Search

The sensitivity of cells to chemotherapeutic agents has a major effect on disease outcome in breast cancer patients. Unfortunately, there are numerous factors involved in the regulation of chemosensitivity, and the mechanisms need to be further investigated. Autophagy/Beclin 1 regulator 1 (Ambra1) is a key protein in the crosstalk between autophagy and apoptosis. It controls the switch between these two processes, which determines whether cells survive or die. Induction of apoptosis is the primary mechanism by which most chemotherapeutic drugs eliminate cancer cells. Recently, Ambra1 has been shown to modulate paclitaxel-induced apoptosis in breast cancer cells via the Bim/mitochondrial pathway, thereby modifying the sensitivity of cells to paclitaxel. However, how Ambra1 regulates Bim expression remains unclear. Here, we further confirmed that Bim plays an indispensable role in Ambra1's regulation of apoptosis and chemosensitivity in breast cancer cells. Furthermore, Ambra1 was found to regulate Bim expression at the transcriptional level through the Akt-FoxO1 pathway. Therefore, we propose a novel pathway, Ambra1-Akt-FoxO1-Bim, which regulates apoptosis and chemosensitivity in breast cancer cells. Thus, Ambra1 may represent a potential target for breast cancer treatment.

The lockdown due to COVID-19 created a rare opportunity to examine the nonlinear responses of secondary aerosols, which are formed through atmospheric oxidation of gaseous precursors, to intensive precursor emission reductions. Based on unique observational data sets from six supersites in eastern China during 2019-2021, we found that the lockdown caused considerable decreases (32-61%) in different secondary aerosol components in the study region because of similar-degree precursor reductions. However, due to insufficient combustion-related volatile organic compound (VOC) reduction, odd oxygen (Ox = O3 + NO2) concentration, an indicator of the extent of photochemical processing, showed little change and did not promote more decreases in secondary aerosols. We also found that the Chinese provinces and international cities that experienced reduced Ox during the lockdown usually gained a greater simultaneous PM2.5 decrease than other provinces and cities with an increased Ox. Therefore, we argue that strict VOC control in winter, which has been largely ignored so far, is critical in future policies to mitigate winter haze more efficiently by reducing Ox simultaneously.

The North China Plain (NCP) is a region that experiences serious aerosol pollution. A number of studies have focused on aerosol pollution in urban areas in the NCP region; however, research on characterizing aerosols in rural NCP areas is comparatively limited. In this study, we deployed a TD-HR-AMS (thermodenuder high-resolution aerosol mass spectrometer) system at a rural site in the NCP region in summer 2013 to characterize the chemical compositions and volatility of submicron aerosols (PM1). The average PM1 mass concentration was 51.2 ± 48.0 µg m−3 and organic aerosol (OA) contributed most (35.4%) to PM1. Positive matrix factorization (PMF) analysis of OA measurements identified four OA factors, including hydrocarbon-like OA (HOA, accounting for 18.4%), biomass burning OA (BBOA, 29.4%), less-oxidized oxygenated OA (LO-OOA, 30.8%) and more-oxidized oxygenated OA (MO-OOA, 21.4%). The volatility sequence of the OA factors was HOA > BBOA > LO-OOA > MO-OOA, consistent with their oxygen-to-carbon (O:C) ratios. Additionally, the mean concentration of organonitrates (ON) was 1.48–3.39 µg m−3, contributing 8.1%–19% of OA based on cross validation of two estimation methods with the high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) measurement. Correlation analysis shows that ON were more correlated with BBOA and black carbon emitted from biomass burning but poorly correlated with LO-OOA. Also, volatility analysis for ON further confirmed that particulate ON formation might be closely associated with primary emissions in rural NCP areas.

An in-depth analysis of the specific evolution of air pollution in a given city can provide a better understanding of the chronic effects of air pollution on human health. In this study, we reported trends in ambient concentrations of particulate matter (PM) and gaseous pollutants [sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3)] from 1995 to 2017 and PM2.5 composition for the period of 2000-2017 in Guangzhou, Wuhan, Chongqing, and Lanzhou. We provided socio-economic indicators to help explain the pollution trends. SO2 and PM (including PM10 and PM2.5) concentrations showed a downward trend in recent years with the most notable reduction in SO2 in Chongqing and PM2.5 in Guangzhou. There was an overall flat trend for NO2, while O3 showed an upward trend in recent years except in Lanzhou. The majority of PM2.5 mass was SO4 2- (6.0-30 µg/m3) and organic carbon (6.0-38 µg/m3), followed by NO3 - (2.0-12 µg/m3), elemental carbon (2.1-12 µg/m3), NH4 + (1.0-10 µg/m3), K+ (0.2-2.0 µg/m3), and Cl- (0.2-1.9 µg/m3). Except for secondary inorganic aerosols in Wuhan, annual average concentrations of all PM2.5 constituents showed a declining trend after 2013, corresponding to the trend of PM2.5. The secondary sources in PM2.5 were found to be most prominent in Wuhan, while the most abundant EC and Cl- in Lanzhou was attributed to the use of coal. Despite temporal and spatial variabilities across the four cities, coal combustion, traffic emissions, and secondary pollution have been the major sources of PM2.5 pollution. These trends in ambient air pollution levels and PM2.5 composition may help understand changes in health outcomes measured at different times within the time period of 1995-2017 in the four cities.

