A novel anti-inflammatory strategy for myocardial ischemia-reperfusion in rats with cinnamamide derivative compound 7.

Reperfusion after myocardial ischemia would aggravate myocardial structural and functional damage, known as myocardial ischemia-reperfusion (MI/R) injury. Cinnamamide derivatives have been reported to exert cardioprotective effects, and we have previously reported that compound 7 played a role in cardioprotection against MI/R via anti-inflammatory effect. However, exact mechanism underlying such beneficial action of compound 7 is still unclear. The protective effect of compound 7 was determined in H9c2 cells under H2O2 stimulation with or without nigerin (NLRP3 activator). Electrocardiogram, echocardiography, myocardial infarction size, histopathology and serum biochemical assay were performed in MI/R rats. Metabolomics in vivo and mRNA or protein levels of NLRP3, ASC, cleaved caspase-1 and its downstream IL-18 and IL-1ß were detected both in vitro and in vivo. Compound 7 significantly ameliorate H2O2-induced cardiomyocyte damage, which was supported by in vivo data determined by improved left ventricular systolic function and histopathological changes, reduced myocardial infarction area and cellular apoptosis in heart tissue. Cardiac differential metabolites demonstrated that compound 7 indeed altered the cardiac reprogramming of inflammation-related metabolites, which was evidenced by down-regulated cardiac inflammation by compound 7. Additionally, compound 7 alleviated myocardial injury by inhibiting the NLRP3 pathway rather than other members of the inflammasome both in vitro and in vivo, which was further evidenced by CETSA assay. Whereas, nigerin blocked the inhibitory activity of compound 7 against NLRP3. Cinnamamide derivative compound 7 ameliorated MI/R injury by inhibiting inflammation via NLRP3.

[Characteristics of Ozone Concentration in Shanghai and Its Associated Atmospheric Circulation Background During Summer Half-years from 2006 to 2021].

It is of great importance to scientifically evaluate the impact of weather and climate conditions on the occurrence of O3 pollution in order to improve the accuracy of O3 pollution forecasts， as well as to reasonably control and reduce the adverse effects of O3 pollution. The characteristics of O3 concentration and climate background were analyzed based on daily O3 concentration data， meteorological factors， and NCEP/NCER reanalysis data from 2006 to 2021 in Shanghai. In addition， the differences in atmospheric circulation situations during years with anomalous O3 concentrations were compared and diagnosed from the perspective of climatology. Additionally， the monthly O3 concentration prediction model （seasonal autoregressive integrated moving average with exogenous regressors， SARIMAX） was further established by adding the key meteorological factors. The results indicated that both the whole-year average and summer half-year average O3 concentrations in Shanghai were increasing with fluctuation， and the summer half-year average was much higher than the annual average， up to 36.2%. Furthermore， there was a significant negative correlation between O3 concentration and wind speed （correlation coefficient of -0.826） and a significant positive correlation with the frequency of static wind and the number of days in which the low cloud cover was less than 20% （correlation coefficients of 0.836 and 0.724， respectively）. The monthly mean O3 concentration had a clear periodicity， showing a pattern with a high concentration in the middle period （April to September） and a low concentration at the beginning and end of the periods. High O3 concentration years （2013-2021） were accompanied by more polluted days， lower average wind speed， more small wind （≤1.5 m·s-1） days， more days of low cloud cover of less than 20%， more days of high temperature， higher direct solar radiation， and more sunshine hours. When the location of the stronger West Pacific subtropical high was westward and southward in the summer half-year， Shanghai was influenced by an anomalous westerly wind， which was not conducive to the transportation of clean air from the sea to Shanghai and thus led to the high concentration of O3 pollution. When the long wave radiation emitted from the ground was low in the summer half-year， it was favorable for the increase in ground temperature and caused a high concentration of O3 pollution. Adding direct solar radiation， maximum temperature， and wind speed as exogenous variables to the monthly O3 forecast model could significantly improve the effectiveness of the monthly forecast， with the root mean square error decreasing by 47.7% （from 22 to 11.5） and the correlation coefficient increasing by 11.2% （from 0.819 to 0.911）， which could be applied to the practical prediction of monthly O3 concentration.

