Investigating the effects of spatial scales on social vulnerability index: A hybrid uncertainty and sensitivity analysis approach combined with remote sensing land cover data.

Investigating the effects of spatial scales on the uncertainty and sensitivity analysis of the social vulnerability index (SoVI) model output is critical, especially for spatial scales finer than the census block group or census block. This study applied the intelligent dasymetric mapping approach to spatially disaggregate the census tract scale SoVI model into a 300-m grids resolution SoVI map in Davidson County, Nashville. Then, uncertainty analysis and variance-based global sensitivity analysis were conducted on two scales of SoVI models: (a) census tract scale; (b) 300-m grids scale. Uncertainty analysis results indicate that the SoVI model has better confidence in identifying places with a higher socially vulnerable status, no matter the spatial scales in which the SoVI is constructed. However, the spatial scale of SoVI does affect the sensitivity analysis results. The sensitivity analysis suggests that for census tract scale SoVI, the indicator transformation and weighting scheme are the two major uncertainty contributors in the SoVI index modeling stages. While for finer spatial scales like the 300-m grid's resolution, the weighting scheme becomes the uttermost dominant uncertainty contributor, absorbing uncertainty contributions from indicator transformation.

Hydrogen Spillover-Driven Dynamic Evolution and Migration of Iron Oxide for Structure Regulation of Versatile Magnetic Nanocatalysts.

Magnetic nanocatalysts with properties of easy recovery, induced heating, or magnetic levitation play a crucial role in advancing intelligent techniques. Herein, we report a method for the synthesis of versatile core-shell-type magnetic nanocatalysts through "noncontact" hydrogen spillover-driven reduction and migration of iron oxide with the assistance of Pd. In situ analysis techniques were applied to visualize the dynamic evolution of the magnetic nanocatalysts. Pd facilitates the dissociation of hydrogen molecules into activated H*, which then spills and thus drives the iron oxide reduction, gradual outward split, and migration through the carbonaceous shell. By controlling the evolution stage, nanocatalysts having diverse architectures including core-shell, split core-shell, or hollow type, each featuring Pd or PdFe loaded on the carbon shell, can be obtained. As a showcase, a magnetic nanocatalyst (Pd-loaded split core-shell) can hydrogenate crotonaldehyde to butanal (26 624 h-1 in TOF, ∼100% selectivity), outperforming reported Pd-based catalysts. This is due to the synergy of the enhanced local magnetothermal effect and the preferential adsorption of -C═C on Pd with a small d bandwidth. Another catalyst (PdFe-loaded split core-shell) also delivers a robust performance in phenylacetylene semihydrogenation (100% conversion, 97.5% selectivity) as PdFe may inhibit the overhydrogenation of -C═C. Importantly, not only Pd, other noble metals (e.g., Pt, Ru, and Au) also showed a similar property, revealing a general rule that hydrogen spillover drives the dynamic reduction, splitting, and migration of encapsulated nanosized iron oxide, resulting in diverse structures. This study would offer a structure-controllable fabrication of high-performance magnetic nanocatalysts for various applications.

Environmental TEM Study of the Dispersion of Au/α-MoC: From Nanoparticles to Two-Dimensional Clusters.

The synthesis of highly dispersed Au nanoclusters that are stable under elevated temperatures in heterogeneous catalysis is challenging. Here, we directly observe a strong metal-support interaction (SMSI)-induced dispersion of Au nanoparticles (NPs) on α-MoC using an environmentally atomically resolved secondary imaging technique. Under a realistic environment, Au NPs flatten and spread out on the α-MoC to form two-dimensional atomic layered clusters. The formed highly dispersed Au/α-MoC catalyst shows excellent stability at 600 °C for 160 h in the reverse water-gas shift reaction. The X-ray photoelectron spectrum and extended X-ray absorption fine structure results show that Au NPs gradually become low-coordination-number cluster species and lose electrons to become Auδ+; these form chemical bonds with the α-MoC support and are responsible for the dispersion behavior. This work provides an insightful understanding of dispersion behavior and promotes the rational design and synthesis of reverse sintering catalysts.

