, winter and spring) in Harbin, a city located in northeast China. The mass concentrations of PM2.5 in winter were significantly higher than those in fall and spring. Moreover, our results indicated that various aerosol species had obvious seasonality. The proportions of secondary components were higher in winter than other two seasons. In contrast, the ratios of nitrate to sulfate (NO3−/SO42−) showed lower levels in winter, which was because both the ratios of nitrogen dioxide to sulfur dioxide (NO2/SO2) and the ratios of nitrogen oxidation ratio to sulfur oxidation ratio (NOR/SOR) exhibited lower values in winter than in fall and spring. With PM2.5 increased, the NO3−/SO42− ratios showed increasing trends in all three seasons, which was mainly attributed to the increase of NOR/SOR ratios in fall and spring, and the increase of both NO2/SO2 and NOR/SOR ratios in winter. This result highlighted that nitrate was more important than sulfate as a driver for the growth of PM2.5 during the period of heavy air pollution. Additionally, the sources of organic aerosol (OA) in different seasons were also distinctly different. Overall, the sum of biomass burning OA (BBOA) and secondary OA (SOA) contributed >70% of OA in three seasons. The fractional contributions of BBOA to total OA, notably, exhibited higher levels in fall and spring, because of intensive open agricultural fires. The SOA fractions in OA were larger in winter, likely due to higher relative humidity which facilitated the secondary formation. A large increase in the proportions of BBOA was observed during polluted days in fall and spring compared to clean days. In comparison, during heavily-polluted periods, secondary formation made a dominant contribution to organic matter in winter.

Impact of Beijing's “Coal to Electricity” program on ambient PM2.5 and the associated reactive oxygen species (ROS)

The Beijing “Coal to Electricity” program provides a unique opportunity to explore air quality impacts by replacing residential coal burning with electrical appliances. In this study, the atmospheric ROS (Gas-phase ROS and Particle-phase ROS, abbreviated to G-ROS and P-ROS) were measured by an online instrument in parallel with concurrent PM2.5 sample collections analyzed for chemical composition and cellular ROS in a baseline year (Coal Use Year-CUY) and the first year following implementation of the “Coal to Electricity” program (Coal Ban Year-CBY). The results showed PM2.5 concentrations had no significant difference between the two sampling periods, but the activities of G-ROS, P-ROS, and cellular ROS in CBY were 8.72 nmol H2O2/m3, 9.82 nmol H2O2/m3, and 2045.75 µg UD /mg PM higher than in CUY.Six sources were identified by factor-analysis from the chemical components of PM2.5. Secondary sources (SECs) were the dominant source of PM2.5 in the two periods, with 15.90% higher contribution in CBY than in CUY. Industrial Emission & Coal Combustion sources (Ind. & CCs), mainly from regional transport, also increased significantly in CBY. The contributions of Aged Sea Salt & Residential Burning sources to PM2.5 decreased 5.31% from CUY to CBY. The correlation results illustrated that Ind. & CCs had significant positive correlations with atmospheric ROS, and SECs significantly associated with cellular ROS, especially nitrates (r = 0.626, p = 0.000). Therefore, the implementation of the “Coal to Electricity” program reduced PM2.5 contributions from coal and biomass combustion, but had little effect on the improvement of atmospheric and cellular ROS.

Analysis on the Characteristics of Oxidation Potential and Influence Sources of PM2.5 in Baoding City in Winter

In order to explore the characteristics of PM2.5 oxidation potential and its impact sources in the suburbs of Baoding City in the winter of 2018, the dithiothreitol (DTT) method was used to determine the reactive oxygen species in PM2.5. Pearson correlation was used to analyze the relationship between the chemical components in PM2.5 and the oxidation potential. PMF was used to analyze the pollution source of DTTv. Firstly, the results showed that the average value of ρ(PM2.5) in Baoding in winter was (140.96±70.67) μg·m-3 higher than the concentration of PM2.5 in Beijing during the same period. Secondly, both the DTTv and DTTm values of the oxidation potential were higher during the day than those at night[DTTv was (2.37±0.76) nmol·(min·m3)-1 during the day and (2.14±1.17) nmol·(min·m3)-1 at night; DTTm was (0.96±0.60) pmol·(min·μg)-1 during the day and (0.76±0.41) pmol·(min·μg)-1 at night]. This showed that the atmospheric environment during the day was more conducive to the generation and survival of active oxygen. In addition, through the analysis of the correlation between DTTv and carbohydrates, inorganic salt ions, OC, EC, and water-soluble metals, it was found that metal Fe, oxalate, and NH4+ had a high correlation with DTTv both day and night (during the day:r=0.790, P<0.01, at night:r=0.960, P<0.01; during the day:r=0.609, P<0.01, at night:r=0.577, P<0.01; during the day:r=0.627, P<0.01, at night:r=0.586, P<0.01), and OC, levoglucan, mannan, and galactan were only highly correlated with DTTv in the daytime (r=0.675, P<0.01; r=0.701, P<0.01; r=0.662, P<0.01; r=0.671, P<0.01). Finally, according to the PMF source analysis, there were five main pollution sources that affected DTTv:secondary sources (29.9%), biomass combustion (29.2%), dust (11.2%), mineral dust and industrial sources (8.6%), and traffic sources (21.1%). The influence of secondary sources and biomass combustion on DTTv was dominant.

