Sources of Volatile Organic Compounds in a University Building

A total of 34 volatile organic compounds (VOCs) were measured in the indoor of laboratories, offices and classrooms of the Chemical Engineering Department of Hacettepe University in Ankara in 2 week-day passive sampling campaigns. The average concentrations ranged from 0.77 to 265 μg m^?3 at the different indoor sites, with the most abundant VOC found to be toluene (119.6 μg m^?3), followed by styrene (21.24 μg m^?3), 2-ethyltoluene (17.11 μg m^?3), n-hexane (10.21 μg m^?3) and benzene (9.42 μg m^?3). According to the factor analysis, the evaporation of solvents used in the laboratories was found to be the dominant source.     

Solar tracking system – a review

The generation of power from the reduction of fossil fuels is the biggest challenge for the next half century. The idea of converting solar energy into electrical energy using photovoltaic panels holds its place in the front row compared to other renewable sources. But the continuous change in the relative angle of the sun with reference to the earth reduces the watts delivered by solar panel. In this context solar tracking system is the best alternative to increase the efficiency of the photovoltaic panel. Solar trackers move the payload towards the sun throughout the day. In this paper different types of tracking systems are reviewed and their pros and cons are discussed in detail. The results presented in this review confirm that the azimuth and altitude dual axis tracking system is more efficient compared to other tracking systems. However in cost and flexibility point of view single axis tracking system is more feasible than dual axis tracking system.     

Air concentrations of currently used herbicides and legacy compounds in the Canadian prairies,subarctic, and arctic

Passive air samplers were installed in the summers of 2005 and 2007 for 90 days at four locations in the agricultural region of the Canadian Prairies and at five locations in the Canadian Subarctic and Arctic. The presence and masses of ten currently used herbicides and three legacy compounds in the polyurethane foam disks were quantified. Herbicides 2,4-D, bromoxynil and MCPA were detected at all locations in the Canadian Prairies and in both years because these herbicides are widely applied to control broadleaf weeds in cereal crops that are an integral part of Prairie agricultural production systems. MCPA was also detected at one location in the Arctic in 2007. The detection of the other seven herbicides in the 2 years combined ranged from no detections (atrazine only) to five detections for the relatively volatile herbicides trifluralin and triallate. Triallate was the only other herbicide detected in the Arctic (2005). Legacy compounds were either not detected (alachlor) or at levels near their detection level (γ-HCH and α-HCH). γ-HCH and α-HCH were more frequently detected in 2005 than in 2007 indicating that their concentrations in Canadian air have decreased over time. γ-HCH, widely used as an insecticide in Prairie oilseed production until 2002, was detected at larger concentrations in the Canadian Prairies than in the Subarctic and Arctic. α-HCH, a manufacturing by-product in technical HCH prior to 1971 in Canada, was not detected in the Canadian Prairies but was at detectable levels in the Subarctic and Arctic as the Arctic Ocean is reported to be a major source of α-HCH to the atmosphere. We conclude that some of the most widely used herbicides in Canadian agriculture today are commonly present in the air in regions where they are applied and that a portion of these herbicides may be traveling as parent molecules to the Canadian Arctic. To the authors’ knowledge, this is the first evidence of the presence of MCPA and triallate in Arctic air samples, perhaps because previous research has seldomly monitored for currently used herbicides in this region.     

Fe^0钝化膜的生物还原及其脱氮除磷

微生物的异化Fe（Ⅲ）还原是一种能够利用Fe（III）作为末端电子受体在无氧条件下氧化有机物的产能过程。结合这一特性,考察了在兼性厌氧／严格厌氧条件下Fe^0钝化膜作为Fe（111）源时的生物还原能力以及对N、P等营养元素的去除效果。结果表明,严格厌氧条件下微生物异化Fe（Ⅲ）还原能力较好,富集培养至7d,累计Fe（II）浓度达到最大,最大产生速率为98．69mg／（L·d）,同时TP去除率高达97．1％以上。而体系对NH4-N、TN的去除相对滞后,培养至13d,去除率开始增大,最终分别达到86．6％和76．1％。这为装填有海绵铁＋聚氨酯泡沫载体的SBBR中填料的原位再生问题提供了解决思路。     

挡土墙地震被动土压力的拟动力分析

对地震土压力的研究是地震区挡土墙安全设计的一项重要课题.地震条件下,目前的研究主要是给出了土压力的近似拟静力解析解.本文采用可考虑动力荷载下的周期和纵波及横波效应的拟动力方法,对挡土墙后的地震被动土压力进行分析.在挡土墙后平面滑裂面假设的基础上,考虑了水平和垂直向地震加速度、纵波速度、横波速度、挡土墙摩擦角、填土内摩擦...     

