Analysis of severe ozone-related human health and weather influence over China in 2019 based on a high-resolution dataset.

Ozone pollution in 2019 in China is particularly severe posing a tremendous threat to the health of Chinese inhabitants. In this study, we constructed a more reliable and accurate 1-km gridded dataset for 2019 with as many sites as possible using the inverse distance weight interpolation method to analyze spatiotemporal ozone pollution characteristics and health burden attributed to ozone exposure from the perspective of different diseases and weather influence. The accuracy of this new dataset is higher than other public datasets, with the coefficient of determination of 0.84 and root-mean-square error of 8.77 ppb through the validation of 300 external sites which were never used for establishing retrieval methods by the datasets mentioned-above. The averaged MDA8 (the daily maximum 8 h average) ozone concentrations over China was 43.5 ppb, and during April-July, 83.9% of total grids occurred peak-month ozone concentrations. Overall, the highest averaged exceedance days (60 days) and population-weighted ozone concentrations (55.0 ppb) both concentrated in central-eastern China including 9 provinces (only 11.4% of the national territory); meanwhile, all-cause premature deaths attributable to ozone exposure reached up to 142,000 (54.9% of national total deaths) with higher deaths for cardiovascular and respiratory, and the provincial per capita premature mortality was 0.27~0.44‰. The six most polluted weather types in the central-eastern China are in order as follows: westerly (SW and W), cyclonic, northerly, and southerly (NW, N, and S) types, which accounts for approximately 73.2% of health burden attributed to daily ozone exposure and poses the greatest public health risk with mean daily premature deaths ranging from 466 to 610. Our findings could provide an effective support for regional ozone pollution control and public health management in China.

Geochemical characteristics and socioeconomic associations of carbonaceous aerosols in coal-fueled cities with significant seasonal pollution pattern.

Carbonaceous aerosols, comprising organic carbon (OC) and elemental carbon (EC), are critical component of fine particulate matter (PM2.5), with diverse impacts on air quality and human health. This study investigated the concentrations and seasonal patterns of carbonaceous species in PM2.5 during both the heating season (January 2021) and non-heating season (July 2021) in three coal-fueled cities in northern China, as well as the differences in carbonaceous aerosols and their associations with socioeconomic parameters in cities situated on either side of the "Hu Line" in China. The results showed that, owing to intensified coal combustion and unfavorable meteorological conditions, levels of OC, EC, and OC/EC ratios were higher in winter compared to summer. Moreover, the presence of dust (DU) and light pollution (LP) days resulted in elevated OC levels but decreased EC levels. The Char-EC/Soot-EC ratios were highest during LP, followed by CL and DU. A source apportionment analysis demonstrated that coal burning, vehicle exhaust, road dust, and biomass burning were the primary contributors to carbonaceous aerosols, as confirmed by diagnostic ratios, Char-EC/Soot-EC ratios, and PCA analysis. Furthermore, our study found that carbonaceous aerosols concentrations and source apportionment primarily varied with diurnal and seasonal trends and different pollution types. Additionally, at the national scale, population density and urban green space exhibited a positive correlation with OC/EC ratios (p < 0.05), while energy consumption per unit of GDP showed a negative correlation (p < 0.05). The observation that OC/EC ratios were lower in coal-fueled cities than in economy-based cities suggests a more severe pollution scenario. These findings highlight the importance of comprehending of the seasonal variation and chemical characteristics of carbonaceous aerosol for understanding air pollution sources and characteristics, which is essential for both air quality management and human health.

Short-term joint effects of ambient PM2.5 and O3 on mortality in Beijing, China.