Rapid Charge Transfer Endowed by Interfacial Ni-O Bonding in S-scheme Heterojunction for Efficient Photocatalytic H2 and Imine Production.

Cooperative coupling of H2 evolution with oxidative organic synthesis is promising in avoiding the use of sacrificial agents and producing hydrogen energy with value-added chemicals simultaneously. Nonetheless, the photocatalytic activity is obstructed by sluggish electron-hole separation and limited redox potentials. Herein, Ni-doped Zn0.2 Cd0.8 S quantum dots are chosen after screening by DFT simulation to couple with TiO2 microspheres, forming a step-scheme heterojunction. The Ni-doped configuration tunes the highly active S site for augmented H2 evolution, and the interfacial Ni-O bonds provide fast channels at the atomic level to lower the energy barrier for charge transfer. Also, DFT calculations reveal an enhanced built-in electric field in the heterojunction for superior charge migration and separation. Kinetic analysis by femtosecond transient absorption spectra demonstrates that expedited charge migration with electrons first transfer to Ni2+ and then to S sites. Therefore, the designed catalyst delivers drastically elevated H2 yield (4.55 mmol g-1 h-1 ) and N-benzylidenebenzylamine production rate (3.35 mmol g-1 h-1 ). This work provides atomic-scale insights into the coordinated modulation of active sites and built-in electric fields in step-scheme heterojunction for ameliorative photocatalytic performance.

Frost Durability of Self-Compacting Concrete Prepared with Aeolian Sand and Recycled Coarse Aggregate.

Aeolian sand (AS) and recycled coarse aggregate (RCA) can be reasonably utilized as green materials for concrete modification. The paucity of natural sand and gravel in the construction industry is anticipated to be remedied by the use of these two eco-friendly concrete ingredients. This is incredibly important for environmental protection. Study on the damage law of self-compacting concrete with the addition of AS and RCA (ARSCC) under severely cold conditions is of great significance for the promotion and implementation of this material. In this study, 12 groups of ARSCC specimens were prepared for freeze-thaw cycle experiments, with AS substitution rates of 0, 20%, 40%, and 60% as well as RCA replacement rates of 0, 25%, and 50%. Then, the degradation mechanism of ARSCC freeze-thaw damage was discussed from both macroscopic and microscopic perspectives via mass loss rate (Wn), relative dynamic modulus of elasticity (Pn), bubble spacing factor, and SEM analysis. Finally, the response surface method was utilized to determine the damage variable. A freeze-thaw damage model for ARSCC was developed based on the Weibull distribution and Grey theories. The results showed that the Pn could reflect the evolution law of the internal structure of ARSCC. Appropriate addition of AS to fill the large, harmful pores in RCA would inhibit freeze-thaw damage of ARSCC. The optimum substitution rates of AS and RCA were determined to be 20-40% and 25-50%, respectively. In addition, the values obtained from theoretical damage modeling and experiments were in good agreement. The acquired damage model had the potential to predict ARSCC damage under freeze-thaw cycles.

A Dual-mode Ratiometric Fluorometric and Colorimetric Platform Based on Nitrogen-doped Carbon Dots and o-phenylenediamine for the Detection of Nitrite.

In this study, a dual-mode ratiometric fluorometric and colorimetric platform for the determination of nitrite in pickles was proposed by exquisitely employing the fact that non-fluorescent o-Phenylenediamine (OPD) was oxidized by nitrite under acidic conditions to form fluorescent 2,3-diaminophenazine (DAP) (Em = 575), which meanwhile quench the fluorescent nitrogen-doped carbon dots (N-CDs) at 455 nm, the ratio of fluorescence intensity of DAP to N-CDs (F575/F455) changed with the increase of nitrite accompanied by visible color changes. Thus, nitrite can be quantitatively detected within a wide linear range (10-500 µM) with a low detection limit of 0.45 µM due to the high quantum yield of 39.7% of N-CDs. In addition, the colour of the N-CDs/OPD system changed from transparent to yellow when the nitrite was introduced, enabling colorimetric and on-site visual detection. The detection limit of the colorimetric method was 3.03 µM with a linear range of 10-500 µM. The proposed ratiometric fluorometric method has pleasant selectivity and good immunity to interference.

