Efficient dechlorination of chlorinated solvent pollutants under UV irradiation by using the synthesized TiO2 nano-sheets in aqueous phase

Titanium dioxide(TiO2), which is the widely used photo-catalyst, has been synthesized by simple hydrothermal solution containing tetrabutyl titanate and hydrofluoric acid. The synthesized product has been applied to photo-degradation in aqueous phase of chlorinated solvents, namely tetrachloroethene(PCE), trichloroethene(TCE) and 1,1,1-trichloroethane(TCA). The photo-degradation results revealed that the degradation of these harmful chemicals was better in UV/synthesized TiO2 system compared to UV/commercial P25 system and UV only system. The photo-catalytic efficiency of the synthesized TiO2 was 1.4, 1.8 and 3.0 folds higher compared to the commercial P25 for TCA, TCE and PCE degradation, respectively. Moreover, using nitrobenzene(NB) as a probe of hydroxyl radical(.OH), the degradation rate was better over UV/synthesized TiO2, suggesting the high concentration of.OH generated in UV/synthesized TiO2system. In addition,.OH concentration was confirmed by the strong peak displayed in EPR analysis over UV/synthesized TiO2system. The characterization result using XRD and TEM showed that the synthesized TiO2 was in anatase form and consisted of well-defined sheet-shaped structures having a rectangular outline with a thickness of 4 nm, side length of 50 nm and width of 33 nm and a surface 90.3 m2/g. XPS analysis revealed that ≡Ti-F bond was formed on the surface of the synthesized TiO2. The above results on both photocatalytic activity and the surface analysis demonstrated the good applicability of the synthesized TiO2 nano-sheets for the remediation of chlorinated solvent contaminated groundwater.     

Potential bioremediation of mercury-contaminated substrate using filamentous fungi isolated from forest soil

The use of filamentous fungi in bioremediation of heavy metal contamination has been developed recently. This research aims to observe the capability of filamentous fungi isolated from forest soil for bioremediation of mercury contamination in a substrate. Six fungal strains were selected based on their capability to grow in 25 mg/L Hg2+-contaminated potato dextrose agar plates. Fungal strain KRP1 showed the highest ratio of growth diameter, 0.831, thus was chosen for further observation.Identification based on colony and cell morphology carried out by 18S rRNA analysis gave a 98%match to Aspergillus flavus strain KRP1. The fungal characteristics in mercury(Ⅱ) contamination such as range of optimum pH, optimum temperature and tolerance level were 5.5–7 and 25–35℃ and 100 mg/L respectively. The concentration of mercury in the media affected fungal growth during lag phases. The capability of the fungal strain to remove the mercury(Ⅱ) contaminant was evaluated in 100 mL sterile 10 mg/L Hg2+-contaminated potato dextrose broth media in 250 mL Erlenmeyer flasks inoculated with 108spore/mL fungal spore suspension and incubation at 30℃ for 7 days. The mercury(Ⅱ) utilization was observed for flasks shaken in a 130 r/min orbital shaker(shaken) and nonshaken flasks(static) treatments. Flasks containing contaminated media with no fungal spores were also provided as control. All treatments were done in triplicate. The strain was able to remove 97.50%and 98.73% mercury from shaken and static systems respectively. A. flavus strain KRP1 seems to have potential use in bioremediation of aqueous substrates containing mercury(Ⅱ) through a biosorption mechanism.     

Community structure and elevational diversity patterns of soil Acidobacteria

Acidobacteria is one of the most dominant and abundant phyla in soil,and was believed to have a wide range of metabolic and genetic functions. Relatively little is known about its community structure and elevational diversity patterns. We selected four elevation gradients from 1000 to 2800 m with typical vegetation types of the northern slope of Shennongjia Mountain in central China. The vegetation types were evergreen broadleaved forest,deciduous broadleaved forest,coniferous forest and sub-alpine shrubs. We analyzed the soil acidobacterial community composition,elevational patterns and the relationship between Acidobacteria subdivisions and soil enzyme activities by using the 16 S rRNA meta-sequencing technique and multivariate statistical analysis. The result found that 19 known subdivisions as well as an unclassified phylotype were presented in these forest sites,and Subdivision 6 has the highest number of detectable operational taxonomic units(OTUs). A significant single peak distribution pattern(P 0.05) between the OTU number and the elevation was observed. The Jaccard and Bray–Curtis index analysis showed that the soil Acidobacteria compositional similarity significantly decreased(P 0.01) with the increase in elevation distance. Mantel test analysis showed the most of the soil Acidobacteria subdivisions had the significant relationship(P 0.01) with different soil enzymes. Therefore,soil Acidobacteria may be involved in different ecosystem functions in global elemental cycles. Partial Mantel tests and CCA analysis showed that soil pH,soil temperature and plant diversity may be the key factors in shaping the soil Acidobacterial community structure.     

科技期刊常用量的符号、名称及释义

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科技期刊常用量的符号、名称及释义

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科技期刊常用量的符号、名称及释义

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科技期刊常用量的符号、名称及释义

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新城市主义范本:TOD模式——从《TOD在中国》新书签发暨研讨会谈起

<正>"APEC蓝"的启示——低碳TOD模式刚刚结束的APEC会议让"APEC蓝"变成一道风景和网络热词,为了炼成"APEC蓝",我国政府对症下药里的重要一剂就是采用了机动车单双号限行、公车封存70%来防止空气污染。相关统计显示,APEC会议期间通过全市单双号限行等措施,机动车排放污染物总量大幅下降,其中颗粒物(PM)减排58%。仅就11月3日启动机动车单双号限行以来,交通运行指数就降低70%,车流量比黄金周第一天下降30%,道路属于完全畅通状态。     

美国饮用水化学候选污染物的筛选过程

介绍美国国家环境保护局建立饮用水化学候选污染物清单(contaminant candidate list,CCL)的总体情况。通过第3次化学候选污染物清单的建立过程,详细介绍了CCL3的建立程序和技术内容,对化学候选污染物结合健康危害和暴露程度的筛选方法和分步实施筛选的程序进行了说明,对我国确定管制化学物质的筛选工作提供了实践参考。     

珠江三角洲地区大气和土壤中多氯联苯分布特征研究

为了考察珠江三角洲地区大气和土壤中多氯联苯(PCBs)残留现状,于2012年在珠江三角洲地区采集了空气和土壤样品,并利用GC-MS进行PCBs分析测定。结果表明,大气中Σ24PCBs的总浓度为240~2 258 pg/m3,平均为1 243 pg/m3,且PCBs主要存在于气相中,占24种PCBs总浓度的90%以上,单体分布主要以三氯~五氯联苯为主。自2001年以来珠江三角洲地区大气中PCBs浓度有小幅波动,说明部分地区有PCBs源释放的可能。土壤中24种PCBs的总浓度为ND~20.68 ng/g,平均为3.77 ng/g。三氯联苯是土壤中PCBs的主要同类物,平均占土壤中24种PCBs总浓度的45%,其次是四氯联苯,平均占19%。部分地点低氯代PCBs比例下降,高氯代比例升高。