Introduction: In recent years, air pollution caused by co-occurring PM2.5 and O3, named combined air pollution (CAP), has been observed in Beijing, China, although the health effects of CAP on population mortality are unclear. Methods: We employed Poisson generalized additive models (GAMs) to evaluate the individual and joint effects of PM2.5 and O3 on mortality (nonaccidental, respiratory, and cardiovascular mortality) in Beijing, China, during the whole period (2014-2016) and the CAP period. Adverse health effects were assessed for percentage increases (%) in the three mortality categories with each 10-µg/m3 increase in PM2.5 and O3. The cumulative risk index (CRI) was adopted as a novel approach to quantify the joint effects. Results: The results suggested that both PM2.5 and O3 exhibited the greatest individual effects on the three mortality categories with cumulative lag day 01. Increases in the nonaccidental, cardiovascular, and respiratory mortality categories were 0.32%, 0.36%, and 0.43% for PM2.5 (lag day 01) and 0.22%, 0.37%, and 0.25% for O3 (lag day 01), respectively. There were remarkably synergistic interactions between PM2.5 and O3 on the three mortality categories. The study showed that the combined effects of PM2.5 and O3 on nonaccidental, cardiovascular, and respiratory mortality were 0.34%, 0.43%, and 0.46%, respectively, during the whole period and 0.58%, 0.79%, and 0.75%, respectively, during the CAP period. Our findings suggest that combined exposure to PM2.5 and O3, particularly during CAP periods, could further exacerbate their single-pollutant health risks. Conclusion: These findings provide essential scientific evidence for the possible creation and implementation of environmental protection strategies by policymakers.

Refractory black carbon aerosols in rainwater in the summer of 2019 in Beijing: Mass concentration, size distribution and wet scavenging ratio.

Black carbon (BC) aerosols in the atmosphere play a significant role in climate systems due to their strong ability to absorb solar radiation. The lifetime of BC depends on atmospheric transport, aging and consequently on wet scavenging processes (in-cloud and below-cloud scavenging). In this study, sequential rainwater samples in eight rainfall events collected in 2 mm interval were measured by a tandem system including a single particle soot photometer (SP2) and a nebulizer. The results showed that the volume-weighted average (VWA) mass concentrations of refractory black carbon (rBC) in each rainfall event varied, ranging from 10.8 to 78.9 µg/L. The highest rBC concentrations in the rainwater samples typically occurred in the first fraction from individual rainfall events. The geometric mean median mass-equivalent diameter (MMD) decreased under precipitation, indicating that rBC with larger sizes was relatively aged and preferentially removed by wet scavenging. A positive correlation (R2 = 0.73) between the VWA mass concentrations of rBC in rainwater and that in ambient air suggested the important contribution of scavenging process. Additionally, the contributions of in-cloud and below-cloud scavenging were distinguished and accounted for 74% and 26% to wet scavenging, respectively. The scavenging ratio of rBC particles was estimated to be 0.06 on average. This study provides helpful information for better understanding the mechanism of rBC wet scavenging and reducing the uncertainty of numerical simulations of the climate effects of rBC.

The feedback effects of aerosols from different sources on the urban boundary layer in Beijing China.

The interaction of aerosols and the planetary boundary layer (PBL) plays an important role in deteriorating urban air quality. Aerosols from different sources may have different effects on regulating PBL structures owing to their distinctive dominant compositions and vertical distributions. To characterize the complex feedback of aerosols on PBL over the Beijing megacity, multiple approaches, including in situ observations in the autumn and winter of 2016-2019, backward trajectory clusters, and large-eddy simulations, were adopted. The results revealed notable distinctions in aerosol properties, vertical distributions and thermal stratifications among three types of air masses from the West Siberian Plain (Type-1), Central Siberian Plateau (Type-2) and Mongolian Plateau (Type-3). Low loadings of 0.28 ± 0.26 and 0.15 ± 0.08 of aerosol optical depth (AOD) appeared in the Type-1 and Type-2, accompanied by cool and less stable stratification, with a large part (80%) of aerosols concentrated below 1500 m. For Type-3, the AOD and single scattering albedo (SSA) were as high as 0.75 ± 0.54 and 0.91 ± 0.05, demonstrating severe pollution levels of abundant scattering aerosols. Eighty percent of the aerosols were constrained within a lower height of 1150 m owing to the warmer and more stable environment. Large-eddy simulations revealed that aerosols consistently suppressed the daytime convective boundary layer regardless of their origins, with the PBL height (PBLH) decreasing from 1120 m (Type-1), 1160 m (Type-2) and 820 m (Type-3) in the ideal clean scenarios to 980 m, 1100 m and 600 m, respectively, under polluted conditions. Therefore, the promotion of absorbing aerosols below the residual layer on PBL could be greatly hindered by the suppression effects generated by both absorbing aerosols in the upper temperature inversion layer and scattering aerosols. Moreover, the results indicated the possible complexities of aerosol-PBL interactions under future emission-reduction scenarios and in other urban regions.

