[Analysis of the Jumping Characteristics and Influencing Factors of Ozone Pollution in Beijing].

Based on environmental monitoring data and meteorological observation data from 2016 to 2022 in Beijing, combined with backward trajectory clustering and potential source area contribution analysis, the characteristics, meteorological impacts, and potential source areas of ozone (O3) pollution were analyzed. The results showed that there was a total of 41 O3 pollution processes with jumping characteristics in Beijing from 2016 to 2022, with an average of 5.9 times a year. The occurrence time was concentrated in May to July, and the day of the jump (OJD2) was higher than the day before the jump (OJD1). The average value of ρ(O3-8h) was 78.3% higher, and the peak concentration was 78.9% higher. The high O3 concentration zone in the OJD2 region exhibited a characteristic of advancing from south to north. The main reasons for the occurrence of jumped O3 pollution in Beijing could be summarized as local accumulation caused by unfavorable meteorological conditions and regional transmission impact. The occurrence of jump-type ozone pollution was characterized by an increase in southerly wind frequency, temperature rise, pressure decrease, and precipitation decrease. The increase in southerly wind frequency provided conditions for the transport of O3 and its precursors, and rapid photochemical reactions occurred under local high temperatures, with less superimposed precipitation, comprehensively pushing up the ozone concentration level of OJD2. Six air mass transporting pathways were identified through clustering analysis; the air mass from the direction north of OJD2 decreased by 11.2%, whereas the air mass from the south and east directions increased by 6.7% and 4.4%, respectively, with the air masses mainly transmitting over short distances. The ozone concentration corresponding to the south and east directions was relatively high, making a significant contribution to Beijing's pollution. The analysis of potential source areas revealed that the main potential source areas of OJD2 ozone pollution were the central, southern, and eastern parts of Beijing-Tianjin-Hebei, which contributed 82.6% to the pollution trajectory. There was a significant contribution of regional transport during jump-type ozone pollution, and it is necessary to strengthen joint prevention and control in the Beijing-Tianjin-Hebei Region.

The synergistic effect of full-spectrum light therapy and transient immunosuppressants prolonged allotransplant survival.

BACKGROUND: The lifelong administration of immunosuppressants remains its largest drawback in vascularized composite allotransplantation (VCA). Therefore, developing alternative strategies to minimize the long-term use of immunosuppressive agents is crucial. This study investigated whether full-spectrum bright light therapy (FBLT) combined with short-term immunosuppressant therapy could prolong VCA survival in a rodent hindlimb model. METHODS: Hindlimb allotransplantation was conducted from Brown-Norway to Lewis rats, and the rats were divided into 4 groups. Group 1 did not receive treatment as a rejection control. Group 2 received FBLT alone. Group 3 was treated with short-term anti-lymphocyte serum and cyclosporine-A. Group 4 was administered short-term ALS/CsA combined with FBLT for 8 weeks. Peripheral blood and transplanted tissues were collected for analysis. RESULTS: The results revealed median survival time of FBLT alone (group 2) did not increase allograft survival compared to the control (group 1). However, group 4 with FBLT combined with short-term ALS/CsA significantly prolonged median composite tissue allograft survival time (266 days) compared with groups 1 (11 days), 2 (10 days), and 3 (41 days) (p<0.01). Group 4 also showed a significant increase in Treg cells (p = 0.04) and TGF-ß1 levels (p = 0.02), and a trend toward a decrease in IL-1ß levels (p = 0.03) at 16 weeks after transplantation as compared to control Group 1. CONCLUSIONS: FBLT combined with short-term immunosuppressants prolonged allotransplant survival by modulating T-cell regulatory functions and anti-inflammatory cytokine expression. This approach could be a potential strategy to increase VCA survival.

Supercritical Carbon Dioxide Decellularized Bone Matrix Seeded with Adipose-Derived Mesenchymal Stem Cells Accelerated Bone Regeneration.

