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Identification of various emission sources and quantification of their contributions comprise an essential step in formulating scientifically sound pollution control strategies. Most previous studies have been based on traditional offline filter analysis of aerosol major components (usually inorganic ions, elemental carbon – EC, organic carbon – OC, and elements). In this study, source apportionment of PM2.5 using a positive matrix factorization (PMF) model was conducted for urban Shanghai in the Yangtze River Delta region, China, utilizing a large suite of molecular and elemental tracers, together with water-soluble inorganic ions, OC, and EC from measurements conducted at two sites from 9 November to 3 December 2018. The PMF analysis with inclusion of molecular makers (i.e., MM-PMF) identified 11 pollution sources, including 3 secondary-source factors (i.e., secondary sulfate; secondary nitrate; and secondary organic aerosol, SOA, factors) and 8 primary sources (i.e., vehicle exhaust, industrial emission and tire wear, industrial emission II, residual oil combustion, dust, coal combustion, biomass burning, and cooking). The secondary sources contributed 62.5 % of the campaign-average PM2.5 mass, with the secondary nitrate factor being the leading contributor. Cooking was a minor contributor (2.8 %) to PM2.5 mass while a significant contributor (11.4 %) to the OC mass. Traditional PMF analysis relying on major components alone (PMFt) was unable to resolve three organics-dominated sources (i.e., biomass burning, cooking, and SOA source factors). Utilizing organic tracers, the MM-PMF analysis determined that these three sources combined accounted for 24.4 % of the total PM2.5 mass. In PMFt, this significant portion of PM mass was apportioned to other sources and thereby was notably biasing the source apportionment outcome. Backward trajectory and episodic analysis were performed on the MM-PMF-resolved source factors to examine the variations in source origins and composition. It was shown that under all episodes, secondary nitrate and the SOA factor were two major source contributors to the PM2.5 pollution. Our work has demonstrated that comprehensive hourly data of molecular markers and other source tracers, coupled with MM-PMF, enables examination of detailed pollution source characteristics, especially organics-dominated sources, at a timescale suitable for monitoring episodic evolution and with finer source breakdown.

The aim of this study was to evaluate the mechanical properties and coloration of silicon nitride ceramics in the presence of RE2O3 (RE = Nd, Eu or Dy). Dense Si3N4 ceramics were prepared by gas pressure sintering at 1800 °C for 2 h. XRD analysis confirmed the complete transformation of α-Si3N4 to β-Si3N4. The fracture toughness and flexure strengths were 11.93 ± 0.56 MPa·m1/2, 667 ± 40.98 MPa with the addition of Eu2O3 (SE). Base on the SEM image, the pull-out, bridging and deflection of large grains were observed and contributed to the increase in mechanical properties. The chromaticity of sintered bodies was measured using a spectrophotometer. The color difference of the ceramics is due to the formation of different color developing compounds according to the EDS. Results showed that high-toughness and colorful Si3N4 ceramics can be prepared using YAG:Ce3+ as sintering additive and RE2O3 as the colorant.

High-purity silicon powder is used as the starting material for cost-effective preparation of silicon nitride ceramics with both high thermal conductivity and excellent mechanical properties using RE2O3 (RE=Y, La or Er) and MgO as sintering additives. Nitridation is a key procedure that would affect the properties of green bodies and the sintered samples. The β: (α+β) ratio can be increased as the samples nitrided at 1450oC and a large amount of long rod-like β-Si3N4 grains were developed in the samples. It was found that the addition of Er2O3-MgO could help to improve the mechanical properties of the sintered Si3N4 ceramics, the thermal conductivity, flexural strength and fracture toughness of the sample were 90 W/(m∙K), 953±28.3 MPa and 10.64±0.61 MPa·m1/2, respectively. The RE3+ species with larger ionic radius tended to increase the oxygen of nitrided samples and decrease N/O ratio (triangle grain boundary) of sintered samples.

The Na+ super-ionic conductor (NASICON) type solid electrolytes Li1.3Al0.3Ti1.7(PO4)3 (LATP) are of increasing interest because of their high total ionic conductivity and excellent stability against moist air. However, they are not stable when contacting with lithium metal because of the rapid Ti4+ reduction by Li metal, which greatly restrict their application in lithium batteries. Here, we propose a Al2O3-doped ZnO (AZO) surface coating method by magnetron sputtering to improve the stability of the Li1.3Al0.3Ti1.7(PO4)3 electrolyte against the attack of lithium-metal anode and to avoid the growth of lithium dendrite. The Al2O3-doped ZnO coating of the electrolyte Li1.3Al0.3Ti1.7(PO4)3 demonstrates high chemical stability against the attack of lithium-metal in a wide electrochemical potential ranges (>5 V), as well as an excellent performance of suppressing of lithium dendrites. Furthermore, the Al2O3-doped ZnO coated Li1.3Al0.3Ti1.7(PO4)3 was found to be the candidate electrolyte for the all-solid-state lithium battery. An all-solid-state Li/LiFePO4 battery with Al2O3-doped ZnO coated Li1.3Al0.3Ti1.7(PO4)3 as the solid electrolyte shows good cyclability and a high columbic efficiency for 50 charge/discharge cycles. Furthermore, the surface-modified electrolyte Li1.3Al0.3Ti1.7(PO4)3 by Al2O3-doped ZnO coating also enables the lithium metal battery to exhibit extremely long cycling for nearly 1000 h due to the ability of suppressing of lithium dendrites.

