Salidroside promotes angiogenesis after cerebral ischemia in mice through Shh signaling pathway.

AIMS: The purpose of this study was to explore the impacts of salidroside on vascular regeneration, vascular structural changes and long-term neurological recuperation following cerebral ischemia and its possible mechanism. MAIN METHODS: From Day 1 to Day 28, young male mice with middle cerebral artery blockage received daily doses of salidroside and measured neurological deficits. On the 7th day after stroke, the volume of cerebral infarction was determined using TTC and HE staining. Microvascular density, astrocyte coverage, angiogenesis and the expression of the Shh signaling pathway were detected by IF, qRTPCR and WB at 7, 14 and 28 days after stroke. Changes in blood flow, blood vessel density and diameter from stroke to 28 days were measured by the LSCI and TPMI. KEY FINDINGS: Compared with the dMACO group, the salidroside treatment group significantly promoted the recovery of neurological function. Salidroside was found to enhance cerebral blood flow perfusion and reduce the infarct on the 7th day after stroke. From the 7th to the 28th day after stroke, salidroside treatment boosted the expression of CD31, CD31+/BrdU+, and GFAP in the cortex around the infarction site. On the 14th day after stroke, salidroside significantly enhanced the width and density of blood vessels. Salidroside increased the expression of histones and genes in the Shh signaling pathway during treatment, and this effect was weakened by the Shh inhibitor Cyclopamine. SIGNIFICANCE: Salidroside can restore nerve function, improve cerebral blood flow, reduce cerebral infarction volume, increase microvessel density and promote angiogenesis via the Shh signaling pathway.

STZ-induced diabetes exacerbates neurons ferroptosis after ischemic stroke by upregulating LCN2 in neutrophils.

Diabetic is a major contributor to the unfavorable prognosis of ischemic stroke. However, intensive hypoglycemic strategies do not improve stroke outcomes, implying that diabetes may affect stroke outcomes through other ways. Ferroptosis is a novel programmed cell death pathway associated with the development of diabetes and ischemic stroke. This study aimed to investigate the effect of streptozotocin (STZ)-induced diabetes on ferroptosis after stroke from the immune cell perspective, and to provide a theoretical foundation for the clinical management of ischemic stroke in patients with diabetes. The results revealed that STZ-induced diabetes not only facilitates the infiltration of neutrophils into the brain after stroke, but also upregulates the expression of lipocalin 2 (LCN2) in neutrophils. LCN2 promotes lipid peroxide accumulation by increasing intracellular ferrous ions, which intensify ferroptosis in major brain cell populations, especially neurons. Our findings suggest that STZ-induced diabetes aggravates ischemic stroke partially by mediating ferroptosis through neutrophil-derived LCN2. These data contribute to improved understanding of post-stroke immune regulation in diabetes, and offer a potentially novel therapeutic target for the management of acute-stage ischemic stroke complicated with diabetes.

Th17 Cells and IL-17A in Ischemic Stroke.

The neurological injury and repair mechanisms after ischemic stroke are complex. The inflammatory response is present throughout stroke onset and functional recovery, in which CD4 + T helper(Th) cells play a non-negligible role. Th17 cells, differentiated from CD4 + Th cells, are regulated by various extracellular signals, transcription factors, RNA, and post-translational modifications. Th17 cells specifically produce interleukin-17A(IL-17A), which has been reported to have pro-inflammatory effects in many studies. Recently, experimental researches showed that Th17 cells and IL-17A play an important role in promoting stroke pathogenesis (atherosclerosis), inducing secondary damage after stroke, and regulating post-stroke repair. This makes Th17 and IL-17A a possible target for the treatment of stroke. In this paper, we review the mechanism of action of Th17 cells and IL-17A in ischemic stroke and the progress of research on targeted therapy.

Ultrafast synthesis of halogen-doped Ru-based electrocatalysts with electronic regulation for hydrogen generation in acidic and alkaline media.

Developing a facile and time-saving method for preparing hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts can accelerate the practical applications of hydrogen energy. In this study, halogen (X = F, Cl, Br and I) doped Ru-RuO2 on carbon cloth (CC) (X-Ru-RuO2/MCC) was synthesized via an ultrafast microwave-assisted method for 30 s. Particularly, the doped Br (Br-Ru-RuO2/MCC) significantly improved the electrocatalytic performances of the catalyst through the regulation of electronic structures. Then, the Br-Ru-RuO2/MCC catalyst featured HER overpotentials of 44 mV and 77 mV in 1.0 M KOH and 0.5 M H2SO4, and the OER overpotential of 300 mV at 10 mA cm-2 in 1.0 M KOH. This study provides a novel method for developing of halogen-doped catalysts.