Large bone fractures with segmental defects are a vital phase to accelerate bone integration. The present study examined the role of supercritical carbon dioxide (scCO2) decellularized bone matrix (scDBM) seeded with allogeneic adipose-derived mesenchymal stem cells (ADSC) as bio-scaffold for bone regeneration. Bio-scaffold produced by seeding ADSC to scDBM was evaluated by scanning electron microscopy (SEM). Rat segmental femoral defect model was used as a non-union model to investigate the callus formation in vivo. Histological analysis and osteotomy gap closure in the defect area were analyzed at 12 and 24 weeks post-surgery. Immunohistochemical expression of Ki-67, BMP-2 and osteocalcin was evaluated to assess the ability of new bone formation scDBM. ADSC was found to attach firmly to scDBM bioscaffold as evidenced from SEM images in a dose-dependent manner. Callus formation was observed using X-ray bone imaging in the group with scDBM seeded with 2 × 106 and 5 × 106 ASCs group at the same time-periods. H&E staining revealed ASCs accelerated bone formation. IHC staining depicted the expression of Ki-67, BMP-2, and osteocalcin was elevated in scDBM seeded with 5 × 106 ASCs group at 12 weeks after surgery, relative to other experimental groups. To conclude, scDBM is an excellent scaffold that enhanced the attachment and recruitment of mesenchymal stem cells. scDBM seeded with ASCs accelerated new bone formation.

Combination of a CD26 Inhibitor, G-CSF, and Short-term Immunosuppressants Modulates Allotransplant Survival and Immunoregulation in a Rodent Hindlimb Allotransplant Model.

BACKGROUND: Recent studies have demonstrated that inhibition of CD26 potentiates stromal cell-derived factor-1α (SDF-1α), promotes tissue regeneration, and suppresses the rejection of organ transplants. This study investigated whether the combination of a CD26 inhibitor (CD26i) with granulocyte colony-stimulating factor (G-CSF) and short-term immunosuppressants modulates vascularized composite tissue allotransplant survival in a rodent orthotopic hindlimb allotransplant model. METHODS: The hindlimb allotransplantation from Brown-Norway to Lewis rats was divided into 4 groups. Group 1 (controls) did not receive any treatment. Group 2 was treated with short-term antilymphocyte serum (ALS) and cyclosporine-A (CsA). Group 3 was administrated CD26i and G-CSF. Group 4 received a combination of CD26i/G-CSF/ALS/CsA. Each subgroup comprised 10 rats. Peripheral blood and sampling of transplanted tissues were collected for immunological and histological analysis. RESULTS: The results revealed that allotransplant survival was found to be significantly prolonged in group 4 with CD26i/G-CSF/ALS/CsA treatment compared with those in the other groups. The interleukin-10 and transforming growth factor-ßl levels, the percentage of CD4+/CD25+/FoxP3+ T cells, as well as the levels of SDF-1α expressions were significantly increased in group 4 compared with those in the other groups. Group 4 revealed a statistical increase in the percentage of donor cells (RT1n) expression in the recipient peripheral blood, and the mixed lymphocyte reaction showed hyporesponsiveness of the T cells to donor alloantigens. CONCLUSION: The combination of CD26i/G-CSF and short-term immunosuppressants prolongs allotransplant survival by inducing immunoregulatory effects and enhancing the percentage of SDF-1α expression. This immunomodulatory approach has great potential as a strategy to increase vascularized composite allotransplantation survival.

Adipose-derived stromal cells modulating composite allotransplant survival is correlated with B cell regulation in a rodent hind-limb allotransplantation model.

BACKGROUND: Our previous studies demonstrated that adipose-derived mesenchymal stromal cells (ASCs) have immunomodulatory effects that prolong allograft survival in a rodent hind-limb allotransplant model. In this study, we investigated whether the effects of immunomodulation by ASCs on allograft survival are correlated with B cell regulation. METHODS: B cells isolated from splenocytes were cocultured with ASCs harvested from adipose tissue from rodent groin areas for in vitro experiments. In an in vivo study, hind-limb allotransplantation from Brown-Norway to Lewis rats was performed, and rats were treated with ASCs combined with short-term treatment with anti-lymphocyte serum (ALS)/cyclosporine (CsA) as immunosuppressants. Peripheral blood and transplanted tissue were collected for further analysis. RESULT: An in vitro study revealed that ASCs significantly suppressed lipopolysaccharide-activated B cell proliferation and increased the percentage of Bregs. The levels of immunoregulatory cytokines, such as TGF-ß1 and IL-10, were significantly increased in supernatants of stimulated B cells cocultured with ASCs. The in vivo study showed that treatment with ASCs combined with short-term ALS/CsA significantly reduced the B cell population in alloskin tissue, increased the proportion of circulating CD45Ra+/Foxp3+ B cells, and decreased C4d expression in alloskin. CONCLUSION: ASCs combined with short-term immunosuppressant treatment prolong allograft survival and are correlated with B cell regulation, C4d expression and the modulation of immunoregulatory cytokines.