正面碰撞事故中大客车乘员损伤影响因素分析

为研究乘客在大客车正面碰撞事故中的损伤机理,建立某全承载大客车有限元模型,并通过试验验证有限元模型的仿真精度。基于验证模型对不同碰撞速度条件下大客车车身结构力学响应、生存空间、座椅固定件强度、乘员运动响应和损伤等进行综合分析及评价。结果表明:高速碰撞条件下,驾驶员生存空间容易被侵入,座椅固定件强度存在失效的风险;乘员头部、颈部和胸部的损伤值受碰撞速度、安全带类型和乘员位置影响较大;三点式安全带保护效果明显优于两点式安全带。     

Developing a passive air-breathing tubular direct methanol fuel cell fed with concentrated methanol

This study develops and investigates a fully passive air-breathing tubular direct methanol fuel cell (t-DMFC) with a steel-tube anode and a steel-mesh cathode. The effects of methanol concentration, cathode catalyst loading, mesh structure, and forced air convection are experimentally explored. Results indicate that the t-DMFC performs better at a relatively higher methanol concentration of 8 M. It is recommended to use a catalyst loading of 4 mg cm^?2. Both the electrochemical impedance spectroscopy (EIS) and performance tests confirm that the 40-mesh setup is preferred at the cathode. The fuel cell yields a poor performance when the cathode works with forced air convection because the air-blowing operation reduces the cell temperature and this effect dominates the cell performance. The dynamic and constant-load behaviors are also inspected.     

Effects of an invasive ant on land snails in the Ogasawara Islands

We investigated how Pheidole megacephala has affected endemic achatinellid snails because these snails are excellent indicators of the impact of ants and they have high conservation value in Ogasawara. In 2015 we surveyed the Minamizaki area of Hahajima Island of Ogasawara, designated a core zone of the World Heritage Site, for P. megacephala. In Minamizaki, we determined the distribution and density of achatinellid snails in 2015 and compared these data with their distribution and density in 2005. Land cover in the survey area was entirely forest. We also tested whether P. megacephala preyed on achatinellid snails in the laboratory. P. megacephala was present in the forested areas of Minamizaki. Achatinellid snails were absent in 19 of 39 sites where P. megacephala was present, whereas in other areas densities of the snails ranged from 2 to 228 individuals/site. In the laboratory, P. megacephala carried 6 of 7 achatinellid snails and a broken shell was found. Snail distribution and density comparisons and results of the feeding experiments suggest that the presence of P. megacephala has contributed to the decline of achatinellid snails in forests in the survey area. Yet, P. megacephala is not on the official list of invasive non‐native species. Stakeholders using the list of invasive species to develop conservation programs should recognize that invasiveness of non‐native species differs depending on the ecosystem and that official lists may not be complete.     

基于原位被动采样技术研究巢湖沉积物和水体中PAHs的垂直分布及其界面交换

沉积物-水体界面处分子扩散是污染物的一个重要地球化学过程,也是判断沉积物是否为上层水体中污染物汇或源的主要依据.本研究利用低密度聚乙烯膜(LDPE)为吸附相的原位被动采样器,同步确定了巢湖西半湖南淝河入湖口处不同深度的上层水体和沉积物孔隙水中13种多环芳烃(PAHs)浓度,并计算了它们在沉积物-水体界面的分子扩散通量.结果表明,3种性能参考化合物(PRCs)在上层水体中的解析速率较沉积物孔隙水中大,相应地,水体中LDPE膜对PAHs的吸附速率高于沉积物孔隙水.水体中13种PAHs总浓度(130～250 ng·L~(-1))低于沉积物孔隙水(180～253 ng·L~(-1)),且均以低环PAHs为主.2～3环PAHs浓度在上层水体中无明显的垂直变化,但4～6环PAHs浓度呈现随深度增加而降低的趋势.沉积物孔隙水中PAHs浓度的垂直变化规律反映了历史强排放过程.研究区域PAHs在沉积物-水体界面的交换通量变化范围为-384～1445 ng·m~(-2)·d~(-1),除Flu和Pyr外,其它PAHs均从沉积物向水体释放,反映了底部沉积物是上层水体中PAHs的重要二次污染源.     

污染场地土壤气中VOCs定量被动采样技术研究及应用

污染场地中土壤气样品的采集是蒸气入侵风险评估的关键,目前最常用的主动土壤气采集技术包括真空苏玛罐和泵吸附管,其操作繁琐、成本高、易受多种因素影响、只能采集短时间的浓度.土壤气定量被动采样技术是一种新兴的采样技术,很好地克服了主动式采样存在的不足,是目前污染场地中土壤气调查的研究热点.通过总结现有研究,就定量被动采样技术的理论、被动采样器吸附剂和外壳材料的选择、被动采样器吸附速率的研究及定量被动采样在污染场地中的应用进行论述.综合研究发现,只要严格控制吸附速率,被动采样能够提供准确的定量土壤气浓度测量;采样器结构的设计、外壳材料的选择能够有效控制吸附速率;吸附速率受环境因素和土壤性质的影响,场地校正是获得准确结果的有效途径.我国在土壤气采样领域的研究刚刚起步,建议:加大高效、广谱型或混合型吸附材料及相应测试方法和设备的研发;加强吸附速率的影响因子及场地校准方法的研究;加强土壤钻孔内土壤气的补给速率的模型和场地实测研究;增加不同种采样器的现场应用比较研究;进行适合我国国情的技术标准的研究与制订.