Causal effect of PM1 on morbidity of cause-specific respiratory diseases based on a negative control exposure.

BACKGROUND: Extensive studies have linked PM2.5 and PM10 with respiratory diseases (RD). However, few is known about causal association between PM1 and morbidity of RD. We aimed to assess the causal effects of PM1 on cause-specific RD. METHODS: Hospital admission data were obtained for RD during 2014 and 2019 in Beijing, China. Negative control exposure and extreme gradient boosting with SHapley Additive exPlanation was used to explore the causality and contribution between PM1 and RD. Stratified analysis by gender, age, and season was conducted. RESULTS: A total of 1,183,591 admissions for RD were recorded. Per interquartile range (28 µg/m3) uptick in concentration of PM1 corresponded to a 3.08% [95% confidence interval (CI): 1.66%-4.52%] increment in morbidity of total RD. And that was 4.47% (95% CI: 2.46%-6.52%) and 0.15% (95% CI: 1.44%-1.78%), for COPD and asthma, respectively. Significantly positive causal associations were observed for PM1 with total RD and COPD. Females and the elderly had higher effects on total RD, COPD, and asthma only in the warm months (Z = 3.03, P = 0.002; Z = 4.01, P < 0.001; Z = 3.92, P < 0.001; Z = 2.11, P = 0.035; Z = 2.44, P = 0.015). Contribution of PM1 ranked first, second and second for total RD, COPD, and asthma among air pollutants. CONCLUSION: PM1 was causally associated with increased morbidity of total RD and COPD, but not causally associated with asthma. Females and the elderly were more vulnerable to PM1-associated effects on RD.

The urgent need to control volatile organic compound pollution over the Qinghai-Tibet Plateau.

Owing to the impact of the western development of China, there have been signs of air pollution over the Qinghai-Tibet Plateau in recent years. However, monitoring data on atmospheric volatile organic compounds (VOCs) are lacking in plateau areas. Here, VOCs concentrations in urban and background areas in North China and the Qinghai-Tibet Plateau were observed from 2012 to 2014 and 2020 to 2022, respectively. Compared to 2012-2014, the concentration of VOCs increased to 2.5 times in urban areas on the Qinghai-Tibet Plateau, which was equivalent to that in North China. Oil, gas, and solvent evaporation caused by a low atmospheric pressure is the primary factor for the increase in VOCs in plateau areas, and weak VOCs degradation is the secondary factor. Hence, we put forward the VOCs control strategies in plateau areas and point out the defects in the current research.

Modification effects of ambient temperature on ozone-mortality relationships in Chengdu, China.