The association of chemical composition particularly the heavy metals with the oxidative potential of ambient PM2.5 in a megacity (Guangzhou) of southern China

Atmospheric fine particulate matters (PM2.5) can cause adverse health effects through the generation of reactive oxygen species (ROS), which is normally characterized by the oxidative potential (OP). However, the particulate components that are mainly responsible for the ROS-induced OP remain controversial and warrant further investigation, especially in megacities where high exposure exists and particulate composition is complex. In this study, we measured the OP of PM2.5 using the dithiothreitol (DTT) assay with and without chelation of metals in a megacity in southern China, Guangzhou, in January and April. We explored the correlations between OP and various chemical components in PM2.5, including water-soluble ions, organic carbon (OC), elemental carbon (EC), and metal elements. There are strong correlations between OPDTTv (volume-normalized) and concentrations of PM2.5, OC, and EC, while the correlations between OPDTTm (mass-normalized) and mass-normalized water-soluble ions, OC, EC or metal elements are weak. The OP values with chelation were reduced by ∼90%, indicating that water-soluble heavy metals were the major contributors to OP of PM2.5 in Guangzhou. On the other hand, correlations between OPDTTm and OC improved significantly after the chelation of heavy metals, implying that OC explains the variance of OPDTTm although its contribution to OP is much smaller than that of heavy metals. We postulate that there might be synergetic effects between water-soluble heavy metals (which contribute most to OP) and OC (which explains the variance of OP) in ROS generation by PM2.5. The findings of the current study provide a better understanding on the critical components in PM2.5 and potential synergism that might be responsible for health effects in urban areas.

Enhanced secondary organic aerosol formation during dust episodes by photochemical reactions in the winter in Wuhan

To investigate the effect of frequently occurring mineral dust on the formation of secondary organic aerosol (SOA), 106 volatile organic compounds (VOCs), trace gas pollutants and chemical components of PM2.5 were measured continuously in January 2021 in Wuhan, Central China. The observation period was divided into two stages that included a haze period and a following dust period, based on the ratio of PM2.5 and PM10 concentrations. The average ratio of secondary organic carbon (SOC) to elemental carbon (EC) was 1.98 during the dust period, which was higher than that during the haze period (0.69). The contribution of SOA to PM2.5 also increased from 2.75% to 8.64%. The analysis of the relationships between the SOA and relative humidity (RH) and the odd oxygen (e.g., OX = O3 + NO2) levels suggested that photochemical reactions played a more important role in the enhancement of SOA production during the dust period than the aqueous-phase reactions. The heterogeneous photochemical production of OH radicals in the presence of metal oxides during the dust period was believed to be enhanced. Meanwhile, the ratios of trans-2-butene to cis-2-butene and m-/p-xylene to ethylbenzene (X/E) dropped significantly, confirming that stronger photochemical reactions occurred and SOA precursors formed efficiently. These results verified the laboratory findings that metal oxides in mineral dust could catalyse the oxidation of VOCs and induce higher SOA production.

Seasonal variation of water-soluble brown carbon in Qingdao, China: Impacts from marine and terrestrial emissions