Black carbon (BC) is a key driver of global warming, exerting a strong but highly uncertain effect on the global climate. A key challenge of quantifying BC’s radiative effect is predicting the impact of aging process on BC’s properties. BC is mainly emitted from the incomplete combustion of fossil fuel and biomass burning. After being emitted, it undergoes complex chemical and physical transformations in the atmosphere, through condensation, coagulation and heterogeneous oxidation, which is referred to as BC aging. During aging, BC is gradually coated by other chemical species, which dramatically affects BC properties and alters the corresponding climate effects. The objective of this review is to discuss the current knowledge of BC aging from both laboratory and field measurements. This review first summarizes the methods used in the laboratory experiments and field observations. Then it reviews the effects of aging process on BC mixing state, which comprises both morphology and chemical composition. On this basis, changes to BC light absorption, hygroscopicity, cloud condensation nuclei (CCN) and ice nucleation (IN) activity during the aging process are discussed; these properties are closely related to BC climate effects. Laboratory studies on BC aging are always conducted using single-precursor systems, which do not capture the complex composition of the real atmosphere. In field studies, some state-of-the-art online instruments have been deployed to measure BC properties. However, since the field studies are usually conducted at fixed stations, it is difficult to dynamically track the entire BC aging process. Atmospheric aging process converts BC particles from externally mixed to internally mixed, with other chemical species coated on them. The morphology evolution in the aging process contains three stages: void filling, collapse and subsequent growth, which results in BC morphology changing from the initially chain-like shapes to spherical core-shell structures. The chemical composition of coatings is affected by both emission source and extent of aging, showing an increasing proportion of secondary species during the aging process. BC light absorption is enhanced because of coatings that accumulate during aging. However, the absorption enhancement factors reported in previous studies show large discrepancy because of differences in aging degree, morphology and chemical composition. The particle-to-particle heterogeneity in mixing state can also lead to different enhancement factors for particle populations. Along with the enhancement of light absorption, BC particles hygroscopicity and CCN activity are also enhanced during aging process. However, observational evidence is still lacking. The IN activity of BC is still an open question, and whether aging process enhances or suppresses the IN activity of BC is still debatable. Based on this review of previous studies, we recommend further research on the following topics: (1) Characterize the aging process for BC from different emission sources under realistic combustion conditions. (2) Identify the key factors affecting BC aging in various atmospheric environments. (3) Explore the role of BC particles in regional air pollution. (4) Conduct further studies on the interaction between BC and cloud formation.

Secondary organic aerosol (SOA) is the main component of PM2.5, with great impact on regional air quality and global climate. The traditional view that SOA forms through the partitioning of photochemical processing involving volatile organic compounds (VOCs) cannot fully explain measured SOA concentrations. It has been increasing recognized that SOA can form through aqueous reactions in recent years. Besides cloud/fog aqueous chemistry, aqueous SOA (aqSOA) formation in aerosol liquid water has become one of the frontier scientific problems of atmospheric chemistry. AqSOA precursors enter into aqueous phase through uptake to wet aerosol particles, participate in reactions inside aerosol particles, and then form aqSOA such as organic sulfur compounds and organic nitrogen compounds. This paper provides an overview of the uptake of aqSOA precursors, aqSOA formation mechanism and current research methods of aqSOA. AqSOA precursors include atmospheric oxidants (OH, HO2, O3, etc.), anthropogenic and biogenic VOCs and related gas-phase oxidation products. Aerosol liquid water can influence the uptake of aqSOA precursors on wet aerosols, but related researches are limited. OH uptake coefficient ( γ OH) on different kinds of aerosols varies from 0.02 to 2.41, depending on chemical composition of aerosols and relative humidity. For the uptake of VOCs, take methylglyoxal as an example, measured and theoretical methylglyoxal uptake coefficient ( γ MGLY) differ by 4 to 5 orders of magnitude. Aerosol liquid water may change ionic strength, diffusion limitation and viscosity of wet aerosols, but how these affect the uptake process of aqSOA precursors remain poorly understood. Based on previous analyses of aqueous chemistry, aqueous-phase reactions can be divided into radical reactions and non-radical reactions. Aqueous-phase radical reactions resemble gas-phase reactions in general. However, there are also OH radical reactions unique to the aqueous phase: efficient conversion of aldehydes to carboxylic acids, rapid OH oxidation of carboxylate, and radical induced oligomerization. Recent studies also pay increasing attention to the role of other oxidants in the aqueous radical chemistry, like singlet oxygen, peroxyl radicals, peroxides, molecular oxygen (1O2*), and triplet excited states of organic compounds (3C*). Non-radical reactions include hemiacetal formation, aldol condensation, imine formation and other types of reactions (anhydride formation, organosulfate formation, etc.). Most non-radical reactions lead to the formation of high molecular weight compounds. Although a lot of investigations have been taken to explore aqSOA formation mechanism, the majority are laboratory studies, because of the limit of technology in field measurements. Laboratory simulation includes bulk solution simulation and reaction chamber experiments. Bulk solution cannot simulate typical ambient wet aerosols well, so nowadays reaction chamber is used more widely. There are two types of reaction chambers: smog chamber and flow tube, differing in the volume of reaction chamber and simulated atmospheric oxidation timescale. However, the appropriate application of these laboratory results into field observations and model framework needs further efforts. Moreover, one key factor that has enabled great progress in aqSOA chemistry studies is the development of mass-spectrometric methods, mainly including electrospray ionization-mass spectrometry (ESI-MS), Fourier transform ion cyclotron resonance electrospray ionization mass spectrometry (FTICR-MS), chemical ionization mass spectrometry (CIMS) and extractive electrospray ionization-mass spectrometry (EESI-MS). These techniques can realize accurate molecular level identification of complex compounds. But quantification remains a thorny issue, owing to the absence of available authentic standards. Finally, possible future directions regarding aqSOA chemistry studies are discussed.