Triamcinolone Acetonide Suppresses Keloid Formation Through Enhancing Apoptosis in a Nude Mouse Model.

BACKGROUND: Current understanding of steroid treatments for keloids is in regards to modulation of inflammation, proliferation, and apoptosis, with no in vivo study on the latter. Using a nude mouse model, we investigated whether triamcinolone acetonide (TA) injections induce keloids regression through enhancing apoptosis. MATERIALS AND METHODS: Thirty-six keloid specimens (1 × 1 cm) were harvested from 6 patients and separated into sets of 2 from the same patient: no treatment and intralesional TA injection (0.4 mg/mL/kg) at 8 weeks of postimplantation. One set was implanted in each of 18 randomly selected nude mice, which were separated into 3 groups based on time of keloid harvesting after treatment: group A, 2 weeks; group B, 8 weeks; and group C, 14 weeks. Each group had 1 set of specimen from each patient. Histological staining was performed with hematoxylin and eosin stain. Immunohistochemistry staining was performed for human-prolyl 4-hydroxylase (hPH4) and caspase 3 protein, along with terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. RESULTS: All keloid specimens survived, with no noted overgrowth. Hematoxylin and eosin staining revealed dense extracellular matrix and viable fibroblasts, and hPH4 immunohistochemistry revealed strong expression, demonstrating keloid viability. Caspase 3 protein and TUNEL expressions were significantly increased in the treatment versus control groups, demonstrating that TA injections induced apoptosis. CONCLUSIONS: Triamcinolone acetonide intralesional injections significantly increased apoptosis in keloids, represented by increased caspase 3 protein and TUNEL expressions, supporting that steroids suppress keloids in part owing to enhancement of apoptosis.

[Variation of O3 Concentration in Different Regions of Beijing from 2006-2015].

O3 continuous monitoring data for the Dingling, Guanyuan, Liulihe, and Qianmen sites from 2006-2015 were analyzed to investigate concentration levels, variation trends, temporal variations, and relationships with precursors and meteorological factors. The results showed that the ten year average concentrations of O3 at the Dingling site were the highest at 65.2 µg·m-3, followed by concentrations at Liulihe (53.4 µg·m-3), Guanyuan (49.6 µg·m-3) and Qianmen (40.4 µg·m-3). The O3 concentrations at Dingling showed a decreasing trend[0.5 µg·(m3·a)-1], while O3 concentrations at Guanyuan[0.9 µg·(m3·a)-1], Liulihe[0.3 µg·(m3·a)-1], and Qianmen[0.3 µg·(m3·a)-1] showed an increasing trend. The highest monthly average concentrations appeared during June and August, and the highest frequency occurred in July (17 times) with average concentrations of 99.8 µg·m-3. The lowest monthly average concentrations appeared during November and February, and the highest frequency occurred in January (14 times) with an average concentration of 16.6 µg·m-3. Notably, the time for the peak concentrations of O3 appeared earlier in the day in recent years. The peak concentrations of O3 appeared at 15:00-16:00 during 2013-2015, which was 1-2 hours earlier than previous years. The heavy air pollution of O3 occurred on 11 days at the Dingling site in 2015, which was ten days more than in 2013, indicating O3 pollution in the downwind suburban regions of Beijing in summer became more and more serious. The concentrations of O3 and NO2 at Dingling showed a positive correlation, while the concentrations of O3 and NO2 at the other sites showed a negative correlation, indicating O3 formation in Dingling was sensitive to NO2 chemistry, while O3 formation at the other sites was sensitive to VOC chemistry. The concentrations of O3 showed a positive correlation with temperature and negative correlations with humidity and surface pressure. Temperature had the greatest influence on O3 concentration, followed by surface pressure and humidity. For cases when daily maximum temperature exceeded 30℃ and relative humidity was between 30% and 70%, the probability of the O3 daily maximum 8 h concentration exceeding 200 µg·m-3 was high, indicating the air quality level reached levels for light pollution and moderate pollution.

Psychophysiological Effects of Bamboo Plants on Adults.

