Multi-effects of gravity and geometric flow channel on the performance of continuous microbial fuel cells

Nowadays microbial fuel cells (MFCs) are a rapidly evolving field and studied extensively because of their simultaneous dual functions of decomposing organic waste matter and eco-power generation. Now, facing their low power density, multiple effects including various gravity conditions ranging from 0 G to 2 G and three kinds of geometric flow channel (serpentine channel, serpentine tapered channel and bio-mixer channel) in MFCs were studied because of their ability to significantly impact the performance of MFCs.Numerical simulation technology, with its significant lessening of time needed and saving experimental costs required was used in this study. Results show that a better power performance was found at a condition of 0.125 G and Reynolds number Re = 41.3 regardless of flow channel in MFCs. In addition, the bio-mixer channel of the flow channels in MFCs will have a better performance than the other two channels because of its lower pressure drop and higher power generation. These findings will provide useful information on enhancing the performance of MFCs, especially with the application of low gravity conditions in the future.     

交错齿槛型泥石流排导槽研究初探

排导槽是一种常见的泥石流防治措施,提出了交错齿槛槽定义,即该类槽是指由两束流侧墙及置于其间交错排列的梯级齿槛群构成的一种新型泥石流排导槽,根据流域面积与沟床纵比降可分为3种类型;详细分析了交错槽的结构特征,并根据泥石流的不同阶段阐述了泥石流在交错槽中的流态形式;最后从消能机制、冲刷磨蚀、生态效益等方面将交错槽与东川槽等常规阶梯深潭系统做了比较,指出交错齿槛槽具有明显的优势,为进一步研究泥石流与交错齿槛的作用机制、泥石流在其中的排导特征等打下基础。     

Brief exposure to copper induces apoptosis and alters mediators of olfactory signal transduction in coho salmon

Pacific salmon are particularly susceptible to copper (Cu)-induced olfactory injuries that can ultimately inhibit neurobehaviors critical to survival. However, the molecular mechanisms underlying Cu-mediated olfactory impairment remain poorly understood. In the present study, we conducted a short-term Cu exposure at levels relevant to urban runoff (5, 25 and 50 ppb) , and investigated the roles of impaired olfactory signal transduction and induced apoptosis as underlying mechanisms of olfactory injury. Increased cell death in the olfactory epithelium was evident in coho receiving 4 h exposures to 25 and 50 ppb Cu. Expression of olfactory marker protein (omp), a marker of mature olfactory sensory neurons, also decreased at 50 ppb Cu. Immunohistochemical analysis of coho olfactory epithelium demonstrated a loss of type 3 adenylate cyclase (ACIII) in the apical olfactory epithelium cilia at all levels of Cu exposure, suggesting an inhibitory effect of Cu in olfactory signaling. Accompanying the loss of ACIII in Cu-exposed coho were reduced intracellular cyclic guanosine monophosphate (cGMP) levels in the olfactory rosettes. Collectively, these results support a linkage among the initial steps of olfactory signaling in Cu-induced salmon olfactory injury, and suggesting that monitoring olfactory cGMP levels may aid in the assessment of salmon olfactory injury.     

明渠中有机质微粒沉降过程的随机游走模拟

基于明渠流动的主要特点,考虑紊动强度的垂向非均匀性,及颗粒运动的游荡效应（loitering effect）影响,对微粒运动基本方程进行改进,建立了明渠非均匀紊流中考虑游荡效应的随机游走模型,对明渠中微粒的沉降损失进行了模拟分析.模拟结果显示,不考虑游荡效应影响时,明渠中微粒的沉降损失率可用微粒沉速与水深之比计算;而在游荡效应影响下,微粒沉降损失率会发生约18%~27%的下降,下降百分比与均匀紊流中微粒沉速在游荡效应影响下的折减百分比渐近值（19~25%）基本一致.本文结论基于不考虑微粒重悬浮、游荡效应为紊流对微粒沉降的主导影响机理等前提,主要适用于对明渠中细小有机质微粒沉降至床底过程更准确的计算分析.     

石臼漾湿地冬季有机质的可生化性

在冬季,石臼漾构筑根孔湿地对有机质的去除率不高.若设想这只是一个表观现象,实际上湿地在冬季能够有效地去除水体中难降解有机质,但释放部分易生化的有机物质.为了验证这一假设,研究了冬季石臼漾湿地岸边带和植物床-沟壕系统中有机质可生化性的空间分布.结果表明:湿地内部其有机质可生化性r(BOD₅/COD_Cr)为0.26~0.84,80%数据高于可生化性下限值(0.30),远超过源水(0.0999).经过湿地净化,水体中有机质的性质发生了显著的变化.湿地内部其r(COD_Cr/TOC)比值(0.85~2.57,平均值1.90)远低于源水(5.41),大量的还原性有机物质及部分芳香族类化合物被湿地拦截和持留.这说明即使在冷季,石臼漾湿地仍对源水中的有机质具有较好的去除效果.以人工湿地生态根孔技术为核心的植物床-沟壕系统是整个湿地中水质净化特别是有机质去除的关键区域.     