Mechanistic Insights into Myofibrillar Protein Oxidation by Fenton Chemistry Regulated by Gallic Acid.

Gallic acid (GA, 3,4,5-trihydroxybenzoic acid) is a widely used natural food additive of interest to food chemistry researchers, especially regarding its effects on myofibrillar protein (MP) oxidation. However, existing studies regarding MP oxidation by GA-combined with Fenton reagents are inconsistent, and the detailed mechanisms have not been fully elucidated. This work validated hydroxyl radical (HO·) as the primary oxidant for MP carbonylation; in addition, it revealed three functions of GA in the Fenton oxidation of MP. By coordination with Fe(III), GA reduces Fe(III) to generate Fe(II), which is the critical reagent for HO· generation; meanwhile, the coordination improves the availability and reactivity of Fe(III) under weakly acidic and near-neutral pH, i.e., pH 4-6. Second, the intermediates formed during GA oxidation, including semiquinone and quinone, promoted Fenton reactivity by accelerating Fe catalytic cycling. Finally, GA can scavenge HO· radicals, thus exhibiting a certain degree of antioxidant property. All three functions contribute to MP oxidation as observed in GA-containing meat.

Unearths IFNB1 immune infiltrates in SOP-related ossification of ligamentum flavum pathogenesis.

Background: Ossification of ligamentum flavum (OLF) is a hidden, indolent disease condition with variable unexplained etiology and pathology. Growing evidences show a correlation between senile osteoporosis (SOP) and OLF, but the fundamental relationship between SOP and OLF remains unclear. Therefore, the purpose of this work is to investigate unique SOP-related genes and their potential functions in OLF. Methods: Gene Expression Omnibus (GEO) database was utilized to gather the mRNA expression data (GSE106253) and then analyzed by R software. A variety of methods, including ssGSEA, machine learning (LASSO and SVM-RFE), GO and KEGG enrichment, PPI network, transcription factor enrichment analysis (TFEA), GSEA and xCells were employed to verified the critical genes and signaling pathways. Furthermore, ligamentum flavum cells were cultured and used in vitro to identify the expression of the core genes. Results: The preliminary identification of 236 SODEGs revealed their involvement in BP pathways associated with ossification, inflammation, and immune response, including the TNF signaling pathway, PI3K/AKT signaling pathway and osteoclast differentiation. Four down-regulated genes (SERPINE1, SOCS3, AKT1, CCL2) and one up-regulated gene (IFNB1) were among the five hub SODEGs that were validated. Additionally, they were performed by ssGSEA and xCell to show the relationship of immune cells infiltrating in OLF. The most fundamental gene, IFNB1, which was only found in the classical ossification- and inflammation-related pathways, suggested that it may affect OLF via regulating the inflammatory response. In vitro experiment, we found that IFNB1 expression was dramatically higher in cells cocultured with osteogenic induction than in controls. Conclusion: As far as we are concerned, this is the first observation using transcriptome data mining to reveal distinct SOP-related gene profiles between OLF and normal controls. Five hub SODEGs were ultimately found using bioinformatics algorithms and experimental verification. These genes may mediate intricate inflammatory/immune responses or signaling pathways in the pathogenesis of OLF, according to the thorough functional annotations. Since IFNB1 was discovered to be a key gene and was connected to numerous immune infiltrates in OLF, it is possible that IFNB1 expression has a substantial impact on the pathogenesis of OLF. Our research will give rise to new possibilities for potential therapeutics that target SOP reverent genes and immune-associated pathways in OLF.

Shimia ponticola sp. nov., an aerobic anoxygenic photoheterotrophic bacterium, isolated from surface seawater in the South China Sea.