Associations between ultrafine particle pollution and daily outpatient visits for respiratory diseases in Shanghai, China: a time-series analysis.

Previous epidemiological studies have linked short-term exposure to particulate matter with outpatient visits for respiratory diseases. However, evidence on ultrafine particle (UFP) is still scarce in China. To investigate the association between short-term UFP exposure and outpatient visits for respiratory diseases as well as the corresponding lag patterns, information on outpatient visits for main respiratory diseases during January 1, 2017, to December 31, 2019 was collected from electronic medical records of two large tertiary hospitals in Shanghai, China. Generalized additive models employing a Quasi-Poisson distribution were employed to investigate the relationships between UFP and respiratory diseases. We computed the percentage change and its corresponding 95% confidence interval (CI) for outpatient visits related to respiratory diseases per interquartile range (IQR) increase in UFP concentrations. Based on a total of 1,034,394 hospital visits for respiratory diseases in Shanghai, China, we found that the strongest associations of total UFP with acute upper respiratory tract infection (AURTI), bronchitis, chronic obstructive pulmonary disease (COPD), and pneumonia occurred at lag 03, 03, 0, and 03 days, respectively. Each IQR increase in the total UFP concentrations was associated with increments of 9.02% (95% CI: 8.64-9.40%), 3.94% (95% CI: 2.84-5.06%), 4.10% (95% CI: 3.01-5.20%), and 10.15% (95% CI: 9.32-10.99%) for AURTI, bronchitis, COPD, and pneumonia, respectively. Almost linear concentration-response relationship curves without apparent thresholds were observed between total UFP and outpatient-department visits for four respiratory diseases. Stratified analyses illustrated significantly stronger associations of total UFP with AURTI, bronchitis, and pneumonia among female patients, while that with COPD was stronger among male patients. After adjustment of criteria air pollutants, these associations all remained robust. This time-series study indicates that short-term exposure to UFP was associated with increased risk of hospital visits for respiratory diseases, underscoring the importance of reducing ambient UFP concentrations for respiratory diseases control and prevention.

[A Comparison Study on Multiple Modeling Approaches for Air Pollutant Geographic Model Development in Shanghai].

Geostatistical models have been widely used in the exposure assessment of ambient air pollutants. However, few studies have focused on comparisons of modeling approaches and their prediction results. Here, we collected the NO2 and PM2.5 monitoring data from 55 sites in Shanghai from 2016 to 2019 and the geographic variables, such as road network, points of interest of emission locations, and satellite data were included. We used partial least squares regression (PLS), supervised linear regression (SLR), and random forest (RF) algorithms to develop spatial models and used ordinary kriging (OK) to develop a two-step model. We evaluated the models using a 5-fold cross validation method and selected the best model structure for each modeling approach between one-or two-step models that had been developed with or without OK. The results revealed that the best NO2 models were the RF-OK (Rmse2 was 0.70-0.82) and PLS-OK (Rmse2 was 0.78-0.84) models; the PLS model for PM2.5(Rmse2 was 0.62-0.71) outperformed the other PM2.5 models. We used the best models to predict annual exposures in Shanghai at a 1 km spatial scale and conducted the correlation analysis among the predictions of the best models. The results demonstrated that the NO2 predictions had higher correlation coefficients (r was 0.82-0.91) compared with those of the PM2.5 models (r was 0.66-0.96). Based on the exposure results predicted using the three models in 2019, we evaluated the cumulative population exposure concentrations for NO2 and PM2.5 in Shanghai.

Role of NLRP3 in the exacerbation of ozone-induced allergic rhinitis.

