Chemical Components Of Particulate Matter Research Articles

Gradient variations of formation mechanisms and sources of PM1 at the steep slope from western SiChuan Basin to eastern Tibetan Plateau

Vertical distributions of chemical components of particulate matter (PM) are essential for better understanding the climate, environmental and health effects. The steep slope from western SiChuan Basin (SCB) to eastern Tibetan Plateau (TP) provides a good platform for obtaining the gradient variations of PM chemical components. Daytime and nighttime PM1 (particulate matter smaller than 1 μm) samples were collected with the medium-volume sampler at six sites with elevation ranging from 500 m to 3500 m (Chengdu, Sanbacun, Wenchuan, Lixian, Maerkang and Hongyuan). The secondary inorganic ions and carbonaceous aerosols were the largest contributor to PM1 concentrations. The chemical components from the anthropogenic sources existed strong stratification with high concentrations inside the basin, while primary natural ions showed little discrepancy among the sites. The concentrations of primary inorganic ions from anthropogenic sources were much higher at nighttime than daytime, which was contrary to the diurnal cycle of secondary inorganic ions. Spatial heterogeneity of PM chemical components was large between basin and plateau sites, especially for NO3− and NH4+, large depending on season and daylight. The excess NH4+ concentrations existed in spring, summer and fall, while SO42− and NO3− cannot be completely neutralized by NH4+ in winter. The proportion of secondary formation in all sources significantly increased from about 10 % to 30 %–40 % with the increased elevation, while the contribution of motor vehicles declined from western SCB to eastern TP. This study will fill the scarce observations of PM chemical components at the sloped terrain and deepen the understanding of formation mechanism of heavy pollution inside the basin.

Critical windows for exposure to chemical composition of ambient particulate matter and human semen quality decline

BackgroundCritical windows for exposure to chemical components of particulate matter (PM <2.5 μm in diameter [PM2.5]) associated with the human semen quality decline remain unclear. ObjectivesTo address this gap, we developed a new analytical framework by integrating a Linear Mixed Model (LMM) with subject- and center-specific intercepts and a Distributed Lag Model (DLM) to fully account for correlations between finely vulnerable exposure windows based on complete profile of the spermatogenesis cycle. MethodsWe constructed a multicenter cohort involving 33,234 sperm donors with 78,952 semen samples covering 6 representative regions across China from 2014 to 2020 to investigate the week-scale critical windows for the exposure. Daily exposure to PM2.5 chemical components of donors was derived from grid data based on 1-km spatial resolution surface measurements. ResultsDecreased sperm count was significantly associated with NO3− and SO42− at 9–10 weeks (e.g., β: -0.05 %, 95%CI: [−0.10 %, −0.00 %] at the 9th week) and 0–2 weeks (e.g., β: -0.66 %, 95%CI: [−1.24 %, −0.07 %] at the 1st week), respectively. Critical windows of progressive motility decline were 0–10 weeks for BC (e.g., β: -0.07 %, 95%CI: [−0.11 %, −0.03 %] at the 5th week), Cl− at 1–4 weeks (e.g., β: -2.21 %, 95%CI: [−3.77 %, −0.66 %] at the 2nd week), 0–6 weeks and 9–10 weeks for NO3− (e.g., β: -0.05 %, 95%CI: [−0.09 %, −0.01 %] at the 4th week), 1–3 weeks and the 8th week for NH4+ (e.g., β: -0.06 %, 95%CI: [−0.11 %, −0.01 %] at the 2nd week). Total motility is significantly negatively associated with BC at entire windows, Cl− at 0–3 weeks, the 5th week and 9–10 weeks. ConclusionsThere are week-scale vulnerable windows of exposure to PM2.5 chemical components for human semen quality. This highlights the need for more targeted pollution control strategies addressing PM2.5 and its chemical components.

