High loadings of carbonaceous aerosols from wood smoke in the atmosphere of Beijing from 2015 to 2017: Implications for energy transition policy.

Recently, biomass has been regarded as a promising option for solid energy in China, which is promoted in the residential sector and firing power plants. We collected 200 PM2.5 samples (particulate matter with a aerodynamic diameter smaller than 2.5 µm) at multi-sites across Beijing from three individual sampling cases from 2015 to 2017. The levels of OC, OC fractions, EC, EC fractions, as well as K+ were measured. Then, we adopted the Positive Matrix Factorization 5.0 to apportion the sources of carbonaceous aerosols. The source apportionment results were compared with the estimates of source contribution using the bottom-up technical method with the latest emission inventories after the Action Plan was put into effect in 2013. Our results demonstrate that high pollution of carbonaceous aerosols originated from wood smoking based on the receptor modeling and bottom-up technical method in Beijing from 2015 to 2017. Future energy transition policy should focus on the technologies and regulations for reducing emissions from renewable biomass fuel combustion. This study highlights the importance of regulations that address emissions controls on fuels replacing coal combustion to meet the needs to mitigate air pollution from primary energy use.

Direct measurement of the deposition of submicron soot particles on leaves of Platanus acerifolia tree.

Submicron soot particles (<1.0 µm in aerodynamic diameter) are responsible for global warming and health burdens worldwide. However, studies on bio-monitoring of submicron soot particles and their associated sources by using tree leaves are not comprehensively illustrated. Here, we determined the seasonal trends of submicron soot particles on the leaves of the Platanus acerifolia collected from two cities (Lu'an, Anhui Province, and Nanjing, Jiangsu Province) in the Yangtze River Delta region, China. The source apportionment of submicron soot particles was performed using stable carbon isotopic analyses. Significant seasonal trends of submicron soot particles were observed in two cities with averaged levels of 0.41-1.36 mg m-2 in cold seasons and averaged levels of 0.13-0.24 mg m-2 in warm seasons. The levels of δ13C for submicron soot at the suburban site of Lu'an city were observed to be in the range of -25.6‰ to -18.2‰ with fossil fuels dominated (∼58%) in summer and -23.0‰ to -15.6‰ with biomass burning dominated in winter (∼67%). In comparison, the ranges in the levels of δ13C in submicron soot were found to be from -26.5‰ to -20.4‰ in winter, and -24.2‰ to -17.9‰ in summer at the urban site of Nanjing. Fossil fuels accounted for a large fraction of submicron soot with average contributions of 53% in winter and 73% in summer, respectively. These findings demonstrate that Platanus acerifolia trees could be used as an effective and low-cost bio-monitoring tool for monitoring the pollution status of submicron soot and associated source contribution.

Sensing Gas Mixtures by Analyzing the Spatiotemporal Optical Responses of Liquid Crystals Using 3D Convolutional Neural Networks.

We report how analysis of the spatial and temporal optical responses of liquid crystal (LC) films to targeted gases, when performed using a machine learning methodology, can advance the sensing of gas mixtures and provide important insights into the physical processes that underlie the sensor response. We develop the methodology using O3 and Cl2 mixtures (representative of an important class of analytes) and LCs supported on metal perchlorate-decorated surfaces as a model system. Although O3 and Cl2 both diffuse through LC films and undergo redox reactions with the supporting metal perchlorate surfaces to generate similar initial and final optical states of the LCs, we show that a three-dimensional convolutional neural network can extract feature information that is encoded in the spatiotemporal color patterns of the LCs to detect the presence of both O3 and Cl2 species in mixtures and to quantify their concentrations. Our analysis reveals that O3 detection is driven by the transition time over which the brightness of the LC changes, while Cl2 detection is driven by color fluctuations that develop late in the optical response of the LC. We also show that we can detect the presence of Cl2 even when the concentration of O3 is orders of magnitude greater than the Cl2 concentration. The proposed methodology is generalizable to a wide range of analytes, reactive surfaces, and LCs and has the potential to advance the design of portable LC monitoring devices (e.g., wearable devices) for analyzing gas mixtures using spatiotemporal color fluctuations.