The idea of increasing the mechanical strength of graphene aerogel (GA) and achieving more reliable application performance has aroused wide attention recently. A solution to this challenge is to reinforce the framework of aerogel by adding enhancers to the initial graphene oxide (GO) solution. Herein, organosilicon chains strengthened compressible GA was fabricated in a facile and low-cost method by introducing tetraethyl orthosilicate (TEOS) as the reinforce agent. The effects of TEOS on the porous microstructure and mechanical properties of GA were systematically studied, and the best mechanical performance obtained at the mass ratio of TEOS to GO equal to 3:1. The final well-structured TEOS-3 aerogel exhibits a maximum compression modulus of 29 kPa, which is higher than that reported in previous works. In addition, it showed an excellent hydrophobicity (contact angle, 131.71°), a high adsorption capacity (72 times of its own weight) and excellent regeneration capacity for toluene, a good electrical conductivity of ~ 0.1 S·m−1 and a low density of 15.56 mg·cm−3. This work might provide hints for the large-scale preparation and practical application of graphene aerogel with more reliable application performance.

Among a series of 3D printing techniques, stereolithography provides a new route to produce ceramic architectures with the advantages of high-precision and short cycle time. However, up to now the stereolithography of non-oxide ceramics still face complex and difficult problems. This work focused on the analysis of rheological and curing ability of Si3N4 photocurable slurries. The effects of monomer type, coarse silicon powder, solid loading and ambient temperature on the rheological behavior were intensively studied. The relationships between powder characteristic (involving refractive index, absorbance and the introduce of coarse silicon powder), monomer type and curing ability were discussed in detail. It is expected that this study may benefit the development of Si3N4 or other non-oxide ceramic slurries for stereolithography.

Tropospheric ozone pollution has been continuously worsening in China during the past decade. Identification of long-term evolution of ozone sensitivity to precursors is essential to evaluating the impact of emission reduction measures on ozone pollution. Traditional observation-based model and 3-d numerical model are not suitable for analyzing long-term variation of ozone sensitivity to precursors. In this study, by transforming the conventional ozone isopleth plot into a VOCR isopleth plot in the functional space of NOx and ozone concentrations, we developed a novel approach to identify ozone sensitivity to precursors by simply using long-term monitoring data of ozone, NOx and temperature. This approach estimated ozone formation regimes (OFR) by ozone sensitivity to NOx and temperature separately, and the convergence of OFR serves as a way of mutual verification. We found that ozone formation was generally in the VOCR-limited or transitional regime in Shanghai, the largest metropolitan area in China. However, OFR was shifted to NOx-limited at Pudong station during 2017–19 due much to the stringent NOx emission control. OFR was also shifted to NOx-limited along with the increasing temperature. When temperature was over 30 °C, Shanghai was mostly in a NOx-limited OFR. This highlights that the NOx emission control measures need to be strengthened to reduce peak ozone levels more efficiently. Jinshan station exhibited a different trend with OFR shifted to VOCR-limited in 2017–19, which proved the effectiveness of VOCs emission control on petrochemical sector. However, OFR was shifted to NOx-limited when temperature was over 30 °C, suggesting more stringent VOCs emissions control should be targeted on days with higher temperature.

A high level of ozone (O3) is frequently observed in the suburbs of Shanghai, the reason for this high level remains unclear. To obtain a detailed insight on the high level of O3 during summer in Shanghai, O3 and its precursors were measured at a suburban site in Shanghai from July 1, 2016 to July 31, 2016. Using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and concentration weighted trajectories (CWT), we found that Zhejiang province was the main potential source of O3 in suburban Shanghai. When the sampling site was controlled by south-western winds exceeding 2 m/s, the O3-rich air masses from upwind regions (such as Zhejiang province) could be transported to the suburban Shanghai. The propylene-equivalent concentration (PEC) and ozone formation potential (OFP) were further calculated for each VOC species, and the results suggested that propylene, (m + p)-xylene, and toluene played dominant roles in O3 formation. The Ozone Isopleth Plotting Research (OZIPR) model was used to reveal the impact of O3 precursors on O3 formation, and 4 base-cases were selected to adjust the model simulation. An average disparity of 18.20% was achieved between the simulated and observed O3 concentrations. The O3 isopleth diagram illustrated that O3 formation in July 2016 was in VOC-sensitive regime, although the VOC/NOx ratio was greater than 20. By introducing sensitivity (S), a sensitivity analysis was performed for O3 formation. We found that O3 formation was sensitive to propylene, (m + p)-xylene, o-xylene and toluene. The results provide theoretical support for O3 pollution treatment in Shanghai.

To investigate chemical characteristics, abatement mechanisms and regional transport of atmospheric pollutants during the COVID-19 outbreak control period in the Yangtze River Delta (YRD) region, China, the measurements of air pollutants including fine particulate matter (PM2.5) and volatile organic compounds (VOCs) on non-control period (NCP, 24 December 2019–23 January 2020) and control period (CP, 24 January–23 February 2020) were analyzed at the urban Pudong Supersite (PD) and the regional Dianshan Lake Supersite (DSL). Due to the stricter outbreak control, the levels of PM2.5 and VOCs, and the occurrence frequencies of haze-fog episodes decreased substantially from NCP to CP, with average reduction rates of 31.6%, 38.9% and 35.1% at PD, and 34.5%, 50.7% and 37.9% at DSL, respectively. The major source for PM2.5 was secondary sulfate & nitrate in both periods, and the emission control of primary sources such as coal burning and vehicle exhaust decreased the levels of precursors gas sulfur dioxide and nitrogen oxide, which highly contributed to the abatement of PM2.5 from NCP to CP. The higher levels of ozone at both PD and DSL on CP might be due to the weak nitrogen monoxide titration, low relative humidity and high visibility compared with NCP. Vehicle exhaust and fugitive emission from petrochemical industry were the major contributors of ambient VOCs and their decreasing activities mainly accounted for VOCs abatement. Moreover, the high frequency of haze-fog events was closely impacted by medium-scale regional transport within Anhui and Jiangsu provinces. Therefore, the decreasing regional transported air pollutants coincided with the emission control of local sources to cause the abatement of haze-fog events in YRD region on CP. This study could improve the understanding of the change of atmospheric pollutants during the outbreak control period, and provide scientific base for haze-fog pollution control in YRD region, China., Graphical abstract Image 1, Highlights • PM2.5 and VOCs levels were decreased substantially from NCP to CP. • Declining secondary formation highly contributed to abatement of PM2.5. • Weak NO titration, low RH and high visibility might cause the high O3 level on CP. • Decreasing vehicle exhaust and fugitive emission mainly accounted for VOCs abatement. • Haze-fog events were closely impacted by medium-scale regional transport.