The present study was conducted to clarify the psychophysiological relaxation effects of viewing bamboo on university students. Forty healthy Chinese participants enrolled in this study to clarify the psychophysiological relaxation effects of viewing bamboo. The effects of visual stimulation using a pot both with and without a bamboo were recorded by measuring the student's blood pressure, EEG and STAI. We observed that viewing bamboo plants resulted in significantly lower systolic (female, P < 0.001; male, P < 0.001; P < 0.05) and diastolic (female, P < 0.001; male, P < 0.001; P < 0.05) blood pressures, but no changes in the pulse rate (female, P = 0.09; male, P = 0.07; P > 0.05) were observed. The results of the EEG analysis indicated brainwave variation (all P < 0.05) and lower anxiety scores (P < 0.01) after 3 min of viewing bamboo compared with the control. These findings indicate that visual stimulation with bamboo plants induced psychophysiological relaxation effects on adults.

[Analysis of Atmospheric Particulate Matter Pollution Characteristics by LIDAR in Beijing During Spring Festival, 2016].

Real-time aerosol extinction retrieved by Micro-pulse LIDAR and concentrations of PM2.5 and PM10 in Beijing were analyzed to investigate the air quality during the Spring Festival. The results showed that fireworks on the New Year's Eve resulted in a sharp increase in particulate matter concentrations in a short time. The maximum concentration of PM2.5 at Guanyuan station was 639.3 µg·m-3, which increased by nearly 30 times in 9 h. The maximum hourly concentration of particulate matter at Dingling and Liulihe suburban stations were significantly higher than that in Guanyuan station, the maximum values were more than 1000 µg·m-3. The particulate matter levels were continuously high on February 10-12 and the concentration of particulate matter at Dingling and Liulihe suburban stations were higher than that at Guanyuan. LIDAR results showed no obvious changes in the extinction coefficient at Dingling on the New Year's Eve. The extinction coefficient at Liulihe was greater than 1 km-1, but the particulate matter pollution was concentrated at altitudes less than 400 m. The extinction coefficient at Chegongzhuang was still higher than 0.4 km-1 at 500 m; however, the duration of pollution was shorter than that of Liulihe. The extinction coefficients at 105 m at all three stations during the New Year's Eve were significantly higher than those at 405 m. There were significant differences in the vertical extinction characteristics of the three sites. The background maximum values of Dingling, Chegongzhuang, and Liulihe were 0.09 km-1, 0.20 km-1, and 0.19 km-1 under 1.0 km, respectively. The maximum extinction coefficients at 00:00 (midnight) were 0.23 km-1, 1.36 km-1, and 1.19 km-1, which were 2.6 times, 6.8 times, and 6.0 times higher than the background value at the same time, respectively. In summary, discharge of fireworks led to a dramatic increase in the extinction coefficient of particulate matter. Temperature inversion and lower wind speeds were the main meteorological factors that contributed to this pollution event.

[Exploring the Severe Haze in Beijing During December, 2015: Pollution Process and Emissions Variation].

Severe haze episodes shrouded Beijing and its surrounding regions again during December, 2015, causing major environmental and health problems. Beijing authorities had launched two red alerts for atmospheric heavy pollution in this period, adopted a series of emergency control measures to reduce the emissions from major pollution sources. To better understand the pollution process and emissions variation during these extreme pollution events, we performed a model-assisted analysis of the hourly observation data of PM2.5, and meteorological parameters combined with the emissions variation of pollution sources. The synthetic analysis indicated that: (1) Compared with the same period of last year, the emissions of atmospheric pollution sources decreased in December 2015. However, the emission levels of primary pollutants were still rather high, which were the main intrinsic causes for haze episodes, and the unfavorable diffusion conditions represented the important external factor. High source emissions and meteorological factors together led to this heavy air pollution process. (2) Emergency control measures taken by the red alert for heavy air pollution could decrease the pollutants emission by about 36% and the PM2.5 concentrations by 11% to 21%. Though the implementation of red alert could not reverse the evolution trend of heavier pollution, it indeed played an active role in mitigation of PM2.5 pollution aggravating. (3) Under the heavy pollution weather conditions, air pollutants continued to accumulate in the atmosphere, and the maximum effect by taking emergency measures occurred 48-72 hours after starting the implementation; therefore, the best time for executing emergency measures should be 36-48 hours before the rapid rise of PM2.5 concentration, which requires a more powerful demand on the accuracy of air quality forecast.

[Different Air Pollution Situations of O3 and PM2.5 During Summer in Beijing].