Identification and characterization of biocontrol agent Lysinibacillus boronitolerans P42 against Cerrena unicolor that causes root rot of arecanut palm.

The arecanut palm is one of the most important industrial crops in tropical area around the world. The root rot of arecanut palm, which is caused by Cerrena unicolor, has led to heavy economic losses and restricted greatly the development of arecanut industry, especially in Hainan province of China. The common use of chemical agents has worsened the problems of the emergence of resistant pathogens and the pollution of agricultural environment. This study aims to screen and identify a more effective and environment friendly biocontrol method for the prevention and treatment of root rot of arecanut palm. The mycelium growth rate is investigated to select antagonistic bacteria from tropical crop rotation fields which show improved resistance against soil-borne pathogens, and the strain P42 is revealed with the strongest antagonistic effects (82.18%). Based on 16 s rDNA sequence analysis, the strain P42 is identified as Lysinibacillus boronitolerans. In vitro antimicrobial activity shows that the strain P42 exhibits broad-spectrum antagonistic activity against a wide variety of tropical agricultural fungal pathogens, including Cerrena unicolor, Magnaporthe oryzea, Botryodiplodia theobromae, Neoscytalidium dimidiatum, Thanatephorus cucumeris, Fusarium oxysporum, and Botrytis cinerea Per.. The antagonistic activity of the culture of P42 is tolerant to common proteases, longer storage time, and temperature range of 40-121 °C; and is significantly influenced by alkaline (7-9) and acidic (1-2) pH, as well as by ultraviolet ray treatment for more than 30 min. The investigation on the antagonistic activity of the crude extract of fermentation filtrate indicates that the active compounds might be lipopeptides, polyketones, or proteins. To our knowledge, this is the first report of L. boronitolerans as potential bio-reagents for controlling root rot of arecanut palm caused by Cerrena unicolor.

[Discussion of Air Quality Forecasting Evaluation for Cities Based on Half-level Method].

Ambient air quality forecasting evaluation plays an important role in improving forecasting capability. In order to provide better support for refined air quality management, with reference to the UK air quality forecasting evaluation method, this study divided six air quality index (AQI) levels into 12 half-levels and explored AQI, PM2.5, and O3-8h concentration forecasting evaluation based on the half-level method in "2+26" cities during 2020. Comparison with the AQI range forecasting and AQI level range forecasting evaluation showed that the half-level forecasting evaluation method could combine these two indicators into one, providing feasibility and application value in operational air quality forecasting evaluation. Specific half-level forecasting evaluation showed that the forecasting effect of AQI and O3-8h concentration at the low and high levels was significantly worse than that of the middle levels in "2+26" cities. The forecasting effect of the PM2.5 concentration was relatively stable in different half-levels. The monthly variation curves of AQI, PM2.5, and O3-8h concentration forecasting accuracy exhibited a bimodal pattern, first rising and then falling and a flat pattern, respectively. The overestimate of PM2.5 concentration forecasting was significant in each month. The accuracy gaps of AQI and O3-8h concentration forecasting in different cities was relatively small; however, the PM2.5 concentration forecasting accuracy fluctuated greatly. The AQI forecasting accuracies of Beijing and Tianjin were higher than that of neighboring provinces. Additionally, the PM2.5 and O3-8h concentration forecasting effects in Beijing and Henan province were relatively the best.

Control mechanisms in voluntary versus mandatory language switching: Evidence from ERPs.

The present study measured event-related potentials (ERP) and behavioral performance to examine whether inhibitory control is involved in voluntary language switching, and if so, to explore the differences in inhibitory control between voluntary and mandatory language switching. Unbalanced Chinese-English bilinguals completed two picture naming tasks: one involving mandatory language switches and one in which participants could voluntarily switch between the two languages. Behavioral data showed significant switch costs and a reversed language dominance effect in both switching tasks. Critically, both effects were larger in mandatory compared to voluntary switching. ERP results revealed that neural switch costs during mandatory switching was significantly different than voluntary switching in both N2 and LPC amplitudes. In contrast, a significant difference in the reversed language dominance effect between both tasks was only observed in LPC amplitude. Together, these findings suggest the involvement of inhibitory control in both mandatory and voluntary language switching, but the degree of inhibition and the time-course of control processes between both tasks appear to be distinct.