Prediction of the oxidation potential of PM2.5 exposures from pollutant composition and sources.

The inherent oxidation potential (OP) of atmospheric particulate matter has been shown to be an important metric in assessing the biological activity of inhaled particulate matter and is associated with the composition of PM2.5. The current study examined the chemical composition of 388 personal PM2.5 samples collected from students and guards living in urban and suburban areas of Beijing, and assessed the ability to predict OP from the calculated metrics of carcinogenic risk, represented by ELCR (excess lifetime cancer risk), non-carcinogenic risk represented by HI (hazard index), and the composition and sources of the particulate matter using multiple linear regression methods. The correlations between calculated ELCR and HI and the measured OP were 0.37 and 0.7, respectively. HI was a better predictor of OP than ELCR. The prediction models based on pollutants (Model_1) and pollution sources (Model_2) were constructed by multiple linear regression method, and Pearson correlation coefficients between the predicted results of Model_1 and Model_2 with the measured volume normalized OP are 0.81 and 0.80, showing good prediction ability. Previous investigations in Europe and North America have developed location-specific relationships between the chemical composition of particulate matter and OP using regression methods. We also examined the ability of relationships between OP and composition, sources, developed in Europe and North America, to predict the OP of particulate matter in Beijing from the composition and sources determined in Beijing. The relationships developed in Europe and North America provided good predictive ability in Beijing and it suggests that these relationships can be used to predict OP from the chemical composition measured in other regions of the world.

Temporal trends in the spatial-scale contributions to black carbon in a Middle Eastern megacity.

The analysis of high-resolution changes in black carbon (BC) concentrations was examined to distinguish and quantify various spatial-scale contributions to BC concentrations from nearby sources within 1 km distance to ranges of emission sources distributed over a larger city scale spanning tens of kilometers. Our analysis illustrated that BC emissions on the neighborhood scale only contribute a minor fraction (~15%) to total BC concentrations in the megacity of Tehran. Approximately 62% of the total black carbon is part of the city emissions, and around 23% is transported into the city from local nearby surroundings. Our analysis in highly polluted areas, including industrial and traffic hotspots in Tehran, demonstrated that the contributions of the urban mixture were relatively smaller than the average (~56%) in highly polluted areas; however, larger local-scale (~30%) contributions were observed in these areas. Our analysis in traffic hotspot areas also demonstrated significantly smaller contributions of BC from neighborhood surroundings (~9%). These results imply that the city-scale BC emissions in Tehran are a major contributor to BC exposures even in locations with local high-emitting sources. Polar annulus analysis of BC from city-scales in Tehran showed a mixture of hotspot locations ranging from north to easterly directions implying that city-scale emissions contribute to wider pollution plume expansions and larger-scale transport and vertical mixing corresponding to mixtures of emitters located further away.

Determinants of personal exposure to PM2.5 and black carbon in Chinese adults: A repeated-measures study in villages using solid fuel energy.

Exposure to air pollution is a leading health risk factor. The variance components and contributions of indoor versus outdoor source determinants of personal exposure to air pollution are poorly understood, especially in settings of household solid fuel use. We conducted a panel study with up to 4 days of repeated measures of integrated gravimetric personal exposure to PM2.5 and black carbon in 787 men and women (ages 40-79) living in peri-urban villages in northern (Beijing and Shanxi) and southern (Guangxi) China. We simultaneously measured outdoor PM2.5 and collected questionnaire data on sociodemographic characteristics and indoor pollution sources including tobacco smoking and solid fuel stove use. We obtained over 2000 days of personal exposure monitoring which showed higher exposures in the heating season (geometric mean (GM): 108 versus 65 µg/m3 in the non-heating season for PM2.5) and among northern participants (GM: 90 versus 59 µg/m3 in southern China in the non-heating season for PM2.5). We used mixed-effects models to estimate within- and between-participant variance components and to assess the determinants of exposures. Within-participant variance in exposure dominated the total variability (68-95%). Outdoor PM2.5 was the dominant variable for explaining within-participant variance in exposure to PM2.5 (16%). Household fuel use (PM2.5: 8%; black carbon: 10%) and smoking status (PM2.5: 27%; black carbon: 5%) explained the most between-participant variance. Indoor sources (solid fuel stoves, tobacco smoking) were associated with 13-30% higher exposures to air pollution and each 10 µg/m3 increase in outdoor PM2.5 was associated with 6-8% higher exposure. Our findings indicate that repeated measurements of daily exposure are likely needed to capture longer-term exposures in settings of household solid fuel use, even within a single season, and that reducing air pollution from both outdoor and indoor sources is likely needed to achieve measurable reductions in exposures to air pollution.