Refractory black carbon (rBC) aerosols emitted from incomplete combustion are important climate forcers. Understanding the chemical characteristics and evolution of rBC-related components is particularly crucial to assess rBC environmental impacts. Here, we explored the chemical components of rBC in Shenzhen, China, using a soot-particle aerosol mass spectrometer (SP-AMS). The observations showed that the rBC coating was mainly composed of secondary aerosols with an average mass contribution of 84.7 %. Among them, secondary organic coating occupied ∼57.7 % of the total coating mass. Exploration of the relationship between secondary organic aerosol (SOA) coating and Ox (=NO

During the COVID-19 lockdown, atmospheric PM

Ambient ozone air pollution is one of the most important environmental challenges in China today, and it is particularly significant to identify pollution sources and formulate control strategies. In present study, we proposed a novel method of positive matrix factorization-SHapley Additive explanation (PMF-SHAP) for evaluating the impact of emission sources on ozone formation, which can quantify the main emission sources of ozone pollution. In this method, we first used the PMF model to identify the source of volatile organic compounds (VOCs), and then quantified various emission sources using a combination of machine learning (ML) models and the SHAP algorithm. The R

Atmospheric particles are important reaction vessels for multiphase chemistry. We conducted a meta-analysis of previous field observations in various environments (includes ocean, urban and rural regions), showing that particle hygroscopicity inhomogeneity (PHI) is ubiquitous for the continental atmospheric particles, in which a considerable part of the particulate matters is hydrophobic (10%–33% on average). However, the effects of PHI in quantifying the uptake process of reactive gases are still unclear. Here, taking N2O5 uptake as an example, we showed that using a laboratory-based parameterization scheme without considering the PHI might result in a misestimation of uptake rate coefficient, especially under low ambient relative humidity (RH). Such misestimation may be caused by the differences of the uptake coefficients, as well as the proportion of surface area concentration (SA) between hydrophilic and hydrophobic particles. We suggested that the PHI should be well-considered in establishing the reactive traces gases heterogeneous uptake parameterizations.

Immune checkpoint inhibitors (ICIs), especially pembrolizumab, have improved outcomes in patients with advanced or metastatic gastric cancer (GC). However, there are no reliable markers for the evaluation of its efficacy. GC samples from the UCSC Xena Browser and Gene Expression Omnibus (GEO) databases were performed by bioinformatics analysis. The single sample gene set enrichment (ssGSEA) algorithm was used to calculate the prognostic genes expression differences score (ssGSEA score) for each sample. Weighted gene co-expression network analysis (WGCNA) was applied to identify the score-related key model. The hub gene was identified based on the intersection between tumor-related transcription factors (TFs) and the key module. The predictive ability for pembrolizumab response of the hub gene was evaluated by the area under the receiver operating characteristic (ROC) curve (AUC). The correlations between the hub gene and immune infiltration in GC were investigated by the CIBERSORT algorithm. According to the ssGSEA score, patients with GC were divided into the high- and low-score group. RUNX1T1 was the hub gene of the ICIs treatment in GC. Its high expression was related to the low-score group, which indicated low sensitivity to pembrolizumab and poor prognosis. RUNX1T1 showed good predictive power for pembrolizumab response (AUC = 0.742). The CIBERSORT analysis showed that a high expression for RUNX1T1 weakened the anti-tumor immune response by affecting the immune cell infiltration.Runx1T1 may be a potential predictor of pembrolizumab efficacy in GC and be a prognostic marker for GC.

Oxygenated volatile organic compounds (OVOCs) are important precursors and products of atmospheric secondary pollution. The sources of OVOCs, however, are still quite uncertain, especially in the atmosphere with much pollution in China. To study the sources of OVOCs in rural atmospheres, a proton transfer reaction mass spectrometry (PTR-MS) was deployed at a northern rural site (WD) and a southern rural site (YMK) in China during the summer of 2014 and 2016, respectively. The continuous observation showed that the mean concentration of TVOCs (totally 17 VOCs) measured at WD (52.4 ppbv) was far higher than that at YMK (11.1 ppbv), and the OVOCs were the most abundant at both the two sites. The diurnal variations showed that local sources of OVOCs were still prominent at WD, while regional transport influenced YMK much. The photochemical age-based parameterization method was then used to quantitatively apportion the sources of ambient OVOCs. The anthropogenic primary sources at WD and YMK contributed less (2%–16%) to each OVOC species. At both the sites, the atmospheric background had a dominant contribution (~ 50%) to acetone and formic acid, while the anthropogenic secondary formation was the main source (~ 40%) of methanol and MEK. For acetaldehyde and acetic acid, the biogenic sources were their largest source (~ 40%) at WD, while the background (39%) and anthropogenic secondary formation (42%) were their largest sources at YMK, respectively. This study reveals the complexity of sources of OVOCs in China, which urgently needs explored further.