Transcriptome analysis reveals candidate genes involved in multiple heavy metal tolerance in hyperaccumulator Sedum alfredii.

Sedum alfredii Hance is a perennial herb native to China that can particularly be found in regions with abandoned Pb/Zn mines. It is a Cd/Zn hyperaccumulator that is highly tolerant to Pb, Cu, Ni, and Mn, showing potential for phytoremediation of soils contaminated with multiple heavy metals. A better understanding of how this species responds to different heavy metals would advance the phytoremediation efficiency. In this study, transcriptomic regulation of S. alfredii roots after Cd, Zn, Pb, and Cu exposure was analyzed to explore the candidate genes involved in multi-heavy metal tolerance. Although Zn and Cd, Pb and Cu had similar distribution patterns in S. alfredii, distinct expression patterns were exhibited among these four metal treatments, especially about half of the differentially expressed genes were upregulated under Cu treatment, suggesting that it utilizes distinctive and flexible strategies to cope with specific metal stress. Most unigenes regulated by Cu were enriched in catalytic activity, whereas the majority of unigenes regulated by Pb had unknown functions, implying that S. alfredii may have a unique strategy coping with Pb stress different from previous cognition. The unigenes that were co-regulated by multiple heavy metals exhibited functions of antioxidant substances, antioxidant enzymes, transporters, transcription factors, and cell wall components. These metal-induced responses at the transcriptional level in S. alfredii were highly consistent with those at the physiological level. Some of these genes have been confirmed to be related to heavy metal absorption and detoxification, and some were found to be related to heavy metal tolerance for the first time in this study, like Metacaspase-1 and EDR6. These results provide a theoretical basis for the use of genetic engineering technology to modify plants by enhancing multi-metal tolerance to promote phytoremediation efficiency.

An in situ generated 3D porous nanostructure on 2D nanosheets to boost the oxygen evolution reaction for water-splitting.

Efficient oxygen evolution reaction (OER) electrocatalysts can accelerate the reaction kinetics of water-splitting for large-scale hydrogen generation. In this work, 2D nanosheets decorated with a 3D porous nanostructure, including Fe, Co and Ni elements, are developed via anodic cyclic voltammetry scanning (ACVs) in the presence of sodium sulfide (FeCoNi-NS-ACVs). The formed 2D nanosheets provide metal ions during ACVs to generate a 3D porous structure and also construct a hierarchical morphology to favor the transport of the electrolyte and release of produced gas bubbles. What's more, the developed FeCoNi-NS-ACVs possesses superhydrophilic and excellent electroconductivity properties. Benefiting from the above merits, FeCoNi-NS-ACVs exhibits excellent electrocatalytic performances for the OER with low overpotentials of 170 mV and 198 mV to drive 50 mA cm-2 and 100 mA cm-2, respectively, with a small Tafel slope of 64 mV dec-1 and remarkable durability over 50 h. Moreover, the FeCoNi-NS-ACVs also exhibits outstanding electrocatalytic activity and stability toward overall water-splitting.

Heterostructure of RuO2 -RuP2 /Ru Derived from HMT-based Coordination Polymers as Superior pH-Universal Electrocatalyst for Hydrogen Evolution Reaction.

Searching for Pt-like activity, stable and economic electrocatalysts that can function at various pH values for the hydrogen evolution reaction (HER) is under increasing interest for the scientific community as H2 is a very promising energy carrier with great potential development value for renewable energy conversion. Herein, a unique self-supported heterostructure of RuO2 -RuP2 /Ru on the N, P co-doped carbon matrix (Ru-HMT-MP-7) is demonstrated, which is derived from HMT-based coordination polymers as superior pH-universal electrocatalysts. In the strategy, pyrolysis and phosphating processes are simultaneously proceeded that can produce the unique heterostructure containing three phases of RuO2 , RuP2, and Ru, at the same time the generated RuO2 -RuP2 /Ru can be highly dispersed on the self-assembly N, P co-doped carbon substrates. The resulting heterostructure Ru-HMT-MP-7 exhibits excellent activity superior to that of benchmark Pt/C with low overpotentials at 10 mA cm-2 (33 mV for 1.0 M KOH, 29 mV for 0.5 M H2 SO4 and 86 mV for 1.0 M PBS) and long-term electrocatalysis durability toward HER at various pH values. The rational construction strategy paves a novel avenue for obtaining superior pH-universal catalysts for electrochemical energy storage and conversion.

