Search

Context: To investigate the influence of two typical nitro explosives, 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) and nitroguanidine (NQ), on the thermal decomposition mechanism of 3,4-Bis (3-nitrofurazan-4-yl) furoxan (DNTF). The study simulates the dynamical behavior of the DNTF/DNTF, DNTF/NQ, and DNTF/LLM-105 systems at different temperatures. We analyzed their thermal decomposition mechanisms through decomposition processes, reaction paths, and product evolution. Building on our analysis of thermal decomposition mechanisms, we found that introducing these two components (NQ and LLM-105) significantly alters the decomposition mechanism of DNTF. This introduction promotes the breakdown of DNTF molecules, modifies the thermal decomposition processes, and consequently changes the reaction pathways. In the DNTF/DNTF system, the product C3N4O4 remains stable, while the N–O bond in NO2 undergoes repeated breaking and formation, ultimately converting into NO. Conversely, in the mixed system, NO2 persists throughout the simulation, while the reaction product C3N4O4 undergoes additional reactions and eventually disappears at higher temperatures. This behavioral disparity determines distinct decomposition mechanisms between the mixed and pure DNTF systems. Methods: To investigate the thermal decomposition mechanisms of DNTF/LLM-105 and DNTF/NQ composite energetic materials, the first-principles calculation software CP2K is used. The GFNI-xTB (Geometry, Frequency, and Noncovalent, eXtended Tight Binding) program within CP2K is employed. This method provides a powerful tool for performing calculations with arbitrary accuracy on complex systems. [ABSTRACT FROM AUTHOR]

Proinflammatory cytokines are considered to be one of the key causes of haemophilic cartilage destruction by inducing chondrocyte apoptosis and extracellular matrix degradation. However, few studies have focused on how proinflammatory cytokines regulate the phenotypic changes of chondrocytes, which may be an important factor in haemophilic cartilage degradation pathogenesis. More understanding is needed about the effect of proinflammatory cytokines on phenotypic changes of the chondrocyte. The objective of this study was to examine how IL-6, TNF-α and IL-1β regulate the chondrocyte phenotype, which may be an important factor in haemophilic cartilage degradation pathogenesis. HUM-iCell-s018 chondrocytes were treated with increasing concentrations of TNF-α, IL-6 or IL-1β (0, 1, 5, 10 ng/ml) for 24 h, then FGF23 and SOX9 expression was determined by qRT-PCR and WB, respectively. We found that TNF-α, IL-6 and IL-1β induced FGF23 and suppressed SOX9 expression in chondrocytes in a dose-dependent manner. IL-1β had a stronger regulatory effect on FGF23, while TNF-α and IL-6 had stronger regulatory effects on SOX9. These findings suggest that IL-6, IL-1β and TNF-α may be involved in haemophilic cartilage destruction pathogenesis by altering the chondrocyte phenotype through modulation of FGF23 and SOX9 gene expression. [ABSTRACT FROM AUTHOR]

Iron deposition is closely related to developing haemophilic arthropathy (HA). Studying the relationship between ferroptosis signal expression and iron overload in HA synovium facilitates understanding the pathogenesis of joint synovial hyperplasia in bloodborne arthritis and the development of new protective methods. The knee synovium was collected from HA and osteoarthritis (OA) patients, and pathological changes were analysed by HE and Prussian blue staining. Ferroptosis phenotypes were examined by immunohistochemistry and western blotting. Moreover, ferric ammonium citrate (FAC)-induced was used to construct an in vitro iron overload model to investigate the relationship between iron overload and ferroptosis in synovial fibroblasts (FLS). Furthermore, the factors influencing ferroptosis in FLS were explored. Iron deposition, cell proliferation, and vascular proliferation in the synovium of HA were more obvious. Ferroptosis in HA synovium appears to inhibit. FLS ferroptosis increased with iron accumulation, malondialdehyde (MDA) in cells, and glutathione (GSH) depletion. TNF-α plays a protective role in this process. Blocking the action of TNF-α and inducing ferroptosis significantly reduced synovial proliferation. TNF-α inhibitors combined with a ferroptosis inducer may be a new therapeutic method for HA synovitis. [ABSTRACT FROM AUTHOR]

Introduction: Clarifying the links between iron and FGF23, SOX9 expression in chondrocytes would be helpful for comprehending articular cartilage degradation pathogenesis in blood‐induced arthritis and exploring new protective methods. Aim: The purpose of this study was to determine iron regulation of fibroblast growth factor 23 (FGF23) and SRY‐box 9 (SOX9) in human chondrocytes, an area which is unexplored in blood‐induced arthritis cartilage degradation pathogenesis. Methods: Expression of FGF23, SOX9, MMP13 and collagen Ⅱ in articular cartilage of patients with osteoarthritis (OA) or haemophilic arthritis (HA) was determined by western blot (WB). Iron‐induced FGF23 and SOX9 mRNA and protein expression in primary human normal chondrocyte cells (HUM‐iCell‐s018) was quantified by qRT‐PCR and WB, respectively. Results: We found that compared with OA patients, the expression of FGF23, MMP13 in articular cartilage of patients with HA was up‐regulated, while the expression of SOX9, collagen Ⅱ was down‐regulated. Iron‐induced FGF23 and suppressed SOX9 expression in chondrocytes in a dose‐dependent manner. Conclusions: These findings demonstrated that iron was involved in hemophilic cartilage lesion directly via changing cartilage phenotype through regulation of FGF23 and SOX9 expression in chondrocytes. [ABSTRACT FROM AUTHOR]

The thin soil layer with uneven distribution in karst areas facilitates the migration of phosphorus (P) to groundwater, threatening the safety of water sources seriously. To offer a scientific guidance for water pollution control and land use planning in karst areas, this study examined the relationships between land use and P in groundwater and surface water, and quantified the phosphate sources in Gaoping river basin, a small typical watershed in karst areas. Spatial distribution analysis revealed that the highest mean P concentrations in groundwater and surface water were in farmland and construction-farmland zones, respectively. Land use impact analysis showed that the concentration of P in groundwater was influenced positively by farmland but negatively by forest land. In contrast, the concentration of P in surface water was influenced positively by both farmland and construction land. The mixed end-element and Bayesian-based Stable Isotope Analysis in R (SIAR) model results showed that agricultural fertilizers were the main phosphate source for groundwater in farmland and forest-farmland zones, while urban sewage was the main source in the construction-farmland zone. For surface water, the main phosphate source was agricultural fertilizers in both farmland and construction-farmland zones. This study indicates that controlling P pollution in local water bodies should pay close attention to the management of land use related to human activities, including regulating sewage discharge from construction land and agricultural fertilizer usage. [Display omitted] • Groundwater phosphorus concentration is positively correlated with the proportion of farmland. • Fertilizers and urban sewage were the main sources of groundwater phosphate. • The sources of ground and surface waters phosphate in the karst region were quantified using multiple models. [ABSTRACT FROM AUTHOR]

Objectives. This study is aimed at determining whether CT-based radiomics models can help differentiate renal angiomyolipomas with minimal fat (AMLmf) from other solid renal tumors. Methods. This retrospective study included 58 patients with a postoperative pathologically confirmed AMLmf (observation group) and 140 patients with other common renal tumors (control group). Non-contrast-enhanced CT and contrast-enhanced CT data were evaluated. Radiomics features were extracted from manually delineated volume of interest (VOIs). The least absolute shrinkage and selection operator (LASSO) regression was used for feature screening. Five classifiers, including logistic regression, multilayer perceptron (MLP), support vector machine (SVM), k -nearest neighbor (KNN), and logistic regression (LR), were used, with leave-out validation (128 training, 60 testing). The diagnostic performance of the classifier was evaluated and compared by receiver operating characteristic curve (ROC) analysis. Results. Among the 1029 extracted features, prediction models of AMLmf were composed, by 2, 10, 4, and 9 selected features for precontrast phase (PCP), corticomedullary phase (CMP), nephrographic phase (NP), and excretory phase (EP), respectively. Models of CMP and NP achieved adequate performance after using MLP classifier, with prediction accuracy of 0.767 (AUC 0.85, sensitivity 0.76, and specificity 0.78) and 0.783 (AUC 0.83, sensitivity 0.79, and specificity 0.78), respectively. MLP model of features selected from the combination of the all features had the best diagnostic performance (accuracy 0.8500, sensitivity 0.8095, specificity 0.9444, and AUC 0.9193). Conclusions. Radiomics features may help to distinguish benign AMLmf from common malignant kidney masses, which may contribute to the selection of interventions for renal tumors. [ABSTRACT FROM AUTHOR]