Occurrence of estrogens, androgens and progestogens and estrogenic activity in surface water runoff from beef and dairy manure amended crop fields.

Hormone contamination of aquatic systems has been shown to cause reproductive impairment of aquatic organisms. To assess to what extent beef and dairy farms represent a source of hormones to the aquatic environment, surface water runoff samples from three beef and dairy farms that utilize best manure management practices were evaluated for hormone concentrations (estrogens, androgens, progestogens) and estrogenic activity. Runoff was collected from weirs at the edge of each of six study fields from March 2008 to March 2010 and was analyzed for hormone concentrations using liquid chromatography with tandem mass spectrometry and for estrogenic activity using the E-screen bioassay. The majority of runoff events occurred in February and March when the soil was frozen. Progesterone and 4-androstenedione were the most frequently detected hormones (63% and 50%, respectively) and occurred at event loads up to 49,000 µg/ha and 26,000 µg/ha, respectively. Progesterone, 4-androstenedione, 17α-estradiol had the highest event load concentrations and were found at the field that sustained dairy cattle grazing during the winter and were likely due to application of excreta on frozen soil. The high progesterone event loads could lead to concentrations in receiving streams that exceed the lowest observable effects concentrations for fish. There was a consistent association with the elevated zearalenone presence and corn production. The synthetic hormones, 17α-trenbolone and 17ß-trenbolone, were not detected in runoff from the beef farm that utilized trenbolone acetate implants, which is likely due to their short half lives. Estrogenic activity in runoff samples ranged from 0.09 to 133 ng/L estradiol equivalents, with 39% of runoff events exceeding the 2 ng/L predicted-no-effect-concentration for fish. These results indicate that grazing cattle and application of manure to frozen fields present the greatest risk to elevated hormones in runoff and that progesterone is the primary hormone of concern from beef and dairy operations.

Impacts of stove/fuel use and outdoor air pollution on chemical composition of household particulate matter.

Biomass combustion for cooking and heating releases particulate matter (PM2.5 ) that contributes to household air pollution. Fuel and stove types affect the chemical composition of household PM, as does infiltration of outdoor PM. Characterization of these impacts can inform future exposure assessments and epidemiologic studies, but is currently limited. In this study, we measured chemical components of PM2.5 (water-soluble organic matter [WSOM], ions, black carbon, elements, organic tracers) in rural Chinese households using traditional biomass stoves, semi-gasifier stoves with pelletized biomass, and/or non-biomass stoves. We distinguished households using one stove type (traditional, semi-gasifier, or LPG/electric) from those using multiple stoves/fuels. WSOM concentrations were higher in households using only semi-gasifier or traditional stoves (31%-33%) than in those with exclusive LPG/electric stove (13%) or mixed stove use (12%-22%). Inorganic ions comprised 14% of PM in exclusive LPG/electric households, compared to 1%-5% of PM in households using biomass. Total PAH content was much higher in households that used traditional stoves (0.8-2.8 mg/g PM) compared to those that did not (0.1-0.3 mg/g PM). Source apportionment revealed that biomass burning comprised 27%-84% of PM2.5 in households using biomass. In all samples, identified outdoor sources (vehicles, dust, coal combustion, secondary aerosol) contributed 10%-20% of household PM2.5 .

Exposure­Response Associations of Household Air Pollution and Buccal Cell Telomere Length in Women Using Biomass Stoves.