OBJECTIVE: Allergic rhinitis (AR) is an immunoglobulin E (IgE)-mediated inflammatory disorder of the nasal mucosa, and the impact of ozone on AR is gaining increasing attention. Although NOD-like receptor thermal protein domain associated protein 3 (NLRP3) plays a crucial role in the pathogenesis of AR, its regulatory mechanisms in ozone-induced exacerbation remain unclear. Therefore, we explored the impact of ozone inhalation on inflammation in AR and investigated the regulatory mechanisms involving NLRP3. METHODS: Fifty female Sprague-Dawley rats were selected and divided into five groups: normal control (NC), normal with ozone exposure (NE), AR model, AR with ozone exposure (ARE), and ARE treated with the NLRP3 inhibitor MCC950 (ARE+MCC950). Behavioral changes were observed in the rats, and the expression of NLRP3, active-caspase 1, and GSDMD-N was detected by western blotting. The expression levels of interleukin (IL)- 4, IL-5, IL-13, IL-1ß, and ovalbumin-specific IgE (OVA-sIgE) in nasal lavage fluid as well as IL-6 in the serum were measured by ELISA. The expression and distribution of NLRP3 and IL-1ß in nasal mucosal tissue were detected by immunohistochemistry, and pathological changes and eosinophilic infiltration in nasal mucosal tissue were observed by hematoxylin and eosin (HE) staining. The effects of ozone exposure on inflammation in the nasal mucosal tissue of rats with AR and the relationship between NLRP3 and inflammation were analyzed. RESULTS: Upregulation of NLRP3 was observed in the AR rat model, and ozone further aggravated the expression of NLRP3 in the nasal mucosal tissue. Compared to the AR, NC, and NE groups, NLRP3 inflammasomes were activated in the ARE group, and the expression levels of related indexes active-caspase 1 and GSDMD-N were significantly increased; the expression levels of Th2 inflammatory factors IL-4, IL-5, IL-13, and OVA-sIgE were increased, and inflammatory factors such as IL-1ß and IL-6 expression was also significantly increased. HE staining revealed that ozone aggravated damage to the nasal mucosal tissue in AR. Compared with the ARE group, the expression of NLRP3 inflammasomes was downregulated, sneezing and scratching symptoms were reduced, inflammatory indicators in nasal lavage fluid were decreased, and nasal mucosal tissue damage was alleviated in rats in the ARE+MCC950 group. CONCLUSION: Ozone exposure significantly increased the inflammatory response in an animal model of AR. MCC950 can selectively inhibit the expression of NLRP3, inhibit the activity of inflammasomes, and reduce nasal mucosal inflammation by regulating the NLRP3-caspase-1-IL-1ß pathway.

Atmospheric mercury in a developed region of eastern China: Interannual variation and gas-particle partitioning.

Atmospheric mercury plays a crucial role in the biogeochemical cycle of mercury. This study conducted an intensive measurement of atmospheric mercury from 2015 to 2018 at a regional site in eastern China. During this period, the concentration of particle-bound mercury (PBM) decreased by 13%, which was much lower than those of gaseous elemenral mercury (GEM, 30%) and reactive gaseous mercury (GOM, 62%). The gradual decrease in the correlation between PBM and CO, K, and Pb indicates that the influence of primary emissions on PBM concentration was weakening. Moreover, the value of the partitioning coefficient (Kp) increased gradually from 0.05 ± 0.076 m3/µg in 2015 to 0.16 ± 0.37 m3/µg in 2018, indicating that GOM was increasingly inclined to adsorb onto particulate matter. Excluding the influence of meteorological conditions and the primary emissions, the change in aerosol composition is designated as the main trigger factor for the increasing gas-particle partitioning of reactive mercury (RM). The increasing ratio of Cl-, NO3-, and organics (Org) in the chemical composition of particle matters (PM2.5), as well as the decrease in the proportion of SO42-, NH4+, and K+, are conducive to the adsorption of GOM onto particles, forming PBM, which led to an increase of Kp and a lag of PBM reduction compared to GEM and GOM under the continuous control measures of anthropogenic mercury emissions. The evolution of aerosol compositions in recent years affects the migration and transformation of atmospheric mercury, which in turn can affect the biogeochemical cycle of mercury.

Budget of atmospheric nitrous acid (HONO) during the haze and clean periods in Shanghai: Importance of heterogeneous reactions.

