Nitrogen dioxide (NO2) is a key species in studying photochemical smog and formation mechanisms of nitrate in fine particles. However, the conventional commercially available chemiluminescence ...(CL)‐based method often has uncertainties in measuring NO2 because of interferences with other reactive nitrogen species. In this study, an Aerodyne Cavity Attenuated Phase Shift Spectroscopy (CAPS) NO2 monitor that essentially has no interferences with nitrogen containing species was deployed in Beijing for the first time during August 2012. The CAPS NO2 monitor is highly sensitive with a detection limit (3σ) of 46.6 ppt for 1 min integration. The NO2 measured by CAPS shows overall agreement with that from CL, yet large differences up to 20% were also observed in the afternoon. Further, the discrepancies of NO2 measurements between CAPS and CL appear to be NOz dependent with larger differences at higher NOz concentrations (e.g., > 14 ppb). As a result, the ozone production efficiency of NOx (OPEx) derived from the correlations of Ox‐NOz with the CL NO2 can be overestimated by 19–37% in Beijing. The daily OPEx calculated with the CAPS NO2 ranges from 1.0 to 6.8 ppb/ppb with an average (±1σ) of 2.6 (±1.3) for the entire study. The relatively low OPEx and the relationship between OPEx and NOx suggest that ozone production chemistry is VOC sensitive during summer in Beijing. Two case studies further show that high concentrations of NOx can significantly enhance the formation of nitrate in fine particles in the presence of high O3 and favorable meteorological conditions.
Key Points
NO2 was measured with Cavity Shift Phase Shift Spectroscopy in Beijing, China
Large differences up to 20% between CAPS and CL‐based instruments were observed
The OPE in Beijing was calculated with improved NO2 measurement
Pointer meters are widely used in various industries, and there is a growing demand for automatic and non-intrusive access to meter readings. The existing methods of automatically calculating meter ...readings involve complex processes which are time-consuming and have low automation performance. The paper presents the design of a Separate Dual-Selective Attention Mechanism (SDSAM) module and a Reading Correction Module (RCM). We also introduce the SDSM-DenseNet model, which utilizes dense connections to directly predict meter readings based on meter images. The SDSM-DenseNet model demonstrates high automation performance and reduces reliance on inherent characteristics of the meter. Compared to other attention mechanism models and feature extraction models, the SDSM-DenseNet model achieves lower error rates in calculating meter readings. Furthermore, when compared with representative methods for reading meters, the average error rate of the SDSM-DenseNet model is reduced by approximately 48%, while only requiring 0.021 s to predict a single image.
Strict emission control measures are being implemented in China and India to improve air quality and protect human health, yet current air quality driven and sector based measures without ...consideration of climate effects would likely taccelerate warming. In this study, we attribute aerosol direct radiative forcing in China and India to emitting sectors using a fully online coupled meteorology-chemistry model (WRF-Chem, Weather Research and Forecasting Model coupled with Chemistry) for the entire year of 2013. Our simulations show that the observed spatial and temporal variations of aerosol concentrations and optical properties are generally reproduced by the model, although sulfate is biased low in winter due to missing aqueous/heterogeneous pathways in the model. Aerosols from all sectors result in negative direct forcing at the top of the atmosphere (TOA) in both China (−2.21 W/m2) and India (−3.18 W/m2), which are largely contributed by the power sector. The residential sector in both China and India largely heats the atmosphere because of its dominant contribution to black carbon emissions. In both China and India, the longwave radiative forcing (0.86 and 1.21 W/m2 for China and India) is tiny compared to the shortwave radiative forcing (−3.07 and −4.39 W/m2 for China and India). The seasonality of sectoral radiative forcing in China is different from that in India. These results suggest that residential sector should be targeted to achieve both air quality and climate change goals, yet the control of emissions from the power sector is very likely to accelerate warming.
•Quantify the sector contributions to aerosol forcing in China and India.•Distinguish the relative roles of longwave forcing and shortwave forcing.•Elucidate the seasonal characteristics of aerosol forcing and sector contributions for each season.