BACKGROUND: Telomere shortening is associated with early mortality and chronic disease. Recent studies indicate that environmental exposures, including urban and traffic-related air pollution, may shorten telomeres. Associations between exposure to household air pollution from solid fuel stoves and telomere length have not been evaluated. METHODS: Among 137 rural Chinese women using biomass stoves ([Formula: see text] of age), we measured 48-h personal exposures to fine particulate matter [PM [Formula: see text] in aerodynamic diameter ([Formula: see text])] and black carbon and collected oral DNA on up to three occasions over a period of 2.5 y. Relative telomere length (RTL) was quantified using a modified real-time polymerase chain reaction protocol. Mixed effects regression models were used to investigate the exposure­response associations between household air pollution and RTL, adjusting for key sociodemographic, behavioral, and environmental covariates. RESULTS: Women's daily exposures to air pollution ranged from [Formula: see text] for [Formula: see text] ([Formula: see text]) and [Formula: see text] for black carbon ([Formula: see text]). Natural cubic spline models indicated a mostly linear association between increased exposure to air pollution and shorter RTL, except at very high concentrations where there were few observations. We thus modeled the linear associations with all observations, excluding the highest 3% and 5% of exposures. In covariate-adjusted models, an interquartile range (IQR) increase in exposure to black carbon ([Formula: see text]) was associated with shorter RTL [all observations: [Formula: see text] (95% CI: [Formula: see text], [Formula: see text]); excluding highest 5% exposures: [Formula: see text] (95% CI: [Formula: see text], [Formula: see text])]. Further adjustment for outdoor temperature brought the estimates closer to zero [all observations: [Formula: see text] (95% CI: [Formula: see text], 0.06); excluding highest 5% exposures: [Formula: see text] (95% CI: [Formula: see text], [Formula: see text])]. Models with [Formula: see text] as the exposure metric followed a similar pattern. CONCLUSION: Telomere shortening, which is a biomarker of biological aging and chronic disease, may be associated with exposure to air pollution in settings where household biomass stoves are commonly used. https://doi.org/10.1289/EHP4041.

Source Apportionment of Fine-Particle, Water-Soluble Organic Nitrogen and Its Association with the Inflammatory Potential of Lung Epithelial Cells.

Identifying the key chemical compounds and source contributions in ambient particles associated with the burden of cardiopulmonary disease is important to develop cost-effective air pollution mitigating strategies that maximize the protection of public health. To help address this need, we examined 109 daily ambient fine particulate matter samples (PM2.5) that were collected in Beijing in one year. The samples were analyzed for chemical composition including organic and elemental carbons, metals, ions, as well as organic molecular markers. In addition, the secretion of pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were measured by exposing lung epithelial cells (A549) to water extracts of PM2.5 samples. Single pollutant and constituent-PM2.5 joint linear models were used to estimate the associations. Higher PM2.5 mass and measured chemical components were found in cold seasons than in warm seasons due to the greater contributions of secondary inorganic sources, biomass burning, and coal combustion. Water-soluble organic nitrogen (WSON) had the strongest associations with levels of pro-inflammatory cytokines compared to PM2.5 mass and other chemical species in both the one and constituent-PM2.5 joint linear models. Our study is the first to highlight that ambient WSON from diverse sources dominates the inflammatory potential of lung epithelial cells.

Chemical composition and health risk indices associated with size-resolved particulate matter in Pearl River Delta (PRD) region, China.