Nitrous acid (HONO) plays a significant role in radical cycling and atmospheric oxidative chemistry. While the source and evolution of HONO in the Yangtze River Delta (YRD) region of China after 2018 remains largely unknown, this work monitored HONO and other air pollutants throughout 2019 at an urban site (Pudong, PD) and a suburban site (Qingpu, QP) in Shanghai. Episodes with high HONO mixing ratios but different PM2.5 levels, namely haze and clean episodes, were chosen for HONO budget analysis. Using an observation-based photochemical box model, relative importance of different sources and sinks of HONO were evaluated. Gas-phase reaction of NO with OH was found to be one of the most important daytime HONO formation sources, especially during the QPhaze period (accounting for 40.3 % of daytime HONO formation). In particular, heterogeneous conversion of NO2 on ground and aerosol surface was found to be the dominant source for nocturnal HONO. Photo-enhanced NO2 conversion on ground surface plays an important role in daytime HONO production (19.4 % in PDhaze vs. 27.6 % in PDclean, and 19.8 % in QPhaze vs. 25.9 % in QPclean). In addition, photo-enhanced NO2 conversion at the aerosol surface during haze episodes made more significant contributions to HONO formation compared to the clean periods (20.9 % in PDhaze vs. 17.1 % in PDclean, and 19.7 % in QPhaze vs. 11.2 % in QPclean). The role of multiphase reactions was found to be increasingly important in HONO generation with enhanced relative humidity (RH) during daytime. Significant unknown HONO source was further analyzed and found to be positively related with photolytic as well as multiphase pathways. Overall, our study sheds light on the budget of HONO in one of the biggest megacities in east China, which would help developing future mitigation strategies for urban HONO and atmospheric oxidation capacity.

Comprehensive Assessment of Pollution Sources and Health Impacts in Suburban Area of Shanghai.

Shanghai, one of China's largest metropolises, faces significant environmental pollution challenges due to rapid economic development. Suburban areas of Shanghai are affected by both long-distance transport and local sources of pollutants. This study conducted an integrated analysis that links health-risk assessment of heavy metals and source apportionment of atmospheric constituents to distinguish the contributions of emission sources and the major sources of health risks. Source-apportionment analysis revealed that secondary sources had the greatest contribution to the local pollutants, indicating the significant influence of peripheral and long-distance transport. Health-risk assessment of Cr, Ni, As, and Cd revealed that local residents were exposed to respiratory health risks, in which Cr is the major contributor. This health risk was primarily associated with emissions from nearby industry-related sources. Our study highlights the significant effects of both long-distance transport and local source emissions on atmospheric composition and human health in large urban agglomerations. The findings can inform future efforts to develop more precise emission-reduction strategies and policy improvements to mitigate environmental pollution and protect public health.

Relationship between light absorption properties of black carbon and aerosol origin at a background coastal site.

As a potent climate forcer, black carbon (BC) optical properties can have significant impacts on the regional meteorology and climate. To unveil the seasonal differences of BC and its contribution by various emission sources, a one-year continuous monitoring of atmospheric aerosols was conducted at a background coastal site in Eastern China. By comparing the seasonal and diurnal patterns between BC and elemental carbon, we observed that BC were evidently aged with varying extents among all four seasons. The light absorption enhancement of BC (Eabs) was calculated as 1.89 ± 0.46, 2.40 ± 0.69, 1.91 ± 0.60, and 1.34 ± 0.28, from spring to winter, respectively, indicating that BC was more aged in summer. Contrary to the negligible impact of pollution levels on Eabs, the patterns of air masses arriving to the sampling site had a significant impact on the seasonal optical characteristics of BC. Sea breezes evidently exhibited higher Eabs than land-sourced breezes, and BC was more aged and light-absorbing with an increased contribution of marine airflows. By applying a receptor model, we resolved six emission sources as ship emission, traffic emission, secondary pollution, coal combustion, sea salt, and mineral dust. The mass absorption efficiency of BC for each source was estimated, showing the highest from the ship emission sector. This explained the highest Eabs observed in summer and sea breezes. Our study highlights that curbing emission from shipping activities is beneficial for reducing the warming effect of BC in coastal areas, particularly in the context of future rapid development of international shipping.

Study on Tungsten Metallization and Interfacial Bonding of Silicon Nitride High-Temperature Co-Fired Ceramic Substrates.

