Bioremediation Management Reduces Mass Discharge at a Chlorinated DNAPL Site

Adaptive site management and aggressive bioremediation in the source zone of a complex chlorinated dense nonaqueous phase liquid (DNAPL) site reduced total chlorinated hydrocarbon mass discharge by nearly 80%. Successful anaerobic bioremediation of chlorinated hydrocarbons can be impaired by inadequate concentrations of electron donors, competing electron acceptors, specific inhibitors such as chloroform, and potentially by high contaminant concentrations associated with residual DNAPL. At the study site, the fractured bedrock aquifer was impacted by a mixture of chlorinated solvents and associated daughter products. Concentrations of 1,1,2,2‐tetrachloroethane (1,1,2,2‐TeCA), 1,1,2‐trichloroethane (1,1,2‐TCA), and 1,2‐dichloroethane (1,2‐DCA) were on the order of 100 to 1000 mg/L. Chloroform was present as a co‐contaminant and background sulfate concentrations were approximately 400 mg/L. Following propylene glycol injections, concentrations of organohalide‐respiring bacteria including Dehalococcoides and Dehalogenimonas spp. increased by two to three orders of magnitude across most of the source area. Statistical analysis indicated that reaching volatile fatty acid concentrations greater than 1000 mg/L and depleting sulfate to concentrations less than 50 mg/L were required to achieve a Dehalococcoides concentration greater than the 10⁴ cells/mL recommended for generally effective reductive dechlorination. In a limited area, chloroform concentrations greater than 5 mg/L inhibited growth of Dehalococcoides populations despite the availability of electron donor and otherwise appropriate geochemical conditions. After implementing a groundwater recirculation system targeting the inhibited area, chloroform concentrations decreased permitting significant increases in concentrations of Dehalococcoides and vinyl chloride reductase gene copies.     

The interannual variabilities of chlorophyll and nutrients in San Francisco Bay: a modeling study

Ocean Dynamics - San Francisco Bay (SFB) is a complex ecosystem that has been heavily impacted by human activities. It has experienced strong year-to-year variations in physical, chemical, and...     

陆相沉积盆地泥页岩含气量影响因素探讨—以潍北凹陷为例

页岩气以游离态和吸附态赋存于泥页岩中,泥页岩含气量的多少是页岩气资源潜力评价的重要指标,也是勘查开发过程中最重要的制约因素。该文利用潍北凹陷大量实测数据,分别建立泥页岩含气量与有机地化参数、储集物性参数、矿物成分等相关关系图,探讨各参数与泥页岩含气量的相关性和影响因素。研究表明:含气量与有机碳含量相关性最好,相关强度达到中等正相关;孔隙度与含气量无相关关系;岩石密度与含气量、有机碳含量均具有中等程度的负相关。提出了间接获取泥页岩含气量的方法和手段,为准确地评价页岩气资源潜力提供依据。     

Effects of seepage on a three-layered slope and its stability analysis under rainfall conditions

Natural Hazards - The seepage and stability of unsaturated soil slopes under torrential rain conditions are key issues in geotechnical and hydraulic engineering. In this work, based on...     

芜申运河开通对固城湖水量影响分析

芜申运河是重要的省际干线航道,规划对其整治达到三级航道标准后通航,而芜申运河通航需要固城湖上的通航河道开闸。固城湖为重要的饮用水源地,开闸通航对固城湖水量影响较大。通过建立模型计算得出,每天开闸10次固城湖水量损失约为1.71×10~8m~3/年,每天开闸20次水量损失约为2.87×10~8m~3/年;而固城湖的常态水位为9.5m,相应库容为1.28×10~8m~3,通航对固城湖水量的年损失量占到了固城湖常态水量的1.34~2.24倍左右。如果开闸20次,固城湖需要外调补水以保证水量满足用水需求。经计算,在90%、75%、50%的降水保证率下,需要外调补水保证量达0.64×10~8、0.61×10~8、0.12×10~8m~3/年,占固城湖常态库容的50%~9%。     

公路系统地勘现状分析

公路工程地质勘察和一般工民建相比,具有显著的行业特点,体现在线路长,穿越的工程地质单元较多,工点多,勘察手段多。另外,既要把握全线路地质情况,又要有重点突出,如高陡边坡和特大桥桥址区等工点为勘察工作的重点。随着地勘的无序市场化,公路勘察质量也引人担忧,本文通过整理参与的工程项目,分析其问题,指出勘察和设计脱节依然是客观存在的,是影响勘察成果的最主要因素之一。此外,甲方或设计院一味的压缩克扣勘察费用,难以发挥勘察工程师的才智,也不利于勘察设计水平的提高,甚至造成工程事故; 勘察单位一味地迎合市场,轻视勘察质量,同样不利于自身行业的健康长远发展。     

阿尔泰南缘麦兹盆地康布铁堡组变质酸性火山岩年龄及岩石成因

阿尔泰南缘麦兹盆地康布铁堡组赋存有铁铅锌大、中型矿床,但该组火山岩的形成时代和岩石成因以及构造背景还没有形成一致的认识。本文对该组两个变质流纹岩样品进行了LA-ICP-MS锆石U-Pb年龄测定,获得其年龄分别为410.5±1.3 Ma和400.4±2.1 Ma。岩石地球化学分析结果表明:所有酸性火山岩具有高硅(72.15% ～81.26%),低铝(10.56% ～14.87%)和钛(0.16% ～0.27%),极低的MgO(0.04% ～0.14%)、CaO(0.04% ～2.42%)和TFeO(0.11% ～1.64%)含量; 在原始地幔标准化图上显示出Ti、P、Sr、Ba、Nb和Ta明显负异常,Th、U、Pb、Zr和Hf的正异常,LREE 相对HREE略富集的特征,除个别样品外,大多数样品显示明显的Eu负异常(δEu=0.48～0.91)。结合其区域地质特征,认为本区变质酸性火山岩形成于活动大陆边缘环境,是玄武质岩浆底侵作用使下地壳发生了部分熔融后演化的产物。     

钻屑量采样技术分析及改进

用钻屑量指标预测煤与瓦斯突出时,由于采样装置落后和操作不规范等原因,导致预测结果可靠性降低。从现场实际操作方面分析了造成误差的主要原因,提出采用抽吸方法收集钻屑。在现有的采样设备基础上进行了技术改进和实验验证。结果表明,改进后的防突采样钻机在采样准确性、效率等方面都有显著提高。     

黄土场地地铁车站振动台试验方案设计与研究

为得到可靠的试验数据,对黄土场地典型断面地铁车站大型振动台试验方案进行设计与研究。根据试验目的和特点,提出黄土场地与地铁车站动力相互作用模型体系相似设计原则,并基于Bockingham的π定理对模型结构进行相似设计;通过室内试验研究模型材料配合比、力学特性及模型制作技术;采用有限元-无限元耦合数值建模方法,分析黄土场地地铁车站地震响应,基于数值模拟结果对振动台试验中的传感器布设方案进行研究;根据西安及周边地区地震环境特点,确定振动台试验输入地震动与加载方案。研究结果表明,试验模型结构宏观震害与数值模拟结果较吻合。本研究可为黄土场地地铁车站、地铁隧道及地下商业街等地下结构振动台试验方案设计与深入研究提供参考。