Regarding the continuous worsening of tropospheric ozone pollution, the scenario in Shanghai is a microcosm of the entire China. Understanding the ozone formation regimes (OFRs), their variations, and driving factors is a prerequisite for formulating effective ozone control strategies. Traditional OFR estimation by numerical model, which often involves sensitivity analysis on at least tens of scenarios, is labor-intensive and time-consuming; therefore, it is not appropriate to make OFR forecasts to guide ozone contingency control. In this study, by using a localized modeling system consisting of the Weather Research and Forecasting, Sparse Matrix Operator Kernel Emissions, and Community Multiscale Air Quality models and considering the latest emission inventory over the Yangtze River Delta of China, we discovered a strong connection between the variations of large-scale circulation (LSC) and OFRs over Shanghai in July 2017, thereby providing an alternative way to infer OFR. During the northward movement of Western Pacific Subtropical High from South China Sea, the wind field over Shanghai changed from weak westerly to moderate southwesterly and to one without a distinct direction. The local OFR shifted from anthropogenic volatile organic compounds (AVOCs)-limited to NOx-limited and ultimately to the transitional regime. Such a variation in OFR is essentially driven by the spatial heterogeneity of NOx and AVOC emissions in different directions of Shanghai, brought on by the wind under different LSC patterns. With the existing weather forecasting technology, the LSC patterns can be well-predicted 48–72 h in advance. Hence, we propose the adoption of a dynamic ozone control strategy for Shanghai with the priority control target on AVOC or NOx emission sources adjusted according to the LSC pattern and OFR forecasts in a forthcoming O3 pollution episode. This would serve to maximize the peak ozone reduction under varying pollution conditions.

It is a puzzle as to why more severe haze formed during the New Year Holiday in 2020 (NYH‐20), when China was in an unprecedented state of shutdown to contain the coronavirus (COVID‐19) outbreak, than in 2019 (NYH‐19). We performed a comprehensive measurement and modeling analysis of the aerosol chemistry and physics at multiple sites in China (mainly in Shanghai) before, during, and after NYH‐19 and NYH‐20. Much higher secondary aerosol fraction in PM2.5 were observed during NYH‐20 (73%) than during NYH‐19 (59%). During NYH‐20, PM2.5 levels correlated significantly with the oxidation ratio of nitrogen (r 2 = 0.77, p < 0.01), and aged particles from northern China were found to impede atmospheric new particle formation and growth in Shanghai. A markedly enhanced efficiency of nitrate aerosol formation was observed along the transport pathways during NYH‐20, despite the overall low atmospheric NO2 levels., Key Points Higher concentrations and distinct compositions of aerosol particles were observed during the COVID‐19 shutdownFast formation of secondary inorganic aerosol contributed to high aerosol mass loadingLonger‐range, regional transport facilitated and enhanced particulate nitrate formation

The ongoing outbreak of coronavirus disease 2019 (COVID-19) has spread rapidly on a global scale. Although it is clear that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted through human respiratory droplets and direct contact, the potential for aerosol transmission is poorly understood1-3. Here we investigated the aerodynamic nature of SARS-CoV-2 by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the outbreak of COVID-19 in February and March 2020. The concentration of SARS-CoV-2 RNA in aerosols that was detected in isolation wards and ventilated patient rooms was very low, but it was higher in the toilet areas used by the patients. Levels of airborne SARS-CoV-2 RNA in the most public areas was undetectable, except in two areas that were prone to crowding; this increase was possibly due to individuals infected with SARS-CoV-2 in the crowd. We found that some medical staff areas initially had high concentrations of viral RNA with aerosol size distributions that showed peaks in the submicrometre and/or supermicrometre regions; however, these levels were reduced to undetectable levels after implementation of rigorous sanitization procedures. Although we have not established the infectivity of the virus detected in these hospital areas, we propose that SARS-CoV-2 may have the potential to be transmitted through aerosols. Our results indicate that room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols. Future work should explore the infectivity of aerosolized virus.

Identification of various sources and quantification of their contributions are a necessary step to formulating scientifically sound pollution control strategies. Receptor model is widely used in source apportionment of fine particles. However, most of the previous studies are based on traditional filter collection and lab analysis of aerosol chemical species (usually ions, elemental carbon (EC), organic carbon (OC) and elements) as inputs. In this study, we conducted robust online measurements of a range of organic molecular makers and trace elements, in addition to the major aerosol components (ions, OC and EC), in urban Shanghai in the Yangtze River Delta region, China. The large suite of molecular and elemental tracers, together with water-soluble ions, OC and EC, provide data for establishing measurement-based source apportionment methodology for PM2.5. We conducted source apportionment using positive matrix factorization (PMF) and compared PMF solutions with molecular makers added (i.e. MM-PMF) and those without organic markers. MM-PMF identified 11 types of pollution sources, with biomass burning, cooking and secondary organic aerosol (SOA) as the additional sources identified. The three sources accounted for 4.9 %, 2.6 % and 14.7 % of the total PM2.5 mass, respectively. During the whole campaign, the secondary source is an important source of atmospheric pollution, the average contribution of secondary pollution sources is as high as 63.8 % of the total PM2.5 mass. Grouping different sources to secondary and primary, we note that SOC and POC contributed 45.1 % and 54.9 %, respectively. It is worth noting that the contribution of cooking to PM2.5 mass only account for 2.6 %, but it contributed to 10.7 % of OC. Episodic analysis indicated that secondary nitrate was the always the main cause of PM2.5 pollution, while during non-episodic hours, vehicle exhaust made a significant contribution. Through the application of the above-mentioned techniques to the Yangtze River Delta, more insights are gained on the sources, formation mechanism and pollution characteristics of PM2.5 in this region.