Particle phase state plays a key role in gas-particle partitioning, heterogeneous and multiphase reactions, and secondary aerosol formation. In this work, the rebound fraction and chemical composition of submicron particles were simultaneously measured to investigate the particle phase state and its link to chemical composition in a subtropical coastal urban city (Shenzhen, China). Submicron particles were found to be in the liquid state for most of the measurement period in spring. During the sampling time, both high relative humidity (RH, ranged from 40% to 93%) and inorganic mass fraction in particles (62.6 ± 12.4% of dry particles, on average) resulted in abundant aerosol liquid water (43 ± 6% in the wet PM

Size-resolved particulate matter (PM) was collected at the Heshan Super-Station in the Pearl River Delta (PRD) region, China, to evaluate their chemical characteristics and potential health risks. The chemical mass closures illustrate that the dominant fraction in coarse (2.5 μm

Volatile organic compounds (VOCs) are important precursors of photochemical pollution. However, a substantial fraction of VOCs, namely, oxygenated VOCs (OVOCs), have not been sufficiently characterized to evaluate their sources in air pollution in China. In this study, a total of 119 VOCs, including 60 OVOCs in particular, were monitored to provide a more comprehensive picture based on different online measurement techniques, proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) and online gas chromatography/mass spectrometry (GC/MS), at a receptor site in southeastern China during a photochemically active period. Positive matrix factorization (PMF) and photochemical age-based parameterization were combined to identify and quantify different sources of major VOCs during daytime hours, with the advantage of including VOC decay processes. The results revealed the unexpected role of biomass burning (21%) in terms of ozone (O3) formation potential (OFP) when including the contributions of OVOCs and large contributions (30–32%) of biomass burning to aldehydes, as more OVOCs were measured in this study. We argue that biomass burning could significantly enhance the continental atmospheric oxidizing capacity, in addition to the well-recognized contributions of primary pollutants, which should be seriously considered in photochemical models and air pollution control strategies.

A seven-year long-term comprehensive measurement of non-refractory submicron particles (NR-PM1) in autumn and winter in Beijing from 2012 to 2018 was conducted to evaluate the effectiveness of the clean air actions implemented by the Chinese government in September 2013 on aerosols from different sources and chemical processes. Results showed that the NR-PM1 concentrations decreased by 44.1% in autumn and 73.2% in winter from 2012 to 2018. Sulfate showed a much larger reduction than nitrate and ammonium in both autumn (55%) and winter (86%) and that nitrate even slightly increased by 15.8% in autumn. As a result, aerosol pollution in winter gradually changed from sulfate-rich to nitrate-rich with a sudden change after 2016 and the dominant role of nitrate in autumn was also strengthened after 2016. Among primary organic aerosol (OA) types, biomass burning OA and coal combustion OA exhibited the largest decline in autumn and winter, with reductions of 87.5% and 77.3%, respectively, while hydrocarbon-like OA (HOA) exhibited the smallest decline in both autumn (24.4%) and winter (37.1%). These significant changes in aerosol compositions were highly consistent with the much faster reduction of SO2 (75-85%) than NOx (36-59%) and were mainly due to the clean air actions rather than the impact of meteorological conditions. What's more, the enhanced atmospheric oxidizing capacity, which was indicated by increased O3, altered the chemical processes of oxygenated OA (OOA), especially in autumn. Both of less-oxidized OOA (LO-OOA) and more-oxidized OOA showed elevated contributions in OA by 4% in autumn. The increased oxygen-to-carbon ratios of LO-OOA in autumn (from 0.42 to 0.58) and winter (from 0.44 to 0.52) indicated the enhanced atmospheric oxidizing capacity strengthened photochemical reactions and resulted in the increased oxidation degree of LO-OOA. This study demonstrates the effectiveness of the clean air actions for air quality improvement in Beijing.

Cross-regional transport potentially contributes to PM

Oxygenated volatile organic compounds (OVOCs) are key intermediates in the atmospheric photooxidation process. To further study the primary and secondary sources of OVOCs, their ambient levels were monitored using a proton-transfer reaction mass spectrometer (PTR-MS) at an urban site in the Pearl River Delta of China. Continuous monitoring campaigns were conducted in the spring, summer, fall, and winter of 2016. Among the six types of OVOC species, the mean concentrations of methanol were the highest in each season (up to 13–20 ppbv), followed by those of acetone, acetaldehyde and acetic acid (approximately 2–4 ppbv), while those of formic acid and methyl ethyl ketone (MEK) were the lowest (approximately 1–2 ppbv). As observed from a diurnal variation chart, the OVOCs observed in Shenzhen may have been affected by numerous factors such as their primary and secondary sources and photochemical consumption. The photochemical age-based parameterization method was used to apportion the sources of ambient OVOCs. Methanol had significant anthropogenic primary sources but negligible anthropogenic secondary sources during all of the seasons. Acetone, MEK and acetic acid were mostly attributed to anthropogenic primary sources during each season with smaller contributions from anthropogenic secondary sources. Acetaldehyde had similar contributions from both anthropogenic secondary and anthropogenic primary sources throughout the year. Meanwhile, anthropogenic primary sources contributed the most to formic acid.