[Comparison and Analysis of PM2.5 Forecast in Key Areas Based on the Neural Network Model and Numerical Model].

The PM2.5 forecast models of 95 cities in Beijing-Tianjin-Hebei and its surrounding cities (BTH); the Fenwei Plain (FWP); the border area of Jiangsu, Anhui, Shandong, and Henan (JASH); and the Yangtze River Delta (YRD) regions were established using BP neural network models, and the forecast was carried out for the next seven days in the autumn and winter in 2020. By comparing the forecast results of the BP neural network models, numerical model, and artificial correction, the PM2.5 forecast effects of the three methods were analyzed and evaluated. The results showed:① The performance of the short-term forecast based on the BP neural network was relatively good but was reduced in the medium and long term and systematically overestimated in four regions. The numerical model effects were lower than those of the BP neural network models. ② The accuracy rates of the PM2.5 forecast concentration by the three methods were generally low in the four regions, with an average of less than 50%, and the accuracy values in order from high to low were the BP neural network models, artificial correction, and the numerical model. The accuracy rates of IAQI levels of PM2.5 were significantly improved by the three methods, and the averages were above 65% in the first four days. The effects of the BP neural network models and artificial correction were similar, which were generally higher than those of the numerical model. ③ The numerical model had good effects in the BTH, JASH, and YRD regions, whereas it was the worst when forecasting moderately and above-polluted days in the FWP region. The BP neural network model had a good performance when forecasting short-term PM2.5 in the BTH, JASH, and FWP regions, whereas it was poor in the YRD region. In general, the performance of artificial correction was relatively good when forecasting moderate-level days and was close to the BP neural network model when forecasting heavily polluted days.

N, P-doped carbon supported ruthenium doped Rhenium phosphide with porous nanostructure for hydrogen evolution reaction using sustainable energies.

Developing efficient and cost-effective catalysts for hydrogen evolution reaction (HER) is vital to hydrogen energy's commercial applications. In this study, N,P-doped carbon supported ruthenium (Ru) doped triruthenium tetraphosphide (Re3P4) (Ru-Re3P4/NPC) with porous nanostructure is prepared using the low-toxic melamine phosphate as the carbon and phosphorous source. The in-situ generated N,P-doped carbon layers play a pivotal role in regulating the electrocatalytic activity by avoiding the aggregation of the nanoparticles and increasing the specific surface area. Moreover, Ru doping contributes to the remarkable electrocatalytic performance of the prepared nanomaterials. Impressively, the as-synthesized Ru-Re3P4/NPC presents remarkable electrocatalytic performances toward HER with small overpotentials of 39 mV, 115 mV, and 88 mV to deliver 10 mA cm-2 in alkaline, neutral, and acidic media. Moreover, the prepared electrocatalyst can drive water-splitting with a small potential of 1.45 V@10 mA cm-2 and use sustainable energies, including solar, wind, and thermal, as electric resources. This work paves a novel and valuable way to enhance the electrocatalytic performances of metal phosphides.

Facile Synthesis of MoP-RuP2 with Abundant Interfaces to Boost Hydrogen Evolution Reactions in Alkaline Media.

Exploiting efficient electrocatalysts for hydrogen evolution reactions (HERs) is important for boosting the large-scale applications of hydrogen energy. Herein, MoP-RuP2 encapsulated in N,P-codoped carbon (MoP-RuP2@NPC) with abundant interfaces were prepared via a facile avenue with the low-toxic melamine phosphate as the phosphorous resource. Moreover, the obtained electrocatalyst possessed a porous nanostructure, had abundant exposed active sites and improved the mass transport during the electrocatalytic process. Due to the above merits, the prepared MoP-RuP2@NPC delivered a greater electrocatalytic performance for HERs (50 mV@10 mA cm-2) relative to RuP2@NPC (120 mV) and MoP@NPC (195 mV) in 1 M KOH. Moreover, an ultralow potential of 1.6 V was required to deliver a current density of 10 mA cm-2 in the two-electrode configuration for overall water splitting. For practical applications, intermittent solar energy, wind energy and thermal energy were utilized to drive the electrolyzer to generate hydrogen gas. This work provides a novel and facile strategy for designing highly efficient and stable nanomaterials toward hydrogen production.