Toxic air pollution and cognitive decline: Untangling particulate matter

There is increasing evidence indicating air pollution is an important factor influencing the aging brain. However, much of this work measures air pollution using particulate matter (PM). Yet we know that the chemical components of PM are not consistent across space or time. Rather, the possible chemical mixtures of PM vary and are therefore not reliably measuring the same thing across studies. In this study we attempt to disentangle the effects of the components of measured PM by using estimates of concurrent exposures of 415 industrial air toxics, as well as 44 neuro- and developmental toxics. Using bivariate latent curve models, we leverage individual level panel data from the bi-annual Health and Retirement Study to test how these exposures relate to cognitive score trajectories of respondents across the years 2002–2012. We find that more exposure to neurotoxics was associated with faster rate of cognitive decline by 1.09 points (p < 0.05).

Using DPF to Control Particulate Matter Emissions from Ships to Ensure the Sustainable Development of the Shipping Industry

PM (particulate matter) emissions from ships are the main sources of marine atmosphere pollution. Controlling the emissions of particulate matter from ships is related to the sustainable development of the shipping industry. To reduce PM emissions from marine four-stroke diesel engines, DPFs are effective. Our results show that DPF had more than 90% capturing efficiency for both the number and mass emissions of PM, and the capturing efficiency for the accumulation mode was higher than that of the nuclear mode. DPF can also significantly reduce the chemical components of PM in marine diesel exhaust gas. The removal efficiencies for OC and EC were 89.7–91.6% and 84.8–92.8%, respectively, with each particle size range showing over 80% efficiency. SO42− was the ion with the highest content, followed by NH4+, NO3−, Na+, NO2−, and Cl−, with their reduced proportions remaining consistent with the removal efficiency of particulate matter. DPF can also effectively reduce PAH content and toxicity. The use of DPF can greatly improve the impact of ship emissions on the marine atmospheric environment. The appropriate DPF with the best performance can be selected according to the exhaust parameters and particle size distributions with different characteristics.

Review of in vitro studies evaluating respiratory toxicity of aerosols: impact of cell types, chemical composition, and atmospheric processing.

In recent decades, several cell-based and acellular methods have been developed to evaluate ambient particulate matter (PM) toxicity. Although cell-based methods provide a more comprehensive assessment of PM toxicity, their results are difficult to comprehend due to the diversity in cellular endpoints, cell types, and assays and the interference of PM chemical components with some of the assays' techniques. In this review, we attempt to clarify some of these issues. We first discuss the morphological and immunological differences among various macrophage and epithelial cells, belonging to the respiratory systems of human and murine species, used in the in vitro studies evaluating PM toxicity. Then, we review the current state of knowledge on the role of different PM chemical components and the relevance of atmospheric processing and aging of aerosols in the respiratory toxicity of PM. Our review demonstrates the need to adopt more physiologically relevant cellular models such as epithelial (or endothelial) cells instead of macrophages for oxidative stress measurement. We suggest limiting macrophages for investigating other cellular responses (e.g., phagocytosis, inflammation, and DNA damage). Unlike monocultures (of macrophages and epithelial cells), which are generally used to study the direct effects of PM on a given cell type, the use of co-culture systems should be encouraged to investigate a more comprehensive effect of PM in the presence of other cells. Our review has identified two major groups of toxic PM chemical species from the existing literature, i.e., metals (Fe, Cu, Mn, Cr, Ni, and Zn) and organic compounds (PAHs, ketones, aliphatic and chlorinated hydrocarbons, and quinones). However, the relative toxicities of these species are still a matter of debate. Finally, the results of the existing studies investigating the effect of aging on PM toxicity are ambiguous, with varying results due to different cell types, different aging conditions, and the presence/absence of specific oxidants. More systematic studies are necessary to understand the role of different SOA precursors, interactions between different PM components, and aging conditions in the overall toxicity of PM. We anticipate that our review will guide future investigations by helping researchers choose appropriate cell models, resulting in a more meaningful interpretation of cell-based assays and thus ultimately leading to a better understanding of the health effects of PM exposure.