Online instruments have been widely applied for the measurement of PM2.5 and its chemical components; however, these instruments have a major shortcoming in terms of the lack or limited number of species in field measurements. To this end, a new mass closure PM2.5 online integrated system was developed and applied in this work to develop more comprehensive information on chemical species in PM2.5 . For the new system, one isokinetic sampling system for PM2.5 was coupled with an aerosol chemical speciation monitor (Aerodyne, ACSM), an aethalometer (Magee, AE-31), an automated multi-metals monitor (Cooper Corporation, Xact-625) and a hybrid synchronized ambient particulate real-time analyzer monitor (Thermo Scientific, SHARP-5030i) to enable high-resolution temporal (1 h ) measurements of organic matter, SO 4 2 - , NO 3 - , Cl− , NH 4 + , black carbon, important elements and PM2.5 mass concentrations. The new online integrated system was first deployed in Shenzhen, China, to measure the PM2.5 composition from 25 September to 30 October 2019. Our results showed that the average PM2.5 concentration in this work was 33 µg m−3 , and the measured species reconstructed the PM2.5 well and almost formed a mass closure (94 %). The multi-linear engine (ME-2) model was employed for the comprehensive online PM2.5 chemical dataset to apportion the sources with predetermined constraints, in which the organic ion fragment m/z 44 in ACSM data was used as the tracer for secondary organic aerosol (SOA). Nine sources were determined and obtained reasonable time series and diurnal variations in this study, including identified SOA (23 %), secondary sulfate (22 %), vehicle emissions (18 %), biomass burning (11 %), coal burning (8.0 %), secondary nitrate (5.3 %), fugitive dust (3.8 %), ship emissions (3.7 %) and industrial emissions (2.1 %). The potential source contribution function (PSCF) analysis indicated that the major source area could be the region north of the sampling site. This is the first system in the world that can perform online measurements of PM2.5 components with a mass closure, thus providing a new powerful tool for PM2.5 long-term daily measurement and source apportionment.

The role of coarse particles has recently been proven to be underestimated in the atmosphere and can strongly influence clouds, ecosystems and climate. However, previous studies on atmospheric chemistry of volatile organic compounds (VOCs) have mostly focused on the products in fine particles, it remains less understood how coarse particles promote secondary organic aerosol (SOA) formation. In this study, we investigated water-soluble compounds of size-segregated aerosol samples (0.056 to18 μm) collected at a coastal rural site in southern China during late summer and found that oxygenated organic matter was abundant in the coarse mode. Comprehensive source apportionment based on mass spectrum and

Atmospheric sub-micrometer particles (PM1, particles with an aerodynamic diameter ≤ 1.0 μm) monitoring in Qingdao, a coastal city in Northern China, was conducted for two consecutive years from November 1, 2018 to January 31, 2019 (hereafter referred to as OP2018–2019) and from October 28, 2019 to January 20, 2020 (hereafter referred to as OP2019–2020). The results showed that compared with OP2018–2019, the concentrations of V, Ni, As, Pb, and Cd in PM1 in OP2019–2020 decreased by 61.9%, 31.4%, 49.2%, 25.4%, and 27.1%, respectively. For the indicators of ship emission sources, a significant reduction in V (73.3%) and Ni (22.1%) concentrations were observed after the implementation of the updated Domestic Emission Control Area (DECA 2.0) policy for ships since January 1, 2019 proposed by the Ministry of Transportation. This result demonstrated that the implementation of the DECA 2.0 policy had a significant effect on reducing ship emissions. The Field Emission Scanning Electron Microscope analysis identified the impact of ship emission sources, while the inconsistent distribution of V and Ni revealed other potential sources of Ni. The V/Ni ratios during the pre-policy and post-policy periods decreased by 40.7%. Along with the further implementation of the domestic coastal ship pollution control zone policy, V/Ni ratio should be cautiously used as a parameter for ship emission sources. The positive matrix factorization method identified five source factors: coal combustion/biomass burning (47.8%), crustal sources (21.2%), vehicle exhaust/road dust (15.1%), industrial emissions (11.1%), and ship emissions (4.9%). The contribution rates of ship emission sources before and after the DECA 2.0 policy were analyzed and found to be 5.6% and 3.4%. The potential source contribution factor analysis of As showed that the potential emission source areas were significantly reduced in OP2019–2020, which might be related to the coal fired cleanup operations conducted in Beijing-Tianjin-Hebei and surrounding areas.

Three new chlorido-substituted hydrazone compounds N′-(3,5-dichloro-2-hydroxybenzylidene)benzohydrazide (H2L1), N′-(3,5-dichloro-2-hydroxybenzylidene)-4-fluorobenzohydrazide (H2L2) and N′-(2-hydroxy-3-methylbenzylidene)-4-trifluoromethylbenzohydrazide (H2L3), were prepared and characterized by IR, UV–Vis and 1H NMR spectra. Based on the hydrazone compounds, three new vanadium(V) complexes, [VOL1(OEt)(EtOH)]·[VOL1(OEt)(MeOH)] (1), [VOL2(OEt)(EtOH)] (2) and [VOL3(OEt)(EtOH)] (3), were prepared and characterized by IR and UV–Vis spectra, as well as single crystal X-ray diffraction. X-ray analysis indicates that the complexes are mononuclear vanadium(V) species, with the V atoms coordinated in octahedral geometry. The hydrazone compounds and their vanadium complexes were evaluated against the bacteria Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas fluorescence, and the fungi Candida albicans and Aspergillus niger. The existence of the fluoro groups in the hydrazone ligands can improve the antibacterial activities.

Water-soluble organic matter (WSOM) represents a critical fraction of fine particles (PM2.5) in the air, but its changing behaviors and formation mechanisms are not well understood yet, partly due to the lack of fast techniques for the ambient measurements. In this study, a novel system for the on-line measurement of water-soluble components in PM2.5, the particle-into-liquid sampler (PILS)-Nebulizer-aerosol chemical speciation monitor (ACSM), was developed by combining a PILS, a nebulizer, and an ACSM. High time resolution concentrations of WSOM, sulfate, nitrate, ammonium, and chloride, as well as mass spectra, can be obtained with satisfied quality control results. The system was firstly applied in China for field measurement of WSOM. The mass spectrum of WSOM was found to resemble that of oxygenated organic aerosol, and WSOM agreed well with secondary inorganic ions. All evidence collected in the field campaign demonstrated that WSOM could be a good surrogate of secondary organic aerosol (SOA). The PILS-Nebulizer-ACSM system can thus be a useful tool for intensive study of WSOM and SOA in PM2.5.