Size-resolved particulate matter (PM) was collected at the Heshan Super-Station in the Pearl River Delta (PRD) region, China, to evaluate their chemical characteristics and potential health risks. The chemical mass closures illustrate that the dominant fraction in coarse (2.5 µm < Dp < 10 µm) PM was dust, while organic matter made up a substantial portion of both fine (0.1 < Dp < 2.5 µm) and ultra-fine (Dp < 0.10 µm) PM fractions. The size distribution of most PM components varied substantially. PM, NO3-, K+, Cl-, Na+ and most of the transition/redox metals displayed bimodal size distributions with the dominant peak at 0.32-0.56 µm plus a small peak at 1.8-3.2 µm. In contrast, unimodal size distributions were found for the rest of the species, such as water-soluble organic carbon (WSOC), NH4+, and SO42- and the majority of oxyanion metals with a single peak at 0.32-0.56 µm, and Mg2+, Ca2+, and dust tracer elements which mainly accumulated in coarse particles. Based on the crustal enrichment factor (CEF) analysis, Cd, Zn, Sb, Sn, As, Pb, Mo, Cu, and Cr primarily originated from anthropogenic activities, while Ti in all size fractions and Sr, Mg, Na, and Fe in fine and ultra-fine particles were mainly emitted from natural sources. The potential health risk assessment of trace metals was performed using the hazard quotient (HQ) and excess lifetime cancer risk (ELCR) indices. Although the adverse health effects of most metals were limited, significant potential carcinogenic risks were found for As and Cr in both fine and coarse particle size fractions, which contributed more than 95% of total ELCR. Therefore, considering that these two elements were mainly emitted from industrial processes, improvements in air quality and health risks in the PRD region can be largely achieved by reducing the emissions of local industrial sources.

Seasonal variations in the oxidative stress and inflammatory potential of PM2.5 in Tehran using an alveolar macrophage model; The role of chemical composition and sources.

The current study was designed to assess the association between temporal variations in urban PM2.5 chemical composition, sources, and the oxidative stress and inflammatory response in an alveolar macrophage (AM) model. A year-long sampling campaign collected PM2.5 samples at the Sharif University in Tehran, Iran. PM-induced reactive oxygen species (ROS) production was measured both with an acellular dithiothreitol consumption assay (DTT-ROS; ranged from 2.1 to 9.3 nmoles min-1 m-3) and an in vitro macrophage-mediated ROS production assay (AM-ROS; ranged from 125 to 1213 µg Zymosan equivalents m-3). The production of tumor necrosis factor alpha (TNF-α; ranged from ~60 to 518 pg TNF-α m-3) was quantified as a marker of the inflammatory potential of the PM. PM-induced DTT-ROS and AM-ROS were substantially higher for the colder months' PM (1.5-fold & 3-fold, respectively) compared with warm season. Vehicular emission tracers, aliphatic diacids, and hopanes exhibited moderate correlation with ROS measures. TNF-α secretion exhibited a markedly different pattern than ROS activity with a 2-fold increase in the warm months compared to the rest of the year. Gasoline vehicles and residual oil combustion were moderately associated with both ROS measures (R ≥ 0.67, p < 0.05), while diesel vehicles exhibited a strong correlation with secreted TNF-α in the cold season (R = 0.89, p < 0.05). mRNA expression of fourteen genes including antioxidant response and pro-inflammatory markers were found to be differentially modulated in our AM model. HMOX1, an antioxidant response gene, was up-regulated throughout the year. Pro-inflammatory genes (e.g. TNF-α and IL1ß) were down-regulated in the cold season and displayed moderate to weak correlation with crustal elements (R > 0.5, p < 0.05). AM-ROS activity showed an inverse relationship with genes including SOD2, TNF, IL1ß and IL6 (R ≥ -0.66, p < 0.01). Our findings indicate that Tehran's PM2.5 has the potential to induce oxidative stress and inflammation responses in vitro. In the current study, these responses included NRF2, NF-κB and MAPK pathways.

Chemical characterization and source apportionment of PM2.5 personal exposure of two cohorts living in urban and suburban Beijing.