A multitude of epidemiological studies have demonstrated that both ambient temperatures and air pollution are closely related to health outcomes. However, whether temperature has modification effects on the association between ozone and health outcomes is still debated. In this study, three parallel time-series Poisson generalized additive models (GAMs) were used to examine the effects of modifying ambient temperatures on the association between ozone and mortality (including non-accidental, respiratory, and cardiovascular mortality) in Chengdu, China, from 2014 to 2016. The results confirmed that the ambient high temperatures strongly amplified the adverse effects of ozone on human mortality; specifically, the ozone effects were most pronounced at > 28 °C. Without temperature stratification conditions, a 10-µg/m3 increase in the maximum 8-h average ozone (O3-8hmax) level at lag01 was associated with increases of 0.40% (95% confidence interval [CI] 0.15%, 0.65%), 0.61% (95% CI 0.27%, 0.95%), and 0.69% (95% CI 0.34%, 1.04%) in non-accidental, respiratory, and cardiovascular mortality, respectively. On days during which the temperature exceeded 28 °C, a 10-µg/m3 increase in O3-8hmax led to increases of 2.22% (95% CI 1.21%, 3.23%), 2.67% (95% CI 0.57%, 4.76%), and 4.13% (95% CI 2.34%, 5.92%) in non-accidental, respiratory, and cardiovascular mortality, respectively. Our findings validated that high temperature could further aggravate the health risks of O3-8hmax; thus, mitigating ozone exposure will be brought into the limelight especially under the context of changing climate.

Transport Patterns and Potential Sources of Atmospheric Pollution during the XXIV Olympic Winter Games Period.

The attainment of suitable ambient air quality standards is a matter of great concern for successfully hosting the XXIV Olympic Winter Games (OWG). Transport patterns and potential sources of pollutants in Zhangjiakou (ZJK) were investigated using pollutant monitoring datasets and a dispersion model. The PM2.5 concentration during February in ZJK has increased slightly (28%) from 2018 to 2021, mostly owing to the shift of main potential source regions of west-central Inner Mongolia and Mongolian areas (2015-18) to the North China Plain and northern Shanxi Province (NCPS) after 2018. Using CO as an indicator, the relative contributions of the different regions to the receptor site (ZJK) were evaluated based on the source-receptor-relationship method (SRR) and an emission inventory. We found that the relative contribution of pollutants from NCPS increased from 33% to 68% during 2019-21. Central Inner Mongolia (CIM) also has an important impact on ZJK under unfavorable weather conditions. This study demonstrated that the effect of pollution control measures in the NCPS and CIM should be strengthened to ensure that the air quality meets the standard during the XXIV OWG.

Observational Insights into Isoprene Secondary Organic Aerosol Formation through the Epoxide Pathway at Three Urban Sites from Northern to Southern China.

Isoprene is the most abundant precursor of global secondary organic aerosol (SOA). The epoxide pathway plays a critical role in isoprene SOA (iSOA) formation, in which isoprene epoxydiols (IEPOX) and/or hydroxymethyl-methyl-α-lactone (HMML) can react with nucleophilic sulfate and water producing isoprene-derived organosulfates (iOSs) and oxygen-containing tracers (iOTs), respectively. This process is complicated and highly influenced by anthropogenic emissions, especially in the polluted urban atmospheres. In this study, we took a 1-year measurement of the paired iOSs and iOTs formed through the IEPOX and HMML pathways at the three urban sites from northern to southern China. The annual average concentrations of iSOA products at the three sites ranged from 14.6 to 36.5 ng m-3. We found that the nucleophilic-addition reaction of isoprene epoxides with water dominated over that with sulfate in the polluted urban air. A simple set of reaction rate constant could not fully describe iOS and iOT formation everywhere. We also found that the IEPOX pathway was dominant over the HMML pathway over urban regions. Using the kinetic data of IEPOX to estimate the reaction parameters of HMML will cause significant underestimation in the importance of HMML pathway. All these findings provide insights into iSOA formation over polluted areas.

The environmental benefit of Beijing-Tianjin-Hebei coal banning area for North China.