Sources, chemical components, and toxicological responses of size segregated urban air PM samples in high air pollution season in Guangzhou, China

The sources, sizes, components, and toxicological responses of particulate matter (PM) have demonstrated remarkable spatiotemporal variability. However, associations between components, sources, and toxicological effects in different-sized PM remain unclear. The purposes of this study were to 1) determine the sources of PM chemical components, 2) investigate the associations between components and toxicology of PM from Guangzhou high air pollution season. We collected size-segregated PM samples (PM10–2.5, PM2.5–1, PM1–0.2, PM0.2) from December 2017 to March 2018 in Guangzhou. PM sources and components were analyzed. RAW264.7 mouse macrophages were treated with PM samples for 24 h followed by measurements of toxicological responses. The concentrations of PM10–2.5 and PM1–0.2 were relatively high in all samples. Water-soluble ions and PAHs were more abundant in smaller-diameter PM, while metallic elements were more enriched in larger-diameter PM. Traffic exhaust, soil dust, and biomass burning/petrochemical were the most important sources of PAHs, metals and ions, respectively. The main contributions to PM were soil dust, coal combustion, and biomass burning/petrochemical. Exposure to PM10–2.5 induced the most significant reduction of cell mitochondrial activity, oxidative stress and inflammatory response, whereas DNA damage, an increase of Sub G1/G0 population, and impaired cell membrane integrity were most evident with PM1–0.2 exposure. There were moderate or strong correlations between most single chemicals and almost all toxicological endpoints as well as between various toxicological outcomes. Our findings highlight those various size-segregated PM-induced toxicological effects in cells, and identify chemical components and sources of PM that play the key role in adverse intracellular responses. Although fine and ultrafine PM have attracted much attention, the inflammatory damage caused by coarse PM cannot be ignored.

Advances in air quality research – current and emerging challenges

Abstract. This review provides a community's perspective on air quality research focusing mainly on developments over the past decade. The article provides perspectives on current and future challenges as well as research needs for selected key topics. While this paper is not an exhaustive review of all research areas in the field of air quality, we have selected key topics that we feel are important from air quality research and policy perspectives. After providing a short historical overview, this review focuses on improvements in characterizing sources and emissions of air pollution, new air quality observations and instrumentation, advances in air quality prediction and forecasting, understanding interactions of air quality with meteorology and climate, exposure and health assessment, and air quality management and policy. In conducting the review, specific objectives were (i) to address current developments that push the boundaries of air quality research forward, (ii) to highlight the emerging prominent gaps of knowledge in air quality research, and (iii) to make recommendations to guide the direction for future research within the wider community. This review also identifies areas of particular importance for air quality policy. The original concept of this review was borne at the International Conference on Air Quality 2020 (held online due to the COVID 19 restrictions during 18–26 May 2020), but the article incorporates a wider landscape of research literature within the field of air quality science. On air pollution emissions the review highlights, in particular, the need to reduce uncertainties in emissions from diffuse sources, particulate matter chemical components, shipping emissions, and the importance of considering both indoor and outdoor sources. There is a growing need to have integrated air pollution and related observations from both ground-based and remote sensing instruments, including in particular those on satellites. The research should also capitalize on the growing area of low-cost sensors, while ensuring a quality of the measurements which are regulated by guidelines. Connecting various physical scales in air quality modelling is still a continual issue, with cities being affected by air pollution gradients at local scales and by long-range transport. At the same time, one should allow for the impacts from climate change on a longer timescale. Earth system modelling offers considerable potential by providing a consistent framework for treating scales and processes, especially where there are significant feedbacks, such as those related to aerosols, chemistry, and meteorology. Assessment of exposure to air pollution should consider the impacts of both indoor and outdoor emissions, as well as application of more sophisticated, dynamic modelling approaches to predict concentrations of air pollutants in both environments. With particulate matter being one of the most important pollutants for health, research is indicating the urgent need to understand, in particular, the role of particle number and chemical components in terms of health impact, which in turn requires improved emission inventories and models for predicting high-resolution distributions of these metrics over cities. The review also examines how air pollution management needs to adapt to the above-mentioned new challenges and briefly considers the implications from the COVID-19 pandemic for air quality. Finally, we provide recommendations for air quality research and support for policy.