For the first time, Si3N4 HTCC has been prepared using W as the metal phase by high-temperature co-firing (1830 °C/600 KPa/2 h) as a potential substrate candidate in electronic applications. It was discovered that the addition of Si3N4 to the W paste has a significant impact on thermal expansion coefficient matching and dissolution wetting. As the Si3N4 content increased from 0 to 27.23 vol%, the adhesion strength of W increased continuously from 2.83 kgf/mm2 to 7.04 kgf/mm2. The interfacial bonding of the Si3N4 ceramic and the conduction layer was discussed. SEM analysis confirmed that the interface between Si3N4 and W exhibited an interlocking structure. TEM, HRTEM and XRD indicated the formation of W2C and W5Si3 due to the interface reactions of W with residual carbon and Si3N4, respectively, which contributed to the reactive wetting and good adhesion strength between the interface. Suitable amounts of Si3N4 powder and great interfacial bonding were the main reasons for the tough interfacial matching between the Si3N4 ceramic and the conduction layer.

Involvements of Nrf2 and oxidative stress in the ozone-elicited exacerbation in an allergic rhinitis model.

OBJECTIVE AND DESIGN: An experimental rat allergic rhinitis(AR) model was made to explore the effect of different concentrations of ozone exposure and evaluate the roles of nuclear factor erythroid 2-related factor 2(Nrf2) and oxidative stress in ozone exposure. METHOD: Sprague-Dawley rats were sensitized with ovalbumin (OVA). Three groups of AR rats were exposed respectively to different concentrations of ozone for 2 h on 6 weeks. Nasal symptoms and OVA- specific Ig E in the serum were evaluated. The pathological changes in the nasal mucosa were examined. Malondialdehyde (MDA) level and activity of superoxide dismutase(SOD) and glutathione peroxidase (GSH-Px,GPX) in the nasal mucosa tissue were measured through a spectrophotometry-based method. Nrf2、Kelch-1ike ECH- associated protein-l (Keap1) proteins was measured by western blotting. GPX1、GPX2 mRNA were detected by quantitative real time-PCR(qRT-PCR). RESULTS: Our results showed that ozone exposure induced a significant increase of the number of sneezes, nasal rubs, amount of nasal secretion and OVA-sIgE in the serum of AR model. Ozone effected oxidative stress in different concentration. The content of MDA in AREH group was significantly higher than AR groups. The activities of SOD and GSH-Px in nasal mucosa showed different trends in different concentration groups. The activities of SOD and GSH-Px in AREL and AREM groups were higher than AR group, but decreased at AREH group. The nucleoprotein level of Nrf2 in AREL and AREM groups was higher than AR groups. However, in AREH group, it was significantly decreased, compared with AREL and AREM groups. GPX1 and GPX2 mRNA levels in nasal mucosa showed the same trend in different exposure groups. CONCLUSIONS: Different concentrations of ozone inhalation causes changes of the expression of Nrf2 nuclear protein and its target genes in nasal mucosa of AR. High concentration ozone breaks the redox balance and aggravates oxidative damage in AR. This study suggests that inhibiting oxidative stress might be a solution for ozone-elicited detrimental effects on AR.

Hourly Ultrafine Particle Exposure and Acute Myocardial Infarction Onset: An Individual-Level Case-Crossover Study in Shanghai, China, 2015-2020.

Associations between ultrafine particles (UFPs) and hourly onset of acute myocardial infarction (AMI) have rarely been investigated. We aimed to evaluate the impacts of UFPs on AMI onset and the lag patterns. A time-stratified case-crossover study was performed among 20,867 AMI patients from 46 hospitals in Shanghai, China, between January 2015 and December 2020. Hourly data of AMI onset and number concentrations of nanoparticles of multiple size ranges below 0.10 µm (0.01-0.10, UFP/PNC0.01-0.10; 0.01-0.03, PNC0.01-0.03; 0.03-0.05, PNC0.03-0.05; and 0.05-0.10 µm, PNC0.05-0.10) were collected. Conditional logistic regressions were applied. Transient exposures to these nanoparticles were significantly associated with AMI onset, with almost linear exposure-response curves. These associations occurred immediately after exposure, lasted for approximately 6 h, and attenuated to be null thereafter. Each interquartile range increase in concentrations of total UFPs, PNC0.01-0.03, PNC0.03-0.05, and PNC0.05-0.10 during the preceding 0-6 h was associated with increments of 3.29, 2.08, 2.47, and 2.93% in AMI onset risk, respectively. The associations were stronger during warm season and at high temperatures and were robust after adjusting for criteria air pollutants. Our findings provide novel evidence that hourly UFP exposure is associated with immediate increase in AMI onset risk.