The direct and indirect radiative effects of sea salt aerosols (SSA) over the western Pacific Ocean of East Asia for the year 2014 are investigated by using an online-coupled regional chemistry-climate model (RIEMS-Chem) with a developed sea salt emission scheme (G03SSTRH) by considering the effects of sea surface temperature (SST) and relative humidity (RH) on sea salt generation. Model comparison with observations at coastal and island sites demonstrates the G03SSTRH scheme apparently improve model simulation for sea salt concentration, with the overall model-observation bias for PM 10 concentration reduced from 29% to 16% and more evident improvement at northern sites of the western Pacific. It is noteworthy that compared to the experiment with the old SSA emission scheme (G03), the G03SSTRH experiment substantially alters the spatial distribution of mass concentration and radiative effects of sea salt, shifting the maximum value center from the ocean northeast of Japan to the southern parts of the western Pacific with the maximum value increasing to some extent. SSA exerts a negative radiative effect at the top of atmosphere (TOA), in which direct radiative effect (DRE SSA) dominates over indirect radiative effect (IRE SSA) in the western Pacific. The oceanic and annual mean DRE SSA , IRE SSA , and total radiative effect (TRE SSA) are estimated to be −1.22 W/m2, −0.46 W/m2, and −1.65 W/m2, respectively, from the G03SSTRH experiment, which are 16%, 5%, and 12% stronger than those from the G03 experiment, and the seasonal mean DRE SSA in G03SSTRH are approximately 45% and 32% higher than those in G03 in summer and autumn. Distinct seasonality of SSA radiative effects is revealed in the G03SSTRH experiment, showing stronger DRE SSA and IRE SSA in summer and autumn than those in spring and winter, in marked contrast to the little seasonality in the G03 experiment. This study provides a comprehensive regional estimation of radiative effects induced by SSA and reveals the significant effect of different SSA emission schemes on both mass concentration, radiative effects and seasonal variation of SSA over the western Pacific. [Display omitted] • Sea salt emission scheme is developed by considering the effects of SST and RH. • New scheme improves sea salt prediction with NMB decreasing from 29% to 16%. • DRE SSA is higher in summer/autumn and IRE SSA peaks in autumn over the western Pacific Ocean. • Annual and oceanic mean DRE SSA and IRE SSA at TOA are estimated to be −1.2 and −0.5 Wm−2. [ABSTRACT FROM AUTHOR]

Fluorine-based aluminum thermite have excellent ignition and combustion properties. Nonetheless, its combustion kinetics and energy release are hindered by slow mass diffusion and incomplete reactions. Therefore, this study successfully prepared an Al@PTFE composite with a core-shell structure, utilizing mechanical activation and sintering techniques, to enhance combustion properties and energy release rate. SEM, XRD, FTIR and XPS characterization results demonstrate the unique core-shell structure of the samples and the homogeneous distribution of elements on the surface. In comparison to the physical mixture, the Al@PTFE composite exhibits significantly higher values for P max (2.19 times), P max /Δt (11.30 times), and flame propagation velocity (4.5 times). Furthermore, the combustion duration required to reach the maximum flame height was reduced by 131.75 ms. The adsorption, decomposition and reaction processes of PTFE on the surface of aluminum particles were demonstrated based on RMD simulations. The promotion mechanism of PTFE on combustion in aluminum particles was elucidated. • Al@PTFE composite particles were successfully prepared by mechanical and thermal activation. • The ignition and combustion properties of Al@PTFE composite particles are much better than Al/PTFE composite particles. • The adsorption, dissociation and reaction processes of PTFE on the surface of alumina were observed at the molecular level. • PTFE destroys the alumina shell, creating a reaction site that induces an ignition reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] Aluminum nanoparticles are often considered attractive choices for fuels in energetic materials. In this study, molecular dynamics simulation with the reactive force field (ReaxFF) was used to study the oxidation process of three different particle sizes (4 nm, 5 nm, 6 nm) of ANPs (aluminum nano-particles). The cavity formation mechanism was obtained during the ANPs oxidation process. The cavity size, the oxide layer thickness, and the active aluminum content of ANPs with time were obtained. The results indicated that the formation of cavities is highly dependent on particle size. Large particle size prevents the formation of cavities. In 0–100 ps, the average growth rate of the oxide layer is 0.33, 0.25, and 0.20 nm/ps, respectively. Within 100–250 ps, the average growth rate of the oxide layer is −0.017, 0.038, and 0.117 nm/ps, respectively. Our results emphasize the effect of particle size on cavity formation, which provides insights into the atomic-scale oxidation mechanism of metal nanoparticles. [ABSTRACT FROM AUTHOR]

The work state of catenary support components (CSCs) is essential for trains’ powering safety under high-speed operation. However, because of the difficulty of positioning the CSCs whose sizes are much different, some detection methods based on classical deep learning technologies only position one specific component, and the others that can position all categories CSCs have poor performance. A new position method for 12 categories of CSCs called CSC structure inference net (CSCSIN) is proposed in this article. This method is composed of three sections, including the feature extraction with a multilevel feature, feature inference with structure prior information, regression, and classification. In the feature extraction section, to extract small-scale CSCs’ features, a modified VGG16, which is used to generate a legible feature map based on the fusion of low and high layers’ features, is proposed, and multiscales anchors for RoIs prediction are applied to suit multiscale CSCs. In the feature inference section, considering application scenarios and fixed position relationship between CSCs, the scene visual feature and position information between targets are used to iteratively update each target state in structure inference net, and the final state of each target is used for its classification in regression and classification section. Based on the modification in the feature extraction section and the combination of relevant information of CSCs, CSCSIN is efficient and sensitive to all 12 CSCs whose scales are much different. The experimental results demonstrate that the position precision of CSCSIN is superior to other classical models and relevant methods. [ABSTRACT FROM AUTHOR]

Background: The Chinese Society of Clinical Oncology guidelines 2018 and the recent update of that (version 2020) recommends accurate examination before major treatment for decision(s) in cases of colon cancer. Also, the difficulty in the identification of the lesion during colectomy may lead to resection of a wrong segment of the colon or a more extensive resection than planned. Accurate pre-colectomy local staging of colon cancer is required to make decisions for treatment of colon cancer. The objective of the study was to evaluate the diagnostic performance of the computed tomography colonography (CTC) for pre-colectomy tumor location and tumor, node, and metastasis (TNM) staging of colon cancer. Methods: Data of preoperative colonoscopies, CTC, surgeries, and surgical pathology of a total of 269 patients diagnosed with colon cancer by colonoscopy and biopsy and underwent pre-colectomy location and TNM staging by CTC were collected and analyzed. The consistency between the radiological and the surgery/surgical-pathological for location and TN stages of colon tumor were estimated with the weighted kappa or kappa coefficient (κ) at 95% confidence interval (CI). Results: CTC detected 261 (93%) and colonoscopy detected 201 (72%) correct locations of tumors. Sensitivity and accuracy of CTC for detection of location of colon tumors were 100% and 92.58% (κ = 0.89; 95% Cl: 0.83–0.95). 72.48% sensitivity, 90.64% specificity, and 83.57% accuracy were reported for CTC in differentiation of tumors confined to the colon wall (T1/T2) from advanced tumors (T3/T4) (κ = 0.69, 95% Cl: 0.51–0.75). 81.01% sensitivity, 89.11% specificity, and 83.93% accuracy of CTC was reported for differentiation of tumors between low–intermediate risk and high risk (κ = 0.68, 95% Cl: 0.53–0.75). 69.31% sensitivity, 66.15% specificity, and 67.14% accuracy of CTC were reported for N staging of tumors (κ = 0.41, 95% Cl: 0.59–0.69). Conclusions: CTC has high diagnostic parameters for pre-colectomy location and T staging of colon tumors except patients of colon cancer who received neoadjuvant chemotherapy. Level of Evidence: III. Technical Efficacy Stage: 2. [ABSTRACT FROM AUTHOR]

The impacts of vertical distribution of biomass burning (BB) emissions on aerosol distributions and direct radiative effects over the BB source regions of Mainland Southeast Asia (MSEA) and downwind East Asian regions during spring (March to May) 2019 were investigated by applying an online coupled regional chemistry-aerosol-climate model (RIEMS-Chem). Model validation against a variety of observations demonstrated a generally good skill of the model in simulating aerosol chemical components, aerosol optical depth (AOD), and vertical distribution of aerosol extinction coefficient (EXT) when BB emissions were included. Four methods were adopted to represent injection height of BB emissions, including (1) a physical process-based parameterization (BB_param), (2) satellite-based prescribed profiles (BB_prof), (3) temporal-spatial varied injection profiles from the GFAS (Global Fire Assimilation System) dataset (BB_GFAS), and (4) BB emissions released at a fixed altitude (BB_high). The BB_param experiment generally produced better statistics compared to observations. Different BB injection height treatments considerably affected concentrations and distributions of BB aerosols, aerosol optical properties, direct radiative effects of BB aerosols (DRE BB), atmospheric heating rate, and cloud fractions. The simulated sub-regional (100–120°E and 19–26°N, including major BB source and downwind areas) and seasonal mean DRE BB at the top of the atmosphere (TOA) were +1.7 W m−2, +1.3 W m−2, +1.2 W m−2, and +1.7 W m−2 in the BB_param, BB_prof, BB_GFAS, and BB_high experiments, respectively, while the corresponding mean DRE BB at the surface were −30.3 W m−2, -19.1 W m−2, -19.0 W m−2, and -22.1 W m−2. It is noticed that the DRE BB at TOA and at the surface in BB_GFAS were just 68% and 63% of the values in BB_param, and the different injection height treatment had larger influences on DRE BB at the surface than at TOA. The BB aerosol-induced atmospheric heating rate was up to 0.8–1.2 K/day in BB_param, which was larger than those in other experiments. Low cloud was enhanced while middle and high clouds were reduced by BB aerosols over northern MSEA. The BB aerosol-induced changes in cloud fractions in the BB_param experiment (up to 0.15 for low cloud and −0.05 for middle and high cloud) were approximately twice those in the other experiments. This study demonstrates the importance and necessity of properly representing the injection height of BB emissions in model estimation of radiative and climatic effects of BB aerosols. [Display omitted] • The direct radiative effects of four methods for BB injection height were explored. • Surface direct radiative effect of BB aerosols varied from −19 to −30 W m-2 among the methods. • BB aerosols induced the largest HR of 0.8–1.2 K/day at 3–5 km by the physically based method. • The BB aerosol-induced changes in cloud fraction with these methods varied by a factor of two. [ABSTRACT FROM AUTHOR]