In the study, personal PM2.5 exposures and their source contributions were characterized for 159 subjects living in the Beijing Metropolitan area. The exposures and sources were examined as functions of residential location, season, vocation, cigarette smoking, and time spent outdoors. Sampling was performed for two categories of volunteers, guards and students, that lived in urban and suburban areas of Beijing. Samples were collected using portable PM2.5 monitors during summer and winter. Exposure measurements were supplemented with a questionnaire that tracked personal activity and time spent in microenvironments that may have impacted exposures. Simultaneously, ambient PM2.5 data were obtained from national network stations located at the Gucheng and Huairouzhen sites. These data were used as a comparison against the personal PM2.5 exposures and produced poor correlations between personal and ambient PM2.5. These results demonstrate that individual behavior strongly affects personal PM2.5 exposure. Six primary sources of personal PM2.5 exposure were determined using a positive matrix factorization (PMF) source apportionment model. These sources included Roadway Transport Source, Soil/Dust Source, Industrial/Combustion Source, Secondary Inorganic Source, Cd Source, and Household Heating Source. Averaged across all subjects and seasons, the highest source contribution was Secondary Inorganic Source (24.8% ±â€¯32.6%, AVG ±â€¯STD), whereas the largest primary ambient source was determined to be Roadway Transport (20.9% ±â€¯13.6%). Subjects were classified according to the questionnaire and were used to help understand the relationship between personal activity and source contribution to PM2.5 exposure. In general, primary ambient sources showed only significant spatial and seasonal differences, while secondary sources differed significantly between populations with different personal behavior. In particular, Cd source was found to be related to smoking exposure and was the most unpredictable source, with significant differences between populations of different sites, vocations, smoking exposures, and outdoor time.

Polycyclic aromatic hydrocarbons (PAHs) present in ambient urban dust drive proinflammatory T cell and dendritic cell responses via the aryl hydrocarbon receptor (AHR) in vitro.

Atmospheric particulate matter (PM) is a complex component of air pollution that is a composed of inorganic and organic constituents. The chemically-extracted organic fraction (OF) of PM excludes inorganics but retains most organic constituents like polycyclic aromatic hydrocarbons (PAHs). PAHs are ubiquitous environmental toxicants and known aryl hydrocarbon receptor (AHR) ligands. The AHR is a ligand activated transcription factor that responds to endogenous ligands and exogenous ligands including PAHs. Activation of the AHR leads to upregulation of cytochrome P450 (CYP) metabolizing enzymes which are important for the biotransformation of toxicants to less toxic, or in the case of PAHs, more toxic intermediates. Additionally, the AHR plays an important role in balancing regulatory and effector T cell responses. This study aimed to determine whether PAHs present in PM aggravate inflammation by driving inflammatory T cell and dendritic cell (DC) responses and their mechanism of action. This study tests the hypothesis that PAHs present in PM activate the AHR and alter the immune balance shifting from regulation to inflammation. To test this, the effects of SRM1649b OF on T cell differentiation and DC function were measured in vitro. SRM1649b OF enhanced Th17 differentiation in an AHR and CYP-dependent manner and increased the percent of IFNγ positive DCs in an AHR-dependent manner. SRM1649b PAH mixtures enhanced Th17 differentiation in an AHR-dependent but CYP-independent manner and increased the percent of IFNγ positive DCs. Cumulatively, these results suggest that PAHs present in PM are active components that contribute to immune responses in both T cells and BMDCs through the AHR and CYP metabolism. Understanding the role of AHR and CYP metabolism of PAHs in immune cells after PM exposure will shed light on new targets that will shift the immune balance from inflammation to regulation.

Quantum chemical calculations to determine partitioning coefficients for HgCl2 on iron-oxide aerosols.

Gas-to-particle phase partitioning controls the pathways for oxidized mercury deposition from the atmosphere to the Earth's surface. The propensity of oxidized mercury species to transition between these two phases is described by the partitioning coefficient (Kp). Experimental measurements of Kp values for HgCl2 in the presence of atmospheric aerosols are difficult and time-consuming. Quantum chemical calculations, therefore, offer a promising opportunity to efficiently estimate partitioning coefficients for HgCl2 on relevant aerosols. In this study, density functional theory (DFT) calculations are used to predict Kp values for HgCl2 on relevant iron-oxide surfaces. The model is first verified using a NaCl(100) surface, showing good agreement between the calculated (2.8) and experimental (29-43) dimensionless partitioning coefficients at room temperature. Then, the methodology is applied to six atmospherically relevant terminations of α-Fe2O3(0001): OH-Fe-R, (OH)3-Fe-R, (OH)3-R, O-Fe-R, Fe-O3-R, and O3-R (where R denotes bulk ordering). The OH-Fe-R termination is predicted to be the most stable under typical atmospheric conditions, and on this surface termination, a dimensionless HgCl2Kp value of 5.2 × 103 at 295 K indicates a strong preference for the particle phase. This work demonstrates DFT as a promising approach to obtain partitioning coefficients, which can lead to improved models for the transport of mercury, as well as for other atmospheric pollutant species, through and between the anthroposphere and troposphere.