Two different pollution situations of O3 and PM2.5 during summer in Beijing were analyzed from theperspective of synoptic situations, meteorological elements, precursors, atmospheric oxidation, back-trajectories of air mass and chemical compositions of PM2.5. The results showed that the synoptic situations in the pollution situation that O3 reached middle level pollution and PM2.5 maintained low concentrations (O3high-PM2.5 low) could be characterized as northwest gas flow in 500 hPa height and high-pressure rear in the ground. Whereas the synoptic situations in the pollution situation that O3 and PM2.5 both reached middle level pollution (O3-PM2.5 high) could be characterized as westerly gas flow in 500 hPa height and low pressure in the ground. Compared with the O3high-PM2.5 low situation, meteorological elements in O3-PM2.5 high situation could be characterized as stronger southerly winds and higher relative humidity. In the O3-PM2.5 high situation, initial concentrations of O3 and PM2.5 were higher and diurnal variations of PM2.5 were more significant, nevertheless, the average concentrations of O3 were lower than those in the O3high-PM2.5 low situation, respectively. The analysis of precursors, atmospheric oxidation and chemical compositions of PM2.5 showed that the accumulation and hygroscopic growth of PM2.5 under unfavorable meteorological conditions as well as the regional transport caused by strong southerly winds might be the main factors leading to high PM2.5 concentrations in O3-PM2.5 high situation.

[Improvement of Air Quality During APEC in Beijing in 2014].

Variations of air quality, meteorological conditions and the effect of pollution control measures on particle matter concentrations in Beijing were all analyzed during APEC (from 1st to 12th in November) in 2014 based on the atmospheric pollutant monitoring data, monitoring components of PM2.5, meteorological and remote sensing data and CMB model. The results showed that the average concentrations of PM2.5, PM10, SO2, NO2 were 43,62,8,46 [g.m respectively during APEC and the average concentrations of PM2.5, PM10, SO2, NO2 were decreased by 45%, 43%, 64% and 31% compared to those in the same period of the last 5 years (PM2. was the average of the last 2 years); the concentrations of PM25 at different sites were decreased by 27.4%-35.5%; the concentrations of PM2.5 in the center of city and northern mountainous areas were the lowest, which dropped by 30%-45% compared to those in the same period of the last 5 years while in the southern area the decrement was below 25%; the main component SO4(2-), the substance of the crust, and NO3- were decreased by 50%, 76%, 35% respectively compared to those in the same period in 2013 and the chemical mass balance (CMB) model analysis results indicated that contributions of coal boiler, dust, motor vehicle were 2%, 7%, 30% respectively during APEC; air pollution control measures (coal, dust and traffic management) had a significant effect on reducing pollutant emissions and the pollutant emissions control reduced the concentration peak and delayed the accumulation speed.

[Characteristics of Ozone Background Concentration in Beijing from 2004 to 2015].

Based on the hourly O3 monitoring data from 2004 to 2015 of Beijing, a comprehensive discussion on the characteristics of O3 concentration at a background station Dingling in Beijing was conducted. The results showed that the annual concentration of O31h was increasing with a growth rate of 4.40 µg·m-3 while the annual concentration of O38h was decreasing with annual average rates of -1.0 µg·m-3 and -1.5 µg·m-3 from May to October in 2004 and 2015. Over the past 3 years, number of O38h severe pollution days increased significantly and the situation of O3 pollution in Beijing became more serious. O3 concentration reached its peak in June in a year and its diurnal peak concentration occurred at about 15:00-18:00 at Dingling station which was 101-1.56 times larger than that in the urban center of Beijing. In different years, the ozone peak concentration at Dingling Station was 1h later than that in the urban center from May to October in diurnal variation and the difference of peak concentration was significantly reduced in recent years, which on the one hand may be related to regional ozone pollution, on the other hand may be related to the expansion of Beijing's urbanization.

[Characteristics of Ozone over Standard and Its Relationships with Meteorological Conditions in Beijing City in 2014].