Exposure to Outdoor Particulate Matter Air Pollution and Risk of Gastrointestinal Cancers in Adults: A Systematic Review and Meta-Analysis of Epidemiologic Evidence.

Background:Outdoor air pollution is a known lung carcinogen, but research investigating the association between particulate matter (PM) and gastrointestinal (GI) cancers is limited.Objectives:We sought to review the epidemiologic literature on outdoor PM and GI cancers and to put the body of studies into context regarding potential for bias and overall strength of evidence.Methods:We conducted a systematic review and meta-analysis of epidemiologic studies that evaluated the association of fine PM [PM with an aerodynamic diameter of ()] and (aerodynamic diameter ) with GI cancer incidence or mortality in adults. We searched five databases for original research published from 1980 to 2021 in English and summarized findings for studies employing a quantitative estimate of exposure overall and by specific GI cancer subtypes. We evaluated the risk of bias of individual studies and the overall quality and strength of the evidence according to the Navigation Guide methodology, which is tailored for environmental health research.Results:Twenty studies met inclusion criteria and included participants from 14 countries; nearly all were of cohort design. All studies identified positive associations between PM exposure and risk of at least one GI cancer, although in 3 studies these relationships were not statistically significant. Three of 5 studies estimated associations with and satisfied inclusion criteria for meta-analysis, but each assessed a different GI cancer and were therefore excluded. In the random-effects meta-analysis of 13 studies, exposure was associated with an increased risk of GI cancer overall [; 95% CI: 1.01, 1.24]. The most robust associations were observed for liver cancer (; 95% CI: 1.07, 1.56) and colorectal cancer (; 95% CI: 1.08, 1.62), for which all studies identified an increased risk. We rated most studies with “probably low” risk of bias and the overall body of evidence as “moderate” quality with “limited” evidence for this association. We based this determination on the generally positive, but inconsistently statistically significant, effect estimates reported across a small number of studies.Conclusion:We concluded there is some evidence of associations between and GI cancers, with the strongest evidence for liver and colorectal cancers. Although there is biologic plausibility for these relationships, studies of any one cancer site were few and there remain only a small number overall. Studies in geographic areas with high GI cancer burden, evaluation of the impact of different PM exposure assessment approaches on observed associations, and investigation of cancer subtypes and specific chemical components of PM are important areas of interest for future research. https://doi.org/10.1289/EHP9620

Intensified wintertime secondary inorganic aerosol formation during heavy haze pollution episodes (HPEs) in Beijing, China

Air pollution in China is complex, and the formation mechanism of chemical components in particulate matter is still unclear. This study selected three consecutive heavy haze pollution episodes (HPEs) during winter in Beijing for continuous field observation, including an episode with heavy air pollution under red alert. Clean days during the observation period were selected for comparison. The HPE characteristics of Beijing in winter were: under the influence of adverse meteorological conditions such as high relative humidity, temperature inversion and low wind speed; and strengthening of secondary transformation reactions, which further intensified the accumulation of secondary aerosols and other pollutants, promoting the explosive growth of PM2.5. PM2.5/CO values, as indicators of the contribution of secondary transformation in PM2.5, were approximately 2 times higher in the HPEs than the average PM2.5/CO during the clean period. The secondary inorganic aerosols (sulfate nitrate and ammonium salt) were significantly enhanced during the HPEs, and the conversion coefficients were remarkably improved. In addition, it is interesting to observe that the production of sulfate tended to exceed that of nitrate in the late stage of all three HPEs. The existence of aqueous phase reactions led to the explosive growth sulfur oxidation ratio (SOR) and rapid generation of sulfate under high relative humidity (RH>70%).