Volatile organic compounds (VOCs) have vital implications for secondary pollutants, atmospheric oxidation and human health. Ambient VOCs were investigated using an online system, gas ...chromatography–mass spectrometry/flame ionization detector (GC–MS/FID), at a suburban site in Xianghe in the North China Plain from 6 November 2017 to 29 January 2018. Positive matrix factorization (PMF) receptor model was applied to identify the major VOC contributing sources. Four-step health risk assessment method was used to estimate risks of all risk-posing VOC species. A total of 101 VOCs were quantified, and the mean concentration of total VOCs was 61.04 ± 65.18 ppbv. The VOCs were dominated by alkanes (38.76%), followed by alkenes, aromatics, halocarbons, OVOCs, acetylene and acetonitrile. The results of PMF revealed that vehicle exhaust, industrial emissions, liquefied petroleum gas & natural gas, solvent utilization and secondary and long-lived species contributed 31.0%, 26.4%, 18.6%, 13.6% and 10.4%, respectively, to the total VOCs. Pollutant-specific and source-specific noncarcinogenic and carcinogenic risk estimates were conducted, which showed that acrolein and vehicle exhaust had evident noncarcinogenic risks of 4.9 and 0.9, respectively. The carcinogenic risks of specific species (1,3-butadiene, acetaldehyde, benzene, chloroform and 1,2-dichloroethane) and identified sources were above the United States Environmental Protection Agency (USEPA) acceptable level (1.0 × 10−6) but below the tolerable risk level (1.0 × 10−4). Vehicle exhaust was the largest contributor (56.2%) to noncarcinogenic risk, but solvent utilization (32.6%) to carcinogenic risk. Moreover, with the evolution of pollution levels, almost all VOC species, contributions of alkenes, aromatics, solvent utilization and vehicle exhaust, and pollutant-specific and source-specific risks increased continuously and noticeably. Collectively, our findings unraveled the importance of alkenes, aromatics, solvent utilization and vehicle exhaust in the evolution of pollution levels. Future studies should consider targeting these VOC groups and sources when focusing on effective reduction strategies and assessing public health risks.
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•Ambient VOCs were measured using an online GC-FID/MS for the first time in Xianghe.•Concentrations, sources and health risks of VOCs were investigated at different pollution levels.•High levels of VOCs were spotted and vehicle exhaust was the main source of VOCs.•Alkenes, aromatics, vehicle exhaust and solvent usage were of great significances during the evolution of air pollution.•Vehicle exhaust and solvent utilization contributed most to noncarcinogenic risk and carcinogenic risk, respectively.
An intensive and persistent regional ozone pollution event occurred over eastern China from 25 June to 5 July 2017. 73 out of 96 selected cities, most located in the Beijing-Tianjin-Hebei and the ...surrounding area (BTHS), suffered severe ozone pollution. A north-south contrast ozone distribution, with higher ozone (199 ± 33 μg/m3) in the BTHS and lower ozone (118 ± 25 μg/m3) in the Yangtze River Delta (YRD), was found to be dominated by the position of the West Pacific Subtropical High (WPSH) and mid-high latitude wave activities. In the BTHS, the positive anomalies of geopotential height at 500 hPa and temperature at the surface indicated favorable meteorological conditions for local ozone formation. Prevailing northwesterly winds in the mid-high troposphere and warm advection induced by weak southerly winds in the low troposphere resulted in low-moderate relative humidity (RH), less total cloud cover (TCC), strong solar radiation and high temperatures. Moreover, southerly winds prevailing over the BTHS aggravated the pollution due to regional transportation of O3 and its precursors. On one hand, the deep sinking motion and inversion layer suppressed the dispersion of pollutants. On the other hand, O3-rich air in the upper layer was maintained at night due to temperature inversion, which facilitated O3 vertical transport to the surface in the next-day morning due to elevated convection. Generally, temperature, UV radiation, and RH showed good correlations with O3 in the BTHS, with rates of 8.51 (μg/m3)/°C (within the temperature range of 20–38°C), 59.54 (μg/m3)/(MJ/m2) and −1.93 (μg/m3)/%, respectively.
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Nitrate (NO3−), sulfate (SO42−) and ammonium (NH4+) in airborne fine particles (PM2.5) play a vital role in the formation of heavy air pollution in northern China. In particular, the increasing ...contribution of NO3− to PM2.5 has attracted worldwide attention. In this study, a highly time-resolved analyzer was used to measure water-soluble inorganic ions in PM2.5 in one of the fastest-developing megacities, Tianjin, China, from November 15 to March 15 (wintertime heating period) in 2014–2019. Severe PM2.5 pollution episodes markedly decreased during the heating period from 2014 to 2019. The highest concentrations of NO3− and SO42− were recorded in the heating period of 2015/2016. Afterwards, NO3− decreased from 2015/2016 (20.2 ± 23.8 μg/m3) to 2017/2018 (11.6 ± 14.8 μg/m3) but increased with increasing NOx concentrations during the heating period of 2018/2019. A continuous decrease in the SO2 concentration led to a decrease in SO42− from 2015/2016 (16.8 ± 21.8 μg/m3) to 2018/2019 (6.5 ± 8.9 μg/m3). The NO3− and SO42− concentrations increased as the air quality deteriorated. However, the proportion of NO3− and SO42− in PM2.5 slightly increased when the air quality deteriorated from moderate pollution (MP) to severe pollution (SP) levels. The average molar ratios of NH4+ to NO3−+2 × (SO42−) were 1.7, 0.9, 1.2, 1.2 and 1.5 for the heating periods of 2014/2015, 2015/2016, 2016/2017, 2017/2018 and 2018/2019, respectively, most of which were higher than 1.0, thus revealing an overall excess of NH4+ during the heating periods. However, the molar equivalent ratios of NH4+ to NO3−+2 × (SO42−) were less than 1 under increasing PM2.5 pollution. The molar equivalent ratios of NO3−/SO42− were positively correlated with those of NH4+/SO42−. When the molar equivalent ratios of NH4+/SO42− were more than 1.5, those of NO3−/SO42− increased from close to 1 to higher values, indicating that the dominance of NO3− formation played an important role. The results of nonparametric wind regression exhibited distinct hot spots of NO3−, SO42− and NH4+ (higher concentrations) in the wind sectors between NE and SE at wind speeds of approximately 6–21 km/h. The southern areas in the North China Plain and parts of the western areas of China contributed more NO3−, SO42− and NH4+ than other areas to the study site. The abovementioned areas were also characterized by a higher contribution of NO3− than of SO42− to the study site and by NH4+-rich conditions. In summary, more efforts should be made to reduce NOx in the Beijing-Tianjin-Hebei region. This study provides observational evidence of the increasingly important role of nitrate as well as scientific support for formulating effective control strategies for regional haze in China.