Reactive oxygen species (ROS) activity of ambient fine particles (PM2.5) measured in Seoul, Korea.

Substantial increase in level of particulate matter has raised concerns in South Korea recently. Ambient particulate matter is classified as Group I carcinogen (IARC, 2013) and multiple epidemiological studies has demonstrated adverse health effects due to exposure of particulate matter. Fine particulate matter (PM2.5) which has a diameter <2.5 µm is likely to penetrate deeply into lung and is known to be eliciting adverse health effects. A number of epidemiological studies have been conducted on adverse health effects of PM-related diseases and mortality rate, yet particulate matter (PM)-induced reactive oxygen species (ROS) activity at the cellular level has not been actively studied in Korea. This study assessed PM-induced oxidative potential by exposure of collected ambient PM2.5 samples to the rat alveolar macrophage cell line. The characteristics of PM2.5 in Korea were further characterized by linking chemical constituents and contributing sources to ROS. PM2.5 mass concentration during the cold season was relatively higher than mass concentration during the warm season and chemical constituents except for Secondary Organic Carbon (SOC) and SO42- which both showed similar trends in both the cold and cold seasons. The concentration of crustal elements was especially high during the cold season which can be an indication of long range transport of Asian dust. Water soluble organic carbon and water soluble transition metals (Cr and Zn) were also shown to be correlated to oxidative potential and metals such as As and V were shown to have a high contribution to ROS activity according to stepwise multiple linear regression. Principal Component Analysis (PCA) results identified six factors that can be interpreted as soil, mobile, industry, secondary inorganic aerosol, secondary organic aerosol and oil combustion. Moreover, through Principal Component Regression (PCR), industry, soil, mobile and SIA were shown to be statistically significant sources in a relation to ROS activity.

Relationship between reactive oxygen species and water-soluble organic compounds: Time-resolved benzene carboxylic acids measurement in the coastal area during the KORUS-AQ campaign.

This study investigated the relationship between water-soluble organic compounds of ambient particulate matter (PM) and cellular redox activity collected from May 28 to June 20 of 2016 at the west coastal site in the Republic of Korea during the KORea-US Air Quality (KORUS-AQ) campaign. Automatic four-hour integrated samples operated at a flow rate of 92 L per minute for the analysis of organic carbon (OC), water-soluble organic carbon (WSOC), elemental carbon (EC), water-soluble ions (WSIs), and benzene carboxylic acids (BCAs) were collected on a 47 mm quartz fiber filter. The influence of atmospheric transport processes was assessed by the Weather Research and Forecasting (WRF) model. OC, EC, WSOC, and BCA were determined by SUNET carbon analyzer, total organic carbon (TOC) analyzer, and liquid chromatography-mass spectrometry mass spectrometry (LC-MSMS), respectively. Twenty-four-hour integrated samples were collected for reactive oxygen species (ROS) analysis using a fluorogenic cell-based method to investigate the main chemical classes of toxicity. The results illustrate that WSOC and specific water-soluble species are associated with the oxidative potential of particulate matter. Pairwise correlation scatterplots between the daily-averaged WSOC and ROS (r2 of 0.81), and 135-BCA and ROS (r2 of 0.84), indicate that secondary organic aerosol production was highly associated with ROS activity. In addition, X-ray spectral analysis together with secondary electron images (SEIs) of PM2.5 particles collected during high ROS concentration events clearly indicate that water-soluble organic aerosols are major contributors to PM2.5 mass. This study provides insight into the components of particulate matter that are drivers of the oxidative potential of atmospheric particulate matter and potential tracers for this activity.

Impacts of regional transport on black carbon in Huairou, Beijing, China.