Comparison of cytotoxicity effects induced by four different types of nanoparticles in human corneal and conjunctival epithelial cells

The impact of particulate matter (PM) on ocular surface health has attracted increased attention in recent years. Previous studies have reported that differences in the chemical composition of PM can affect the toxicological response. However, available information on the toxic effects of chemical components of PM on the ocular surface is insufficient. In this paper, we aimed to investigate the toxicity effects of chemical components of PM on the ocular surface, focusing on the effects of four different types of nanoparticles (NPs) in human corneal epithelial cells (HCECs) and human conjunctival epithelial cells (HCjECs), which include titanium dioxide (TiO2), carbon black (CB), zinc dioxide (ZnO), and silicon dioxide (SiO2). We found that the in vitro cytotoxic effects of CB, ZnO, and SiO2 NPs are dependent on particle properties and cell type as well as the exposure concentration and time. Here, the order of increasing toxicity was SiO2 → CB → ZnO, while TiO2 demonstrated no toxicity. Moreover, toxic effects appearing more severe in HCECs than HCjECs. Reactive oxygen species (ROS)-mediated oxidative stress plays a key role in the toxicity of these three NPs in HCECs and HCjECs, leading to apoptosis and mitochondrial damage, which are also important contributors to aging. Sirtuin1 (SIRT1) as an NAD+-dependent protein deacetylase that seems to play a potential protective role in this process. These findings implied that ROS and/or SIRT1 may become a potential target of clinical treatment of PM- or NP-related ocular surface diseases.

Chemical components of ambient particulate air pollution affecting suicides in Thailand

This research studied correlation between suicide risks and chemical components of particulate matter in Thailand. It employed satellite data on atmospheric particulate matter. Analysis for correlation between data on chemical components of particulate matter—a type of accumulated pollution in Thailand from 2010 to 2017—and suicidal incidents in 2018. The methodologies consisted of Bayesian hierarchical spatiotemporal model and the Poisson log-linear model, which referred to the NASA database; aerosol diagnostics model, Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2); and database from the Bureau of Policy and Strategy Ministry of Public Health, Thailand. A total of 4,756 patients selected for this study accounted for annual suicide rate of 7.16 per 100,000 population. Suicides in Thailand are related to chemical components of particulate matter. This research thus found that every 1 μg/m 3 increase of dust- PM2.5, only PM2.5 was related to the risks of suicide (which increased for approximately 63.5 %). Black carbon, Organic carbon, and sulfate, however, had no statistically significant effects. Volume of atmospheric accumulated dust- PM2.5 correlated to increase in suicide risks, with statistical significance.

Constituents of fine particulate matter and asthma in 6 low- and middle-income countries

Evidence concerning the effects of different chemical components of particulate matter with an aerodynamic diameter of 2.5 μm or less (PM2.5) on asthma is limited, and the methodology to compare the relative importance of different PM2.5 components is lacking. Our aim was to examine the associations between PM2.5 components and asthma and investigate which constituent of PM2.5 possessed the most harmful effect on asthma. A total of 45,690 subjects in 6 countries were surveyed from 2007 to 2010. We geocoded the residential community addresses of the participants and used satellite remote sensing and chemical transport modeling to estimate their annual average concentrations of PM2.5 constituents. Mixed-effects generalized additive models were utilized to examine the associations between PM2.5 constituents and prevalence of asthma. We further used counterfactual analyses to determine the potential number of asthma cases. We identified 6178 patients with asthma among the participants, producing an asthma prevalence of 13.5%. The odds ratio for asthma associated with per-SD increment was 1.12 for PM2.5 mass, 1.12 for organic carbon, 1.18 for black carbon, 1.19 for sulfate, 1.28 for ammonium, and 1.21 for nitrate after controlling for potential confounders. Our counterfactual analyses suggested that ammonium was responsible for a substantial decline in asthma cases (by 1382 cases, corresponding to 22.37% of overall cases) if the concentration was reduced to the 5th percentile of the current level. Our study suggests that some chemical components of PM2.5 (including black carbon, organic carbon, sulfate, ammonium, and nitrate) might be hazardous constituents contributing to the prevalence of asthma; among them, ammonium might be responsible for a substantial proportion of asthma cases if reduced to a certain level.