•Five-year wintertime nitrate, sulfate and ammonium were observed in Tianjin.•NO3− concentrations surpassed SO42− concentrations in the whole study period.•In most cases the atmosphere was ammonium-rich in Tianjin.•Parts of western region of China were also source areas of SNA.
A flexible sensor that simultaneously senses temperature and pressure is crucial in various fields, such as human‐machine interaction, artificial intelligence, and biomedical applications. Previous ...research has mainly focused on single‐function flexible sensors for e‐skins or smart devices, and integrated bimodal sensing of temperature and pressure without complex crosstalk decoupling algorithms remains challenging. In this work, a flexible bimodal sensor is proposed that utilizes spatial orthogonality between in‐plane thermoelectricity and out‐plane piezoresistivity, which enables fully decoupled temperature‐pressure sensing. The proposed bimodal sensor exhibits a high sensitivity of 281.46 µV K−1 for temperature sensing and 2.181 kPa−1 for pressure sensing. In the bimodal sensing mode, the sensor exhibits negligible mutual interference, providing a measurement error of ± 7% and ± 8% for temperature and pressure, respectively, within a 120 kPa pressure range and a 40 K temperature variation. Additionally, simultaneous spatial mapping of temperature and pressure with a bimodal sensor array enables contact shape identification with enhanced accuracy beyond the limit imposed by the number of sensing units. The proposed integrated bimodal sensing strategy does not require complex crosstalk decoupling algorithms, which represents a significant advancement in flexible sensors for applications that necessitate simultaneous sensing of temperature and pressure.
The demand for simultaneous temperature and pressure sensing with minimal interference is on the rise, particularly in the fields of robotics and wearable devices. A flexible bimodal sensor, which integrates in‐plane thermoelectricity and out‐plane piezoresistivity, is developed to fulfill this need. This sensor exhibits negligible mutual interference, marking a significant advancement in flexible sensor technology.
•CS@Se inhibits Aβ aggregation and protects SH-SY5Y cells from Aβ1–42-induced cytotoxicity.•CS@Se protects the cytoskeleton structures and decreases the cytoskeleton instability that is induced by ...okadaic acid.•CS@Se suppresses the oxidative stress induced by Aβ1–42 in SH-SY5Y cells.•CS@Se attenuates the hyperphosphorylation of tau at Ser396 and Ser404 sites by regulating the expression of GSK-3β.
The purpose of this study was to ascertain the effect of selenium-chondroitin sulfate nanoparticles (CS@Se) on multi-target-directed therapy for the treatment of Alzheimer's disease (AD). CS@Se nanoparticles were successfully synthesized, and their therapeutic effects were studied in in vitro AD models. CS@Se effectively inhibited amyloid-β (Aβ) aggregation and protected SH-SY5Y cells from Aβ1–42-induced cytotoxicity. Moreover, CS@Se significantly decreased okadaic acid-induced actin cytoskeleton instability in SH-SY5Y cells. In addition, CS@Se decreased the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) and increased the levels of glutathione peroxidase (GSH-Px). The Western blot results indicated that CS@Se attenuated the hyperphosphorylation of tau (Ser396/Ser404) by regulating the expression of GSK-3β. In summary, this study demonstrated that CS@Se could inhibit the aggregation of Aβ, reduce damage to the cytoskeleton, mitigate oxidative stress and attenuate the hyperphosphorylation of tau protein. CS@Se might be a potent multi-functional agent for the treatment of AD and thus warrants further research and evaluation.
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