First Report of Grammothele lineata Causing Stem Rot of Areca catechu in Hainan Province, China.

Areca catechu L. (areca) belongs to the Arecaceae family, which is composed of 181 genera and 2,600 species (Christenhusz and Byng 2016), is cultivated extensively in Southern and Southeastern Asia (Peng et al. 2015). Areca has a long history for its important economic and medicinal benefits and is one of the most important commercial crops in Hainan province, China. In recent years, root rot and stem rot diseases have occurred, causing areca plants to wither and even die. The serious symptoms mainly appeared in the Hainan province (Li et al. 2006). In March 2018, the rotten tissues of the diseased plants were observed to become brittle, brown, and even black from the stem base to the root; the outer leaves turned yellow, dry, and dropping in areca plantations of Qionghai county. The disease can spread from individual plants to the whole plantation in one to two years, with the characteristics of large-scale occurrence and rapid transmission, causing huge economic losses. Diseased tissues (5 × 5 mm) were disinfected with 75% ethanol for 30 s, 1% HgCl2 for 1 min, washed in sterile water, placed on potato dextrose agar (PDA) medium and incubated at 28°C (Gao et al. 2019). Pure isolates were obtained by transferring the mycelium around the diseased tissues to PDA several times. The colonies were white and cottony after culturing for 7 days. The reverse side of the colony was yellowish white. Basidiospores were hyaline, thin-walled, smooth, 1.7-1.8 x 1.6-1.7 µm (n=30) in size and circular or ellipse in shape, in addition to a dimitic hyphal system (Das et al. 2017). For molecular identification, the genomic DNA of the isolate was extracted using the thermolysis method (Zhang et al. 2010). The ribosomal internal transcribed spacer (ITS) region was amplified using the primer pairs ITS1/ITS4 (White et al. 1990), and the amplified DNA fragments were sequenced. The obtained ITS sequence (GenBank accession No. MW534416) had 99.36% identity with the reference sequence (GenBank accession No. KX013157) of Grammothele lineata Berk. & M.A. Curtis. A phylogenetic tree was constructed with software MEGA7 using the neighbor-joining method, showing that the isolate was grouped in the same clade as G. lineata. To fulfil Koch's postulates, a pathogenicity test was performed using the stems of 6-month-old healthy areca seedlings. Stem surfaces were sterilized with 70% ethanol for 30 s, rinsed three times with sterile water, and gently stabbed with a sterile needle, and then inoculated with a 1-cm-diameter colonized PDA disk from a 7-day culture on wounds, moistened with wet cotton, and wrapped with a fresh plastic wrap. Plants inoculated with sterile PDA medium plugs were used as a control. The inoculation assay was carried out twice, with five plants in both control and treatment in each test. After 20 days, the stems of the plants inoculated with the pathogen exhibited rotten symptoms, and the leaves began to become yellow and shrunken, while the control plants had only the surface of the stems discolored slightly and the inner tissue was undamaged. The fungus was re-isolated from the infected stems. Based on the morphological observations and ITS sequence analysis, the isolate was identified as G. lineata. As far as we know, this is the first report of G. lineata causing the stem rot of areca in China.

Suppression of lncRNA SNHG15 protects against cerebral ischemia-reperfusion injury by targeting miR-183-5p/FOXO1 axis.

BACKGROUND: Cerebral ischemia/reperfusion (I/R) injury is a severe complication during the treatment of patients with stroke. It has been shown that the expression of SNHG15 was increased in patients with ischemic stroke (IS). However, the function and regulatory mechanism of SNHG15 in IS remains unclear. METHODS: An oxygen glucose deprivation/reoxygenation (OGD/R) cell model was use to establish an in vitro model of I/R injury. RT-qPCR assay was used to detect the level of SNHG15 in OGD/R-treated SH-SY5Y cells. Meanwhile, middle cerebral artery occlusion (MCAO) was used to establish an in vivo model of cerebral I/R injury. RESULTS: The expression of SNHG15 was upregulated in OGD/R-treated SH-SY5Y cells. Downregulation of SNHG15 during reperfusion reduced cell death in OGD/R-treated SH-SY5Y cells. In addition, SNHG15 knockdown suppressed OGD/R-induced apoptosis in SY-SY5Y cells by attenuating intracellular ROS generation and reducing mitochondrial membrane potential (MMP) lost. In addition, SNHG15 knockdown promoted cell cycle transition in SY-SY5Y cells after OGD/R insult accompany with PI3K/Akt signaling activation. Meanwhile, mechanism investigations suggested SNHG15 knockdown downregulated the expression of FOXO1 through acting as a competitive 'sponge' of miR-183-5p. Most importantly, knockdown of SNHG15 expression in vivo inhibited neuronal apoptosis and decreased infarct area in MCAO rats. CONCLUSION: Thus, the present study indicated that SNHG15 knockdown protected against cerebral I/R injury via targeting miR-183-5p/FOXO1 axis, which may represent a potential therapeutic option for the treatment of cerebral IS.