Instruments based on light scattering used to measure total suspended particulate (TSP) concentrations have the advantages of fast response, small size, and low cost compared to the gravimetric reference method. However, the relationship between scattering intensity and TSP mass concentration varies nonlinearly with both environmental conditions and particle properties, making it difficult to make corrections. This study applied four machine learning models (support vector machines, random forest, gradient boosting regression trees, and an artificial neural network) to correct scattering measurements for TSP mass concentrations. A total of 1141 hourly records of collocated gravimetric and light scattering measurements taken at 17 urban sites in Shanghai, China were used for model training and validation. All four machine learning models improved the linear regressions between scattering and gravimetric mass by increasing slopes from 0.4 to 0.9&ndash, 1.1 and coefficients of determination from 0.1 to 0.8&ndash, 0.9. Partial dependence plots indicate that TSP concentrations determined by light scattering instruments increased continuously in the PM2.5 concentration range of ~0&ndash, 80 &micro, g/m3, however, they leveled off above PM10 and TSP concentrations of ~60 and 200 &micro, g/m3, respectively. The TSP mass concentrations determined by scattering showed an exponential growth after relative humidity exceeded 70%, in agreement with previous studies on the hygroscopic growth of fine particles. This study demonstrates that machine learning models can effectively improve the correlation between light scattering measurements and TSP mass concentrations with filter-based methods. Interpretation analysis further provides scientific insights into the major factors (e.g., hygroscopic growth) that cause scattering measurements to deviate from TSP mass concentrations besides other factors like fluctuation of mass density and refractive index.

Air pollution has become one of the most stubborn environmental problem in China, the traditional environmental monitoring mainly focus on the horizontal distribution of the pollutants, while it is still of great importance to have the knowledge of the vertical profiles of them. The present study, for the first time, attempted to acquire the vertical distributions of O3 and one of its precursors, volatile organic compounds (VOCs) within 1000 m of lower troposphere by using a tethered balloon in the suburban of Shanghai, a Chinese megacity. We analyze the concentration and the ozone formation potential (OFP) at three height level of 50–350, 350–700, and 700–1000 m. According to our measurement, the total concentration of VOC decreased with the altitude increasing. In addition, the dominant species of OFP was alkene, aromatics, and alkene at height level of 50–350, 350–700 and 700–1000 m, respectively. Our results suggest that, in the morning, the fresh emission contributed a lot to the high concentration of benzene and toluene near ground. Furthermore, the regression analyzes showed toluene decreased faster than benzene in the troposphere. The VOC concentration can be used as initial values for numerical simulations of chemical reaction in the lower troposphere.

Mercury (Hg) has a complex atmospheric transformation cycle and acts as a global pollutant. Size-specific particle bound mercury (PBM) was implemented in different functional (industrial, urban and suburban) areas in Shanghai, China. The total concentration of 13-staged PBM (rang of 0.01-18.0 μm) varied of 99.0-611 pg/m3, with an average value of 318 ± 144 pg/m3. The Gaoqiao petrochemical industry (GQPI) site showed the highest concentrations, whereas the suburban Shanghai Jiao Tong University (SJTU) displayed the lowest. The PBM in nucleation, accumulation and coarse modes were 7.63-96.7, 69.5-455, and 9.43-176 pg/m3, respectively, and the fractions of 0.56-1.00 and 0.32-0.56 μm were the two most abundant. Both OC and EC displayed unimodal distribution patterns (peak of 0.56-1.00 μm) at GQPI, while bimodal distributions were observed at urban and suburban sites. Statistically positive correlations between the overall PBM and the corresponding PM and carbonaceous compounds (r = 0.38-0.54, p 80%), but smaller (

Concerning the safety problems of conventional Li-ion batteries with liquid electrolytes, it is crucial to develop reliable solid-state electrolytes with high ionic conductivity. Li 1+x Al x Ti 2−x (PO 4 ) 3 (LATP, x = 0.3) is regarded as one of the most promising solid electrolytes due to its high ionic conductivity and excellent chemical stability to humidity. Herein, a new strategy is proposed for improving the sintering behavior and enhancing the ionic conductivity of LATP by using LiBO 2 as the sintering aid via liquid phase sintering. The as-prepared sample LATP with homogeneous microstructure and high relative density of 97.1% was successfully synthesized, yielding high total ionic conductivity of 3.5 × 10 −4 S cm −1 and low activation energy of 0.39 eV at room temperature. It was found that the addition of LiBO 2 could effectively enhance the densification and increase the ionic conductivity of LATP electrolyte, proving an effective way to synthesis LATP ceramics by a simple and reliable route.

TiO2-MgO is proposed as new sintering additive for low temperature pressureless sintering of Si3N4 ceramics to be circuit substrate in power electronic devices. The effects of additive content on densification, mechanical and thermal properties of Si3N4 substrate were investigated systemically. Si3N4 ceramics with density of 3.20 g cm−3 could be obtained with the addition of 10 wt% TiO2-MgO and sintered at 1780 °C. The flexural strength, fracture toughness and thermal conductivity were 668 MPa, 5.13 MPa m1/2 and 55.3 W/(m K), respectively, and the highest thermal conductivity was 60 W/(m K) could be obtained after annealing. Phase compositions at different temperature were characterized by high temperature in-situ XRD. TiC0.3N0.7 s phase was observed and its formation mechanism was investigated. Results showed TiO2-MgO to be effective sintering additive for developing Si3N4 ceramics at low cost and with acceptable mechanical and thermal properties.

