Synthesis,separation and structure determination of 2,3,3'‐trichlorobiphenyl (PCB 20)† and 3,3’,4‐trichlorobiphenyl (PCB35)†

The combined synthesis and spectrometric characterization of 2,3,3'‐trichlorobiphenyl (PCB 20) and 3,3’,4‐trichlorobiphenyl (PCB 35) is described for the first time. By a combination of highly efficient column distillation and repeated recrystallizations it was possible to isolate the two products as reference materials with a purity exceeding 99%. X‐ray analysis of crystals of 2,3,3'‐trichlorobiphenyl positively identified the substitution pattern of the biphenyl moiety by chlorine atoms. The two phenyl rings are at an angle of 52°, while the relative disposition of the chlorine atoms on both rings is closer to anti than to syn.     

面向综合应用型安全工程人才培养的实验教学研究

综合应用型人才培养是当前经济社会发展人才需求的迫切需要.安全工程是一门综合性很强的学科,基础理论和实践环节两者缺一不可,是输送综合应用型人才的重要学科之一.实验教学是安全工程学科教育培养体系中的重要组成部分,是工程人才技能培养的基础.实验教学改革研究对激发学生的探索能力、实践能力和主观能动性意义重大.笔者综述了我国安全工程实验教学现状及存在的问题;分析了面向培养综合应用型工程人才的积极意义;介绍了福州大学安全工程实验教学改革的四“转变”模式,为我国安全工程实验教学改革指出了方向.从以往几届毕业生反馈得知,很好地提高了学生的综合素质和动手能力.     

小型养殖塘水体中CH4、CO2和N2O浓度的时空变化特征及影响因素

养殖塘作为重要的温室气体排放源,水体中温室气体浓度的变化不仅是准确量化温室气体排放量的基础,还是明确其影响因素的重要依据.基于顶空平衡-气相色谱仪法对长三角一处典型的小型养殖塘水体中CH₄、CO₂和N₂ O浓度的时空变化特征以及影响因素进行了分析.结果表明,除春季外,在水温影响下,CH₄和N₂ O浓度在午间或午后出现高值;受水温和水生植物光合作用影响,CO₂浓度的高值出现在晨间光合作用较弱的时候.养殖塘水体中CH₄和CO₂浓度呈现秋季最高、冬季最低的季节变化特征,c（CH₄）在秋季和冬季的均值分别为176.34 nmol·L^-1和32.75 nmol·L^-1,主要受气温、水温和溶解氧（DO）影响;c（CO₂）秋季和冬季的均值分别为134.37 μmol·L^-1和23.10 μmol·L^-1,主要受水生植物光合作用和pH影响;c（N₂ O）在夏季最高,冬季最低,均值分别为97.05 nmol·L^-1和19.41 nmol·L^-1,主要受气温和水温影响.在空间上,垂直方向上,夏季养殖塘c（CH₄）随水深的加深而降低,表层与底层、中间层的浓度差值为71.28 nmol·L^-1和42.80 nmol·L^-1,秋季随水深的加深而升高,底层与表层的浓度差值为163.94 nmol·L^-1.c（CO₂）在夏季和秋季都表现为随着水深的加深而升高,其底层与表层的浓度差值分别为18.69 μmol·L^-1和29.90 μmol·L^-1.N₂ O浓度在垂直方向上无明显变化规律.水平方向上,夏季饲料及春季鸡粪投放的区域会出现CH₄、CO₂和N₂ O浓度的高值,春季和夏季CH₄浓度约为其他区域的1.34~1.98倍和1.95~2.42倍,春季N₂ O浓度和夏季CO₂浓度约为其他区域的1.13~1.26倍和1.39~1.74倍.     