The cantilever structure of catenary system (CSCS) is crucial to support whole catenary system. CSCS may deform after a long-time operation because of the bad environment and repeated vibration. It is significant to monitor the parameters of CSCS, which may be helpful for guiding the maintenance. In this paper, a new method of CSCS status detection based on the concave and convex characteristics of CSCS’ 3-D point cloud data is proposed, which avoids the low efficiency of manual measurement and recognition problem of 2-D images. First, the object extraction of CSCS and denoising is performed. The supervoxel clustering (SVC) is used to over segment each single component. The original locally convex connected patches (LCCP) algorithm cannot completely acquire the linear parts of the CSCS, so the CSCS is divided by an improved slope constrained locally convex connected patches (SC-LCCP) algorithm proposed here. Second, according to the segmentation results, an improved projection random sample consensus (P-RANSAC) algorithm is used to fit the linear characteristics of CSCS components and calculate the coordinates of each connection location between different CSCS components. This new improvement can overcome the intersection detection problem of different cantilevers more effective than the original random sample consensus (RANSAC) algorithm. Finally, experiments on the point clouds of CSCS obtained from a depth camera show that this method can effectively segment the linear parts of CSCS. The average error of point-ratio (P-R) is 2.3%–5.3%, the average error of the 3-D coordinates is 1.3–3.0 mm, and the average error of the proportional position coefficients (PPC) is 0.68%–0.9%. The method can better monitor the connection state of CSCS and can satisfy the practical engineering requirement. [ABSTRACT FROM AUTHOR]

The goal of this article is to develop a universal anomaly detection approach for catenary support components (CSCs) based on the generative adversarial networks (GANs). As the long-term operation of railway system, a wide range of failures, which threaten the safe operation of vehicles, perhaps happen to CSCs. Until now, it is hard to design a generic detection system to recognize all these kinds of failures because each defect needs a special detecting algorithm for different fault signatures. The lack of anomaly samples also makes it difficult for supervised learning methods to detect effectively. In this article, a novel approach, which combines deep convolution neural networks (DCNNs) with GANs, is proposed to estimate whether failures happen and give an alarm to stop the accident. First, an object location model is trained by DCNNs to obtain numerous samples of CSCs. Second, a generative model based on deep convolutional GAN (DCGAN) is constructed to find a good mapping from image space to high-dimensional feature spaces implicitly. Finally, an anomaly rating criterion is used to diagnose images. Two typical components of CSCs, the insulator that has big body and the isoelectric line that has tiny characters, are tested here. Experiments show that the proposed method can correctly judge anomalous images of CSCs and possess a good generic failure detection ability in this single framework. [ABSTRACT FROM AUTHOR]

As a tool to monitor marine environments and to perform dangerous tasks instead of manned vessels, unmanned surface vehicles (USVs) have extensive applications. Because most path planning algorithms have difficulty meeting the mission requirements of USVs, the purpose of this study was to plan a global path with multiple objectives, such as path length, energy consumption, path smoothness, and path safety, for USV in marine environments. A global path planning algorithm based on an improved quantum ant colony algorithm (IQACA) is proposed. The improved quantum ant colony algorithm is an algorithm that benefits from the high efficiency of quantum computing and the optimization ability of the ant colony algorithm. The proposed algorithm can plan a path considering multiple objectives simultaneously. The simulation results show that the proposed algorithm's obtained minimum was 2.1–6.5% lower than those of the quantum ant colony algorithm (QACA) and ant colony algorithm (ACA), and the number of iterations required to converge to the minimum was 11.2–24.5% lower than those of the QACA and ACA. In addition, the optimized path for the USV was obtained effectively and efficiently. [ABSTRACT FROM AUTHOR]

Abstract The characteristics, distributions, and direct radiative effects (DRE) of marine aerosols in the western Pacific Ocean over East Asia during the period from 17 March to 22 April 2014 were investigated by an online-coupled regional atmospheric chemistry/aerosol-climate model RIEMS-Chem (Regional Integrated Environmental Model System with Chemistry). The emissions and relevant processes of sea salt, marine primary organic aerosol (MPOA), sulfate and Methyl sulfonic acid (MSA) produced from dimethylsulfide (DMS) were parameterized and coupled with RIEMS-Chem. The model results for total aerosol masses (PM 10 and PM 2.5), inorganic and carbonaceous aerosols, gas precursors, and aerosol optical depth (AOD) were compared with various observational data sets including a research cruise Dongfanghong II from the Yellow Sea to the open oceans, near-surface aerosol and gas concentrations from the Acid Deposition Monitoring Network in East Asia (EANET) and China National Environmental Monitoring Center (CNEMC), and AOD from the Aerosol Robotic Network (AERONET). Model comparisons demonstrated a generally good skill of the RIEMS-Chem in representing the temporal and spatial variations of these variables. The distributions of marine aerosols were characterized by the maximum sea salt concentration up to 70 μg m−3 in the ocean northeast of Japan, the maximum concentration of MPOA >2 μg m−3 in the East China Sea and in portions of the northwest Pacific (NWP) region, and the maximum DMS-produced aerosol concentration >0.3 μg m−3 in the southern parts of the ocean. It was noteworthy that marine aerosols can be easily transported to the inland areas of south China. The clear-sky DREs by sea salt ranging from −9 to −17 W/m2 occurred in the open oceans northeast of Japan, comparable to the DREs of −10 ~ −20 W/m2 by anthropogenic aerosols, whereas the DREs by MPOA were strongest (up to −1.3 Wm−2) in the East China Sea and the oceans northeast of Japan due to active phytoplankton blooms there and comparable in magnitude to the DREs by sea salt (around −3 Wm−2) in the East China Sea. The maximum DRE by the DMS-produced aerosols was −0.4 Wm−2 mainly in the northern parts of the South China Sea. Sea salt exhibited an increasing radiative importance from the China marginal seas to the open oceans, accounting for 10% and 33% of the DREs by all aerosols, respectively. Under all-sky conditions, the sum of DREs by all the marine aerosols were estimated to be −2.2 W/m2, −3.5 W/m2, −2.3 W/m2, and −4.3 W/m2 averaged over the entire domain, ocean, East China Sea, and the NWP region, accounting for 20%, 27%, 13%, and 36% of the DREs by all aerosols, respectively, which demonstrated the important role of marine aerosols in modulating shortwave radiation in springtime in the western Pacific Ocean which was just downwind of the Asian continent with large amounts of anthropogenic and dust emissions. Graphical abstract The model simulated mean near-surface concentrations (unit: μg m−3) of (a) sea salt, (b) MPOA, (c) DMS-produced aerosols, and clear-sky direct radiative effects (unit: W/m2) at the top of the atmosphere by (d) sea salt, (e) MPOA, (f) DMS aerosols in spring 2014. Unlabelled Image Highlights • The distributions and direct radiative effects of marine aerosols were explored with RIEMS-Chem. • The maximum mean levels of sea salt and MPOA exceeded 70 μg m−3 and 2 μg m−3 in the western Pacific Ocean. • The all-sky DRE by marine aerosols was −3.5 W/m2, accounting for 27% of the DRE by total aerosols over the ocean. • The DRE by MPOA was comparable to that by sea salt in regions of plankton bloom, such as the East China Sea. [ABSTRACT FROM AUTHOR]

Abstract An online coupled regional chemistry-aerosol-climate model was developed and applied to explore the distribution, evolution and indirect effects of marine primary organic aerosols (MPOA) over East Asia during the period from 12 March to 22 April 2014. Model results were compared with a variety of observations from ground measurement, cruise experiment and satellite retrievals, which demonstrated the model was capable of reproducing reasonably well the major features in meteorological variables, gas species, aerosol components and cloud properties in the western Pacific Ocean in springtime. Active bloom events were observed in the western Pacific Ocean during the study period, with mean surface seawater Chlorophyll a (Chl-a) concentrations up to 10 mg m−3 in the Yellow Sea, East China Sea, Sea of Japan, as well as the ocean northeast of Japan. The mean surface MPOA concentration was simulated to be up to 2.5 μg m−3 in the East China Sea, followed by that in the ocean northeast of Japan, and about 0.5 μg m−3 in the coastal areas of east China. MPOA generally caused increases in the cloud condensation nuclei (CCN), cloud droplet number concentration (CDNC), cloud optical depth (COD) and cloud liquid water path (CLWP), but decrease in the cloud droplet effective radius (CDER). The above changes in cloud properties induced a negative indirect radiative effect (IRE), with the mean values being −5.3 Wm-2, −8.2 Wm-2 and -12.2 Wm-2 over the ocean, East China Sea and the north western Pacific Ocean, which accounted for about 40%, 35% and 51% of the IRE due to all aerosols in these regions, respectively. It was noteworthy that the MPOA induced IRE was −3.6 Wm-2 in east China, accounting for 20% of the IRE by all aerosols and the percentage contribution was about 32% for the whole domain, suggesting its important influence on cloud and radiation during the study period. The sensitivity of MPOA activation to the factors affecting hygroscopicity and surface tension was examined by sensitivity simulations. The indirect effects of MPOA tended to suppress precipitation in most of the domain, with the maximum decrease in the accumulated precipitation up to 50 mm in parts of south China and the East China Sea. In terms of domain average, MPOA accounted for 16%, 22%, 18% of the precipitation reduction due to all aerosols over the land, ocean and the whole domain, respectively, indicating its nonnegligible influence on precipitation over East Asia in springtime 2014. Highlights • The indirect effect of marine primary organic aerosol (MPOA) was investigated. • MPOA led to an increase in cloud droplet number and a decrease in effective radius. • The indirect radiative effect by MPOA was −5.3Wm-2 over the western Pacific Ocean. • MPOA caused a decrease in precipitation in the East China Sea and southeast China. [ABSTRACT FROM AUTHOR]