Organic aerosols (OAs), which consist of thousands of complex compounds emitted from various sources, constitute one of the major components of fine particulate matter. The traditional positive matrix factorization (PMF) method often apportions aerosol mass spectrometer (AMS) organic datasets into less meaningful or mixed factors, especially in complex urban cases. In this study, an improved source apportionment method using a bilinear model of the multilinear engine (ME-2) was applied to OAs collected during the heavily polluted season from two Chinese megacities located in the north and south with an Aerodyne high-resolution aerosol mass spectrometer (HR-ToF-AMS). We applied a rather novel procedure for utilization of prior information and selecting optimal solutions, which does not necessarily depend on other studies. Ultimately, six reasonable factors were clearly resolved and quantified for both sites by constraining one or more factors: hydrocarbon-like OA (HOA), cooking-related OA (COA), biomass burning OA (BBOA), coal combustion (CCOA), less-oxidized oxygenated OA (LO-OOA) and more-oxidized oxygenated OA (MO-OOA). In comparison, the traditional PMF method could not effectively resolve the appropriate factors, e.g., BBOA and CCOA, in the solutions. Moreover, coal combustion and traffic emissions were determined to be primarily responsible for the concentrations of PAHs and BC, respectively, through the regression analyses of the ME-2 results.

Ground-level ozone is an air pollutant that has adverse impacts on human health and vegetation growth. The accurate prediction of ozone concentrations is essential for developing strategies for ozone mitigation. To obtain a better forecasting model to predict ozone, this study provides a detailed discussion of the application of three model optimization strategies (i.e., adding decomposition algorithms, adding data and adding factors) to benchmark models, including long short-term memory (LSTM) and support vector regression (SVR), to predict ozone concentrations in Shenzhen. The results showed that adding a decomposition strategy, particularly the wavelet decomposition (WD) algorithm, provided the greatest improvement to the prediction accuracy. Based on this, a novel hybrid forecasting model (WD-LSTMSVR) was further developed that first used the WD algorithm to convert the original data from one dimension to multiple dimensions. Subsequently, each layer of the data set was trained and forecast by the LSTM and SVR models, which involved parameters that were optimized by the autoregressive integrated moving average (ARIMA) partial algorithm and particle swarm optimization (PSO) algorithm. The hybrid forecasting model had the best prediction accuracy performance compared with the benchmark models and optimization models in this study. Our results indicate that the developed hybrid forecasting model is a good technique to provide accurate ozone concentration prediction results.

High ozone concentrations have adverse effects on human health and ecosystems. In recent years, the ambient ozone concentration in China has shown an upward trend, and high-quality prediction of ozone concentrations has become critical to support effective policymaking. In this study, a novel hybrid model combining wavelet decomposition (WD), a gated recurrent unit (GRU) neural network and a support vector regression (SVR) model was developed to predict the daily maximum 8 h ozone. We used the ground ozone observation data in six representative megacities across China from Jan. 1, 2015 to Jun. 15, 2020 for model training, and we used data from Jun. 15 to Dec. 31, 2020 for model testing. The results show that the developed model performs very well for megacities; against observations, the model obtains an average cross-validated R2 (coefficient of determination) ranging from 0.90 for Shanghai to 0.97 for Chengdu in the one-step predictions, thereby indicating that the model outperformed any single algorithm or other hybrid algorithms reported. The developed model can also capture high ozone pollution episodes with an average accuracy of 92% for the next five days in inland cities. This study will be useful for the environmental health community to prevent high ozone exposure more efficiently in megacities in China and shows great potential for accurate ozone prediction using machine learning approaches.

With the rapid economic development and urbanization of China, haze and photochemical smog events have been frequently observed during the last decade. To explore the temporal and spatial pollution characteristics in Ningbo, a medium-sized coastal city located in the Yangtze River Delta (YRD) in southeast China, 24-h PM2.5 (particulate matter with aerodynamic diameter ≤ 2.5 µm) samples were simultaneously collected at five sites (two urban residential sites, two urban coastal sites, and one suburban site) from winter 2012 to autumn 2013. The average PM2.5 concentration was 53.2 ± 30.4 µg m–3. Furthermore, the concentration exhibited a seasonal variation: It was highest in winter and lowest in summer. The urban residential sites had the highest PM2.5 concentrations, followed by the urban coastal sites, and the suburban site had the lowest concentration. OM (Organic Matters) and secondary inorganic ions (sulfate, nitrate, and ammonium) were the dominant components of the PM2.5. As a coastal city with industrial zones, sources are more complex in Ningbo than in inland cities due to ship emissions and the interactions between land and sea, and the marine and atmospheric environments. Positive matrix factorization (PMF) was used to apportion the particle sources. Nine factors were resolved in this study: secondary nitrate, vehicle exhaust, secondary sulfate, coal combustion, industrial emission, ship emission, dust, biomass burning, and aged sea salt, with average contributions of 26%, 21%, 13%, 12%, 9%, 7%, 5%, 4%, and 3%, respectively. Secondary nitrate and vehicle exhaust were the major sources of PM2.5 pollution in Ningbo. Coal combustion contributed significantly in winter and autumn, whereas sea salt formed a considerable contribution in summer. This study suggests that decreasing the PM2.5 pollution in Ningbo requires not only strategies for reducing local primary sources but also joint inter-regional prevention and the control of air pollution in the YRD.