Dust and Organic Carbon in Ambient Air Pollution Associated with Increased Mortality in Chronic Obstructive Pulmonary Diseases in Thailand

Objective: Particulate matter(PM) is associated with mortality in chronic obstructive pulmonary disease (COPD). The present study aimed to assess the association between the chemical components in PM and COPD mortality in Thailand. Materials and Methods: The Poisson log-linear model and Bayesian hierarchical spatio-temporal with R package Integrated Nested Laplace Approximation (R-INLA) were used to determine the factor associated with COPD mortality, the database from the National Strategy and Planning Division, Office of the Permanent Secretary, Ministry of Public Health of Thailand and the concentration of five PM chemical components including dust-PM2.5, organic carbon, black carbon, sea salt, and sulfate, the database from Modern-Era Retrospective Analysis for Research and Application, version 2 (MERRA-2) to analyze the spatial-temporal association of COPD mortality related to chemical components between 2014 to 2016. Results: A cumulative incident rate of COPD death was 19,285 cases or 29.49 per 100,000 populations. Health region 1 located in North of Thailand had the highest mortality, 95.86 per 100,000 population while the lowest mortality was in health region 8 located in Northeast of Thailand, 12.50 per 100,000 population. Average dust-PM2.5 and organic carbon concentrations in PM were high in North of Thailand. The spatial-temporal analysis found the association between COPD mortality and dust-PM2.5 exposure with incidence rate ratio (IRR) 2.191 (95% confidence interval (CI) 2.102 to 2.283), and organic carbon exposure with IRR 1.074 (95% CI 1.065 to 1.084). The posterior marginal for linear predictor IRR and fitted value computed of COPD mortality showed that an increase of 1 &mu;g/m3 in dust-PM2.5 and organic carbon exposure were associated with increase of COPD mortality by 64.0% and 35.3%. Conclusion: Dust-PM2.5 and organic carbon were associated with increase COPD mortality in Thailand. Health region 1 (North of Thailand) had the greatest magnitude of COPD mortality associated with dust-PM2.5 and organic carbon exposure. Keywords: COPD; Mortality; Dust; Organic carbon; Thailand

Invited Perspective: Air Pollution and Breast Cancer Risk: Current State of the Evidence and Next Steps.

Invited Perspective: Air Pollution and Breast Cancer Risk: Current State of the Evidence and Next Steps.

Cell cycle arrest of human bronchial epithelial cells modulated by differences in chemical components of particulate matter.

There is increasing interest in understanding the role of airborne chemical components in modulating the cell cycle of human bronchial epithelial (HBE) cells that is associated with burden of cardiopulmonary disease. To address this need, our study collected ambient PM10 (particles with aerodynamic diameter less than or equal to 10 μm) and PM2.5 (particles with aerodynamic diameter less than or equal to 2.5 μm) across four sampling sites in Beijing during the year of 2015. Chemical components including organic carbon (OC), elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs), metals and water soluble ions were determined. Spearman's rank-order correlation was performed to examine the associations between chemical components in ambient particles and cell cycle distributions with p-values adjusted by Bonferroni methodology. Our results demonstrated the significant associations between certain chemical compositions (i.e., PAHs, EC, As and Ni) and percentages of HBE cells in G0/G1 and G1/G2 phases, respectively. Our results highlighted the need to reduce the specific toxins (e.g., PAHs, EC, As and Ni) from ambient particles to protect cardiopulmonary health associated with air pollution. Future study may focus on illustrating the mechanism of certain chemical compositions in altering the cell cycle in HBE cells.