A regional air quality model system (RAQMS) was developed by coupling the treatment of heterogeneous reactions between sea salt aerosols (SSAs) and trace gases and applied to the investigation of aerosol properties and evolutionary features in the western Pacific Ocean in the spring of 2014. Model results for meteorological variables, PM concentrations, and size-resolved water soluble inorganic aerosol (WSIA) concentrations were compared and analyzed with a variety of observations from in situ measurements and the research cruise Dongfanghong II . Model validation demonstrated that the model can simulate the spatial-temporal distribution and size distribution of aerosol inorganic components in the marine atmosphere over East Asia, and the inclusion of heterogeneous reactions on SSAs apparently improved the model simulation for WSIA concentration, especially for aerosol size distribution. In the western Pacific Ocean, the non-sea salt SO 4 2− and NO 3 − formed on SSAs accounted for up to 30% and 90% of surface SO 4 2− and NO 3 − concentrations on average, respectively. The atmospheric depositions of total inorganic sulfur and nitrogen were estimated to be 13184 × 10 3 kgS/d and 10728 × 10 3 kgN/d, respectively. Wet deposition was the dominant removal pathway, which accounted for 75% and 68% of sulfur and nitrogen depositions, respectively. The deposition of fine-mode SO 4 2− exceeded that of coarse-mode SO 4 2− , whereas the deposition of coarse-mode NO 3 − was comparable to that of fine-mode NO 3 − . The non-sea salt SO 4 2− and NO 3 − formed on SSAs contributed 16% and 9% of total sulfur and nitrogen depositions on average, respectively. The above results revealed the important role of SSAs in both atmospheric chemistry and deposition in the western Pacific Ocean. [ABSTRACT FROM AUTHOR]

In this study, some key geometric and thermal parameters derived from recent field and satellite observations in Beijing were collected and incorporated into WRF-UCM (Weather Research and Forecasting) model instead of previous default ones. A series of sensitivity model simulations were conducted to investigate the influences of these parameters on radiation balance, meteorological variables, turbulence kinetic energy (TKE), as well as planetary boundary layer height (PBLH) in regions around Beijing in summer 2014. Model validation demonstrated that the updated parameters represented urban surface characteristics more realistically and the simulations of meteorological variables were evidently improved to be closer to observations than the default parameters. The increase in building height tended to increase and slightly decrease surface air temperature at 2 m (T2) at night and around noon, respectively, and to reduce wind speed at 10 m (WS10) through a day. The increase in road width led to significant decreases in T2 and WS10 through the whole day, with the maximum changes in early morning and in evening, respectively. Both lower surface albedo and inclusion of anthropogenic heat (AH) resulted in increases in T2 and WS10 over the day, with stronger influence from AH. The vertical extension of the impact of urban surface parameters was mainly confined within 300 m at night and reached as high as 1600 m during daytime. The increase in building height tended to increase TKE and PBLH and the TKE increase was larger at night than during daytime due to enhancements of both mechanical and buoyant productions. The increase in road width generally reduced TKE and PBLH except for a few hours in the afternoon. The lower surface albedo and the presence of AH consistently resulted in increases of TKE and PBLH through both day and night. The increase in building height induced a slight divergence by day and a notable convergence at night, whereas the increase in road width led to a remarkable divergence through the entire day. Both AH and lower surface albedo induced a wind convergence over the day, which tended to strengthen nighttime mountain downslope wind and daytime southerly wind to the south of Beijing, but to weaken daytime upslope wind in mountain areas. [ABSTRACT FROM AUTHOR]

In order to clarify the combustion-supporting mechanism of fluoropolymers, this work focuses on the atomic details of the oxidation of Al nanoparticles with the fluoropolymers and O2, using reactive dynamics simulations. The results show that the combustion properties of Al–fluoropolymer composites are positively correlated with the fluorine content contained in the fluoropolymers. This is because more Al–O and Al–F bonds are formed, resulting in greater energy release, and the fluoropolymer is efficient in preventing the sintering of aluminum powder during combustion. In addition, the erosion of the alumina layer during the ignition phase results in a considerable boost in the combustion performance of the aluminum particles. Surprisingly, a micro-explosion behavior is found in Al–fluoropolymer composites during combustion, which leads to a much higher oxidation rate of aluminum powder. Our results emphasize the erosion of the alumina layer by F atoms, which provides insights into the atomic-scale reaction mechanism between Al and the fluoropolymers. [ABSTRACT FROM AUTHOR]

By using WRF-Chem coupled with a heterogeneous reaction mechanism for sulfate formation, this study investigated the impact of meteorological condition and emission changes on chemical species, atmospheric oxidizing capacity (AOC), and secondary aerosol formation during the COVID-19 lockdown period from 23 January to April 8, 2020, focusing on a severe haze event on 7–14 February. The model with the new sulfate formation scheme reasonably reproduces the spatial-temporal distribution of meteorological variables and chemical species, and significantly improves predictions for both sulfate and SO 2 concentrations, as well as for PM 2.5 , ammonium, and nitrate to some extent. It is found that the adverse meteorological conditions were the main cause for the haze event formation, whereas emission reduction due to the lockdown somewhat decreased PM 2.5 concentration on average in the Beijing-Tianjin-Hebei (BTH) region. Compared with the same period in 2019, increased surface air temperature and relative humidity (RH) and decreased planetary boundary layer height (PBLH) facilitated accumulation of pollutants and formation of secondary aerosols during the haze episode in 2020, whereas the emission reduction due to the lockdown led to decreases in SO 2 , NO 2 , primary PM 2.5 (PPM 2.5), black carbon (BC), primary organic aerosols (POA), nitrate and ammonium concentrations, but increases in O 3 , sulfate and secondary organic aerosol (SOA) concentrations, due to the combined effect of changes in emissions and AOC. Gas and aqueous phase oxidation of SO 2 accounted for approximately 24% of sulfate formation, while the heterogeneous reaction of Mn-catalytic oxidation of SO 2 on aerosol surfaces dominated sulfate formation (76%) during the haze episode in the BTH region. Both adverse meteorological conditions and emission reductions increased heterogeneous sulfate formation rate mainly through altering aerosol surface area (ASA), pH, and Mn2+ concentration. Chemical species varied diversely during the three subperiods before (Period-1, 15–22 January) and during the lockdown (Period-2, 23 January to 5 March and Period-3, 6 March to 8 April) over the BTH. NO 2 concentration firstly decreased and then rebounded, whereas O 3 concentration increased gradually from the Period-1 to Period-3. All aerosols except SOA decreased throughout the lockdown period, whereas SOA peaked in the Period-2 due to its strong sensitivity to increasing AOC. Sulfate concentration decreased from the Period-1 to Period-2, mainly due to more adverse meteorological conditions in the Period-1, although sulfate increased slightly due to increasing AOC in the Period-2. The large difference in the direction and magnitude of species variations during the COVID-19 lockdown indicates the complex interplay among meteorology, emission, and chemistry. The model simulated mean differences in near surface species concentrations between the BASE and EMIS19 cases (BASE minus EMIS19) during the haze period of 7–14 February 2020, representing the impact of emission reduction due to the COVID-19 lockdown on the chemical species. The units for PM 2.5 and aerosol components are μg·m−3, and the units for SO 2 , NO 2 , and O 3 are ppb. [Display omitted] • Heterogeneous sulfate formation by Mn-catalytic reaction was coupled into WRF-Chem. • Haze event during the COVID lockdown was caused by adverse meteorological conditions. • Emission reduction led to a decrease in PM 2.5 in Beijing but increases in portions of the BTH. • Sulfate and SOA increased but nitrate decreased in the BTH in response to the lockdown. [ABSTRACT FROM AUTHOR]

The presence of antibiotics in the environment causes increasing attention due to their potential risks to ecosystems and public health. Laccases are versatile oxidases capable of degrading various organic contaminants including pharmaceuticals. However, the performance of bacterial laccases on tetracycline antibiotics (TCs) degradation is seldom investigated. In this work, a bacterial laccase from Bacillus amyloliquefaciens was immobilized as laccase-inorganic hybrid nanoflowers (Lac-hNFs) by a facile and rapid method. The immobilized laccase was employed to remove different TCs including tigecycline, which is a third-generation TC that its degradation by laccase has not been reported. Lac-hNFs were synthesized by sonication-mediated self-assembly of laccase and copper ions in 5 min at room temperature. About 95% of laccase could be encapsulated in the nanoflowers, and the obtained Lac-hNFs exhibited great enhancement in stability under harsh conditions. The immobilized laccase showed a half-life of 11.7 h at 60 °C, which was about 1.4-fold higher than that of the free enzyme. Meanwhile, Lac-hNFs retained 81% of the initial activity after incubation at 25 °C for 10 days. The laccase in combination with acetosyringone could efficiently decompose tetracycline, doxycycline, and tigecycline. More than 79% of the three TCs were transformed in 1 h. Compared with the free enzyme, Lac-hNFs demonstrated higher capacity in the removal of TCs. Furthermore, Lac-hNFs remained their high degradation capacity after five cycles of reuse. Bacterial growth inhibition test revealed that most of the toxicity of TCs was eliminated after Lac-hNFs treatment. The main transformation products were identified by LC-MS, and the possible degradation pathways were proposed. The interaction mechanism between laccase and TCs was also analyzed using molecular docking. This work provides an efficient way to remove toxic organic pollutants. [ABSTRACT FROM AUTHOR]

