[Chemical Composition Characteristics and Source Apportionment of PM2.5 During the Heating Period of 2016-2017 in the Eastern Part of the North China Plain].

To study the composition characteristics and source apportionment of PM2.5 in the eastern part of the North China Plain, manual samples during the two-year heating period of 2016 and 2017 were collected in seven cities, including Hengshui, Cangzhou, Ji'nan, Dezhou, Binzhou, Zibo, and Liaocheng. The results showed that the average values of ρ(PM2.5) during the observation periods were 137.23 µg·m-3 and 111.83 µg·m-3, respectively, which exceeded the daily average secondary standard limit of GB 3095-2012 "Environmental Air Quality Standard" by 1.8 and 1.5 times, respectively. The mean mass of water-soluble ions accounted for 53.32% and 47.04% of ρ(PM2.5), respectively, of which SNA (NO3-, SO42-, and NH4+) were the main ions. During the 2016 and 2017 observation periods, NO3-/SO42- increased from 1.35 to 1.60, while the concentration of Cl- decreased, indicating a decrease in the impact of coal burning. The proportions of secondary organic carbon (SOC) in organic carbon (OC) were 71.63% and 55.35%, respectively, indicating the source of secondary organic carbon had decreased. Analysis of characteristic elements Fe/Al and Ba/Ni showed that dust sources and vehicle sources had increased significantly. The backward trajectories of air mass results showed that the polluted air mass mainly came from the northwest direction during the observation period. However, the PM2.5 concentration was highest when the air mass came from the Anhui and Jiangsu provinces.

[Concentration Characteristics and Sources of Trace Metals in PM2.5 During Wintertime in Beijing].

To study the characteristics and sources of trace metals in PM2.5 during wintertime in Beijing, PM2.5 samples were collected from December 2014 to January 2015 by a middle volume sampler in the urban area of Beijing for 30 consecutive days. The mass concentration of PM2.5 was measured by filter membrane weighting method, and 16 kinds of trace metals were determined by inductively couple plasma-mass spectrometry (ICP-MS). In addition, the pollution characteristics and sources of trace metals were analyzed by enrichment factor (EF) method and factor analysis, respectively. The results showed that the concentrations of five elements (i. e. K, Ca, Fe, Al and Mg) accounted for 90.7% of the total metal elements. The concentrations of the metal elements changed obviously between day and night. Compared with daytime, crustal elements like Mg and Al decreased by more than 30% while anthropogenic elements like Cu and Pb increased by more than 40% in nighttime. Although the concentrations of metal elements increased by nearly one time in heavy pollution days compared with clean days, the mass percent of which in PM2.5 decreased from 10.9% in clean days to 4.6% in heavy pollution days. This result suggested the accumulation of metal elements in heavy pollution days had a minor contribution to the increased mass concentration of PM2.5. As the pollution episode progressed, anthropogenic elements (Cu,Zn,As,Se,Ag and Cd) increased faster than crustal elements (Al,Mg,Ca,Mn and Fe), which showed ratios ranging from 2.9 to 5.3 for anthropogenic elements and ratios ranging from 1.2 to 1.8 for crustal elements, when compared between heavy pollution days and clean days. In addition, the EF value of anthropogenic elements was also increased in the pollution days, indicating the concentrations of these elements was further influenced by the anthropogenic sources. Factor analysis showed that metal elements of PM2.5 during wintertime of Beijing were mainly from coal combustion and biomass burning, motor vehicle and industry emissions, and re-suspension of road dust, with the contributions of 34.2%,25.5% and 17.1%, respectively.

[Characteristics of the Size Distribution of Water Soluble Inorganic Ions During a Typical Haze Pollution in the Autumn in Shijiazhuang].