准噶尔盆地夏盐11井区三工河组沉积相特征

本文在对准噶尔盆地夏盐11井区各井所取的侏罗系三工河组岩芯观察描述及室内粒度分析的基础上,根据沉积相标志确定夏盐11井区侏罗系三工河组为水下分流河道沉积;通过单井划相、剖面相分析及平面相分析,编制出夏盐11井区侏罗系三工河组沉积相图,解决了夏盐11井区储集层的沉积相问题。     

长株潭城市群大气污染潜在源区分析及传输通道研究——以株洲市为例

利用Hysplit、MeteoInfo模型,计算株洲2017—2019年特护期(10月至次年3月)的后向轨迹,并进行轨迹聚类、潜在源贡献因子(PSCF)和浓度权重轨迹(CWT)分析。结果表明,10—12月,污染物潜在源区主要分布在偏北方向,1—3月,偏南方向的源区不断扩大,这与季节更替、季风转换有关;12和1月,潜在源区面积最大,强度最强,传输通道最清晰。对特护期各月份进行权重潜在源贡献因子(WPSCF)和加权浓度权重轨迹(WCWT)分析,结果表明,12月有1条明显的WPSCF高值带起源于河南省中北部,一路向南,经平顶山、过南阳、再经襄阳进入湖北省,该高值带蛇形前进,过荆州跨长江经岳阳华容县进入湖南,再过常德、益阳,以弧形路径到达长株潭地区,这条路径是12月北方污染物影响长株潭的主要传输通道。WCWT分析也有类似结果,且通道路径更宽广,1月的潜在源区在偏北方向呈扇形分布,在较远距离上的河南、安徽等省份呈指状分布。经2017年12月5日重污染个例检验发现,传输轨迹与分析的传输通道一致。     

外源碳氮输入对沟道底泥反硝化潜势与阈值影响——以宁夏引黄灌区排水沟为研究对象

采集宁夏引黄灌区排水沟道底泥,开展上覆水土柱培养试验,分别模拟0,5,10,20mg/L 4种外源氮输入梯度和0,100mg/L 2种外源碳输入梯度处理下沟道水质的变化情况.在水力停留培养47d内对上覆水NO₃^--N、NH₄⁺-N、DOC及反硝化速率进行测定,并计算氮素消纳量以评估底泥反硝化脱氮潜势与阈值.结果表明：上覆水NO₃^--N浓度随时间延长而降低（P<0.01）,且同时段内上覆水NO₃^--N浓度在外源碳添加较无碳源条件下显著降低（P<0.05）,试验末期NO₃^--N浓度在无碳源和添加碳源条件下分别下降52.1%,93.6%;添加碳源条件下上覆水NO₃^--N浓度在20d时已稳定至较低水平,而未添加碳源处理NO₃^--N浓度在试验47d后仍有较大消纳空间;无碳源和添加碳源条件下底泥反硝化氮素消纳量阈值分别为263.7,865.6μmol/L,氮素累积消纳量占培养柱体系内总氮量的比率随外源碳氮的增加而增大（P<0.05）,未添加碳源条件下反硝化过程可以消纳培养土柱体系内10.3%~11.4%的氮量,而在添加碳源后提高至17.7%~37.3%本研究可为引黄灌区农业面源污染高效治理提供科学依据.     

地铁盾构隧道下穿南水北调干渠的沉降控制研究

通过对地铁盾构隧道下穿南水北调干渠时沉降现场监测数据和数值模拟结果的分析,对干渠结构、干渠上部倒虹吸结构和地表的沉降控制进行了研究。结果表明:(1)盾构隧道下穿南水北调干渠时,干渠结构最大沉降发生在干渠底部。在盾构隧道与干渠渠底净距为2.5D(D为盾构隧道外径)并采用克泥效工法时,干渠结构的最大沉降量为11.26 mm,未采用克泥效工法时,干渠结构的最大沉降量为14.52 mm,说明采用克泥效工法能够有效减少干渠结构的沉降量,减少幅度为22%,同时也能够有效降低地表和倒虹吸结构的沉降量;(2)随着盾构隧道与干渠的距离越来越接近,干渠底部、地表和倒虹吸结构的沉降量逐渐增大,且随着盾构隧道与干渠渠底净距的减少,其沉降量的增大幅度逐渐提高;(3)采用克泥效工法时,盾构隧道与干渠的净距不少于2.0D时,能够保证干渠底部的沉降量不大于15 mm。该研究结果可为类似工程提供参考。