Increased contribution to PM2.5 from traffic-influenced road dust in Shanghai over recent years and predictable future.

Traffic contributes to fine particulate matter (PM2.5) in the atmosphere through engine exhaust emissions and road dust generation. However, the evolution of traffic related PM2.5 emission over recent years remains unclear, especially when various efforts to reduce emission e.g., aftertreatment technologies and high emission standards from China IV to China V, have been implemented. In this study, hourly elemental carbon (EC), a marker of primary engine exhaust emissions, and trace element of calcium (Ca), a marker of road dust, were measured at a nearby highway sampling site in Shanghai from 2016 to 2019. A random forest-based machine learning algorithm was applied to decouple the influences of meteorological variables on the measured EC and Ca, revealing the deweathered trend in exhaust emissions and road dust. After meteorological normalization, we showed that non-exhaust emissions, i.e., road dust from traffic, increased their fractional contribution to PM2.5 over recent years. In particular, road dust was found to be more important, as revealed by the deweathered trend of Ca fraction in PM2.5, increasing at 6.1% year-1, more than twice that of EC (2.9% year-1). This study suggests that while various efforts have been successful in reducing vehicular exhaust emissions, road dust will not abate at a similar rate. The results of this study provide insights into the trend of traffic-related emissions over recent years based on high temporal resolution monitoring data, with important implications for policymaking.

Hourly organic tracers-based source apportionment of PM2.5 before and during the Covid-19 lockdown in suburban Shanghai, China: Insights into regional transport influences and response to urban emission reductions.

During the Covid-19 outbreak, strict lockdown measures led to notable reductions in transportation-related emissions and significantly altered atmospheric pollution characteristics in urban and suburban areas. In this work, we compare comprehensive online measurements of PM2.5 major components and organic molecular markers in a suburban location in Shanghai, China before lockdown (Dec. 28, 2019 to Jan. 23, 2020) and during lockdown (Jan. 24 to Feb. 9, 2020). The NOx levels declined sharply by 59% from 44 to 18 ppb during the lockdown, while O3 rose two times higher to 42 ppb. The PM2.5 level dropped from 64 to 49 µg m-3 (-24%). The major components all showed reductions, with the reduction of nitrate most prominent at -58%, followed by organics at -19%, and sulfate at -17%. Positive matrix factorization analysis identifies fourteen source factors, including nine primary sources and five secondary sources. The secondary sources consist of sulfate-rich factor, nitrate-rich factor, and three secondary organic aerosol (SOA) factors, with SOA_I being anthropogenic SOA, SOA_II associated with later generation products of organic oxidation, and SOA_III being biogenic SOA. The combined secondary sources contributed to 69% and 63% (40 and 22 µg m-3) of PM2.5 before and during lockdown, respectively, among which the reductions in the nitrate-rich (-55%) factor was the most prominent. Among primary sources, large reductions (>80%) were observed in contributions from industrial, cooking, and vehicle emissions. Unlike some studies reporting that the restriction during the Covid-19 resulted in enhanced secondary sulfate and SOA formation, we observed decreases in both secondary inorganic and SOA formation despite the overall elevated oxidizing capacity in the suburban site. Our results indicate that the formation change in secondary inorganic and organic compounds in response to substantial reductions in urban primary precursors are different for urban and suburban environments.

High Resolution On-Road Air Pollution Using a Large Taxi-Based Mobile Sensor Network.

Traffic-related air pollution (TRAP) was monitored using a mobile sensor network on 125 urban taxis in Shanghai (November 2019/December 2020), which provide real-time patterns of air pollution at high spatial resolution. Each device determined concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), and PM2.5, which characterised spatial and temporal patterns of on-road pollutants. A total of 80% road coverage (motorways, trunk, primary, and secondary roads) required 80-100 taxis, but only 25 on trunk roads. Higher CO concentrations were observed in the urban centre, NO2 higher in motorway concentrations, and PM2.5 lower in the west away from the city centre. During the COVID-19 lockdown, concentrations of CO, NO2, and PM2.5 in Shanghai decreased by 32, 31 and 41%, compared with the previous period. Local contribution related to traffic emissions changed slightly before and after COVID-19 restrictions, while changing background contributions relate to seasonal variation. Mobile networks are a real-time tool for air quality monitoring, with high spatial resolution (~200 m) and robust against the loss of individual devices.