A Gram-stain-negative marine bacterium, designated as WX04T, was isolated from the South China Sea. The genome of strain WX04T contained a complete photosynthetic gene cluster and is the first identified photoheterotroph of the genus Shimia with high photochemical efficiency (Fv/Fm=0.705±0.010), indicating its diverse metabolic and growth strategies, and unique evolution in the genus Shimia. The genome size of strain WX04T is 3.78 Mbp, and the G+C content is 58.8 %. Its isolate formed pink colonies and the cells were non-flagellated and rod-shaped. Growth was observed at 15-35 °C (optimum, 30 °C), at pH 5.0-11.0 (optimum, pH 7.0) and in the presence of 3-5 % (w/v) NaCl (optimum, 3 %). Both catalase activity and oxidase activity were found to be negative. The 16S rRNA gene sequence analyses revealed that this isolate represents a novel species within the genus Shimia, sharing 96.8 and 95.6% sequence identities with Shimia aestuarii DSM 15283T and Shimia marina DSM 26895T, respectively. The respiratory quinone was ubiquinone-10 (100 %). The primary cellular fatty acids (>5 %) were summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), C18 : 0,C18 : 1 ω7c 11-methyl and C10 : 0 3-OH. The dominant polar lipids of strain WX04T comprised phosphatidylcholine, phosphatidylethanolamine and phosphatidylglycerol. The combined polyphasic data shows that strain WX04T is a novel species within the genus Shimia, which is proposed as Shimia ponticola sp. nov., and the type strain is WX04T (=KCTC 62628T=MCCC 1K02295T).

Nanoengineered Design of inside-Heating Hot Nanoreactor Surrounded by Cool Environment for Selective Hydrogenations.

Catalysts with designable intelligent nanostructure may potentially drive the changes in chemical reaction techniques. Herein, a multi-function integrating nanocatalyst, Pt-containing magnetic yolk-shell carbonaceous structure, having catalysis function, microenvironment heating, thermal insulation, and elevated pressure into a whole is designed, which induces selective hydrogenation within heating-constrained nanoreactors surrounded by ambient environment. As a demonstration, carbonyl of α, ß-unsaturated aldehydes/ketones are selectively hydrogenated to unsaturated alcohols with a >98% selectivity at a nearly complete conversion under mild conditions of 40 °C and 3 bar instead of harsh requirements of 120 °C and 30 bar. It is creatively demonstrated that the locally increased temperature and endogenous pressure (estimated as ≈120 °C, 9.7 bar) in the nano-sized space greatly facilitate the reaction kinetics under an alternating magnetic field. The outward-diffused products to the "cool environment" remain thermodynamically stable, avoiding the over-hydrogenation that often occurs under constantly heated conditions of 120 °C. Regulation of the electronic state of Pt by sulfur doping of carbon allows selective chemical adsorption of the CO group and consequently leads to selective hydrogenation. It is expected that such a multi-function integrated catalyst provides an ideal platform for precisely operating a variety of organic liquid-phase transformations under mild reaction conditions.

Particle Attachment Growth of Au@Ag Core-Shell Nanocuboids.

In the templated synthesis of colloidal core-shell nanoparticles, the monomer attachment growth mechanism has been widely accepted to describe the growth process of shells. In this work, by using advanced transmission electron microscope techniques, we directly observe two alternative particle attachment growth pathways that dominate the growth of Au@Ag core-shell nanocuboids. One pathway involves the in situ reduction of AgCl nanoparticles attached to Au nanorods and the subsequent epitaxial growth of the Ag shell. The other pathway involves the adherence of Ag-AgCl Janus nanoparticles to Au nanorods with random orientations, followed by nanoparticle redispersion and the resulting formation of epitaxial Ag shells on the Au nanorods. The particle-mediated growth of Ag shells is accompanied by the redispersion of surface atoms, tending to form a uniform structure. The validation of the particle attachment growth processes at the atomic scale provides a new mechanistic understanding of core-shell nanostructure synthesis.

Chemical Electron Microscopy (CEM) for Heterogeneous Catalysis at Nano: Recent Progress and Challenges.

Chemical electron microscopy (CEM), a toolbox that comprises imaging and spectroscopy techniques, provides dynamic morphological, structural, chemical, and electronic information about an object in chemical environment under conditions of observable performance. CEM has experienced a revolutionary improvement in the past years and is becoming an effective characterization method for revealing the mechanism of chemical reactions, such as catalysis. Here, we mainly address the concept of CEM for heterogeneous catalysis in the gas phase and what CEM could uniquely contribute to catalysis, and illustrate what we can know better with CEM and the challenges and future development of CEM.