Haze in China is primarily caused by high pollution of atmospheric fine particulates (PM 2.5 ). However, the detailed source structures of PM 2.5 light extinction have not been well established, especially for the roles of various organic aerosols, which makes haze management lack specified targets. This study obtained the mass concentrations of the chemical compositions and the light extinction coefficients of fine particles in the winter in Dongguan, Guangdong Province, using high time resolution aerosol observation instruments. We combined the positive matrix factor (PMF) analysis model of organic aerosols and the multiple linear regression method to establish a quantitative relationship model between the main chemical components, in particular the different sources of organic aerosols and the extinction coefficients of fine particles with a high goodness of fit ( R 2 = 0.953). The results show that the contribution rates of ammonium sulphate, ammonium nitrate, biomass burning organic aerosol (BBOA), secondary organic aerosol (SOA) and black carbon (BC) were 48.1%, 20.7%, 15.0%, 10.6%, and 5.6%, respectively. It can be seen that the contribution of the secondary aerosols is much higher than that of the primary aerosols (79.4% versus 20.6%) and are a major factor in the visibility decline. BBOA is found to have a high visibility destroying potential, with a high mass extinction coefficient, and was the largest contributor during some high pollution periods. A more detailed analysis indicates that the contribution of the enhanced absorption caused by BC mixing state was approximately 37.7% of the total particle absorption and should not be neglected.

The phase state of biomass burning aerosols (BBA) remains largely unclear, impeding our understanding of their effects on air quality, climate and human health, due to its profound roles in mass transfer between gaseous and particulate phase. In this study, the phase state of BBA was investigated by measuring the particle rebound fraction ƒ combining field observations and laboratory experiments. We found that both ambient and laboratory-generated BBA had unexpectedly lower rebound fraction ƒ (0.6) under the dry conditions (RH = 20-50%), indicating that BBA were in non-solid state at such low RH. This was obviously different from the secondary organic aerosols (SOA) derived from the oxidation of both anthropogenic and biogenic volatile organic compounds, typically with a rebound fraction ƒ larger than 0.8 at RH below 50%. Therefore, we proposed that the diffusion coefficient of gaseous molecular in the bulk of BBA might be much higher than SOA under the dry conditions.

To study the aerosol chemistry and regional transport changes in Beijing under different stagnant meteorological conditions, a simultaneous combined observation of the nonrefractory submicron aerosol (NR-PM1) chemical compositions and vertical wind profiles was conducted at an urban site (Beijing) and a regional background site (Xinglong) in the North China Plain (NCP) from November 2018 to January 2019. The backward trajectories of PM1 species in Beijing under different pollution stages were calculated. The results showed that the proportion of backward trajectories from southern regions increased from 0% in the clean stage (PM1 75 μg m−3), suggesting the aerosol pollution in winter Beijing was greatly affected by regional transport from southern regions. Although the proportion of trajectories from the northwestern regions of Beijing decreased from the clean stage to the pollution stage, the trajectories still comprised a large proportion (53%), which indicates that the northwestern air mass can also cause heavy pollution in winter. Therefore, two typical episodes with air masses from the southwest (episode 1) and northwest (episode 2) regions were selected for further study. The results showed that episode 1 in Beijing lasted for several days and was initiated by regional transport and dominated by heterogeneous reactions, while episode 2 was dominated by rapid regional transport in a short time. Both water vapor and pollutants were transported from southern regions in episode 1, while only pollutants were transported in episode 2. Because of the stronger heterogeneous reactions in episode 1, inorganic aerosols in Beijing accounted for 71% of PM1 in episode 1, which was higher than that in episode 2 (56%). In addition, the transport of water vapor from southern China enhanced the secondary aerosol formation in Xinglong and expanded the scope of regional pollution. In comparison, the systematic south wind did not reach the background area in episode 2. Correspondingly, the PM1 concentration in Beijing was 62% higher than that in Xinglong in episode 2, which was much higher than that in episode 1 (11%). Our results showed that in addition to the enhancement of heterogeneous reactions caused by the increase in humidity, the rapid transport of pollutants because of the sudden change of wind field from north to south can also dominant heavy haze episodes in winter Beijing.

Rapid economic development and urbanization in China has been concentrated in coastal cities, resulting in haze and photochemical smog issues, especially in the densely-populated Yangtze River Delta. In this study, we explore particulate matter (specifically PM 2.5 ) pollution in a city in Zhejiang Province (Ningbo), chosen to represent a typical, densely-populated urban city with residential and industrial sections. PM 2.5 samples were collected at five sites in four seasons from Dec. 2012 to Nov. 2013. The annual average PM 2.5 mass concentration was 53.2 ± 30.4 μg/m 3 , with the highest concentration in winter and lowest in summer. Among the five sites, PM 2.5 concentration was highest in an urban residential site and lowest in a suburban site, due to effects of urbanization and the anthropogenic influences. The chemical components of PM 2.5 show significant seasonal variation. In addition, secondary transformation was high in Ningbo, with the highest proportion of secondary components found at a suburban site and the lowest at the industrial sites. Ningbo is controlled by five major air masses originating from inland China, from the Bohai Sea, offshore from the southeast, the Yellow Sea, and off the east coast of Korea. The relative contributions of these air masses differ, by season, with the Bohai Sea air mass dominating in winter and spring, the maritime southeast air mass in summer, and the Yellow Sea and coastal Korean air masses dominating in autumn. The continental air mass is associated with a high PM 2.5 concentration, indicating that it is primarily transports primary emissions. In contrast, the concentration ratios among secondary formed pollutants were higher in the maritime air masses, which suggests that sea breezes control temporal and spatial variations of air pollution over coastal cities.