In this study, the effect of anthropogenic heat release (AHR) on meteorological variables and atmospheric diffusion capability and implication for haze pollution in the Beijing-Tianjin-Hebei region in January 2013 were investigated by using Weather Research and Forecasting (WRF) model with an urban canopy model (UCM) and an AHR scheme. The comparison with observation demonstrated the WRF/UCM model taking AHR into account apparently improved meteorological prediction, especially for surface air temperature at 2 m (T2). The model also exhibited a better performance for planetary boundary layer (PBL) height. This study revealed that AHR from cities exerted a significant impact on meteorology by generally increasing surface air temperature and wind speed, decreasing relative humidity, and elevating PBL height and near surface turbulent kinetic energy (TKE), which could consequently reduce surface pollutant concentration and mitigate haze pollution by enhancing atmospheric instability and turbulent mixing and reducing aerosol hygroscopic growth. [ABSTRACT FROM AUTHOR]

The horizontal and vertical distributions of aerosol extinction coefficient (AEC) and mass concentration over east China in October 2010 were investigated by using an online-coupled regional climate model and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) data. Model performance was evaluated comprehensively against ground observations of meteorological variables and PM 10 concentrations and CALIPSO retrieved AEC profiles, which demonstrated a good ability of the model in simulating spatial distribution and evolution of aerosol concentration and optical properties. Severe pollution episodes were found over wide areas of east China during the study period, with the maximum mean PM 10 concentration exceeding 200 μg m −3 in the Chongqing district and a part of the lower reaches of the Yellow River on 8–10 October. Both CALIPSO retrievals and model simulations revealed high AEC values (≥1 km −1 ) often occurred within 2 km above ground over most areas of east China. AEC vertical profile in or in the vicinity of China major cities along CALIPSO orbit track exhibited two typical features: one was AEC reached its maximum (∼4 km −1 ) near the surface (<200 m) and decreased rapidly to < 0.1 km −1 at altitudes above 1 km, another one was AEC peaked at higher altitudes of about 0.5–1 km with a maximum up to 3 km −1 . AEC vertical profile was strongly dependent on vertical distribution of both aerosol concentration, composition and relative humidity. The vertical cross sections over typical regions of east China exhibited a decreasing AEC in magnitude from the continent to the China seas. Over the continent, AEC was either maximum near the surface or peaked at higher altitudes (0.5–1.0 km) due to increases of relative humidity or aerosol concentration in those regions, whereas over the seas of China, AEC profile was characterized by peak values at an altitude around 1 km, mainly due to an elevated relative humidity there, which favored rapid aerosol hygroscopic growth and consequently AEC increase. [ABSTRACT FROM AUTHOR]

A regional air quality model system (RAQMS), coupled with a biogenic emission model was applied to investigate the variations of summertime biogenic volatile organic compound (BVOC) emission and secondary organic aerosols (SOA) during 2001–2018 over China. During 2001–2018, evident land use changes occurred, especially in the Sichuan Basin, the Qinling Mountains, and the megacities over east China. Leaf aera index (LAI) increased significantly over the western parts of northeast China, the Qinling Mountains, the North China Plain (NCP), and most areas of south China. The domain-average LAI and BVOC emission increased by 0.2 m2 m−2 (19%) and 3.0 Tg (26%), respectively, over China during 2001–2018, mainly due to the increases in LAI and air temperature. It is found that near surface BSOA concentration increased apparently over China from 2001 to 2018, with the maximum increment exceeded 2 μg m−3 (75%) in the middle reaches of the Yangtze River. The domain-average surface BSOA concentration increased remarkably by 0.44 μg m−3 (41%) over China, resulting from the combined effect of LAI and anthropogenic emission increases, and meteorological change, in which the land use and LAI changes were the dominant driving factors, explaining over 50% of the BSOA increase, while the changes in meteorology and anthropogenic emission contributed almost equally to the remaining BSOA increase. The changes in near surface BSOA concentration (μg m−3) between summer 2001 and 2018 due to (a) land use and LAI changes; (b) meteorology change; (c) anthropogenic emission change; (d) all the above factor changes. [Display omitted] • Summer BVOC emissions and BSOA concentration over China during 2001–2018 are explored. • The domain-average LAI increased by 0.2 m2 m−2 (19%) over China from 2001 to 2018. • BVOC emissions in China increased by 3.0Tg (26%) due to increased LAI and air temperature. • BSOA concentration increased by 0.4 μg m−3 (41%) due to land use, meteorology, and anthropogenic emission variability. [ABSTRACT FROM AUTHOR]

The quantitative study of lignin valorization by H 2 O 2 generated through ORR process on the cathode in [Et 3 NH][HSO 4 ] was performed, that is approximately 20 molecules of H 2 O 2 were needed to produce one molecule of vanillin from lignin depolymerization. [Display omitted] • H 2 O 2 generated through ORR process on cathode in electrolyte of [Et 3 NH][HSO 4 ]. • Application of H 2 O 2 electro-generated in situ to lignin valorization. • About 2 molecules of H 2 O 2 needed for breaking one α-O-4 ether bond in PBP molecule. • About 19.4 molecules of H 2 O 2 required for producing one molecule of vanillin from lignin. Lignin valorization to obtain small aromatic compounds requires selective oxidation to break the linkage bonds among the C9 units in lignin molecules. It has been reported that hydrogen peroxide (H 2 O 2) generated through the oxygen reduction reaction (ORR) on the cathode could be an appropriate oxidizing reagent to depolymerize lignin, but the current efficiency was still unsatisfactory. In this study, a protic ionic liquid [Et 3 NH][HSO 4 ] is used as electrolyte instead of aqueous solution, and the generation rate of H 2 O 2 is determined as 0.0563 mmol cm−2 min−1 and the current efficiency of 79.7 % by the Ti-TPyP colorimetric method. Then using p -benzylethoxyphenol (PBP) as a lignin model compound, it is figured out that approximately-two molecules of H 2 O 2 are consumed for breaking one α-O-4 ether bond. Finally, in the electrolysis of an actual lignin sample, it is evaluated that about 19.4 molecules of H 2 O 2 are needed for producing one molecule of vanillin when taking vanillin as a representative degradation product of lignin. [ABSTRACT FROM AUTHOR]

A Regional Air Quality Model System (RAQMS) with a series of ground observations and satellite retrievals was utilized to investigate haze events in January 2013, in which the observed maximum daily mean surface PM 2.5 concentrations in Beijing exceeded 400 μg m − 3 . The model predicted a monthly mean PM 2.5 concentration of 200–300 μg m − 3 over southern Beijing, Tianjin, and the southern Hebei province, with most aerosols restricted within 500 m above ground. Meteorology played an important role in haze formation. Aerosols were transported into Beijing and Tianjin from the south to the north at altitudes below 1.5 km during haze episodes. Sensitivity simulations revealed that nearly 44% of surface PM 2.5 in Beijing was contributed by local emissions with the remaining 56% coming from surrounding sources in terms of monthly mean and the outside contribution increased to 62% during episode 2, suggesting the important influence of regional trans-boundary transport on Beijing haze pollution. [ABSTRACT FROM AUTHOR]

A volatility basis set approach with chemical aging mechanism has been incorporated into a regional air quality model system (RAQMS) and used to investigate the distribution of organic aerosols (OA) over east China in April 2009, with focus on secondary organic aerosols (SOA) in fine particle and relative contributions from a series of anthropogenic and biogenic VOC precursors. The comparison between the VBS approach prediction and observation at four sites in east China demonstrates a significant improvement in SOA and OA concentrations compared with the traditional two-product model, which predicts very low SOA level. The average value of secondary organic carbon (SOC) for all sites predicted by the VBS approach with chemical aging is 2.8 μgC m −3 , quite close to the estimated value of 3.3 μgC m −3 . The SOC fraction of organic carbon (OC) also increases from just 5% predicted by the two-product model to 33% by the VBS approach with aging, close to the estimated fraction of 32%, suggesting a more realistic and precise representation of SOA formation by the VBS approach. The enhanced SOC prediction further improve OC prediction, reducing the normalized mean bias from −43% to −18%. The VBS approach with aging predicts SOA concentration in PM 2.5 of 5–10 μg m −3 over most parts of east China. The predicted ASOA concentrations vary from 5.0 to 7.5 μg m −3 in the Pearl River Delta, the Yangtze River Delta and the wide areas north of the Yangtze River. BSOA is predicted to be 1.0–2.5 μg m −3 across the regions from southeast China to the middle reaches of the Yangtze River and the Yellow River. Prediction with the VBS approach exhibits that ASOA becomes dominant component of SOA, which is more realistic as compared to the BSOA dominance by the two-product model. The domain-average surface POA and SOA concentrations predicted by the VBS approach with aging over east China are 4.86 μg m −3 and 4.45 μg m −3 , with the SOA fraction of total OA and the ASOA fraction of SOA being 48% and 85%, respectively. This indicates the comparable contributions to OA from SOA and POA, and the predominant contribution of ASOA to SOA over east China in springtime. The mean SOA concentrations over east China produced from aromatics, alkanes, alkenes, isoprene, monoterpene and sesquiterpene are predicted to be 2.44, 0.57, 0.8, 0.17, 0.42 and 0.06 μg m −3 , respectively, which contribute 55%, 13%, 18%, 4%, 9% and 1% of the total SOA. Aromatics are the dominant contributors to SOA formation. [ABSTRACT FROM AUTHOR]