In order to achieve the targets specified in the Action Plan for Air Pollution Prevention and Control (APAPPC), a limited coal banning area (10,000 km2) was designated in the heavily polluted Beijing-Tianjin-Hebei region (BTH) for the first time in 2017. PM2.5 and elements were sampled by the network of BTH to evaluate the effectiveness of this policy. This study found that the fine days with PM2.5 < 75 µg m-3 accounted for 74.3% in the autumn and winter of 2017, which was significantly higher than that in 2016 (43%). The heavily polluted days (PM2.5 > 150 µg m-3) also decreased from 32.2% in 2016 to 4.9% in 2017. Arsenic (As) is an important tracer in coal consumption, which can be used to reflect the influence of the establishment of coal banning areas on north China. The cluster analysis of air mass forward trajectory identified that the number of polluted trajectories with PM2.5 and As in 2017 decreased by 47.6% and 49.7%, respectively. Under the implementation of the coal banning policy, the weighted concentration of PM2.5 and As decreased by 94.2 µg m-3 and 5.1 ng m-3 in the coal banning area, 60.9 µg m-3 and 3.4 ng m-3 in the no coal banning area in BTH, respectively. The influence of weighted concentration of PM2.5 and As in coal banning area on North China were 1.6-49.2 µg m-3 and 0.15-2.8 ng m-3, respectively, which was 38.8% and 29.7% lower than 2016. In coal banning area, BTH and other parts of North China, the reduction of the weight concentration of PM2.5 in 2017 accounted for 41.4%, 26.8% and 31.8% of the total reduction, respectively, so was the As in 39%, 26.3% and 34.6%, indicating that setting up a coal banning area scientifically in limited areas can produce remarkable regional benefit.

Mass and number concentration distribution of marine aerosol in the Western Pacific and the influence of continental transport.

We quantify for the first time marine aerosol properties and their differences in the offshore and remote ocean in the mid-latitude South Asian waters, low-latitude South Asian waters, and equatorial waters of the Western Pacific Ocean, based on shipboard cruise observations conducted by the Western Pacific Ocean Scientific Observation Network in winter 2018, and further investigate the effects of long-range transport of continental aerosols on the marine environment. During the overall observation period, the average number concentration of particle matter which aerodynamic diameters<2.5 µm (PM2.5N) was 35.1 ± 87.4 cm-3 and the mass concentration (PM2.5M) was 12.3 ± 9.1 µg/m3. The PM2.5N and PM2.5M during the continental air mass transport period were 7.2 and 1.3 times higher than those during the non-transport period (109.2 ± 169.3 cm-3, 15.9 ± 14.9 µg/m3), respectively. Excluding transport period, the average PM2.5N and PM2.5M are reduced by 120% and 7%. Coarse mode particle number concentration (PM2.5-10N) and mass concentration (PM2.5-10M) are not significantly influenced by continental air masses (only a reduction of 7% and 2%). The variation of marine aerosol concentrations in different latitudes zones is greatly influenced by continental aerosol transport. The offshore PM2.5M/PM10M was 30%, 21%, and 22% in the mid-latitude sea of South Asia, a low-latitude sea of South Asia, and the equatorial sea, respectively. In comparison, in the remote ocean, the distribution ratio of PM2.5M/PM10M tended to be steady (22%-23%), and the background characteristics of marine aerosols were clearly represented. The aerosol concentration decreases with the increase of wind speed during the transport period, and the wind speed reflects the scavenging effect on aerosol. In the non-transport period, the wind speed at the sea surface promotes the generation of marine aerosols, and the impact in wind speed is strongest in the PM2.5-PM5 particle size range.

Air stagnation in China: Spatiotemporal variability and differing impact on PM2.5 and O3 during 2013-2018.