[Assessment of Emergency Emission Reduction Effect During the Heavy Air Pollution Episodes in Beijing, Tianjin, Hebei, and Its Surrounding Area("2+26" Cities) from October to December 2019].

To evaluate the effect of emergency emission reduction measures during the heavy air pollution episodes in Beijing, Tianjin, Hebei, and its surrounding areas, a scenario simulation method was used. The concentrations of PM2.5, PM10, SO2, NO2, CO, and O3-8h, air quality index (AQI), characteristics of heavy air pollution, and climate and meteorological factors were analyzed using the observation data available from October to December 2019. The 24 h, 72 h, and 144 h prediction results of NAQPMS model were analyzed. The uncertainties of the assessment and model prediction were discussed. The results showed that the average PM2.5 concentration in Beijing, Tianjin, and its surrounding 26 cities ("2+26" cities) from October to December 2019 was 64 µg ·m-3, indicating a decrease of 10 µg ·m-3 as compared with that during the same period in 2018. There were 4 occurrences of regional heavy air pollution episodes, with the average PM2.5 concentration of 156 µg ·m-3 of affected cities. The value of evaluation on meteorological condition index of PM2.5 pollution (EMI) of "2+26" cities ranged from -15.6%-16.8%. The meteorological conditions of 12 cities, including Beijing, Tianjin, and Shijiazhuang, deteriorated as compared with those during the same period in 2018, and the changes ranged from 3.2%-16.8%. However, the emergency emission reduction measures effectively reduced the occurrence of regional heavy air pollution episodes, the peak concentration of PM2.5 was decreased significantly, and no severe regional pollution episode occurred. The daily PM2.5 concentrations reduced by 2% to 9% in Beijing, Shijiazhuang, Baoding, Tangshan, and other cities during a typical heavy air pollution period. The quarterly average concentrations of PM2.5 in the "2+26" cities reduced by 1 to 3 µg ·m-3. The regional emergency emission reduction measures have played an active role in protecting the health of the people and improving the quality of ambient air.

[Heavy Pollution Characteristics and Assessment of PM2.5 Predicted Model Results in Beijing-Tianjin-Hebei Region and Surrounding Areas During November 23 to December 4, 2018].

This study discusses the concentration characteristics of PM2.5 and PM10, as well as pollution meteorology in large-scale and long-term heavy pollution in the Beijing-Tianjin-Hebei region and its surrounding areas from November 23 to December 4, 2018, where the primary pollutants are comprised of PM2.5 and PM10. The monitoring results obtained from ground-based and vehicle-mounted lidars, as well as the HYSPLIT-4 backward trajectory combined with meteorological factors analysis are discussed. The accuracy and uncertainty of the air quality forecast model of NAQPMS, CMAQ, and CAMx during heavy air pollution were analyzed retrospectively. The results show that PM2.5 and sand dust in most cities in the south-central region contribute to severe pollution levels. The hourly peak concentrations of PM10 in Zhangjiakou, Beijing, Shijiazhuang, Handan, and Zhengzhou were 1589, 864, 794, 738, and 766 µg·m-3, respectively. The respective hourly peak concentrations of PM2.5 were 239, 319, 387, 321, and 380 µg·m-3. Ground static pressure field, high humidity, inversion, and other static and stable conditions, as well as sand dust transmitted from the northwest, were important pollution meteorological and weather factors. The monitoring data of ground-based lidar and vehicle-mounted lidar combined with the HYSPLIT-4 backward trajectory analysis showed that the air pollutant transmitted from the Southwest and Southeast during the heavy pollution period was primarily PM2.5. The air pollutant transmitted from the Northwest during the two sand dust processes. Moreover, the model of NAQPMS, CMAQ, and CAMx performed well in forecasting the heavy pollution process in the Beijing-Tianjin-Hebei region and its surrounding areas. However there are slight deviations for some individual cities, related to uncertainty in the meteorological model prediction, atmospheric chemical reaction mechanism, and pollution source list. Furthermore, the reduction in pollution source emissions caused by pollution emergency measures was also one of the main reasons for the overestimation.