Exposure to Particulate Matter Air Pollution and the Incidence and Mortality of GI Cancers: A Systematic Review

PURPOSE High levels of particulate matter (PM) air pollution increase the risk of developing cardiovascular diseases, asthma, and cancer. Outdoor air pollution, especially PM, is classified as a human carcinogen on the basis of associations with lung cancer, but research investigating other cancer sites is limited. This systematic review investigates the scope and quality of existing literature on PM and the incidence and mortality of GI cancers. METHODS This review was conducted in accordance with the PRISMA protocol guidelines and submitted under PROSPERO ID: 139597. Initial searches of 5 databases yielded 2,041 articles, of which 762 duplicates were removed. Eligible studies evaluated an association between PM and at least one GI cancer. The titles and abstracts of 1,279 articles were screened independently and 102 articles were selected for additional screening. Ten studies were included in the final analysis. We evaluated the overall quality of included studies using GRADE criteria. RESULTS All articles meeting the criteria for inclusion were of cohort study design and published in 2015 or later. Methods for assessing PM exposure varied. More than one half (n = 6) of the studies investigated liver cancer. Most met the GRADE criteria for moderate certainty or greater. Six studies found a statistically significant positive association, and none found evidence of a negative association. CONCLUSION Evidence of a positive association between the incidence and mortality of GI cancers exists; however, few studies have evaluated this association. Methods of assessing exposure are highly variable. Future researchers should strive to conduct more studies in the most affected geographic areas to evaluate the impact of different PM exposure assessment approaches on observed associations, and include the evaluation of cancer subtypes and specific chemical components of PM.

Different roles of nitrate and sulfate in air pollution episodes in the North China Plain

Different chemical substances make different contributions to particles with different diameters. It is important to determine which species play important roles to control air pollution. In this study, the concentrations of water-soluble inorganic ions, elemental carbon, organic carbon and metal elements in PM1 (particulate matter with a diameter less than 1 μm) and PM2.5 (particulate matter with a diameter less than 2.5 μm) in the Shijiazhuang suburban area were measured by synchronous sampling for one month in the summer of 2016. The results showed that the chemical components of particulate matter are mainly SO42−, NO3−, NH4+ and organic matter (OM), accounting for 14%, 8%, 11%, and 11%, respectively, in PM1 and 13%, 8%, 10%, and 9%, respectively, in PM2.5. PM1 and PM2.5 have similar sources, including secondary nitrate, secondary sulfate, industrial sources, motor vehicle sources, dust, biomass combustion and coal burning, which contribute 29%, 30%, 10%, 9%, 8%, 8% and 6%, respectively, to PM1 and 29%, 33%, 12%, 13%, 8%, 2%, and 4%, respectively, to PM2.5. Based on the analysis of a typical pollution episode, the concentrations of PM1 and PM2.5 increase synchronously in the explosive growth stage, with nitrate acting as the key chemical component. In the most polluted period, the concentration of PM2.5 continues to increase because of the increase in sulfate, while that of PM1 is almost constant. The results show that the prevention and control of PM1 and PM2.5 should be different in different pollution stages.

Seasonal Variations and Chemical Predictors of Oxidative Potential (OP) of Particulate Matter (PM), for Seven Urban French Sites

Epidemiological studies suggest that the main part of chronic effects from air pollution is likely to be linked with particulate matter (PM). Oxidative potential (OP) of PM is gaining strong interest as a promising health exposure metric. This study combined atmospheric detailed composition results obtained for seven different urban background environments over France to examine any possible common feature in OP seasonal variations obtained using two assays (acid ascorbic (AA) and dithiothreitol (DTT)) along a large set of samples ( N &gt; 700 ). A remarkable homogeneity in annual cycles was observed with a higher OP activity in wintertime at all investigated sites. Univariate correlations were used to link the concentrations of some major chemical components of PM and their OP. Four PM components were identified as OP predictors: OC, EC, monosaccharides and Cu. These species are notably emitted by road transport and biomass burning, targeting main sources probably responsible for the measured OP activity. The results obtained confirm that the relationship between OP and atmospheric pollutants is assay- and location-dependent and, thus, the strong need for a standardized test, or set of tests, for further regulation purposes.