In recent years, winter PM2.5 and summer O3 pollution which often occurred with air stagnation condition has become a major concern in China. Thus, it is imperative to understand the air stagnation distribution in China and elucidate its impact on air pollution. In this study, three air stagnation indices were calculated according to atmospheric thermal and dynamics parameters using ERA5 data. Two improved indices were more suitable in China, and they displayed similar characteristics: most of the air stagnant days were found in winter, and seasonal distributions showed substantial regional heterogeneity. During stagnation events, flat west or northwest winds at 500 hPa and high pressure at surface dominated, with high relative humidity (RH) and temperature (T), weak winds in most regions. The pollutants concentrations on stagnant days were higher than those on non-stagnant days in most studied areas, with the largest difference of the 90th percentiles of maximum daily 8-h average (MDA8) O3 up to 62.2 µg m-3 in Pearl River Delta (PRD) and PM2.5 up to 95.8 µg m-3 in North China Plain (NCP). During the evolution of stagnation events, the MDA8 O3 concentrations showed a significant increase (6.0 µg m-3 day-1) in PRD and a slight rise in other regions; the PM2.5 concentrations and the frequency of extreme PM2.5 days increased, especially in NCP. Furthermore, O3 was simultaneously controlled by temperature and stagnation except for Xinjiang (XJ), with the average growth rate of 19.5 µg m-3 every 3 °C at 19 °C-31 °C. PM2.5 was dominated by RH and stagnation in northern China while mainly controlled by stagnation in southern China. Notably, the extremes of summer O3 (winter PM2.5) pollution was most associated with air stagnation and T at 25 °C-31 °C (air stagnation and RH >50%). The results are expected to provide important reference information for air pollution control in China.

Effects of the sea-land breeze on coastal ozone pollution in the Yangtze River Delta, China.

Aim at the effects of the coastal characteristic on ozone pollution in the Yangtze River Delta (YRD), a campaign was launched at the Ningbo, China in the summer of 2020, which mainly covered the monitoring of the vertical profiles of ozone (O3) concentration, three-dimensional wind field, temperature and humidity profiles and parameters of boundary layer dynamic-thermodynamic structure. At the coastal research station, a sea-land breeze (SLB) circulation accompanied by a concurrent coastal low-level jets (CLLJ) structure was observed and identified during 11-12 May 2020. The sea breeze first formed at 10:00 LT on 11 May, turned to land breeze at night, and returned to sea breeze again at 10:00 LT the next morning, prevailing at altitudes of 0-0.5 km and 0-0.3 km respectively. Land breeze at night carries O3 from the inland to the sea forming high ozone levels over the sea, and the shift of the sea breeze during daytime further blew pollution back to the land. Additionally, the conversion of SLB contributed to the occurrence of CLLJ at the altitudes of ~0.3-0.7 km by 02:00 and 06:00 LT, of which the center of wind speed reached ~13 m s-1. The CLLJ-induced turbulent activity decoupled the residual layer (RL) and stable boundary layer, leading to a reduction of RL-O3 levels and an increase of ~50 µg m-3 in surface-O3 concentration. The YRD's unique coastal characteristics make O3 pollution causes in coastal areas more complicated.

How do aerosols above the residual layer affect the planetary boundary layer height?

We revealed that the absorption aerosol lying below or above the morning residual layer (MRL) promotes (stove effect, heating the MRL layer) or strongly inhibits (dome effect, heating the temperature inversion layer) the development of planetary boundary layer (PBL) after sunrise, while scattering aerosol exhibits similar suppression (surface or aloft umbrella effect) on the PBL regardless of its vertical location. However, the role of different type of aerosols (i.e., strong absorption aerosol and purely scattering aerosol) present from MRL to upper atmosphere remains lacking and therefore, needs to be further explored. Utilizing a large-eddy simulation model constrained by the in-situ observations in urban Beijing, we observed that the dome inhibition of absorption aerosols on PBL development becomes weaker as elevating the aerosol layer, and the effect (virtual dome effect) remains no change beyond a certain height, which is defined as the dome effective height z. This height z is highly related to the surface sensible heat flux. By comparison, the altitude of light-scattering aerosols relative to the MRL was less important. The scattering aerosols exhibit similar inhibition from MRL to upper atmosphere (aloft umbrella effect), but to a weaker extent than the virtual dome effect. The virtual dome effect and aloft umbrella effect play a leading role during some extremely polluted scenarios with deep aerosol layer, such as sandstorms and volcanic eruptions. Aerosol dome, virtual dome, and aloft umbrella effects, together with aerosol stove and surface umbrella effects, further advance the understanding on aerosol-PBL interactions, which is, more broadly, applied to interpret the impact of aerosol on PBL over other ecosystems as well as exoplanet atmospheres.