Atmospheric deposition of microplastics in the megalopolis (Shanghai) during rainy season: Characteristics, influence factors, and source.

Urban areas are the hardest hit by microplastic pollution, and deposition is an important part of microplastic migration and transport in the atmosphere, therefore, the study of microplastics in an urban atmospheric deposition is of great significance. This study aims to investigate the deposition characteristics of atmospheric microplastics in megapolis, to clarify the influence of meteorological and anthropogenic factors, and to analyze the sources of atmospheric microplastics. Six sampling sites in Shanghai were selected to collect atmospheric deposition samples during the rainy season. The mean deposition flux of microplastics was 3261.22 ± 2847.99 P·m-2·d-1 (median: 2559.70 P·m-2·d-1), and the types were mainly polyamide (PA, 27.79 %), polyethylene terephthalate (PET, 27.29 %), polypropylene (PP, 16.95 %), and polyvinyl fluoride (PVF, 12.88 %). The microplastic with the particle size of <1000 µm accounted for 88.23 %, and the shape was mainly fiber (73.55 %). The results of correlation analysis and variance analysis of microplastic characteristics with meteorological and anthropogenic factors (land-use, atmospheric pollutants, and urban indicators) showed that wind and precipitation had effects on deposition flux, size and shape, and were more significant at small scales (individual cities), while at large scales, the population was the main influence of microplastics. Atmospheric microplastics in Shanghai may be dominated by exogenous sources, through a combination of microplastic characteristics, wind and backward trajectories. This study further reveals the fate of urban atmospheric microplastics, which has implications for the study of global microplastic pollution.

Response of PM2.5-bound elemental species to emission variations and associated health risk assessment during the COVID-19 pandemic in a coastal megacity.

The coronavirus (COVID-19) pandemic is disrupting the world from many aspects. In this study, the impact of emission variations on PM2.5-bound elemental species and health risks associated to inhalation exposure has been analyzed based on real-time measurements at a remote coastal site in Shanghai during the pandemic. Most trace elemental species decreased significantly and displayed almost no diel peaks during the lockdown. After the lockdown, they rebounded rapidly, of which V and Ni even exceeded the levels before the lockdown, suggesting the recovery of both inland and shipping activities. Five sources were identified based on receptor modeling. Coal combustion accounted for more than 70% of the measured elemental concentrations before and during the lockdown. Shipping emissions, fugitive/mineral dust, and waste incineration all showed elevated contributions after the lockdown. The total non-carcinogenic risk (HQ) for the target elements exceeded the risk threshold for both children and adults with chloride as the predominant species contributing to HQ. Whereas, the total carcinogenic risk (TR) for adults was above the acceptable level and much higher than that for children. Waste incineration was the largest contributor to HQ, while manufacture processing and coal combustion were the main sources of TR. Lockdown control measures were beneficial for lowering the carcinogenic risk while unexpectedly increased the non-carcinogenic risk. From the perspective of health effects, priorities of control measures should be given to waste incineration, manufacture processing, and coal combustion. A balanced way should be reached between both lowering the levels of air pollutants and their health risks.

A unified empirical modeling approach for particulate matter and NO2 in a coastal city in China.