The spatial-temporal distribution characteristics of O3 and the correlations between O3 and meteorological elements in Beijing urban area were investigated based on the hourly O3 monitoring data from January to December in 2014 released by Beijing Municipal Environmental Monitoring Center. The annual concentration of O3 in Beijing was about 56.18 µg·m-3 in 2014. In the over polluted days during May and September, the O3 concentration could reach as high as 148.05 µg·m-3. The diurnal distribution of ozone presented a clear unimodal pattern with its peak appearing at 15:00 or 16:00 and trough at 06:00 or 07:00 and the concentrations of O3 during 09:00 and 23:00 was significantly higher than those in the Summer time. For the spatial distribution of O3, the concentration was lower in central urban area with the highest concentration appearing at plant garden site in the west of the urban area. Ground weather type of O3 over polluted days was divided into three categories including high-pressure, low-pressure, equalizing field, which accounted for 16%, 36%, 48%, respectively. The concentration of O3 was negatively correlated with the air pressure, humidity and visibility while it was positively correlated with the wind speed and temperature. In one heavy pollution episode of O3 caused by local photochemical pollution and regional transport from May 29th to June 1st in 2014 in Beijing, regional transport showed a very important influence on the concentration of O3 in Beijing.

[Karyotype and evolutionary trend analysis of Scutellaria species in Jinyun mountain, Chongqing].

Traditional squash method was used to analyze chromosome number and karyotypes of four Scutellaria species in Chongqing Jinyun Mountain Natural Reserve： Scutellaria tsinyunensis, S.yunnanensis, S.franchetiana and S.indica.The result showed that the chromosome numbers were 26 except for S.franchetiana, which had 24 chromosomes.These species were all diploid with metacentric and submetacentric chromosomes.Their karyotypes were symmetrical and primitive.The karyotype formula of S.tsinyunensis is 2n=2x=26=24m+2sm, 1B type, As.k=55.28%; the karyotype formula of S.yunnanensis var.salicifolia is 2n=2x=26=26m, 1B type, As.k=56.11%; the karyotype formula of S.franchetiana is 2n=2x=24=20m+4sm, 2B type, As.k=58.50%; the karyotype formula of S.indica is 2n=2x=24=20m+4sm, 2B type, As.k=58.41%.The results were compared with the reported data of S.baicalensis and S.alaschanica.S.alaschanica is expected to be the most advanced one whereas S.tsinyunensis, and S.yunnanensis var. salicifolia primitive.These results are expected to provide some references to the origin and differentiation of genus Scutellaria.

Targeted Mesoporous Iron Oxide Nanoparticles-Encapsulated Perfluorohexane and a Hydrophobic Drug for Deep Tumor Penetration and Therapy.

A magneto-responsive energy/drug carrier that enhances deep tumor penetration with a porous nano-composite is constructed by using a tumor-targeted lactoferrin (Lf) bio-gate as a cap on mesoporous iron oxide nanoparticles (MIONs). With a large payload of a gas-generated molecule, perfluorohexane (PFH), and a hydrophobic anti-cancer drug, paclitaxel (PTX), Lf-MIONs can simultaneously perform bursting gas generation and on-demand drug release upon high-frequency magnetic field (MF) exposure. Biocompatible PFH was chosen and encapsulated in MIONs due to its favorable phase transition temperature (56 °C) and its hydrophobicity. After a short-duration MF treatment induces heat generation, the local pressure increase via the gasifying of the PFH embedded in MION can substantially rupture the three-dimensional tumor spheroids in vitro as well as enhance drug and carrier penetration. As the MF treatment duration increases, Lf-MIONs entering the tumor spheroids provide an intense heat and burst-like drug release, leading to superior drug delivery and deep tumor thermo-chemo-therapy. With their high efficiency for targeting tumors, Lf-MIONs/PTX-PFH suppressed subcutaneous tumors in 16 days after a single MF exposure. This work presents the first study of using MF-induced PFH gasification as a deep tumor-penetrating agent for drug delivery.

[Formation Mechanism of a Serious Pollution Event in January 2013 in Beijing].

The weather conditions, atmospheric environmental background and formation mechanism of a heavy air pollution episode in Beijing City from January 9th to 15th, 2013 was preliminarily investigated by combining observed data and the WRF meteorology model. The results showed that the average concentration of PM2.5 was 323 µg x m(-3) from January 10th to 14th; the heavy pollution episode was closely related to the local meteorological conditions; the stable atmospheric circulation pattern provided favorable environmental field for the lasting of this heavy air pollution; small wind speed, high humidity, low PBL, and lasting temperature inversion were the main reasons for this heavy air pollution incident; further analysis showed that contributions of regional transmission to the receptor sites in Beijing were between 53% - 69% and there were obvious secondary conversions and transformations; overall regional transportation played a more important role during this serious air pollution incident; the meteorological conditions played a key role in the formation and destruction of the heavy air pollution, therefore we need to strengthen the study on early warning of heavy air pollution, in order to prevent and control the air heavy pollution effectively.