Sub-10 nm Corrugated TiO2 Nanowire Arrays by Monomicelle-Directed Assembly for Efficient Hole Extraction.

Precise synthesis of well-ordered ultrathin nanowire arrays with tunable active surface, though attractive in optoelectronics, remains challenging to date. Herein, well-aligned sub-10 nm TiO2 nanowire arrays with controllable corrugated structure have been synthesized by a unique monomicelle-directed assembly method. The nanowires with an exceptionally small diameter of ∼8 nm abreast grow with an identical adjacent distance of ∼10 nm, forming vertically aligned arrays (∼800 nm thickness) with a large surface area of ∼102 m2 g-1. The corrugated structure consists of bowl-like concave structures (∼5 nm diameter) that are closely arranged along the axis of the ultrathin nanowires. And the diameter of the concave structures can be finely manipulated from ∼2 to 5 nm by simply varying the reaction time. The arrays exhibit excellent charge dynamic properties, leading to a high applied bias photon-to-current efficiency up to 1.4% even at a very low potential of 0.41 VRHE and a superior photocurrent of 1.96 mA cm-2 at 1.23 VRHE. Notably, an underlying mechanism of the hole extraction effect for concave walls is first clarified, demonstrating the exact role of concave walls as the hole collection centers for efficient water splitting.

Cooperative Coupling of H2 O2 Production and Organic Synthesis over a Floatable Polystyrene-Sphere-Supported TiO2 /Bi2 O3 S-Scheme Photocatalyst.

Cooperative coupling of photocatalytic H2 O2 production with organic synthesis has an expansive perspective in converting solar energy into storable chemical energy. However, traditional powder photocatalysts suffer from severe agglomeration, limited light absorption, poor gas reactant accessibility, and reusable difficulty, which greatly hinders their large-scale application. Herein, floatable composite photocatalysts are synthesized by immobilizing hydrophobic TiO2 and Bi2 O3 on lightweight polystyrene (PS) spheres via hydrothermal and photodeposition methods. The floatable photocatalysts are not only solar transparent, but also upgrade the contact between reactants and photocatalysts. Thus, the floatable step-scheme (S-scheme) TiO2 /Bi2 O3 photocatalyst exhibits a drastically enhanced H2 O2 yield of 1.15 mm h-1 and decent furfuryl alcohol conversion to furoic acid synchronously. Furthermore, the S-scheme mechanism and dynamics are systematically investigated by in situ irradiated X-ray photoelectron spectroscopy and femtosecond transient absorption spectrum analyses. In situ Fourier transform infrared spectroscopy and density functional theory calculations reveal the mechanism of furoic acid evolution. The ingenious design of floatable photocatalysts not only furnishes insight into maximizing photocatalytic reaction kinetics but also provides a new route for highly efficient heterogeneous catalysis.

A PtPdCoCuNi high-entropy alloy nanocatalyst for the hydrogenation of nitrobenzene.

High-entropy alloys (HEAs) with multiple elements in near-equiatomic proportions hold great promise in heterogeneous catalysis because of their exceptional physicochemical properties governed by synergy. Herein, we prepared PtPdCoCuNi HEA nanoparticles via a one-step colloid-based route and tested their catalytic performance for nitrobenzene hydrogenation to aniline. The SiO2 supported PtPdCoCuNi displays 93.9% yield of aniline at 80 °C, which is 2.11 times that of PtPd/SiO2. Even at room temperature, a 47.4% yield of aniline is attained with the PtPdCoCuNi/SiO2 catalyst. DRIFTS experiments indicate formation of isolated Pt and Pd sites after alloying the transition metals and evidence a stronger interaction between the HEA catalyst and nitrobenzene. Both XPS data and DFT calculations disclose charge transfer to Pt and Pd species, which eventually enhance the interaction between nitrobenzene and the isolated metal sites and the hydrogenation activity as well. The experimental and theoretical results shed light on mechanistic understanding of the unique catalytic performance of the HEA nanocatalyst and pave a new avenue to realize the high catalytic performance of nitrobenzene hydrogenation over well-isolated noble metal sites with specific geometries.