Severe PM2.5 pollution has become a great challenge to atmospheric pollution control in China. Most of previous aerosol source apportionment studies in China focused only on part of PM2.5 (e.g., organic matter in composition or PM1 in size) or lacked source contributions identified with necessary tempo-spatial variations, which makes the results not convincible enough for policy making. In this study, five various sites were selected for simultaneous PM2.5 observation in an industrial city in the Pearl River Delta (PRD) of South China during all four seasons of 2014. A positive matrix factorization (PMF) model was applied to the datasets of measured chemical species to perform source apportionment with the results as: (1) The annual mean PM2.5 concentration was 53 μg/m3, with vehicle emissions, secondary sulfate, biomass combustion, and secondary organic aerosol (SOA) identified as the major sources, contributing 21%, 20%, 11%, and 10% to PM2.5, respectively. Ship emissions, fugitive dust, secondary nitrate, industrial emissions, and coal burning each contributed 5%–8%. (2) The tempo-spatial variations of sources reveal that secondary sulfate, biomass combustion, SOA, and ship emissions had obvious regional pollution characteristics; however, vehicle emissions, secondary nitrate, coal burning, fugitive dust, and industrial emissions showed obvious local emission characteristics. (3) The exceeding standard days (PM2.5>75 μg/m3) appeared with secondary nitrate, SOA, and biomass burning increasing mostly in concentration, indicating that the relevant primary sources or precursor emissions should be controlled more strictly. This study highlights the importance of SOA in PM2.5 pollution in China, which has been scarcely quantified for bulk PM2.5 in the literature.

The emission of pollutants is extremely reduced during the annual Chinese Spring Festival (SF) in Shenzhen, China. During the SF, traffic flow drops by ∼ 50 % and the industrial plants are almost entirely shut down in Shenzhen. To characterize the variation in ambient air pollutants due to the Spring Festival effect, various gaseous and particulate pollutants were measured in real time in urban Shenzhen over three consecutive winters (2014–2016). The results indicate that the concentrations of NOx, volatile organic compounds (VOCs), black carbon (BC), primary organic aerosols, chloride, and nitrate in submicron aerosols decrease by 50–80 % during SF periods relative to non-Spring Festival periods, regardless of meteorological conditions. This decrease suggests that these pollutants are mostly emitted or secondarily formed from urban local emissions. The concentration variation in species mostly from regional or natural sources, however, is found to be much less, such as for bulk fine particulate matter (PM2. 5). More detailed analysis of the Spring Festival effect reveals an urgent need to reduce emissions of SO2 and VOCs on a regional scale rather than on an urban scale to reduce urban PM2. 5 in Shenzhen, which can also be useful as a reference for other megacities in China.

Highly time-resolved in situ measurements of airborne particles were conducted at Mt. Yulong (3410 m above sea level) on the southeastern edge of the Tibetan Plateau in China from 22 March to 14 April 2015. The detailed chemical composition was measured by a high-resolution time-of-flight aerosol mass spectrometer together with other online instruments. The average mass concentration of the submicron particles (PM1) was 5.7 ± 5.4 µg m−3 during the field campaign, ranging from 0.1 up to 33.3 µg m−3. Organic aerosol (OA) was the dominant component in PM1, with a fraction of 68 %. Three OA factors, i.e., biomass burning organic aerosol (BBOA), biomass-burning-influenced oxygenated organic aerosol (OOA-BB) and oxygenated organic aerosol (OOA), were resolved using positive matrix factorization analysis. The two oxygenated OA factors accounted for 87 % of the total OA mass. Three biomass burning events were identified by examining the enhancement of black carbon concentrations and the f60 (the ratio of the signal at m∕z 60 from the mass spectrum to the total signal of OA). Back trajectories of air masses and satellite fire map data were integrated to identify the biomass burning locations and pollutant transport. The western air masses from South Asia with active biomass burning activities transported large amounts of air pollutants, resulting in elevated organic concentrations up to 4-fold higher than those of the background conditions. This study at Mt. Yulong characterizes the tropospheric background aerosols of the Tibetan Plateau during pre-monsoon season and provides clear evidence that the southeastern edge of the Tibetan Plateau was affected by the transport of anthropogenic aerosols from South Asia.

Taiwan Strait is a special channel for subtropical East Asian Monsoon and its western coast is an important economic zone in China. In this study, a suburban site in the city of Xiamen on the western coast of Taiwan Strait was selected for fine aerosol study to improve the understanding of air pollution sources in this region. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and an Aethalometer were deployed to measure fine aerosol composition with a time resolution of 5 min from May 1 to 18, 2015. The average mass concentration of PM1 was 46.2 ± 26.3 μg/m3 for the entire campaign. Organics (28.3%), sulfate (24.9%), and nitrate (20.6%) were the major components in the fine particles, followed by ammonium, black carbon (BC), and chloride. Evolution of nitrate concentration and size distribution indicated that local NOx emissions played a key role in high fine particle pollution in Xiamen. In addition, organic nitrate was found to account for 9.0%-13.8% of the total measured nitrate. Positive Matrix Factorization (PMF) conducted with high-resolution organic mass spectra dataset differentiated the organic aerosol into three components, including a hydrocarbon-like organic aerosol (HOA) and two oxygenated organic aerosols (SV-OOA and LV-OOA), which on average accounted for 27.6%, 28.8%, and 43.6% of the total organic mass, respectively. The relationship between the mass concentration of submicron particle species and wind further confirmed that all major fine particle species were influenced by both strong local emissions in the southeastern area of Xiamen and regional transport through the Taiwan Strait.