In this work, a high-performance microwave absorption ceramic together with high thermal conductivity was proposed through the introduction of phenolic resin as the carbon source into AlN ceramic substrate. The phenolic resin was initially mixed with AlN powder and sintering additives in ethanol to form homogeneous slurries, followed by drying, pyrolysis, dry pressing and pressureless sintering to develop nano carbon in situ in AlN substrate. The well controlled microstructure with homogeneous distribution of nano sized carbon lead to the high thermal conductivity and excellent microwave absorption properties. by adjusting the phenolic resin content, the ceramic showed a minimal reflection coefficient of about −30 dB with an effective bandwidth of about 2 GHz together with a high thermal conductivity of about 135.1 W/m K.

Indoor gaseous pollutants pose a great threat to human health, graphene aerogel (GA) has attracted more and more attention due to its high adsorption performance. However, the increase of the adsorption capacity together with high strength for long time and repeat using is still a challenge. In this study, a novel silica modification method was proposed to modify graphene aerogels with high strength and ultrahigh adsorption capability. Apart from its high adsorption capacity for liquid toluene, the adsorption capability to benzene, an indoor pollutant gas, was increased to 809.51 mg/g, which is higher than pure graphene aerogel and other carbon-based adsorbents such as graphene, activated carbon and single-wall carbon nanotubes. The enhanced adsorption performance is due to two reasons in addition to the electrostatic interactions. On one hand, tetraethyl orthosilicate (TEOS) could help to modify the pore structure of aerogel, reducing its average pore diameter and increasing its BET specific surface area. On the other hand, the addition of TEOS could help to improve the hydrophobicity of aerogel. The selective adsorption character of graphene aerogels to benzene/toluene binary system in the breakthrough experiment confirmed that the prepared graphene aerogels could also be used in the field of separation of multicomponent indoor pollutant gases.

To investigate the multi-year atmospheric characteristic and population exposure level of black carbon (BC) in the Yangtze River Delta (YRD) region, China, about five years of ambient BC measurement was performed at Dianshan Lake (DSL) regional Supersite from February 2014 to February 2019. BC concentration at DSL was 1.39 ± 1.15 μg m−3, which was at low to medium level compared to other areas in the world, and annual BC level was decreased by an average of 45.4% from 2014 to 2018. The absorption Angstrom exponent (AAE) value was 1.30 ± 0.173, indicating the predominant contribution of liquid fuel sources such as traffic exhaust to BC. Meanwhile, AAE and BC values both showed the winter-high and summer-low temporal patterns, which highlighted the increasing contribution from solid fuels to BC in winter. Moreover, diurnal characteristics of BC, AAE, carbon monoxide and nitrogen oxide demonstrated the dominance of traffic sources for BC. The average estimated daily intakes (EDIs) of BC through inhalation for 17 population age subgroups were 0.0177–0.0811 μg kg−1 day−1, which the highest EDIs for male and female were both observed in infants (9 months ~

Dense AlN-SiBCN ceramics were fabricated by pyrolysis of a commercially available polyborosilazane followed by hot-pressing of AlN and SiBCN mixture in N2 atmosphere. The effect of SiBCN content on phase behavior, microstructure, electrical conductivity, dielectric and microwave absorption properties of the composites were investigated. The results showed that characteristic peaks of Si3N4, SiC, and BNC appeared above 1650°C during the annealing of SiBCN powder. The composites fabricated with 30 wt.% SiBCN had the highest electrical conductivity and dielectric permittivity, which can be attributed to the formation of SiC nanoparticles. With further increase in SiBCN content, the composites showed the lowest reflection coefficient of −30.88 dB at 8.5 GHz and the frequency bandwidth of 1 GHz below −10 dB in X-band.

In this paper, tape casting of Si3N4 substrate were investigated and optimized. The effects of dispersant content, binder, plasticizer/binder ratio, and solid loading on the green sheet properties were studied. An optimal formulation for the tape casting slurries was proposed, green tape with homogeneous microstructure and higher relative density of 56.08% was developed. After gas-pressure sintering and annealing, Si3N4 substrate with a relative density of above 99% and thermal conductivity as 58 W/m/K was obtained. Results showed that the combination of tape casting and gas-pressure sintering is feasible for the development of Si3N4 circuit substrates for power electronic devices.

A tethered balloon-based measurement campaign of particle number concentration (PNC) and particle number size distribution (PNSD) in the size range of 15.7–661.2 nm was conducted within the lower troposphere of 1000 m in Shanghai, a Chinese megacity, during December of 2015. The meteorological conditions, PNC, and PNSD were synchronously measured at the ground-based station as well as by the tethered balloon. On ground level, the 88.2 nm particles were found to have the highest PNC. The Pearson correlation analysis based on the ground level data showed NO 2 had a strong correlation with PNC. The synchronous measurement of PNC and PNSD at the ground station and on the tethered balloon showed that the 15.7–200 nm particles had higher PNC on ground level, but the PNC of 200–661.2 nm particles was higher at 400 m. One haze event (Dec 22nd-Dec 23rd) was selected for detailed discussion on the variation of vertical profiles of PNSD and PNC. The vertical distribution of characteristics of PNC and PNSD were observed and compared. Results indicated that the highest MaxDm (the diameter with the highest PNC) during those three launches all appeared at a high altitude, usually above 300 m. Compared to the clean days, the relatively bigger MaxDm at each height in the haze days also indicated regional transport of pollutants might contribute to more to that haze event.

