Water-soluble organic nitrogen (WSON) is an important component of PM2.5 which may affect air quality, climate and human health. Herein, one-year field samples of atmospheric PM2.5 (June 2017–May ...2018) were collected in northern Nanjing. Chemical characterization of PM2.5 major components as well as WSON were conducted, and WSON composition and sources were further investigated via measurements by a Aerodyne soot particle aerosol mass spectrometer (SP-AMS) as well as positive matrix factorization (PMF). Inorganic ions, mainly consisting of ammonium, sulfate, and nitrate, were found to dominate PM2.5 mass (58.7%), followed by organic matter (OM) (22.6%), and elemental carbon (EC) (2.1%). Water-soluble OM dominated OM (65.1%), and its temporal variation was closely correlated with that of secondary organic matter, while time series of water-insoluble OM concentrations correlated tightly with that of primary organic matter. Average WSON concentration was 2.15 μg/m3, which was highest in winter and lowest in summer. Correlation analysis of WSON with PM2.5 components also indicated that WSON was mainly from secondary sources. SP-AMS revealed that WSON mass spectrum was composed of CxHyNp+ (91.2%) and CxHyOzNp+ (8.8%), indicating dominance of amines and other oxygenated ON compounds. PMF analysis resolved two primary sources (traffic, biomass burning) and two secondary sources (less-oxidized and more-oxidized factors) of WSOM and WSON, and the secondary source dominated both WSOM and WSON. Contribution of the more-oxidized ON factor was very high in winter, and the less-oxidized factor was significant in summer, indicating a likely important role of aqueous-phase processing in winter as well as photochemical oxidation in summer to WSON.
Chemical processing in atmospheric aqueous phases, including cloud and fog drops, might be significant in reconciling the gap between observed and modeled secondary organic aerosol (SOA) properties. ...In this work, we conducted a relatively comprehensive investigation of the reaction products generated from the aqueous-phase photochemical oxidation of three benzene-diols (resorcinol, hydroquinone, and methoxyhydroquinone) by hydroxyl radical (·OH), triplet excited state (3C*) 3,4-dimethoxybenzaldehyde (3,4-DMB), and direct photolysis without any added oxidants. The results show that OH-initiated photo-degradation is the fastest of all the reaction systems. For the optical properties, the aqueous oxidation products generated under different reaction conditions all exhibited photo-enhancement upon illumination by simulated sunlight, and the light absorption was wavelength dependent on and increased as a function of the reaction time. The oxygen-to-carbon (O/C) ratio of the products also gradually increased against the irradiation time, indicating the persistent formation of highly oxygenated low-volatility products throughout the aging process. More importantly, aqueous-phase products from photochemical oxidation had an increased oxidative potential (OP) compared with its precursor, indicating they may more adversely impact health. The findings in this work highlight the importance of aqueous-phase photochemical oxidation, with implications for aqueous SOA formation and impacts on both the chemical properties and health effects of OA.
Air pollution is one of the leading causes for global deaths and understanding pollutant emission sources is key to successful mitigation policies. Air quality data in the urban, suburban, ...industrial, and rural areas (UA, SA, IA, and RA) of Jining, Shandong Province in China, were collected to compare the characteristics and associated health risks. The average concentrations of PM
, PM
, SO
, NO
, and CO show differences of -3.87, -16.67, -19.24, -15.74, and -8.37% between 2017 and 2018. On the contrary, O
concentrations increased by 4.50%. The four functional areas exhibited the same seasonal variations and diurnal patterns in air pollutants, with the highest exposure excess risks (ERs) resulting from O
. More frequent ER days occurred within the 25-30°C, but much larger ERs are found within the 0-5°C temperature range, attributed to higher O
pollution in summer and more severe PM pollution in winter. The premature deaths attributable to six air pollutants can be calculated in 2017 and 2018, respectively. Investigations on the potential source show that the ER of O
(
of 0.86) had the tightest association with the total ER. The bivariate polar plots indicated that the highest health-based air quality index (HAQI) in IA influences the HAQI in UA and SA by pollution transport, and thus can be regarded as the major pollutant emission source in Jining. The above results indicate that urgent measures should be taken to reduce O
pollution taking into account the characteristics of the prevalent ozone formation regime, especially in IA in Jining.