基于“2-4模型”的化工生产事故原因分析

为进一步研究化工生产事故发生的原因,运用“2-4模型”对从安全管理网等网站收集的125起化工生产安全事故进行分析,结果表明对于事故的直接原因方面,作业人员的不安全动作主要表现在违规操作和无证上岗,管理人员的不安全动作主要表现在其工作不认真等方面,不安全物态最主要的是设备年久失修。对于事故的间接原因,主要表现在安全意识不够、安全知识不足、安全习惯不佳3方面。事故的根本原因则主要表现在缺乏安全培训等方面。为制定化工生产事故预防措施提供了依据。     

Room-temperature solid phase surface engineering of BiOI sheets stacking g-C3N4 boosts photocatalytic reduction of Cr(VI)

Cr(VI)-based compounds pollution have attracted global concern due to serious harm to humans and environment. Hence, it is crucial to exploit an effective technique to eliminate Cr(VI) in water. Herein, we in-situ grown BiOI on graphitic carbon nitride to prepare the BiOI/g-C3N4 (BCN) direct Z-scheme heterojunction by solid phase engineering method at room temperature. Experimental result shown the photocatalytic activity of pure BiOI were obviously enhanced by constructing Z-scheme BCN heterostructure, and BCN-3 heterostructure exhibited the optimal photocatalytic degradation of RhB with 98％yield for 2.5 h and reduction of Cr(VI) with more than 99％yield for 1.5 h at pH=2. Stability test shows BCN-3 still kept more than 98％reduction efficiency after 6 cycles. In addition, we also studied the reduction mechanism that shown the ·O2-radicals essentially helped to reduce the Cr(VI) in aqueous solution under illumination, verified the direct Z-scheme charge transfer path by X-ray photoelectron spectroscopy (XPS) and the free radical trapping experiment. The work open a new way for rationally designing photo-catalyst heterostructure to reduce Cr(VI) to Cr(III).     

Fe~0体系降解2,4二氯酚的影响因素及其反应机理

采用铁屑、炉渣及河砂混合介质降解2,4-二氯酚（2,4-DCP）模拟废水,研究铁屑粒径、铁屑投加量、铁屑与炉渣配比、pH值等因素对2,4-DCP脱氯效果的影响,探讨Fe0体系降解2,4-DCP的反应机理。结果表明,铁屑粒径、铁屑投加量、铁屑与炉渣配比、pH对2,4-DCP脱氯效果均有显著影响,在铁屑粒径为2～5 mm、不改变废水pH、铁屑与炉渣质量比为31∶9条件下,Fe0体系对2,4-DCP去除率高达97%。2,4-DCP经脱氯后主要产物为2-氯酚、4-氯酚和苯酚,反应后废水的可生化性明显提高,利于后续的生物处理。     

中小企业“4+1”安全管理与监管模式研究

在对全国中小企业安全生产状况调查的基础上,分析了中小企业的安全生产现状其数量多、绝大多数在乡镇街道、生产安全事故多发、职业病危害严重、从业人员素质低、生产力水平低;政府针对中小企业的安全监管人员数量少;乡镇街道的安全生产中介服务机构数量少,服务内容单一。因此,提出了中小企业安全生产监督管理“4+1”模式,其中“4”是指中小企业、政府安全监管部门、中介机构和社会监督部门的安全生产管理、监管、服务、监督体系,“1”是指提高监管效能的运行保障机制。该模式从宏观上为政府监管中小企业提出了一种新的思路,从微观上为中小企业、政府安全监管部门、中介服务机构、社会监督部门的安全生产工作提出了新的方法。     

Large-scale modeling of reactive solute transport in fracture zones of granitic bedrocks