Brown carbon (BrC) has been attracting more and more attention owing to its significant effects on climate. However, the limited knowledge on its chemical composition and sources limits the precision of aerosol radiative forcing estimated by climate models. In this study, the chemical components of PM2.5 and optical properties of water-soluble BrC (WS–BrC) were investigated from atmospheric particles collected in summer and winter in Qingdao, China. On the whole, though there were slight diurnal variations, seasonal differences were more obvious. Due to the influence of emission sources and meteorological conditions, the heavier pollution of carbonaceous aerosols occurred in winter. By comparison, the absorption Ångström exponent (AAE) and mass absorption efficiency of WS-BrC at 365 nm (MAE365) showed that WS-BrC in winter had stronger wavelength dependence and light absorption capacity, which might be associated with biomass burning source contributions. This was further confirmed by a strong correlation between the light absorption coefficient at 365 nm (Abs365) and non-sea salt K+, an indicator for biomass burning emissions. Four fluorescent components (C1∼C4) with high unsaturation in water-soluble organic carbon (WSOC) were identified by excitation-emission matrix fluorescence spectroscopy combined with parallel factor analysis method, which showed that WSOC in Qingdao was mainly related to humic-like chromophores. It is worth noting that C1 was similar to the water-soluble chromophore of simulated marine aerosols, which proved that marine emissions do have a certain impact on atmospheric particulate matter in coastal areas. In addition, the results of source analysis showed that WS-BrC originated from different terrestrial sources in different seasons. The current results may help to improve the knowledge of optical properties of WS-BrC in coastal cities, optimize the global climate model and formulate air management policies.

Significant reduction in atmospheric organic and elemental carbon in PM2.5 in 2+26 cities in northern China

To better understand the change characteristics and reduction in organic carbon (OC) and elemental carbon (EC) in particulate matter (PM) with a diameter of ≤2.5 μm (PM2.5) driven by the most stringent clean air policies and pandemic-related lockdown measures in China, a comprehensive field campaign was performed to measure the carbonaceous components in PM2.5 on an hourly basis via harmonized analytical methods in the Beijing-Tianjin-Hebei and its surrounding region (including 2 + 26 cities) from January 1 to December 31, 2020. The results indicated that the annual average concentrations of OC and EC reached as low as 6.6 ± 5.7 and 1.8 ± 1.9 μg/m3, respectively, lower than those obtained in previous studies, which could be attributed to the effectiveness of the Clean Air Action Plan and the impact of the COVID-19-related lockdown measures implemented in China. Marked seasonal and diurnal variations in OC and EC were observed in the 2 + 26 cities. Significant correlations (p < 0.001) between OC and EC were found. The annual average secondary OC levels level ranged from 1.8–5.4 μg/m3, accounting for 37.7–73.0% of the OC concentration in the 2 + 26 cities estimated with the minimum R squared method. Based on Interagency Monitoring of Protected Visual Environments (IMPROVE) algorithms, the light extinction contribution of carbonaceous PM to the total amount reached 21.1% and 26.0% on average, suggesting that carbonaceous PM played a less important role in visibility impairment than did the other chemical components in PM2.5. This study is expected to provide an important real-time dataset and in-depth analysis of the significant reduction in OC and EC in PM2.5 driven by both the Clean Air Action Plan and COVID-19-related lockdown policies over the past few years, which could represent an insightful comparative case study for other developing countries/regions facing similar carbonaceous PM pollution.

Chemical Composition Characteristics and Source Apportionment of PM2.5 in Ceramic Industrial Base during Winter

The national architectural ceramic industrial center in east China is suffering from serious ambient fine particle pollution. The study reported herein describes an effort to ascertain the degree and sources of the PM2.5 collected in a ceramic industrial base during winter. The major chemical components in PM2.5 were analyzed, including carbonaceous aerosols, water-soluble ions, and inorganic elements. The chemical mass balance (CMB) model, backward trajectory method and potential source contribution function model, etc. were used to track and identify possible sources and contributions in the formation of the PM2.5. The results showed that the average PM2.5 concentration during sampling period was 134 ± 74.7 µg m–3, which exceeding World Health Organization (WHO) Air Quality Guidelines levels. The dominant components in the PM2.5 at this sampling site were found to be secondary ions (sulfate and nitrate) and carbon fractions. Water-soluble ions and total carbon contributed about 48.7% and 13.9% of the PM2.5 mass, respectively. In addition, the SO42–/NO3– ratio in the ambient PM2.5 during the sampling period was 1.16, indicating that it was the result of primarily emissions from stationary sources. Furthermore, source apportionment using the CMB model indicated that a ceramic industry source was the main contributor to the PM2.5 mass, which accounted for about 27.9%, and this was followed by secondary formation dust sources, and gasoline/diesel vehicle exhaust emissions and motor vehicle non-exhaust emissions. Based on the backward trajectory analysis and potential source apportionment, it was found that PM2.5 regional transmission existed, but it originated primarily from local sources and surrounding areas. Hence, this study provided a scientific basis for identifying the sources of PM2.5 pollution during a typical pollution period and provided important input for PM2.5 control strategies in a typical industrial area.