GEM (Gaseous elemental mercury), fine fraction (

Background: Fine particulate matter (PM2.5) has been widely associated with airway inflammation represented by increased fractional concentration of exhaled nitric oxide (FeNO). However, it remains unclear whether various PM2.5 constituents have different impacts on FeNO and its production process from the arginase (ARG)–nitric oxide synthase (NOS) pathway. Objectives: To investigate the acute effects of PM2.5 constituents on FeNO and DNA methylation of genes involved. Methods: We conducted a longitudinal panel study among 43 young adults in Shanghai, China from May to October in 2016. We monitored the concentrations of 25 constituents of PM2.5. We applied the linear mixed-effect model to evaluate the associations of PM2.5 constituents with FeNO and DNA methylation of the ARG2 and NOS2A genes. Results: Following PM2.5 exposure, NOS2A methylation decreased and ARG2 methylation increased only on the concurrent day, whereas FeNO increased most prominently on the second day. Nine constituents (OC, EC, K, Fe, Zn, Ba, Cr, Se, and Pb) showed consistent associations with elevated FeNO and decreased NOS2A methylation or increased ARG2 methylation in single-constituent models and models adjusting for PM2.5 total mass and collinearity. An interquartile range increase of these constituents was associated with respective decrements of 0.27–1.20 in NOS2A methylation (%5mC); increments of 0.48–1.56 in ARG2 methylation (%5mC); and increments of 7.12%–17.54% in FeNO. Conclusions: Our results suggested that OC, EC, and some metallic elements may be mainly responsible for the development and epigenetic regulation of airway inflammatory response induced by short-term PM2.5 exposure. Keywords: Fine particulate matter, Chemical constituents, Airway inflammation, Exhaled nitric oxide, DNA methylation, Panel study

One vertical observation field campaign based on a tethered mega-balloon (with onboard instruments over 200 kg) was conducted at a campus site in rural Shanghai in order to investigate the vertical distributions of key air pollutants (PM2.5, SO2, black carbon (BC) and O3) and regional transport characteristics during a severe air pollution episode in mid-December 2015. Vertical patterns of measured air pollutants show relatively even profiles within the planetary boundary layer (PBL) while declined sharply above PBL during the daytime. Specifically, high concentrations of SO2 were observed near the top of the boundary layer. Lagrangian particle dispersion modeling showed air pollutants within the boundary layer mainly derived from local sources (i.e. Shanghai) and regional transport within the Yangtze River Delta (YRD) region in the morning before the development of boundary layer. Aerosol chemical components measured at a ground site (about 60 km northwest of the balloon site) showed that regional transport brought a large amount of aged sulfate and nitrate. This study provides new insights in the vertical distribution and transport of haze associated with the PBL development and long-range transport.

Real-time measurements of submicron aerosol species including sulfate, nitrate, ammonium, chloride, organics and black carbon were conducted from a regional site (Dianshan Lake) in the rural area of western Shanghai for 1 year from July 2015 to June 2016. An Aerosol Chemical Speciation Monitor (ACSM) and an Aethalometer were deployed to analyze the seasonal and diurnal variations of aerosol properties at 1-h time resolution. The ACSM and Aethalometer measurements of submicron particulate matter (PM1) concentration and composition agreed well with collocated measurements of PM2.5 using a Tapered Element Oscillating Microbalance, a Monitoring Instrument for Aerosols and Gases (MARGA) and a Sunset organic carbon and elemental carbon (OC/EC) analyzer. A rolling-window positive matrix factorization (RW-PMF) algorithm was applied to the ACSM mass spectra to examine organic aerosol (OA) sources and identified three factors representing hydrocarbon-like organic aerosol (HOA), more-oxidized oxygenated organic aerosol (MO-OOA) and less-oxidized oxygenated organic aerosol (LO-OOA), respectively. The annual average mass concentration of PM1 was 43.6 ± 29.9 μg m−3, with the seasonal average ranging from 32.3 ± 21.0 μg m−3 in summer to 60.3 ± 38.3 μg m−3 in winter. OA contributed the most to PM1 with a small seasonal difference (29–32%). More seasonal variations were observed in the mass fractions of nitrate (20–26%) and sulfate (18–26%) in PM1. Nitrate played an important role in PM pollution episodes since its fractional contribution to PM1 mass increased by approximately a factor of 3 (from ~10% to ~30%) from the lowest to the highest aerosol conditions. Photochemical production and gas-particle partitioning were the main drivers for secondary inorganic aerosol formation, leading to significant diurnal and seasonal cycles. The highest mass fractions of sulfate and nitrate occurred in summer and winter, respectively. Diurnal variation profiles of OA changed significantly between seasons, due to seasonal variations in dominant source contributions and meteorological conditions. HOA showed a predominant morning peak corresponding mainly to traffic emissions. Photochemical production of LO-OOA was observed in the afternoons of summer whereas a relatively flat diurnal cycle of MO-OOA suggested that it was mainly formed on a regional scale. Backtrajectory and potential source contribution function (PSCF) analyses indicated that the most important source region of LO-OOA was located in the coastal areas to the south of Shanghai while MO-OOA had a dominant transport pathway in the northwest direction.

High pollution episodes of PM2.5 and O3 were frequently observed at a rural site (N31.0935º, E120.978°) in eastern Yangtze River Delta (YRD) in summer. To study the impacts of photochemical reactions on secondary aerosol formation in this region, we performed real-time measurements of the mass concentration and composition of PM2.5, particle size distribution (13.6~736.5 nm), concentrations of gas pollutants including O3, SO2, NO2, CO, non-methane hydrocarbons (NMHC)), and nitrate radical in 2013. During the sampling period, the average concentration of PM2.5 was 76.1 (± 16.5) μg/m(3), in which secondary aerosol species including sulfate, nitrate, ammonium, and secondary organic aerosol (SOA) accounted for ~ 62%. Gas-phase oxidation of SO2 was mainly responsible for a fast increase of sulfate (at 1.70 μg/m(3)/h) in the morning. Photochemical production of nitric acid was intense during daytime, but particulate nitrate concentration was low in the afternoon due to high temperature. At night, nitrate was mainly formed through the hydrolysis of NO3 and/or N2O5. The correlations among NMHC, Ox (= O3 + NO2), and SOA suggested that a combination of high emission of hydrocarbons and active photochemical reactions led to the rapid formation of SOA. In addition, several new particle formation and fast growth events were observed despite high ambient aerosol loading. Since the onset of new particle events was accompanied by a rapid increase of H2SO4 and SOA, enhanced formation of sulfate and SOA driven by photochemical oxidation likely promoted the formation and growth of new particles. Together, our results demonstrated that strong atmospheric photochemical reactions enhanced secondary aerosols formation and led to the synchronous occurrence of high concentrations of PM2.5 and O3 in a regional scale. These findings are important for better understanding the air pollution in summer in YRD.