Due to the emergence of multi-drug resistant microorganisms, the development and discovery of alternative eco-friendly antimicrobial agents have become a top priority. In this study, a simple, novel, ...and valid green method was developed to synthesize
Litsea cubeba
essential oil-silver nanoparticles (Lceo-AgNPs) using Lceo as a reducing and capping agent. The maximum UV absorbance of Lceo-AgNPs appeared at 423 nm and the size was 5–15 nm through transmission electron microscopy result. The results of Fourier transform infrared and DLS showed that Lceo provided sufficient chemical bonds for Lceo-AgNPs to reinforce its stability and dispersion. The
in vitro
antibacterial effects of Lceo-AgNPs against microbial susceptible multidrug-resistant
Escherichia coli (E. coli)
and
methicillin-resistant Staphylococcus aureus (MRSA)
were determined. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Lceo-AgNPs against
E. coli
were 25 and 50 μg/ml. The MIC and MBC of Lceo-AgNPs against MRSA were 50 and 100 μg/ml, respectively. The results of scanning electron microscopy showed that the amount of bacteria obviously decreased and the bacteria cells were destroyed by Lceo-AgNPs.
In vivo
research disclosed significant wound healing and re-epithelialization effects in the Lceo-AgNPs group compared with the self-healing group and the healing activity was better than in the sulfadiazine silver group. In this experiment, Lceo-AgNPs has been shown to have effects on killing multidrug-resistant bacteria and promoting wound healing. This study suggested Lceo-AgNPs as an excellent new-type drug for wound treatment infected with multidrug-resistant bacteria, and now expects to proceed with clinical research.
Heavy metals are widely recognized as toxic components in urban air particulate matter (PM). However, the major toxic metals and their interactions are poorly understood. In this study, we attempted ...to explore the toxicity contribution and combined effects of PM-bounded metals in human lung epithelial cells (A549). Real-time cell analysis indicated that the critical toxic concentration (EC50) of PM detected in this study was 107.90 mg/L (r2 = 1.00, p < 0.01). The cell viability of A549 increased significantly (12.3%) after metal removal in PM, demonstrating an important contribution of metal components to PM toxicity. Among eleven elements examined (Zn, Cr, Mn, Fe, Ni, Cu, As, Se, Sr, Cd, and Pb), six heavy metals (Zn, Cr, Mn, Fe, Cu, and Pb) might account for PM toxicity in A549 cells, and their co-exposure led to a high mortality of A549 cells (36.5 ± 7.3%). For combination treatments, cell mortality caused by single or multiple metal mixtures was usually alleviated by Fe addition, while it was often aggravated in the presence of Mn. The varying effects of other metals (Zn, Cu, Pb and Cr) on different metal mixtures might be explained by their interactions (e.g., similar or dissimilar membrane transporters and intracellular targets). Furthermore, the concentration addition model (CA), independent action model (IA), integrated addition model (IAM) and integrated addition and interaction model (IAI) were used to predict mixture toxicity, and the IAI model exhibited the least variation between observed and predicted toxic effects (r2 = 0.87, p < 0.01). Our results highlight the potential contribution from heavy metals and their interactions to PM toxicity, and promote the application of toxicity prediction models on metal components in PM.
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•Metal fractions made a great contribution (22.9% ± 11.5%) to PM-related cytotoxicity.•Zn, Cr, Mn, Fe, Cu, and Pb might account for PM toxicity in A549 cells.•Mixture toxicity was increased when co-exposed with Mn, but decreased in the presence of Fe.•The IAI model exhibited better stability in metal mixture toxicity prediction.