[Concentration Characteristics and Assessment of Model-Predicted Results of PM2.5 in the Beijing-Tianjin-Hebei Region in Autumn and Winter].

This paper discusses the concentration characteristics of PM2.5, as well as its relationship with meteorological factors in autumn and winter (from September to the following February), from 2013 to 2018 in the Beijing-Tianjin-Hebei (BTH) region. The accuracy and uncertainty of the air quality forecast models NAQPMS(nested air quality prediction modeling system), CMAQ(community multiscale air quality modeling system), and CAMx (comprehensive air quality model with extensions) were analyzed based on the model-predicted and measured PM2.5 concentration in autumn and winter from 2015 to 2018. The accuracy of NAQPMS, CMAQ, and CAMx during typical heavy air pollution was also tested. Moreover, methods to improve the accuracy of the model forecast were discussed. The results showed that the mean concentrations of PM2.5 in the BTH region were 122, 98, 82, 99, and 65 µg·m-3 in the five autumn and winter periods, respectively. When the air quality index (AQI) exceeded 150 during each autumn and winter, it reached 229, 198, 210, 204, and 180 µg·m-3, respectively. There were 64 occurrences of heavy regional PM2.5 air pollution in autumn and winter from 2013 to 2018. The average duration was longest in the 2013 to 2014 period, and shortest in the 2017 to 2018 period. The peak concentration and average concentration of PM2.5 decreased year on year, except for the period from 2016 to 2017. In autumn and winter, PM2.5 concentration had a relatively close relationship with relative humidity, wind and sunshine duration, compared with a weak relationship with temperature and air pressure. Regional heavy air pollution always happened under the condition of low wind speed(less than 2 m·s-1),higher relative humidity(greater than 65%),and southwest and northeast wind direction. In addition, the heavy air pollution of PM2.5 in BTH in autumn and winter can be effectively forecasted by NAQPMS, CMAQ, and CAMx. The predicted and measured PM2.5 concentration showed a close relationship. The models performed well in forecasting Zhangjiakou, Chengde, and Qinhuangdao, but by contrast overestimated in Tangshan, Shijiazhuang, Baoding, Beijing, and Tianjin. The uncertainty of emission sources, measured and predicted meteorological data, and the atmospheric chemical reaction mechanism may be the main reasons for the overestimate.

[Assessment of Heavy Metals Pollution and Its Health Risk of Atmospheric Dust Fall from East Part of Junggar Basin in Xinjiang].

In order to evaluate the contamination and health risk of heavy metals from atmospheric dust fall in Zhundong opencast coalfield in Xinjiang, samples of atmospheric dust fall were collected from 52 sampling sites covering the entire region and the contents of Zn, Cu, Cr, Pb, Hg and As were tested and analyzed. The contamination was assessed by geo-accumulation index method, and the risk to human health was assessed using the US EPA Health Risk Assessment Model. The results showed that:The contamination of heavy metals from atmospheric dust fall had a significant difference, in the order of Zn > Cr > Cu > As > Pb > Hg, and the average contents were higher than the soil background of Changji. The coefficient of variation of Hg, Cu and As was 381.91%, 99.94% and 97.82%, and human activities had a greater impact on them. The correlation coefficients in 6 heavy metals were complex, the correlation coefficients among Zn-Cu-Cr were more relevant than Hg-As-Pb. The assessment results of geo-accumulation index indicated that the Zn pollution in the atmospheric dust fall should be classified as extreme degree, and that of Cu, Pb, As as between slight and extreme degrees, and Hg as practically uncontaminated. The exposure content of carcinogenic risk and non-carcinogenic risk of the study area had little difference. It was HQCr > HQAs > HQZn > HQPb > HQCu > HQHg, the total non-cancer hazard index was 0.258, the non-cancer hazard indexes were both lower than their threshold values, suggesting that they would not harm the health. The carcinogenic risk hazard indexes were in the order of CRAs > CRCr > CRPb, suggesting that Pb had no cancer risk, while As was the most important carcinogenic factor. The average TCR was 1.95E-05, indicating that the risk was within the limit that human can tolerate.