The three-dimensional evolution of an East Asian dust storm during 23–26 April 2009 was investigated by utilizing a regional air quality model system (RAQMS) and satellite measurements. This severe dust storm hit Mt. Tai in east China with daily mean PM10 concentration reaching 1400 μg/m3 and the model captured the PM10 variation reasonably well. Modeled spatial distributions of AOD and vertical profiles of aerosol extinction coefficient during the dust storm were compared with MODIS and CALIPSO data, demonstrating that RAQMS was able to reproduce the 3D structure and the evolution of the dust storm reasonably well. During early days of the dust storm, daily mean dust-induced AOD exceeded 2.0 over dust source regions (the Gobi desert and the Taklamakan desert) and was in a range of 1.2–1.8 over the North China Plain, accounting for about 98% and up to 90% of total AOD over corresponding areas, respectively. The top of the dust storm reached about 8 km over east China, with high dust concentration locating at around 40°N. Dust aerosol below 2 km was transported southeastward off the Gobi desert while dust above 2 km was transported out of China along 40°–45°N. [ABSTRACT FROM AUTHOR]

The ancient guanine nucleotide-binding (G) proteins are a group of critical regulatory and signal transduction proteins, widely involved in diverse cellular processes of all kingdoms of life. YchF is a kind of universally conserved novel unconventional G protein that appears to be crucial for growth and stress response in eukaryotes and bacteria. YchF is able to bind and hydrolyze both adenine nucleoside triphosphate (ATP) and guanosine nucleoside triphosphate (GTP), unlike other members of the P-loop GTPases. Hence, it can transduce signals and mediate multiple biological functions by using either ATP or GTP. YchF is not only a nucleotide-dependent translational factor associated with the ribosomal particles and proteasomal subunits, potentially bridging protein biosynthesis and degradation, but also sensitive to reactive oxygen species (ROS), probably recruiting many partner proteins in response to environmental stress. In this review, we summarize the latest insights into how YchF is associated with protein translation and ubiquitin-dependent protein degradation to regulate growth and maintain proteostasis under stress conditions. [ABSTRACT FROM AUTHOR]

Abstract: The influence of aerosol hygroscopic growth parameterization on aerosol optical depth (AOD) and aerosol direct radiative forcing (ADRF) over East Asia is investigated by using an online coupled regional climate-chemistry/aerosol model (RIEMS-Chemaero) focusing on the period of summer 2006. Three aerosol hygroscopic growth schemes are tested in this study. Model performances are evaluated with ground observations and satellite retrievals. Comparison with observations of aerosol concentration demonstrates that the model is able to reproduce the spatial and temporal variations of aerosol components over East Asia. Model comparison with AOD measurements shows that AOD is best predicted by the aerosol hygroscopic growth scheme developed based on observations in China (Case B), and the aerosol hygroscopic growth affects AOD simulation significantly. In this study, the domain and seasonal mean AOD, ADRF at the top of the atmosphere, and ADRF at the surface over East Asia are estimated to be 0.31, −9W/m2, and −29W/m2 by Case B, respectively. Compared with Case B, the estimations from Case A (scheme from CCM3 radiation package) differ by +71%, +100%, and +17%, respectively, while those from Case C (κ parameterization) differ by −16%, +11%, and −17%. The large differences in AOD and ADRF among cases suggest the necessity to develop appropriate hygroscopic growth parameterization with geographical characteristics in climate model for estimating regional aerosol optical properties and radiative effects. [Copyright &y& Elsevier]

The investigation of hydrological processes is very important for water resource development in karst basins. In order to understand these processes associated with complex hydrogeochemical evolution, a typical basin was chosen in Houzai, southwest China. The basin was hydrogeologically classified into three zones based on hydrogen and oxygen isotopes as well as the field surveys. Isotopic values were found to be enriched in zone 2 where paddy fields were prevailing with well-developed underground flow systems, and heavier than those in zone 1. Zone 3 was considered as the mixture of zones 1 and 2 with isotopic values falling in the range between the two zones. A conceptual hydrological model was thus proposed to reveal the probable hydrological cycle in the basin. In addition, major processes of long-term chemical weathering in the karstic basin were discussed, and reactions between water and carbonate rocks proved to be the main geochemical processes in karst aquifers. [ABSTRACT FROM AUTHOR]

Abstract: An online coupled regional climate-chemistry-aerosol model was utilized to investigate the dust direct radiative feedbacks on dust deflation, transport and meteorological elements in March 2010, when a severe dust storm originated from the Gobi desert near the China–Mongolia border swept across most areas of East Asia during the period of 19–22 March. The predicted meteorology and aerosol concentration agree generally well with observations, and it clearly shows that the predictions of both dust concentration and meteorological elements with dust radiative feedback are closer to observation than that without feedback, suggesting the superiority of on-line coupled model in chemical and climate predictions. The direct radiative forcing by dust aerosol caused significant reductions in ground temperature and wind speed in dust deflation region, with maximums up to −7 °C and −4.0 m s−1, respectively. The reduced wind speed and increased atmospheric stability resulted in smaller dust emission and weakened vertical diffusion, and consequently less dust aerosol in upper levels transported further downwind. While the shortwave radiative forcing dominated over longwave forcing in the daytime, leading to decreases of surface air temperature and wind speed, in the nighttime, the warming effect of longwave forcing dominated, causing increases of air temperature and wind speed up to 1 °C and 1 m s−1, respectively, in the dust deflation region. The variation of meteorology during the dust storm period at a rural site (Yuzhong) downwind of the Gobi desert exhibited an evident decrease in surface air temperature due to the dust radiative forcing. In terms of monthly mean, the dust radiative forcing caused a surface cooling of −0.6 to −1.0 °C over wide areas from west China to northern parts of east China and the Korean peninsula, with maximums in the middle reaches of the Yellow River and portions of northeast China. Concurrently, precipitation decreased by 0.1–0.6 mm day−1 in the middle reaches of the Yangtze River and large areas of north China, and alternating bands of increasing and decreasing precipitation (∼1 mm day−1) occurred in south China. [Copyright &y& Elsevier]

Long-term trends of aerosol concentrations and direct radiative forcings in East Asia have been investigated by adopting an online-coupled regional climate-chemistry-aerosol model (RIEMS-Chemaero) and the IPCC AR5 (the Intergovernmental Panel on Climate Change Fifth Assessment Report) emission inventory with the focus on eastern China. Model evaluation against surface observations of aerosol components demonstrates that the model can reproduce the spatial distribution and temporal variation of aerosol components generally well but tends to under-predict aerosol magnitudes especially for carbonaceous aerosols. Model comparison with aerosol optical depth (AOD) from both satellite retrieval and surface measurement shows that the model is capable of reproducing the distribution feature of AOD reasonably well but tends to under-predict magnitude. North of eastern China and the Sichuan basin are high concentration centres for near-surface anthropogenic aerosols. The domain averaged column burden of inorganic aerosol over East Asia increased from 1850 to 2010 with the peak in 1990 (18.7mg m-2), whereas that in eastern China peaked in 2010 (32.9 mg m-2). The burden of carbonaceous aerosol peaked in 1980 (5.2 mg m-2) in East Asia, but it peaked in 1990 (7.1 mg m-2) in eastern China and then decreased thereafter. Both inorganic and carbonaceous aerosol burdens showed little change during 1990-2000 due to effective emission control in China. AOD values over eastern China increased almost continuously from 1850 to 2010 with the Sichuan basin the high AOD centre. All-sky aerosol direct radiative forcing at the surface (ADRFSRF) is negative over all of East Asia, while radiative forcing at the top of the atmosphere (ADRFTOA) is negative over eastern China but positive over west China. Domain and annual mean ADRFSRF in East Asia peaked in 2000 (-11.9 W m-2), but that in eastern China peaked in 2010 (-17.5 W m-2). Mean ADRFTOA became negative since 1970 and showed the strongest forcing in 1990 (-2.9 W m-2) for East Asia and in 2010 (-4.8 W m-2) for eastern China. Sensitivity simulation shows that anthropogenic emission change plays the dominant role in the variation of aerosol concentration and direct radiative forcing in this region. [ABSTRACT FROM AUTHOR]

Abstract: A new online coupled regional climate-chemistry-aerosol model (RIEMS-Chemaero) has been developed and applied to investigate direct radiative effects of dust aerosol and mixed aerosols over East Asia in March 2010, when an extremely intense dust storm on 19–22 March swept across almost the entire east China including the Pearl River Delta of south China, where little dust storm was observed before. The model results are evaluated against ground observation of PM10 concentration, aerosol optical depth (AOD) from both AERONET measurement and satellite retrieval (MODIS). The comparison demonstrates a good ability of RIEMS-Chemaero in reproducing major features of aerosol spatial distribution and temporal variation, as well as dust evolution during the dust storm period. However, the model tends to generally underpredict AOD at AERONET sites, with larger biases at urban sites than that at rural sites. Dust aerosols exerted a significant impact on radiation energy budget during the dust storm period, with the 4-day mean values of shortwave and longwave radiative forcings at the surface up to −90 W m−2 and +40 W m−2, respectively, over the Gobi desert. The monthly mean net dust radiative forcings at the surface ranged from −9 to −24 W m−2 over the dust source regions, and from −6 to −21 W m−2 over wide downwind areas including the middle and lower reaches of the Yellow River and the Yangtze River and the Yellow Sea. The net dust radiative forcing at TOA varied from near zero to +6.0 W m−2 in large areas of the continent. The monthly mean values of the net direct radiative forcings due to dust, non-dust aerosols and all aerosols (dust + sea salt + anthropogenic aerosols) averaged over the whole domain are estimated to be −3.9 W m−2, −5.6 W m−2 and −9.3 W m−2, respectively, at the surface, and to be +0.9 W m−2, −3.0 W m−2 and −2.0 W m−2, respectively, at TOA, indicating a light dust warming effect and an overall aerosol cooling effect in the springtime over East Asia. In east China, the net radiative forcings due to dust, non-dust aerosols and all aerosols at the surface are enhanced to −8.4 W m−2, −10.2 W m−2 and −18.0 W m−2, respectively, due to both the frequent dust influence and the intensive anthropogenic emissions in this region. The dust forcing accounts for about 42% of the total aerosol forcing at the surface in the domain, implying a potentially important role of mineral dust in radiation budget and regional climate. The semi-direct effect of dust aerosol tends to reduce cloud cover throughout the domain and it is partly responsible for the direct radiative forcings because of the feedbacks among aerosol, radiation, cloud and dynamics. [Copyright &y& Elsevier]