The 22nd Asia-Pacific Economic Cooperation (APEC) Conference was held near Yanqi Lake, Huairou, in Beijing, China during November 10-11, 2014. To guarantee haze-free days during the APEC Conference, the Beijing government and the governments of the surrounding provinces implemented a series of controls. Three months of Aethalometer 880 nm black carbon (BC) measurements were examined to understand the hourly fluctuations in BC concentrations that resulted from emission controls and meteorology changes. Measurements were collected at the University of Chinese Academy of Sciences near the APEC Conference site and in Central Beijing at the Institute of Remote Sensing and Digital Earth of the Chinese Academy of Sciences. Synoptic conditions are successfully represented through analysis of backward trajectories in six cluster groups. The clusters are identified based on air mass transport from various areas such as Inner Mongolia, Russia, three northeastern provinces, and Hebei industrial areas, to the measurement sites. Air pollution control measures during the APEC Conference significantly reduced BC at the conference site (Huairou) and in Central Beijing, with greater reductions in BC concentrations at the conference site than in Central Beijing. The highest BC concentrations in Huairou were associated with air masses originating from Central Beijing rather than from the Hebei industrial region. The success of the control measures implemented in Beijing and the surrounding regions demonstrates that BC concentrations can be effectively reduced to protect human health and mitigate regional climate forcing. This study also demonstrates the need for regional strategies to reduce BC concentrations, since urban areas like Beijing are sources as well as downwind receptors of emissions.

Temporal variations of black carbon during haze and non-haze days in Beijing.

Black carbon (BC) aerosol has been identified as one of key factors responsible for air quality in Beijing. BC emissions abatement could help slow regional climate change while providing benefits for public health. In order to quantify its variations and contribution to air pollution, we systematically studied real-time measurements of equivalent black carbon (eBC) in PM2.5 aerosols at an urban site in Beijing from 2010 to 2014. Equivalent black carbon (eBC) is used instead of black carbon (BC) for data derived from Aethalometer-31 measurement. Equivalent BC concentrations showed significant temporal variations with seasonal mean concentration varying between 2.13 and 5.97 µg m(-3). The highest concentrations of eBC were found during autumn and winter, and the lowest concentrations occurred in spring. We assessed the temporal variations of eBC concentration during haze days versus non-haze days and found significantly lower eBC fractions in PM2.5 on haze days compared to those on non-haze days. Finally, we observed a clear inverse relationship between eBC and wind speed. Our results show that wind disperses PM2.5 more efficiently than eBC; so, secondary aerosols are not formed to the same degree as primary aerosols over the same transport distance during windy conditions.

Associations between microvascular function and short-term exposure to traffic-related air pollution and particulate matter oxidative potential.

BACKGROUND: Short-term exposure to ambient air pollution has been associated with acute increases in cardiovascular hospitalization and mortality. However, causative chemical components and underlying pathophysiological mechanisms remain to be clarified. We hypothesized that endothelial dysfunction would be associated with mobile-source (traffic) air pollution and that pollutant components with higher oxidative potential to generate reactive oxygen species (ROS) would have stronger associations. METHODS: We carried out a cohort panel study in 93 elderly non-smoking adults living in the Los Angeles metropolitan area, during July 2012-February 2014. Microvascular function, represented by reactive hyperemia index (RHI), was measured weekly for up to 12 weeks (N = 845). Air pollutant data included daily data from regional air-monitoring stations, five-day average PM chemical components and oxidative potential in three PM size-fractions, and weekly personal nitrogen oxides (NOx). Linear mixed-effect models estimated adjusted changes in microvascular function with exposure. RESULTS: RHI was inversely associated with traffic-related pollutants such as ambient PM2.5 black carbon (BC), NOx, and carbon monoxide (CO). An interquartile range change increase (1.06 µg/m(3)) in 5-day average BC was associated with decreased RHI, -0.093 (95 % CI: -0.151, -0.035). RHI was inversely associated with other mobile-source components/tracers (polycyclic aromatic hydrocarbons, elemental carbon, and hopanes), and PM oxidative potential as quantified in two independent assays (dithiothreitol and in vitro macrophage ROS) in accumulation and ultrafine PM, and transition metals. CONCLUSIONS: Our findings suggest that short-term exposures to traffic-related air pollutants with high oxidative potential are major components contributing to microvascular dysfunction.