Spatial Temporal Characteristics and Cluster Analysis of Chemical Components for Ambient PM2.5 in Wuhan

The characteristics of chemical components of particulate matter are good indicators for analyzing sources and causes of pollution. The spatial and temporal distribution characteristics of particulate matter can reflect regional pollution problems in urban development, providing a basic dataset to support effective control of particulate matter sources. We collected PM2.5 and analyzed its concentration and chemical components at eight sites during different seasons. The results indicated that the average concentration of PM2.5 in Wuhan reached 70.7 μg·m-3. The concentration of PM2.5 in winter (103.1 μg·m-3) was significantly higher than that of other seasons, and the lowest concentration was in autumn (52.4 μg·m-3). The concentrations of PM2.5 in Donghu Gaoxin, Zhuankou New Area, and Qingshan Ganghua Station were significantly higher than those at the other sites. The main chemical components in PM2.5 were OC and SO42-, accounting for 15.4% and 14.2%, respectively. The OC concentration was the highest in winter, whereas SO42-concentration was the highest in summer. The average annual OC/EC ratio was up to 2.80, lower in winter and spring, and higher in summer and autumn. Material reconstruction showed that secondary particles and organic matter (OM) were major substances, accounting for 32.34% and 20.44% of PM2.5 mass, respectively. Coal combustion and vehicle exhaust might be the main contributors to ambient PM2.5. The highest fractions for OM were at the Wujiashan and Donghu Gaoxin sites, whereas the fraction of secondary particles was higher at each site, suggesting that secondary pollution had obvious regional characteristics in Wuhan. Cluster analysis based on the characteristics of chemical components showed that the eight sites were divided into three clusters:1 Hanyang Yuehu, Haze, Donghu Liyuan, and Huangpi sites, where the main characteristics were that the concentrations of components at each point were low; ② Zhuankou New Area and Qingshan Ganghua, which were characterized by higher nitrogen components; and ③ Donghu Gaoxin and Wujiashan, where not only industrial sources were heavily polluted in Wuhan, but also motor vehicles and dust pollution greatly contributed.

Structural Characteristics and Functional Implications of PM2.5 Bacterial Communities During Fall in Beijing and Shanghai, China.

Air pollution characterized by fine particulate matter (PM2.5) frequently has occurred in China, and has posed threats to human health. The physiochemical characteristics of airborne PM2.5 have been extensively studied, but its bacterial structures and functions have not yet been well studied. Herein, we focused on the structural characteristics and functional implications of airborne bacteria under different pollution levels in Beijing and Shanghai. The α- and β-diversities showed no obvious difference in two cities (p > 0.05). The dominant phyla Proteobacteria, Firmicutes, and Actinobacteria with total abundance of over 92% were found in all PM2.5 samples. The results of weighted unifrac non-metric multidimensional scaling (NMDS) suggested that air pollution was no obviously correlated with bacterial community but dispersed disorderly. Furthermore, canonical correlation analysis (CCA) and permutation test indicated that , , and wind speed were the key factors that associated with airborne bacterial community structure. Chemical components of particulate matter played more important role in structuring bacterial community than meteorological conditions based on the result of partial CCA. In addition, the annotation of metabolic pathway suggested that the predominant genus Pseudomonas was obviously correlated with disease infections. Several dominant species might contribute to organic degradation, nitrogen cycles, and ice-nuclei activities in environments. Overall, this work enhanced our understanding of functions of airborne bacteria and highlighted their potential role in atmospheric chemical progresses.