To characterize the size distribution of water soluble inorganic ions (WSⅡ) in haze days, particle samples were collected by an Andersen cascade impactor in Shijiazhuang from October 15 to November 14 in 2013, and the concentrations of eight kinds of WSⅡ (Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO3-and SO42-) during a typical haze episode were analyzed by ion chromatography. Sources and formation mechanism of WSⅡ were analyzed based on their size distributions. The results showed that Shijiazhuang suffers serious air pollution during the autumn season. The daily average concentrations of PM10and PM2.5were (361.2±138.7) µg·m-3 and (175.6±87.2) µg·m-3 and the daily average concentration of PM2.5was 2.3 times as high as the national secondary standard. The total water soluble inorganic ion concentrations (TWSⅡ) in clean days, light haze days and heavy haze days were(64.4±4.6)µg·m-3, (109.9±22.0)µg·m-3 and (212.9±50.1) µg·m-3 respectively. In addition, the ratio of secondary inorganic ions (SNA:SO42-, NO3- and NH4+) in TWSⅡ increased from 44.9% to 77.6% as changed from clean days to the heavy haze days, suggesting the evolution of haze episodes mainly originated from the formation and accumulation of SNA. The size distributions of SO42-, NO3- and NH4+ were bimodal in clean days, peaking at 0.43 -0.65 µm and 4.7-5.8 µm, respectively, which changed to unimodal distribution in both the light and heavy haze days, peaking at 0.65-1.1 µm. Owing to high humidity during the heavy haze days, the aqueous phase reactions of SO42- and NO3- were likely promoted, which led to the transformation of condensation mode in clean days to the droplet mode in haze days. The size distributions of Na+, Mg2+ and Ca2+ were different with that of SNA, which showed a coarse mode peaking at 4.7-5.8 µm both in clean and haze days, whereas K+and Cl- showed a bimodal distribution both in clean and haze days, although the modal size was different in clean and haze days.

Anti-Escherichia coli O157:H7 properties of purple prairie clover and sainfoin condensed tannins.

Condensed tannins (CT) from purple prairie clover (PPC; Dalea purpurea Vent.) and sainfoin (SF; Onobrychis viciifolia) were assessed for anti-Escherichia coli activity by comparing their ability to react with proteins and liposome, cause cell aggregation, and alter outer membrane (OM) morphology and permeability. The PPC CT had greater (P < 0.01) protein-precipitating capacity than SF CT using either bovine serum albumin or ribulose 1,5-disphosphate carboxylase as model proteins. Minimum inhibitory concentration of PPC CT for two strains of E. coli and five strains of E. coli O157:H7 was four to six times lower than that of SF CT. E. coli exposed to 10 µg/mL of both CT had higher (P < 0.05) OM permeability than controls and was greater (P < 0.05) for PPC than for SF CT. Addition of both CT at 50 and 200 µg/mL caused cell aggregation which was more evident (P < 0.05) for PPC than for SF CT. Transmission electron microscopy showed electron dense material on the cell surface when cells were exposed to 50 µg/mL of PPC CT. The greater anti-E. coli activity of PPC than SF CT was due to its enhanced ability to precipitate protein that increased OM permeability and promoted cell aggregation.

An improved gas chromatography for rapid measurement of CO2, CH4 and N2O.

Combining improved injector, gas line and valve-driving modules, a GC equipped with FID and ECD, could simultaneously measure CH4, CO2 and N2O in an air sample within 4 min. Test results showed that the system has high sensitivity, resolution and precision; the linear response range of the system meets the requirement of in situ flux measurements. Thus, the system is suitable for monitoring fluxes of main greenhouse gases in terrestrial ecosystem since it is easy to use, efficacious, stable and reliable to collect data.

[Effect of hyperthermia on tight junctions between endothelial cells of the blood-brain barrier model in vitro].

OBJECTIVE: To investigate the effect of hyperthermia in vitro on tight junctions between the endothelial cells of the blood-brain barrier. METHODS: An in vitro blood-brain barrier model was established by coculture of ECV304 cells with astrocytes. Transendothelial resistance (TER) of in vitro blood-brain barrier was determined by Millicell-ERS system, and the morphological change of tight junctions examined by silver staining. The expression level of zonula occluden-1(ZO-1) was analyzed by semi-quantitative reverse transcriptase-PCR. RESULTS: The integrity of tight junctions was disrupted and the expression level of ZO-1 decreased after treatment with hyperthermia. CONCLUSIONS: Tight junctions between the endothelial cells of the blood-brain barrier can be destroyed by hyperthermia, and decreased expression level of ZO-1 induced by hyperthermia is one of the most important molecular mechanisms.