The dynamic multi-box algorithm of atmospheric environmental capacity.

It is very important for air pollution prevention and control to accurately quantify atmospheric environment capacity (AEC) in the planetary boundary layer (PBL). This study developed a high temporal-resolution dynamic multi-box algorithm to estimate PM2.5 AEC with a PBL ceilometer and Doppler wind profile lidar in Beijing City. Compared with the traditional A-value method, two primary improvements are introducing the time coefficient and vertical multi-box assumption into the original box model. The algorithm can accurately calculate the PM2.5 AEC under different circulation patterns and predict the short-time dynamic change of AEC. The results show that the time coefficient effectively reduced the estimation errors when the initial PM2.5 concentration, horizontal wind speed and PBL heights change greatly with time, such situation is consistent with most circulation patterns. And the improvement of multi-box model is much more remarkable when the PM2.5 concentration and horizontal wind change greatly in the vertical direction, such as A, NE and W type circulations. The ideal AEC under polluted circulation patterns won't increase infinitely with wind speed and PBL height, generally less than 30 t/h. The horizontal advection has a much greater effect on expanding the capacity of PM2.5 than the vertical diffusion under clean circulation patterns, and the maximum value of ideal AEC can reach 50 t/h. The positive residual AEC under clean circulations indicates surplus capacity for PM2.5 because of vigorous turbulences, while weak diffusion and ventilation conditions under polluted circulations lead to negative residual AEC and insufficient capacity of atmosphere.

Vertical evolution of black and brown carbon during pollution events over North China Plain.

The vertical distribution of carbonaceous aerosol impacts climate change, air quality and human health, but there is a lack of in-situ vertical observations of black (BC) and brown carbon (BrC). Thus, the characteristic of vertical profiles of BC concentration, particle number concentration (PNC), O3 concentration and optical absorption of BC and BrC were observed in a suburban site over North China Plain, where heavy pollution of PM2.5 and O3 always occurred in winter and summer, respectively. In winter, during a heavy pollution episode, the BC and PNC was near uniformly distributed within mixing layer (ML) (15.2 ± 6.7 µg m-3 and 678 ± 227 p cm-3, respectively) and decreased with altitude above the ML. The BC heating rate reached about 0.13 K h-1 during the heaviest pollution day. In summer, the BC concentration (2.9 ± 1.3 µg m-3) in ML during the middle O3 pollution events was higher than that (1.7 ± 0.6 µg m-3) during the light O3 pollution. The light absorption coefficients of BC at 880 nm and BrC at 375 nm measured in the early morning were lower than that in the daytime, and the contribution of BrC to total light absorption of carbonaceous aerosols was in the range of 27-47%. In addition, BC was effectively transported to high altitude than BrC in the daytime. The light absorption of secondary BrC in the daytime was higher 10-20% than that in the early morning. Simultaneously, the contribution of secondary BrC to the total BrC light absorption at 375 nm was range from 32% to 68% within 1000 m.

Exploring the variation of black and brown carbon during COVID-19 lockdown in megacity Wuhan and its surrounding cities, China.

Absorbing carbonaceous aerosols, i.e. black and brown carbon (BC and BrC), affected heavily on climate change, regional air quality and human health. The nationwide lockdown measures in 2020 were performed to against the COVID-19 outbreak, which could provide an important opportunity to understand their variations on light absorption, concentrations, sources and formation mechanism of carbonaceous aerosols. The BC concentration in Wuhan megacity (WH) was 1.9 µg m-3 during lockdown, which was 24% lower than those in the medium-sized cities and 26% higher than those in small city; in addition, 39% and 16-23% reductions occurred compared with the same periods in 2019 in WH and other cities, respectively. Fossil fuels from vehicles and industries were the major contributors to BC; and compared with other periods, minimum contribution (64-86%) mainly from fossil fuel to BC occurred during the lockdown in all cities. Secondary BrC (BrCsec) played a major role in the BrC light absorption, accounting for 65-77% in WH during different periods. BrCsec was promoted under high humidity, and decreased through the photobleaching of chromophores under higher Ox. Generally, the lockdown measures reduced the BC concentrations significantly; however, the variation of BrCsec was slight.