The COVID-19 epidemic broke out in Wuhan, Hubei in December 2019 and in January 2020 and was later transmitted to the entire country. Quarantine measures during Chinese New Year effectively alleviated the spread of the epidemic, but they simultaneously resulted in a decline in anthropogenic emissions from industry, transportation, and import and export of goods. Herein, we present the major chemical composition of non-refractory PM2.5 (NR-PM2.5) and the concentrations of gaseous pollutants in an urban site in Shanghai before and during the quarantine period of the COVID-19 epidemic, which was Jan. 8―23 and Jan. 24―Feb. 8, respectively. The observed results show that the reduction in PM2.5 can be mainly attributed to decreasing concentrations of nitrate and primary aerosols. Nitrate accounted for 37% of NR-PM2.5 before the quarantine period when there was no emission reduction. During the quarantine period, the nitrate concentration decreased by approximately 60%, which is attributed to a reduction in the NOx concentration. Ammonium, as the main balancing cation, showed an approximately 45% simultaneous decrease in concentration. The concentrations of chloride and hydrocarbon-like organic aerosols from primary emissions also declined due to limited human activities. By contrast, sulphate and oxygenated organic aerosols showed a slight decrease in concentration, with their contributions increasing to 27% and 18%, respectively, during the quarantine period, which resulted in two pollution episodes with PM2.5 exceeding 100 μg/m3. This study provides a better understanding of the impact of quarantine measures on variations of the PM2.5 concentration and chemical compositions. Atmospheric oxidation capacities based on the oxidant (Ox = O3 + NO2) and oxidation ratios have been discussed for elucidating the source and formation of haze in an environment with lower anthropogenic emissions. With increasing contribution of secondary aerosols, lower NOx and nitrate concentrations did not completely avoid haze in Shanghai during the epidemic., Graphical abstract Unlabelled Image, Highlights • Quarantine measures led to a reduction in the concentrations of PM2.5, SO2, NOx, and CO in Shanghai. • Reduction in NOx led to increasing O3 and decreasing nitrate. • Reduction in PM2.5 is attributed to the decreasing concentrations of primary aerosols and nitrate. • The increasing contribution of sulphate and OOA inhibited further PM2.5 reduction.

Nitrate became the most significant component of secondary inorganic aerosols (SNA, the sum of sulfate, nitrate and ammonium ions) as the emissions of sulfur dioxide (SO2) have been greatly reduced in China in recent years. In the Yangtze River Delta (YRD), nitrate could contribute 56% of SNA and 34% of total PM2.5 during haze episodes. In this study, a modified Community Multiscale Air Quality (CMAQ) model was used to provide a comprehensive understanding of nitrate source and formation under severe pollution during winter 2015 and 2016. Three haze episodes (HEP1, HEP2 and HEP3) and one clean episode (CEP) were selected to investigate the emission sector and regional contributions to nitrate at six environmental monitoring sites in the YRD. Source apportionment results showed that industry (35%), transportation (32%) and power (28%) sectors were the important sources of nitrate during haze episodes. Regional transport (60–98%) was responsible for the high nitrate concentrations in the YRD. During haze episodes, the high ozone production (PO3) rate (up to 700 ppb/h) and hydroxyl radicals (OH) removal rate (up to 9 ppb/h) were observed in the daytime indicating the important atmospheric oxidation capacity in the YRD. Also, the nitrogen oxidation ratio (NOR) analysis elucidated that daytime photochemistry played an important role in nitrate formation and the heterogeneous chemistry enhanced the high nitrate at night. Results from emission scenario analysis demonstrated that averaged nitrate concentration in Shanghai decreased by 18% during haze episodes under emission reductions of 20% NOx, NH3 and VOC in the YRD, and Shandong, Shanxi, Henan and Hebei provinces. Emission reduction on the regional scale (one city and its surrounding areas) is an efficient strategy to reduce nitrate concentration in the YRD.

Ambient heavy fine particulate matter (PM2.5) pollution events occur frequently during winter seasons in eastern China. Investigating the evolution of source contributions during heavy pollution episodes is critical for strategies of pollution relief. In this study, a two-month field campaign was conducted in the winters of 2015 and 2016 at a regional supersite in eastern China and over one thousand hourly online measurements for twenty PM2.5 species were obtained. Hourly source apportionment for the total mass of PM2.5, and its major species (primary organic carbon, elemental carbon, nitrate, sulfate and ammonium), were then performed by Positive Matrix Factorization (PMF) and Multilinear Engine-2 (ME2) models. Three PM2.5 heavy pollution episodes including ten high concentration peaks were identified for further analysis. Results showed that ME2 performed better than PMF by fixing source profiles of secondary nitrate, secondary sulfate and sea salt, although they have dominant consistencies. Two types of pollution sources were identified from high PM2.5 mass peaks: coal combustion-oriented responsible for four peaks and secondary inorganic aerosol-oriented responsible for the remaining six peaks. Low wind speed and planetary boundary layer favorited the coal combustion-oriented peaks, but also weakened the secondary inorganic formation due to low temperature and accumulated nitric oxide. Primary emissions from coal combustion can contribute 18% to ammonium in addition to 72% from secondary inorganic aerosol. Secondary organic aerosol would contribute 20% of PM2.5 mass during the heaviest episodes. Findings in this study provide insights into the causes of heavy pollution episodes and support implementing effective control strategies to mitigate heavy pollution events in eastern China.