PM2.5 pollution is of great concern in China due to its adverse health effects. Many diseases have been proven to be associated with PM2.5 components, but the effects of chemical characteristics of ...PM2.5 on toxicological properties, especially in different human organs, are poorly understood. In this study, two seasonal PM2.5 samples (summer and winter) were collected in Nanjing, and their chemical compositions (heavy metals, water-soluble ions, organic carbon (OC), and elemental carbon (EC)) were analyzed. Human lung epithelial carcinoma cells (A549), human hepatocellular liver carcinoma cells (HepG2), and human neuroblastoma cells (Sh-Sy5y) were employed to evaluate the toxicological properties of the collected PM2.5. The results showed that the average mass concentrations of PM2.5 were lower in summer (51.3 ± 21.4 μg/m3) than those in winter (62.1 ± 21.5 μg/m3). However, the mass fractions of heavy metals, OC, and EC exhibited an opposite seasonal difference. Among all tested fractions, water-soluble ions were the major compositions of particles in both summer and winter, especially the secondary ions (SO42−, NO3− and NH4+). Besides, the ratio of OC/EC in PM2.5 was greater than two, indicating serious secondary pollution in this area. The NO3–/SO42− ratio (< 1) suggested that fixed sources made important contributions. The toxicological results showed that PM2.5 in the summer and winter significantly inhibited cell viability (p < 0.01) and induced intracellular reactive oxygen species (ROS) production (p < 0.01). Moreover, the viability inhibition in A549, Sh-Sy5y, and HepG2 cells was more prominent in summer, especially at high PM2.5 (400 μg/mL) (p < 0.05), and the induction of reactive oxygen species (ROS) in A549 and Sh-Sy5y cells was also more evident in summer. Such seasonal differences might be related to the variations of PM2.5 components.
Events of severe air pollution occurred frequently in China recently, thus understanding of the air pollution characteristics and its health risks is very important. In this work, we analyzed a ...two-year dataset (March 2014 – February 2016) including daily concentrations of six criteria pollutants (PM2.5, PM10, CO, SO2, NO2, and O3) from 18 cities in Henan province. Results reveal the serious air pollution status in Henan province, especially the northern part, and Zhengzhou is the city with the worst air quality. Annual average PM2.5 concentrations exceed the second grade of Chinese Ambient Air Quality Standard (75μg/m3) at both 2014 and 2015. PM2.5 is typically the major pollutant, but ozone pollution can be significant during summer. Furthermore, as the commonly used air quality index (AQI) neglects the mutual health effects from multiple pollutants, we introduced the aggregate air quality index (AAQI) and health-risk based air quality index (HAQI) to evaluate the health risks. Results show that based on HAQI, the current AQI system likely significantly underestimate the health risks of air pollution, highlighting that the general public may need stricter health protection measures. The population-weighted two-year average HAQI data further demonstrates that all population in the studied cities in Henan province live with polluted air – 72% of the population is exposed to air that is unhealthy for sensitive people, while 28% of people is exposed to air that can be harmful to healthy people; and the health risks are much greater during winter than during other seasons. Future works should further improve the HAQI algorithm, and validate the links between the clinical/epidemiologic data and the HAQI values.
•Two-year air quality data shows the serious air pollution status in Henan province.•Average PM2.5 concentration is above the CAAQS Grade II standard.•Current AQI likely significantly underestimates the health risks of air pollution.•Population-weighted HAQI shows that all people in the studied cities is exposed to polluted air.
Ni based catalysts are usually used for catalyzing the CO2 methanation to produce synthetic natural gas due to their low cost, though their catalytic activities cannot be comparable with the noble ...metal counterparts. In order to address this challenge, a series of rare earth (La, Ce, Sm, and Pr) doped Ni based mesoporous materials had been facilely fabricated by the one-pot evaporation induced self-assembly (EISA) strategy and directly employed as the catalysts for CO2 methanation. These mesoporous catalysts had been systematically characterized by means of X-ray diffraction, N2 physisorption, transmission electron microscope, X-ray photoelectron spectroscopy, H2 temperature programmed reduction, CO2 temperature programmed desorption, and so on. It was found that the Ni species were highly dispersed among the mesoporous framework and the strong metal-framework interaction had been formed. Thus, the thermal sintering of the metallic Ni nanoparticles could be effectively suppressed under CO2 methanation conditions, promising these mesoporous catalysts with 50 h excellent catalytic stabilities without evident deactivation. Besides, the rare earth dopants could greatly increase the surface basicity of the catalysts and intensify the chemisorption the CO2. Further, the rare earth elements were also functioned as the electron modifiers, which was also helpful in activating the CO2 molecule. The apparent activation energies of CO2 could be obviously decreased by rare earth dopants. As a result, their low-temperature catalytic activity had been greatly intensified over these rare earth elements promoted catalysts.
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•Rare earth doped mesoporous catalysts were prepared by one-pot EISA method.•The strong metal-framework interaction endowed anti-sintering property of Ni.•Rare earth dopants strengthened the basic and/or electronic properties.•Rare earth dopants decreased the apparent activation energies of CO2.•Rare earth dopants enhanced the low-temperature catalytic activities and stabilities.