Final disposal of high-level radioactive waste in deep repositories located in fractured granite formations is being considered by several countries. The assessment of the safety of such repositories requires using numerical models of groundwater flow, solute transport and chemical processes. These models are being developed from data and knowledge gained from in situ experiments such as the Redox Zone Experiment carried out at the underground laboratory of Äspö in Sweden. This experiment aimed at evaluating the effects of the construction of the access tunnel on the hydrogeological and hydrochemical conditions of a fracture zone intersected by the tunnel. Most chemical species showed dilution trends except for bicarbonate and sulphate which unexpectedly increased with time. Molinero and Samper [Molinero, J. and Samper, J. Groundwater flow and solute transport in fracture zones: an improved model for a large-scale field experiment at Äspö (Sweden). J. Hydraul. Res., 42, Extra Issue, 157–172] presented a two-dimensional water flow and solute transport finite element model which reproduced measured drawdowns and dilution curves of conservative species. Here we extend their model by using a reactive transport which accounts for aqueous complexation, acid–base, redox processes, dissolution–precipitation of calcite, quartz, hematite and pyrite, and cation exchange between Na⁺ and Ca²⁺. The model provides field-scale estimates of cation exchange capacity of the fracture zone and redox potential of groundwater recharge. It serves also to identify the mineral phases controlling the solubility of iron. In addition, the model is useful to test the relevance of several geochemical processes. Model results rule out calcite dissolution as the process causing the increase in bicarbonate concentration and reject the following possible sources of sulphate: (1) pyrite dissolution, (2) leaching of alkaline sulphate-rich waters from a nearby rock landfill and (3) dissolution of iron monosulphides contained in Baltic seafloor sediments. Based on these results, microbially mediated processes are postulated as the most likely hypothesis to explain the measured increase of dissolved bicarbonates and sulphates after tunnel construction.     

Depth profiles of radiocarbon and carbon isotopic compositions of organic matter and CO2 in a forest soil

Depth profiles of the specific activities of (14)C and carbon isotopic compositions (Delta(14)C, delta(13)C) in soil organic matter and soil CO(2) in a Japanese larch forest were determined. For investigating the transport of CO(2) in soil, specific activities of (14)C, Delta(14)C and delta(13)C in the organic layer, and atmospheric CO(2) in the same forest area were also determined. The specific activity of (14)C and Delta(14)C in the soil organic matter decreased with the increase in depth of 0-60cm, while that of soil CO(2) did not vary greatly at a soil depth of 13-73cm and was more prevalent than that of atmospheric CO(2). Peaks of specific activities of (14)C appeared at the depth of 0-4cm and Delta(14)C values were positive in the depth range from 0 to 15cm. These results suggest that the present soil at a depth of 0-4cm had been produced from the mid-1950s up until 1963, and the bomb C had reached the depth of 15cm in the objective soil area. The delta(13)C in the soil organic matter increased at the depth of 0-55cm, while that of soil CO(2) collected on 8 November 2004 decreased rapidly at the depth of 0-13cm and only slightly at the depth of 53-73cm. By combining the Delta(14)C and delta(13)C of the respective components and using the Keeling plot approach it was made clear that the entering of atmospheric CO(2) showed a large contribution to soil CO(2) at the depth of 0-13cm and a negligible contribution at the depth of 53-73cm for soil air collected on 8 November 2004. Respiration of live roots was presumed to be the main source of soil CO(2) at the depth of 53-73cm on 8 November 2004.     

Efficacy of Control Measures for European Buckthorn (<Emphasis Type="Italic">Rhamnus cathartica</Emphasis> L.) in Saskatchewan

Introduced to Saskatchewan in the 1930s as a potential shelterbelt species, European buckthorn is now a prominent understory shrub in riparian woodland and shrub communities around Saskatoon. Locally, the Meewasin Valley Authority (MVA) is actively controlling buckthorn as part of its mandate to conserve natural heritage resources of the South Saskatchewan River Valley, with the goal of restoring the natural biodiversity of remnant patches of native vegetation. European buckthorn is normally dioecious, and MVA has chosen to treat only fruiting stems in an attempt to limit seed production. Two control techniques have been used. In one treatment, glyphosate was applied to stems after cutting; alternatively Garlon 4 Dow AgroSciences herbicide (active ingredient triclopyr) was applied as a chemical girdle directly to the stems using a streamline basal bark spray method. To date, more than 347,000 fruiting stems of buckthorn have been treated. Results indicate good initial progress in limiting seed production in dense buckthorn sites, but at a high cost. Although seed eradication is not a practical short-term goal for the Saskatoon buckthorn population, chemical girdling can substantially and strategically reduce seed and effectively limit spread. Field-tested strategies to reduce costs and improve efficiencies are discussed.