Directing the Architecture of Surface-Clean Cu2O for CO Electroreduction.

Tailoring the morphology of nanocrystals is a promising way to enhance their catalytic performance. In most previous shape-controlled synthesis strategies, surfactants are inevitable due to their capability to stabilize different facets. However, the adsorbed surfactants block the intrinsic active sites of the nanocrystals, reducing their catalytic performance. For now, strategies to control the morphology without surfactants are still limited but necessary. Herein, a facile surfactant-free synthesis method is developed to regulate the morphology of Cu2O nanocrystals (e.g., solid nanocube, concave nanocube, cubic framework, branching nanocube, branching concave nanocube, and branching cubic framework) to enhance the electrocatalytic performance for the conversion of CO to n-propanol. Specifically, the Cu2O branching cubic framework (BCF-Cu2O), which is difficult to fabricate using previous surfactant-free methods, is fabricated by combining the concentration depletion effect and the oxidation etching process. More significantly, the BCF-Cu2O-derived catalyst (BCF) presents the highest n-propanol current density (-0.85 mA cm-2) at -0.45 V versus the reversible hydrogen electrode (VRHE), which is fivefold higher than that of the surfactant-coated Cu2O nanocube-derived catalyst (SFC, -0.17 mA cm-2). In terms of the n-propanol Faradaic efficiency in CO electroreduction, that of the BCF exhibits a 41% increase at -0.45 VRHE as compared with SFC. The high catalytic activity of the BCF that results from the clean surface and the coexistence of Cu(100) and Cu(110) in the lattice is well-supported by density functional theory calculations. Thus, this work presents an important paradigm for the facile fabrication of surface-clean nanocrystals with an enhanced application performance.

Designing a Redox Heterojunction for Photocatalytic "Overall Nitrogen Fixation" under Mild Conditions.

Ammonia and nitrates are the most fundamental and significant raw ingredients in human society. Till now, industrial synthetic ammonia by Haber-Bosch process and industrial synthetic nitrates by the Ostwald process have encountered increasingly serious challenges, i.e., high energy consumption, high cost, and environment-harmful gas emissions. Therefore, developing alternative approaches to achieve nitrogen fixation to overcome the inherent deficiencies of the well-established Haber-Bosch and Ostwald processes has fascinated scientists for many years, especially the simultaneous formation of ammonia and nitrate directly from N2 molecules, which has been rarely studied. Herein, a heterojunction-based photocatalytic system is designed to successfully achieve "overall nitrogen fixation," a sustainable and simultaneous conversion of N2 molecules into ammonia and nitrate products under mild conditions. In this heterojunction, interfacial charge redistribution (ICR) promotes selective accumulations of photogenerated electrons and holes in the CdS and WO3 components. As a result, N2 molecules can be activated and reduced to ammonia products with yields of 35.8 µmol h-1 g-1 by a multi-electron process, and synchronously oxidized into nitrate products with yields of 14.2 µmol h-1 g-1 by a hole-induced oxidation coupling process. This work provides a novel insight and promising approach to realize artificial nitrogen fixation under mild condition.

[Spatio-Temporal Characteristics and Potential Source Areas of Seasonal Atmospheric Pollution in Shijiazhuang].