In this study, a regional air quality model system (RAQMS) was applied to investigate the spatial distributions and seasonal variations of atmospheric aerosols in 2006 over East Asia. Model validations demonstrated that RAQMS was able to reproduce the evolution processes of aerosol components reasonably well. Ground-level PM10 (particles with aerodynamic diameter ≤10 µm) concentrations were highest in spring and lowest in summer and were characterized by three maximum centers: the Taklimakan Desert (∼1000 µg m), the Gobi Desert (∼ 400 µg m), and the Huabei Plain (∼ 300 µg m) of China. Vertically, high PM10 concentrations ranging from 100 µg m to 250 µg m occurred from the surface to an altitude of 6000 m at 30°-45°N in spring. In winter, the vertical gradient was so large that most aerosols were restricted in the boundary layer. Both sulfate and ammonium reached their highest concentrations in autumn, while nitrate reached its maximum level in winter. Black carbon and organic carbon aerosol concentrations reached maximums in winter. Soil dust were strongest in spring, whereas sea salt exerted the strongest influence on the coastal regions of eastern China in summer. The estimated burden of anthropogenic aerosols was largest in winter (1621 Gg) and smallest in summer (1040 Gg). The sulfate burden accounted for ∼42% of the total anthropogenic aerosol burden. The dust burden was about twice the anthropogenic aerosol burden, implying the potentially important impacts of the natural aerosols on air quality and climate over East Asia. [ABSTRACT FROM AUTHOR]

Abstract: A Regional Air Quality Model System (RAQMS) is utilized to investigate the spatial and temporal distributions of PM10 concentrations and soil dust aerosol over East Asia in March 2010, when a severe dust storm occurred on 19–23 March. Dust aerosols were primarily generated in Gobi Deserts on 19 March and then swept across vast areas of East Asia. Model results are verified by in-situ observations from 17 Chinese cities, satellite retrievals, as well as lidar measurements in Japan. Validations demonstrate a good skill of RAQMS in representing the distribution and variation of PM10 concentrations and the major features of dust storm evolution. In general, the model performs better in the eastern parts of China than that in the western parts of China. Monthly mean surface PM10 concentrations were above 400 μg m−3 in west China, about 200–400 μg m−3 in north and central China, and below 100 μg m−3 in the remaining parts of China and East Asia. Dust aerosol was the major contributor to PM10 mass concentration during the study period, accounting for more than 80% in west China, 30%–60% in north and central China, and about 20%–40% in south China and the western Pacific regions. The dust storm in March 2010 was unique in its influential extent and transport pathway because it impacted as far as the Pearl River Delta of China, such as Hong Kong. Interannual variability of dust budget is analyzed, showing the dust emission, deposition and atmospheric loading in March 2010 are all larger than those in 2002 and 2006. Of the total dust emission (110.4 Mt), about 68% was redeposited onto the underlying surface by dry and wet deposition processes, and the remaining 32% was suspended in the atmosphere or subject to long-range transport. [Copyright &y& Elsevier]

This study is intended to understand and quantify the impacts of biogenic emissions of volatile organic compounds (VOC) and nitrogen oxides (NO x ) on the formation of tropospheric ozone during summertime in eastern China. The model system consists of the non-hydrostatic mesoscale meteorological model (MM5) and a tropospheric chemical and transport model (TCTM) with the updated carbon-bond chemical reaction mechanism (CBM-IV). The spatial resolution of the system domain is 30 km×30 km. The impacts of biogenic emissions are investigated by performing simulations (36 h) with and without biogenic emissions, while anthropogenic emissions are constant. The results indicate that biogenic emissions have remarkable impacts on surface ozone in eastern China. In big cities and their surrounding areas, surface ozone formation tends to be VOC-limited. The increase in ozone concentration by biogenic VOC is generally 5 ppbv or less, but could be more than 10 ppbv or even 30 ppbv in some local places. The impacts of biogenic NO x are different or even contrary in different regions, depending on the relative availability of NO x and VOC. The surface ozone concentrations reduced or increased by the biogenic NO x could be as much as 10 ppbv or 20 ppbv, respectively. The impacts of biogenic emissions on ozone aloft are generally restricted to the boundary layer and generally more obvious during the daytime than during the nighttime. This study is useful for understanding the role of biogenic emissions and for planning strategies for surface ozone abatement in eastern China. Due to limitations of the emission inventories used and the highly non-linear nature of zone formation, however, some uncertainties remain in the results. [Copyright &y& Elsevier]

Abstract: In this study, MM5 predictions with five PBL parameterizations in combination with three land-surface models (LSMs) are intercompared and evaluated by using a wide variety of observations derived from WMO routine surface weather stations, TRACE-P aircraft experiments, intense radiosonde soundings and satellite measurements. Six scenarios with various PBL schemes and LSMs are designed to investigate the similarities and differences in model predictions. For near-surface variables, all scenarios yield good correlation between prediction and observation for 2m-temperature (T2) and 2m-water vapor mixing ratio (Q2), and relatively poor ones for wind fields. On average, T2 was consistently underpredicted by all scenarios, whereas Q2 was overpredicted by five of the six scenarios. It is found that the application of Noah land-surface model instead of the five-layer soil model is able to enhance the prediction accuracy of Q2. For 10m-wind speed, the GSE scenario (Gayno–Seaman scheme with the five-layer soil model) produces somewhat smaller correlation, but better consistency in magnitude than those of the other scenarios. Model predictions are more consistent for upper air as a result of using FDDA reanalysis nudging and the reducing influence of underlying surface with altitude. All scenarios show the tendencies to underpredict temperature and to overpredict wind speed at altitudes <1km and to underpredict wind speed at altitudes >3km. The correlations for water vapor mixing ratio are much smaller at altitudes >3km than that in the boundary layer. The differences in predicted PBL height among scenarios are large. GSE scenario performs best for phase (correlation), whereas PCX scenario (Pleim–Chang scheme with Pleim–Xiu LSM) produces the best statistics for magnitude of PBL height. Diurnal variation of PBL height over the western Pacific region during the study period is characterized by the typical day and night cycling superimposed by occasional expansion associated with cold front passage. The scenarios similarly predict precipitation spatial variability, but the difference in absolute magnitude is comparatively large among them, even for the scenarios using the same LSM, suggesting the important impact of PBL turbulence parameterization on precipitation. All scenarios predict larger precipitation amount averaged over the entire domain with the exception of GSE scenario. The statistics for satellite estimates are better than those for model predictions, but satellite data tends to underpredict observation by a similar range to that of GSE scenario. In the study period, latent heat fluxes are about twice the sensible heat fluxes over the western Pacific region, with maximum being 300–600 and 100–300Wm−2, respectively. The differences in surface fluxes among scenarios are mainly determined by various LSMs rather than different PBL schemes applied. [Copyright &y& Elsevier]

A regional air quality model (RAQM) has been introduced, evaluated and applied to investigate the behaviors of tropospheric O3 and relevant species in East Asia. Model simulation is performed with an up-to-date monthly emission inventory [Streets, D. G. , Bond, T. C. , Carmichael, G. R. , Fernandes, S. D. , Fu, Q. , He, D. , Klimont, Z. , Nelson, S. M. , Tsai, N. Y. , Wang, M. Q. , Woo, J. -H. And Yarber, K. F. , 2003. An inventory of gaseous and primary emissions in Asia in the year 2000. Journal of Geophysical Research 108 (D21), 8809. Doi:10. 1029/2002JD003093] for March 2001 when extensive experimental data sets were available, including ground-level observations and the TRACE-P (TRAnsport and Chemical Evolution over the Pacific) aircraft experiments, which allow a comprehensive evaluation for this model system. Model validation demonstrates that RAQM is able to represent most of the major processes of chemical species in the troposphere, with model results agreeing with observations reasonably well. Statistical analysis has been conducted for both meteorological parameters (wind speed, temperature and humidity) and chemical components (10 key gaseous species) by comparing with the TRACE-P data sets. At altitudes <5km, the correlations (R) for meteorological parameters are all above 0. 8, with temperature the highest (0. 97). The model produces the highest R for O3 (around 0. 75), followed by CO (0. 66–0. 72) and HO2 (0. 7), and the lowest R for NO x (0. 1–0. 2), with R =0. 4–0. 7 for the remaining species. The model successfully reproduces the major features in chemical transport associated with the Asian outflow and reasonably explains the observed fluctuation in species concentrations at downwind monitoring sites over the western Pacific. [Copyright &y& Elsevier]