Background Systemic inflammation is considered one of the key mechanisms in the development of cardiovascular diseases induced by fine particulate matter (PM2.5) air pollution. However, evidence concerning the effects of various PM2.5 constituents on circulating inflammatory biomarkers were limited and inconsistent. Objectives To evaluate the associations of short-term exposure to a variety of PM2.5 constituents with circulating inflammatory biomarkers. Methods We conducted a panel study from May to October 2016 among 40 healthy adults in Shanghai, China. We monitored the concentrations of 27 constituents of PM2.5. We applied linear mixed-effect models to analyze the associations of PM2.5 and its constituents with 7 inflammatory biomarkers, and further assessed the robustness of the associations by fitting models adjusting for PM2.5 mass and/or their collinearity. Benjamini-Hochberg false discovery rate was used to correct for multiple comparisons. Results The associations of PM2.5 were strongest at lag 0 d with tumor necrosis factor-α (TNF-α), at lag 1 d with interleukin-6, interleukin-8, and interleukin-17A, at lag 02 d with monocyte chemoattractant protein-1 (MCP-1) and intercellular adhesion molecule-1 (ICAM-1). After correcting for multiple comparisons in all models, Cl−, K+, Si, K, As, and Pb were significantly associated with interleukin-8; SO42− and Se were marginally significantly associated with interleukin-8; SO42−, As, and Se were marginally significantly associated with TNF-α; and Si, K, Zn, As, Se, and Pb were marginally significantly associated with MCP-1. Conclusions Our results suggested that some constituents (SO42−, Cl−, K+, and some elements) might be mainly responsible for systemic inflammation triggered by short-term PM2.5 exposure.

Background The identification of constituents of fine particulate matter (PM2.5) air pollution that had key impacts of ischemic stroke (the predominant subtype of stroke) is important to understand the underlying biological mechanisms and develop air pollution control policies. Objectives To explore the associations between PM2.5 constituents and hospitalization for ischemic stroke in Shanghai, China. Methods We conducted a time-series study to explore the associations between 27 constituents of PM2.5 and hospitalization for ischemic stroke in Shanghai, China from 2014 to 2016. The over-dispersed generalized additive models with adjustment for time, day of week, holidays, and weather conditions were used to estimate the associations. We also evaluated the robustness of the effect estimates for each constituent after adjusting for the confounding effects of PM2.5 total mass and gaseous pollutants and the collinearity (the residual) between this constituent and PM2.5 total mass. We also compared the associations between seasons. Results In total, we identified 4186 ischemic stroke hospitalizations during the study period. The associations of ischemic stroke were consistently significant with elemental carbon and several elemental constituents (Chromium, Iron, Copper, Zinc, Arsenic, Selenium, and Lead) at lag 1 day in single-constituent models, models adjusting for PM2.5 total mass or gaseous pollutants and models adjusting for collinearity. The associations were much stronger in cool season than in warm season. Conclusions The current study provides suggestive evidence that elemental carbon and some metallic elements may be mainly responsible for the risks of ischemic stroke hospitalization induced by short-term PM2.5 exposure.

Background Few studies have investigated respiratory effects of particulate matter air pollution using a full range of particle size distribution. Objectives To explore the short-term associations between size-fractionated particle number concentration (PNC) and chronic obstructive pulmonary disease (COPD) mortality. Methods We conducted a time-series study to explore the associations between size-fractionated PNC and daily COPD mortality in the Pudong New Area of Shanghai, China, from 2014 to 2016. We evaluated particle size distribution from 0.01 μm to 10 μm, which was segregated into 7 ranges to better explore the size-dependent associations. We used over-dispersed generalized additive models to estimate the associations after controlling for time trends, temperature, humidity, day of the week and holidays. Results A total of 5430 deaths due to COPD were identified during the study period. For size ranges from 2.5 – 10 μm, 1–2.5 μm to 0.3–1 μm, there were stronger associations between PNC and COPD mortality, but the associations were statistically insignificant. However, for the smaller size ranges from 0.3 to 0.01 μm, the associations became statistically significant and the magnitude of association remained stable. An interquartile range increase in PNC at lag 0–1 day for size ranges 0.01–0.03 μm, 0.03–0.05 μm, 0.05–0.1 μm and 0.1–0.3 μm was associated with increments of 4.44% (95% CI: 1.16%, 7.73%), 4.31% (95% CI: 1.16%, 7.47%), 4.22% (95% CI: 1.05%, 7.40%), and 4.28% (95% CI: 0.48%, 8.09%) in COPD mortality, respectively. Conclusion This study suggested that particles below 0.3 μm in diameter might be mainly responsible for the adverse effect of particulate air pollution on CDPD mortality in Shanghai, China.

Atmospheric particulate polycyclic aromatic hydrocarbons (PAHs) have been drawing sustained attention due to their health risk and effects on air pollution. It is essential to determine the main sources and reduce atmospheric levels of PAHs to protect human health. PAHs in PM2.5 have been detected at five sites located in five districts in Shanghai, a modern metropolitan city in China. Spatial and temporal variations of composition profiles and sources of PAHs at each site in each season were investigated. The results showed that atmospheric particulate PAHs level in Shanghai was the lowest in summer and the highest in winter, dominated by high molecular weight (HMW) PAHs. Analysis with a combination of coefficients of Pearson's correlation and coefficient of divergences indicated heterogeneous spatial and temporal distribution for LMW PAHs and homogenous distribution for HMW PAHs. Diagnostic ratios and positive matrix factorization (PMF) model both identified pyrogenic sources as the main contributor of PAHs in Shanghai, with vehicular source contribution of 32-43% to the total PAHs annually and around 20% from biomass burning emissions in urban and urban buildup areas. While in winter, coal combustion and biomass burning could act as two major sources of PAHs in suburban areas, which could contribute to >70% of total PAHs measured in PM2.5 in Shanghai.