In order to systematically study the transmission characteristics of seasonal and typical pollutants in Shijiazhuang, hourly data of ground-level pollutants(PM2.5, PM10, O3, NO2, SO2, and CO) from 46 state-and provincial-controlled stations, and meteorological(temperature, humidity, and wind speed) data from 17 counties in Shijiazhuang City from December 2018 to November 2019 was analyzed. The interpolation(IDW) and correlation analysis were applied to seasonal and temporal spatial patterns of pollutant concentration. The backward trajectories analysis was performed to explore the seasonal transmission pattern and potential source areas of pollution in Shijiazhuang by combining with the global data assimilation system(GDAS). The results indicate that the different seasons have characteristic pollutants, as follows:spring(PM10, 48.91%), summer(O3, 81.97%), autumn(PM10 and PM2.5, 47.54% and 32.79%), and winter(PM2.5, 74.44%), which are related to the variation of meteorological conditions. Furthermore, the PM10(spring) concentration correlated negatively with the wind speed, presenting a high distribution in the northwest and low in the southeast, with a southerly transmission direction(53.32%). Central and southern Hebei, central and northern Henan, and central Shanxi are the potential sources of pollution(WPCWTij ≥ 160 µg·m-3), impacting western Shandong and northwest Shanxi(WPSCFij ≥ 0.3) with PM10. Moreover, the O3(summer) concentration correlated positively with temperature, and negatively with humidity. The southeast-south(54.24%) is the source direction of the transmission, and the potential source of O3 pollution is an arc area with Shijiazhuang in the center and Cangzhou and Heze as the double wings. Lastly, the PM2.5(autumn and winter) concentration correlated positively with humidity, and the winter concentration shows an increasing gradient from west to east. The trajectories of PM2.5 clustered the source directions:autumn(northeast-southeast, 74.75%), winter(northwest, 55.47%); central and southern Hebei, central and western Shanxi and northern Henan are the concentrated sources of potential pollution(WPCWTij ≥ 180 µg·m-3).

[Seasonal Variation and Source Apportionment of Carbonaceous Species in PM2.5 in Chengde].

In order to study the seasonal variations and pollution sources of carbonaceous species in PM2.5 in Chengde, the concentration of these components was determined in atmospheric PM2.5 samples collected in January, April, July, and October 2019. The change in carbonaceous species were analyzed based on the estimation of the ratio of organic carbon(OC) to elemental carbon(EC), total carbonaceous aerosol(TCA), and secondary organic carbon(SOC). The source of these pollutants was determined by means of the backward trajectory and principal component analysis(PCA). The results showed that the mean mass concentrations of PM2.5, OC, and EC during the sampling period were(31.26±21.39) µg·m-3,(13.27±8.68) µg·m-3, and(2.80±1.95) µg·m-3, respectively. The seasonal variations of PM2.5 were:winter[(47.68±30.37) µg·m-3]>autumn[(28.72±17.12) µg·m-3]>spring[(26.59±15.32) µg·m-3]>summer[(23.17±8.38) µg·m-3], consistent with the trend of total carbon(TC), OC, and EC. The source of OC and EC during winter(R2=0.85) was similar. Based on the ratio of OC/EC, all four seasons were affected by traffic and coal-burning source emissions, and the most affected season by bituminous coal emissions was winter. The average concentration of TCA was(21.38±13.68) µg·m-3, which accounted for 68.39% of PM2.5. The order of secondary conversion rate(SOC/OC) was:spring(54.09%) >autumn(37.64%) >summer(32.91%) >winter(25.43%). The results of the backward trajectory simulation show that the pollutant concentrations carried by air masses are relatively low in spring and summer, and the transport channels of pollutants are southwest in autumn and northwest in winter. The results of the PCA showed that the key to reducing PM2.5 in Chengde is to control emissions from vehicle exhausts, and coal and biomass combustion sources.

Fluorescent whitening agents in Baiyangdian Lake in North China: Analysis, occurrence, distribution and ecological risk assessment.

Fluorescent whitening agents (FWAs) are very important chemical additives that are widely applied in the industrial production field. The history of global FWA production and use spans more than 60 years, but the environmental fate of FWAs has been less reported in the public literature and most studies predate 2000; in addition, the studied FWAs were still limited to FWA71 and FWA351. In this study, the occurrence and distribution of 9 commonly used FWAs in a lake in North China were reported for the first time. We found that 6 target FWAs were prevalent in the lake, and the concentration levels were usually at the ng L-1 level. Decreasing FWA levels with increasing distance from the estuary area were observed in summer. FWA135, FWA185, and FWA367, the most detected 3 FWAs, with the ecological risk at high levels, and ΣRQ >10 were obtained from all the investigated samples, suggesting that all the sampling sites could be considered with certain ecological risk for aquatic life. As a category of heavily and widely used dyes, FWAs in environmental media have been ignored for a long time. Substantial additional research needs to be conducted to determine the environmental behavior and ecological toxicology of FWAs.