Abstract: A regional air quality model (RAQM) has been developed and applied together with an aerosol model to investigate the states and characteristics of wet deposition in East Asia in December 2001. Model simulation is performed with monthly based emission inventory [Streets, D.G., Bond, T.C., Carmichael, G.R., Fernandes, S.D., Fu, Q., He, D., Klimont, Z., Nelson, S. M., Tsai, N.Y., Wang, M.Q., Woo, J.-H., Yarber, K.F., 2003. An inventory of gaseous and primary emissions in Asia in the year 2000. Journal of Geophysical Research 108(D21), 8809] and meteorological fields derived from MM5. Model results are compared with extensive monitoring data including relevant gaseous species and ions in precipitation. The validation demonstrates that this model system is able to represent most of the major physical and chemical processes involved in acid deposition and reproduces concentrations reasonably well, within a factor of 2 of observations in general. The study shows that the regions with pH less than 4.5 are mainly located in southwestern China, parts of the Yangtze Delta, the Yellow Sea and the Korean peninsula, indicating wide regions of acid precipitation in East Asia in wintertime. Japan islands mainly exhibit pH values of 4.5–5.0, whereas over wide areas of northern China, pH values are relatively high (⩾5.0) due to neutralization by alkaline materials such as calcium-laden particles and ammonia, which are more abundant in northern China than that in southern China. While acid rain over most of China is still characterized by sulfur-induced type, considerable areas of eastern China and the western Pacific Rim are found to be more affected by nitric acid than sulfuric acid in acidification of precipitation, which is supposed to result from a combined effect of variations in photochemistry and emission, suggesting the increasing importance of NO x emission in these regions. [Copyright &y& Elsevier]

The impact of biogenic emission on regional ozone and emission control scenarios has been numerically studied through a series of sensitivity model simulations. A typical episode with elevated ozone over eastern China from 12 to 16 August 2001 was investigated by using a tropospheric chemistry and transport model (TCTM), driven by a non-hydrostatic mesoscale model MM5. The meteorological conditions during this period were characterized by high-pressure systems associated with low wind speeds, high temperatures and clear skies. Afternoon ozone concentrations exceeding 80 parts per billion (ppb) occurred over broad areas of eastern China. There is a generally good agreement between simulation and observation, indicating that the TCTM is able to represent major physical and chemical processes of tropospheric ozone and well reproduce the diurnal and day-to-day variability associated with synoptic conditions. The sensitivity analysis reveals a significant influence of biogenic hydrocarbons on regional ozone. Ozone levels are apparently enhanced by biogenic emission over large areas of eastern China. The largest increase up to 30 ppb in daytime average concentration is found in portions of the middle reaches of the Yangtze River, Yangtze Delta and northeast China. However, the response of ozone to biogenic emission varies spatially, showing more sensitivity in polluted areas than that in clean rural areas. The regimes limited by nitrogen oxides (NOx) and volatile organic carbon (VOC) in eastern China are further investigated with respect to biogenic emission. Ozone shows a clear tendency to shift from VOC limitation to NOx limitation as it moves from urban and industrial areas to rural areas. Most of the rural areas in southern China tend to be NOx limited, whereas most of the northern parts of China appear to be VOC limited. By considering biogenic emission, ozone tends to become more NOx limited and less VOC limited, both in extent and intensity, over eastern china. Furthermore, some regions have completely shifted from being VOC limited to being NOx limited. [ABSTRACT FROM AUTHOR]

The number of construction offshore wind turbines (OWTs) is gradually increasing with high clean energy demand and low technology costs. During their service life, a large number of ships will inevitably collide with OWTs, which results in collapse load acting on the OWT foundation. This paper proposes a novel fender for the OWT exposed to extreme collision using the fractal structure, as the first step toward protecting the safety of the OWT structure. The proposed the fractal structure is based by the cartesian circle, which defined by tangent circle theorem, applied to ring protection design. The paper investigates the anti-collision performance of fractal structure fender on the simulated response of the tripod OWT installed in the coastal waters by comparing tradition and fractal structure. Furthermore, the difference of external diameter and different orders are discussed under the collision actions, which are implemented in the LS-DYNA. The results show that with the increase of the order of fractal pores, structure of the first-order fractal pores is good for the fender to absorb enough collision energy and the anti-collision performance of fender increases by the greater mass. • A fender of tripod with fractal structure was proposed. • The circular fractal fender proposed is based on Cartesian circle theorem. • It comes from the two directions to study the anti-collision performance of the fender. [ABSTRACT FROM AUTHOR]

A regional air quality model system (RAQMS) was developed by incorporating an aqueous reaction mechanism for secondary organic aerosol (SOA) formation and primary semi-volatile (SVOC) and intermediate volatile organic compounds (IVOC) precursors to investigate various chemical pathways for SOA formation in the Beijing-Tianjin-Hebei (BTH) region in wintertime. Model comparison against observations demonstrates that the model is able to well reproduce meteorological variables and major aerosol chemical components, and the model improves SOA simulation significantly by including primary S/IVOCs (SVOC + IVOC) and aqueous reactions into the model. SVOC and IVOC emissions were relatively higher over the regions from southern Hebei province to Beijing and Tianjin, with the emission rates up to 0.15 mg m−2 hr−1 and 0.3 mg m−2 hr−1, respectively. The glyoxal (GLY) and methylglyoxal (MGLY) emissions were similar in distribution to those of S/IVOC emissions, with the maximum of 0.08 mg m −2 hr−1. The simulated SOA concentrations exhibited a southwest-northeast belt extending from southern Hebei to Beijing, with the maximum of 35 μg m−3 in southern Hebei province. The average contributions from various precursors or chemical pathways to SOA formation during the study period were estimated, in which AVOCs (anthropogenic VOCs), SVOCs, IVOCs, BVOCs (biogenic VOCs), GLY and MGLY contributed 38.4%, 24.9%, 28.4%, 0.2% and 8.1% of SOA mass concentration, respectively, in the BTH region. The maximum average contribution of GLY and MGLY to SOA reached 16% in southern Hebei province during a severe haze episode. From the clean to haze periods, concentrations of all SOA components apparently increased along with increasing atmospheric stability and weakening dispersion, but the increasing rates of SOA concentration produced by AVOCs and aqueous reactions were larger than those by primary S/IVOCs due to different chemical processes, and the AVOC-produced SOA dominated over the other SOA components during the haze periods. Figure Contributions (%) of various chemical pathways to surface SOA concentration in PM 2.5 during the entire study period (a, e), haze episode 1 (b, f), haze episode 2 (c, g) and haze episode 3 (d, h) in Beijing (a, b, c. d) and in the BTH region (e, f, g, h). Image 1 • Various chemical formation pathways for SOA are explored and quantified. • SOA simulation is remarkedly improved by inclusion of new pathways. • Primary S/IVOC precursors play an important role in SOA formation. • Aqueous uptake of dicarbonyls contributes up to 16% of SOA in haze days. [ABSTRACT FROM AUTHOR]

The model simulated surface mean SOA concentrations produced from (a) AVOCs, (b) SVOCs, (c) IVOCs, (d) aromatics, (e) alkenes and (f) alkanes (unit: μg m−3) during February 20-March 13, 2014 in the BTH region of eastern China. • Evolution of organic aerosols in winter in Beijing is investigated. • SOA simulation is apparently improved by considering S/IVOCs. • The SOA/OA ratio gradually increases from clean days to hazy days. • The SOA increase in haze days results from competing processes. A regional air quality model system (RAQMS) with a volatility basis set approach for secondary organic aerosol (SOA) formation and an emission inventory of semi-volatile (SVOC) and intermediate volatile organic compounds (IVOC) are applied to investigate the distribution and evolution of organic aerosols over the Beijing-Tianjin-Hebei (BTH) region in winter 2014, with focus on Beijing. Model validation demonstrates the model is capable of reproducing meteorological variables and major aerosol components, and the model significantly improves SOA and organic aerosol (OA) simulations by taking S/IVOCs (SVOC + IVOC) and relevant aging processes into account. SVOC and IVOC emissions in the BTH region are estimated to be 0.47 Tg and in a range of 0.09–0.36 Tg, respectively, which are about 18% and 4–14% of the emission amounts of volatile organic compounds (VOCs). The distribution of mean organic aerosols is characterized by a high concentration belt oriented southwest-northeast from southern Hebei to Beijing, with the maximum concentration up to 50 μg m−3 in Beijing and Shijiazhuang. The simulated SOA concentration is comparable in magnitude to primary organic aerosol (POA) concentration, and the SOA/OA ratio is around 50% in most areas of the BTH region. In terms of domain average, the percentage contributions to SOA mass concentration from anthropogenic volatile organic compounds (AVOCs), SVOCs, IVOCs and biogenic VOCs are estimated to be 46.1%, 40.1%, 9.4% and 4.4%, respectively, in the BTH region during the study period, which indicates an important role of S/IVOCs in SOA formation. From clean to haze periods, both POA and SOA concentrations apparently increase, with an increasing (decreasing) trend of the SOA/OA (POA/OA) ratio. SOA dominates over POA in fine organic aerosols during the haze periods. The increase of POA in hazy days is mainly due to the weakened vertical diffusion and accumulation near the surface, whereas the increase of SOA is likely attributed to both the reduced diffusivity and a series of competing chemical processes, in which the decreased photolysis rate by aerosol attenuation tends to decrease SOA concentration by about 6% during the most severe haze day, whereas the lower surface air temperature and higher POA and S/IVOC concentrations in haze days both enhance gas to particle partition, and consequently lead to higher SOA concentration. [ABSTRACT FROM AUTHOR]