[Air Quality Characteristics in Beijing During Spring Festival in 2015].

To analyze the impacts of emissions from fireworks on the air quality, monitoring data of PM2.5, PM10, SO2, NO2 chemical compositions of PM2.5 of automatic air quality stations in Beijing during Spring Festival(February 18th-24th) in 2015 were investigated. Moreover, we also estimated the fireworks on the New Year's Eve produced based on the ratio of PM.5 to CO. Analysis results showed that the concentrations of PM2.5, PM10, SO2, NO2 during 2015 Spring Festival was 116. 85, 184.71, 22. 14, and 36. 27 µg.m-3 respectively, which raised 52. 61%, 92. 41%, - 40. 15%, - 0.46% respectively compared to the same period in 2014; the concentration peaks of PM2.5, PM10, SO2, NO2 at 1 : 00 am on 19th was 412. 69, 541. 63, 152. 73, 51. 09 µg.m-3, respectively, which was increased 19. 02%, 14. 37%, 76. 57%, 11. 35% compared to that of 2014; the concentration peaks at dense population area were significantly higher than that in other districts; fireworks had great influence on the chemical compositions of PM2.5 especially on the concentrations of chloride ion, potassium ion, magnesian ion, which were 18. 85, 66. 72, and 70. 10 times than that in 2013-2014; fireworks resulted in severe air pollution in a short time and the estimated fireworks on the New Year's Eve was approximately 2. 13 x 10(5) kg of PM2.5. Reduction of pollutants during Spring Festival had a positive significant impact on air quality in Beijing.

[PM2.5 Background Concentration at Different Directions in Beijing in 2013].

PM2.5, background concentration at different directions in 2013 in Beijing was analyzed combining the techniques of mathematical statistics, physical identification and numerical simulation (CMAQ4.7.1) as well as using monitoring data of six PM2.5 auto-monitoring sites and five meteorological sites in 2013. Results showed that background concentrations of PM2.5 at northwest, northeast, eastern, southeast, southern and southwest boundary sites were between 40.3 and 85.3 µg · m⁻³ in Beijing. From the lowest to the highest, PMPM2.5 background concentrations at different sites were: Miyun reservoir, Badaling, Donggaocun, Yufa, Yongledian and Liulihe. Background concentration of PM2.5 was the lowest under north wind, then under west wind, and significantly higher under south and east wind. Calculated PM2.5 background average concentrations were 6.5-27.9, 22.4-73.4, 67.2-91.7, 40.7-116.1 µg · m⁻³ respectively in different wind directions. Simulated PM2.5 background concentration showed a clear north-south gradient distribution and the surrounding area had a notable effect on the spatial distribution of PM2.5 background concentration in 2013 in Beijing.

[Analysis About Spatial and Temporal Distribution of SO2 and An Ambient SO2 Pollution Process in Beijing During 2000-2014].

Spatial and temporal distribution of SO2 during 2000-2014 was all analyzed based on the SO2 monitoring data that Beijing Municipal Environmental Monitoring Center released and the formation mechanism of a typical air pollution episode in January 2014 was also investigated by combining numerical model CAM(x). Analysis results showed that mass concentration of ρ(SO2) in Beijing in 2014 decreased 69% compared to that in 2000 with an annual gradient from 2000 to 2014 of - 3.5 µg x (m3 x a)(-1). Monthly average concentration of SO2 changed in a U shape curve and from the lowest to the highest, and seasonal variations of SO2 concentrations were as follows: winter > spring > autumn > summer; concentration of SO2 in heating season was significantly higher than that in non heating season. Annual average concentration of SO2 was lower in northern and western regions while higher in six city area and southern area. Concentrations of SO2 at Shijingshan, Dongsi, Tongzhou monitoring sites were significantly decreased related to SO2 emission reduction measures. During a heavy air pollution process in January 14 - 18th 2014 there was obviously SO2 regional transportation and model simulation analysis based on PAST showed that the contribution of SO2 regional transport to Beijing was 83% with elevated power plants surrounding Beijing accounting for 21% and the four major Beijing power plants contributing about 3.5% to the SO2 concentration during this heavy air pollution process.