Polycyclic aromatic hydrocarbons induce endothelial injury through miR-155 to promote atherosclerosis.

Polycyclic aromatic hydrocarbons (PAHs) are considered as an external factor that induces atherosclerotic cardiovascular disease. Although miR-155 is known to be involved in cardiovascular disease, whether it is involved in PAH-induced arteriosclerosis remains unclear. We evaluated the effects of PAHs on vascularization, permeability, and miR-155 expression in HUVECs. We found that PAHs-induced sclerosis of HUVECs was characterized by increasing permeability, decreasing proliferation, and vascular lumen number. The expression of miR-155 was upregulated by PAHs treatment, and transfection with miR-155 inhibitor could reverse above effect of PAHs-induced sclerosis. Meanwhile, transcriptome sequencing revealed that 63 genes were downregulated in the group of PAHs treatment alone, and were then upregulated in the miR-155 inhibitor group. These genes were mainly involved in complement and coagulation cascades, cytokine-cytokine receptor interaction, TNF signaling pathway, and NF-kappa B signaling pathway. Among these 63 genes, SERPIND1 was directly targeted and regulated by miR-155. Further in vivo experiments in ApoE-/- mice confirmed that PAH accelerates the development of arteriosclerosis by promoting the expression of miR-155 to downregulate the SERPIND1. Therefore, PAH exaggerates atherosclerosis by activating miR-155-dependent endothelial injury. This study provides a fundamental insight on the miR-155 mechanism for PAHs enhancing atherosclerosis and miR-155 potentially serving as a novel drug target.

A comprehensive evaluation of aerosol extinction apportionment in Beijing using a high-resolution time-of-flight aerosol mass spectrometer.

An aerosol mass spectrometer (AMS) was used to measure the chemical composition of non-refractory submicron particles (NR-PM1) in Beijing from 2012 to 2013. The average concentration of NR-PM1 was 56 µg·m-3, with higher value of 106 µg·m-3 when Beijing was influenced by air masses from south in winter. Organics was the primary chemical component with a concentration of 26 µg·m-3, accounting for 46% of the total NR-PM1. The ratio of NO3-/SO42- was utilized to identify the relative contribution of stationary and traffic related resource to PM pollution. When NR-PM1 concentration was between 50 and 200 µg·m-3, NO3-/SO42-was larger than 1, indicating traffic resource contributed more than stationary resource during the aerosol growth. A new method was developed to calculate aerosol extinction coefficient (σ) as a function of aerosol optical depth (AOD) and the mixing layer height (MLH). σ derived from the new method showed a statistically significant correlation with that obtained from traditional method, which was calculated using visibility (y = 0.99x + 85 R2 = 0.69). Multiple linear regressions in dependence of chemical component were performed to evaluate light extinction apportionment. Under the overall condition, NR-PM1 contributed about 88% to the whole aerosol light extinction; organics, ammonium chloride, ammonium nitrate, ammonium sulfate, black carbon contributed 30%, 6%, 24%, 26% and 6% of the NR-PM1 light extinction, respectively. By further comparing the light extinction apportionment under the different dominated air masses, we concluded that the organics and ammonium sulfate contributed more in polluted days (36% and 23%) than that in clean days (21% and 21%). Mass ratio (MR) between NR-PM1 and black carbon (MR = massNR-PM1/massBC) was used to identify black carbon aging degree, and the result showed that aerosol mass extinction efficiency increased rapidly after MR reached about 7 in the process of black carbon aging.