This work presents the temporal and spatial characteristics of the major air pollutants and their associated health risks in China from 2019 to 2020, by using the monitoring data from 367 cities. The ...annual average PM2.5, PM10, NO2, SO2, CO, and O3 concentrations decreased by 10.9%, 13.2%, 9.3%, 10.1%, 9.4%, and 5.5% from 2019 to 2020. National average PM2.5 concentration in 2020 met the standard of 35 μg/m3, and that of O3 decreased from 2019. COVID-19 lockdown affected NO2 level dramatically, yet influences on PM2.5 and O3 were less clear-cut. Positive correlations between PM2.5 and O3 were found, even in winter in all five key regions, e.g., Jing-Jin-Ji (JJJ), FenWei Plain (FWP), Yangtze River Delta (YRD), Pearl River Delta (PRD) and Chengdu-Chongqing Region (CCR), indicating importance of secondary production for both PM2.5 and O3. Large seasonal variability of PM2.5-SO2 correlation indicates a varying role of SO2 to PM2.5 pollution in different seasons; and generally weak correlations in winter between PM2.5 and NO2 or SO2 reveal the complexity of secondary formation processes to PM2.5 pollution in winter. Multilinear regression analysis between PM2.5 and SO2, NO2 and CO demonstrates that PM2.5 is more sensitive to the change of NO2 than SO2 in JJJ, FWP, PRD and CCR, suggesting a priority of NOx emission control for future PM2.5 reduction. Furthermore, the new World Health Organization Air Quality Guidelines (WHO AQG2021) were adopted to calculate the excess health risks (ER) as well as the health-risk based air quality index (HAQIWHO) of the pollutants. Such assessment points out the severity of air pollution associated health risks under strict standards: 40.0% of days had HAQIWHO>100, while only 14.4% days had AQI>100. PM2.5 ER was generally larger than O3 ER, but O3 ER in low PM2.5 region (PRD) and during summer became more serious. Notably, NO2 ER became even more important than PM2.5 due to its strict limit of WHO AQG2021. Overall, our results highlight the increasing importance of O3 in both air quality evaluation and health risk assessment, and the importance of coordinated mitigation of multiple pollutants (mainly PM2.5, O3 and NO2) in protecting the public health.
•O3 level decreased from 2019 to 2020, opposite to its recent increasing trend.•COVID-19 lockdown affected the NO2 more significantly than other pollutants.•Overall positive correlations between PM2.5 and O3 were found, even in winter.•Health risks from NO2, PM2.5, PM10 and O3 using WHO AQG2021 are all important.
Health risk assessment of trace elements (TrElems) in fine particulate matter (PM2.5) has been studied based on the total element concentrations or more recently on the phosphate buffered saline ...(PBS)-soluble concentrations. However, behaviors of the TrElems released from PM2.5 change considerably as the interacting media change. In this study, the bioaccessibility of particulate-bound TrElems (V, Mn, Co, Ni, Cu, As, Cd and Pb) were investigated using three kinds of simulated body fluids, artificial lung fluid (ALF), artificial sweat (AS), and artificial gastric juice (AGJ), comparing with the commonly used PBS. Many TrElems, especially Pb, showed lower solubility in PBS than that in other fluids. Cu, Mn, V and As were observed to be the most soluble TrElems in all simulated body fluids. Carcinogenic and non-carcinogenic effects were evaluated using ALF, AS and AGJ-soluble fractions (representing the corresponding exposure routes: inhalation, dermal contact and ingestion) according to the United States Environmental Protection Agency (USEPA) human health risk assessment model. The carcinogenic risks of As and Pb were higher than 1 × 10−6 (the acceptable level) for both adults and children. High hazard quotient (HQ) values for As and Pb were also observed for children, indicating a potential non-carcinogenic risk posed by these toxic elements. Our results demonstrated that the health risks of particulate-bound TrElems might be misjudged if using the PBS-soluble or total element contents alone.
•Bioaccessibility of PM2.5-bound TrElems were analyzed in three simulated body fluids.•Health risks were assessed using ALF, AS and AGJ-soluble fractions.•As and Pb showed potential carcinogenic and non-carcinogenic risks.•Children were more sensitive than adults to PM2.5 exposure.•Traditional evaluation methods might overestimate or underestimate the health risks.
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