Modeling air pollutants on a fine spatiotemporal scale is necessary for health studies that focus on critical short-term exposure windows. A unified empirical modeling approach is useful for health studies; however, it is unclear whether this approach can be used in a coastal city for air pollutants driven by local emissions and regional meteorological factors. An advanced empirical modeling approach was used to develop exposure models from October 2012 to December 2019, for particulate matter with aerodynamic diameters less than or equal to 2.5 and 10 µm (PM2.5 and PM10) and nitrogen dioxide (NO2) in the coastal city of Shanghai, China. Air pollutant concentrations were obtained from daily measurements at 55 administrative monitoring sites that were integrated into three-day average concentrations. Data on a large array of geographic variables were collected, and their dimensions were reduced using the partial least squares regression method. A geostatistical model using the land-use regression approach in a universal kriging framework was developed to estimate short-term exposure concentrations. The prediction ability of the models were determined by leave-one (site)-out cross-validation (LOOCV) and external validation (EV). Compared to the LOOCV results, the EV results for PM2.5 and PM10 were consistently reliable, but the EV for NO2 had a larger root mean squared error. The temporal random effects involved in the model structure were interpreted using sensitivity analyses. This affected the short-term PM2.5 and PM10 model predictions. This unified empirical modeling approach was successfully used for particulate matter in Shanghai, where air pollution is affected by complex regional and meteorological conditions. These exposure models are going to be applied for making exposure predictions at residential locations for short-term exposure predictions in the "Growth trajectories and air pollution" (GAAP) study in Shanghai that focuses on maternal and early life exposure to air pollutants.

Gas-to-Aerosol Phase Partitioning of Atmospheric Water-Soluble Organic Compounds at a Rural Site in China: An Enhancing Effect of NH3 on SOA Formation.

Partitioning gaseous water-soluble organic compounds (WSOC) to the aerosol phase is a major formation pathway of atmospheric secondary organic aerosols (SOA). However, the fundamental mechanism of the WSOC-partitioning process remains elusive. By simultaneous measurements of both gas-phase WSOC (WSOCg) and aerosol-phase WSOC (WSOCp) and formic and acetic acids at a rural site in the Yangtze River Delta (YRD) region of China during winter 2019, we showed that WSOCg during the campaign dominantly partitioned to the organic phase in the dry period (relative humidity (RH) < 80%) but to aerosol liquid water (ALW) in the humid period (RH > 80%), suggesting two distinct SOA formation processes in the region. In the dry period, temperature was the driving factor for the uptake of WSOCg. In contrast, in the humid period, the factors controlling WSOCg absorption were ALW content and pH, both of which were significantly elevated by NH3 through the formation of NH4NO3 and neutralization with organic acids. Additionally, we found that the relative abundances of WSOCp and NH4NO3 showed a strong linear correlation throughout China with a spatial distribution consistent with that of NH3, further indicating a key role of NH3 in WSOCp formation at a national scale. Since WSOCp constitutes the major part of SOA, such a promoting effect of NH3 on SOA production by elevating ALW formation and WSOCg partitioning suggests that emission control of NH3 is necessary for mitigating haze pollution, especially SOA, in China.

Characteristics of aerosol chemistry and acidity in Shanghai after PM2.5 satisfied national guideline: Insight into future emission control.

With continuous endeavors to control air pollutant emissions, the average concentration of PM2.5 in Shanghai in 2019-2020 satisfied the national secondary standard (35 µg m-3) for the first time. In this study, the two-year dataset of hourly resolution PM2.5 compositions observed in downtown Shanghai was used to investigate the relative contribution of sulfate and nitrate as well as particulate acidity. The average concentration of SO2 was reduced to 7.7 µg m-3, while the concentration of NOx remained above 40 µg m-3, indicating that the control of SO2 was more effective than that of NOx during the 13th Five-Year Plan period. Thus, the sulfate pollution was significantly reduced whereas the nitrate loading remained almost constant. The monthly N/S ratio varied from below 0.6 to above 2.0, indicating that the contribution of automobile exhaust to PM2.5 is seasonally dependent. Contrary to sulfate, the nitrate fraction increased rapidly with the increase of PM2.5 mass, suggesting that the explosive growth of nitrate has become a major driver of haze formation. ISORROPIA simulations show that PM2.5 was moderately acidic with pH values following the trend of winter > spring > autumn > summer. The diurnal variation of nitrate was related to the changes in aerosol water content, indicating the effect of heterogeneous aqueous reactions on secondary aerosol formation. The effectiveness of emission control for reducing inorganic PM2.5 varied with different gas precursors and seasons. The abatement of NH3 emissions will increase particle acidity and acid rain pollution, although it is more effective than that of NOx when the emission reduction is larger than 60%. This study suggests that the control of vehicle exhaust should be given priority in the Yangtze River Delta for coordinately mitigating PM2.5 and acid rain pollution.