Effect of the inlet-outlet positions on the hydraulic performance of horizontal subsurface-flow wetlands constructed with heterogeneous porous media

Effects of the inlet and outlet position on flow patterns of saturated fluids in a horizontal subsurface-flow constructed wetland were investigated experimentally using a quasi two-dimensional flow cell representing a vertical cross-section in the longitudinal direction of the wetland. The filter medium consisted of glass beads that were either uniformly sized or a mixture of sizes with a distribution corresponding to wetland filter media. Flow through the filter bed was visualized by injecting dyed fluid into the water-saturated model. Next, breakthrough curves were obtained using chloride tracer. Flow through the homogeneous filter formed by uniformly sized beads displayed a clear density-driven component. Using mixed sizes, finer and coarser beads tended to separate into alternating and incomplete layers. Flow occurred preferentially along roughly horizontal high-conductivity paths of coarser filter material. Density-driven vertical flow was much slower than the horizontal flow. Nevertheless, appropriate positioning of the inlet and less importantly the outlet could to some extent mitigate the dominant effect of the medium stratification on the flow patterns. Using inlet-outlet configurations that forced the flow through larger portions of the filter bed by injecting into low-conductivity layers and opposing the gravity-driven flow increased the treatment efficiency.     

Loss of Pesticides from Agricultural Fields in SE Norway – Runoff Through Surface and Drainage Water

Loss of two pesticides with different mobility characteristics, bentazone (Koc 34) and propiconazole (Koc 1800), were studied at three agricultural fields (Askim, Bjørnebekk and Syverud) in SE Norway. A conservative tracer (Br) was used to follow the flow of water. The loss of pesticides varied among the fields, depending on hydrological characteristics and soil properties. The loss of pesticides was higher from two artificially levelled silty clay loam soils with poor aggregate stability (Askim and Bjørnebekk) compared to a loam/silt loam soil with increased content of organic carbon and better aggregate stability (Syverud). The total accumulated loss was <0.5% from all fields. The highest pesticide concentrations were measured at the first runoff episode after application for both the mobile (bentazone) and less mobile pesticide (propiconazole) in the surface runoff. In the drainage water, the peak for the less mobile pesticide coincided with the Br tracer, while the peak for mobile pesticide appeared earlier than the Br tracer. Rapid movement of water, particles and pesticides through soils indicate flow through macropores. Larger proportions (in percent of total applied) of both the mobile and the strongly sorbed pesticides were lost through the drainage as compared to the loss through surface runoff at Askim. Here, it is suggested that macropore flow contribute to the increased loss of pesticides through the drainage. At Syverud, high infiltration capacity reduces the amount of water available for surface runoff, and somewhat higher loss of the mobile pesticide was registered in the drainage compared to the surface runoff. For the strongly sorbed pesticide, however, propiconazole was neither detected in surface nor in drainage water at Syverud. Generally, there was a higher percentage loss of the mobile compared to the strongly sorbed pesticide in both surface and drainage water, which is in agreement with the pesticides mobility characteristics in soil. An exception was, however, the erodible soil Bjørnebekk, where a higher fraction of propiconazole was lost in the surface runoff compared to bentazone. Large amounts of sediment transport from the Bjørnebekk field probably contributed to enhanced transport of the strongly sorbed pesticide.     

微波辐射香草醛交联壳聚糖对镉(Ⅱ)的吸附性能

采用微波辐射技术合成了香草醛交联壳聚糖(V-CTS)希夫碱,用红外光谱和扫描电镜对产物结构进行了表征,研究了该吸附剂对镉离子的吸附性能。结果表明,香草醛改性壳聚糖粒径约在5~40μm之间,吸附剂对镉离子的的吸附条件是:pH为6.0,100 mg/LCd2+溶液50 mL,吸附剂投加量为0.02 g,吸附震荡时间5 h,温度20℃,吸附量为39.7 mg/g。与水浴法制备的吸附剂以及其他壳聚糖改性产品相比,该吸附剂的吸附量大大提高,且操作方法简单,工艺条件易于控制。     

热处理重组质粒DNA的复性及其在水环境中的降解特性

为了考察热处理后的重组DNA进入水环境后可能存在的环境风险,以pET-28b质粒为材料,以质粒相对转化效率为指标,考察了热变性重组质粒DNA的复性可能性,并在此基础上构建了人工模拟水环境系统,研究了热变性质粒DNA在水环境中的降解速率和影响因素.结果表明,热变性pET-28b质粒经过30min后,其转移活性可以得到恢复,在4～37℃之间,温度越高越有利于热变性质粒的复性.热处理过程中未被降解的质粒DNA进入水环境后,在pH值为7、8时降解速率相对较慢,在pH值为5、6、9的条件下,降解较快,但在任何pH下,1.0h后仍存在未降解的质粒DNA.水环境中的NaCl对热处理质粒DNA有一定的保护作用,而且这种作用是随着NaCl质量分数的提高而增强.进入水环境中的热变性DNA有足够的时间复性,从而可能发生基因转移.因此,这些热处理的质粒DNA进入环境后理论上存在一定的生态风险.     

崇明东滩湿地土壤养分的分布特征及其环境效应

通过研究崇明东滩不同类型天然湿地土壤在不同潮间的有机质(OM)、全氮(TN)、全磷(TP)的含量与分布,进而分析不同类型滨海湿地土壤作为营养盐氮、磷汇与碳沉积的环境效应。结果表明,芦苇型沙质湿地土壤中有机质、全氮、全磷的平均值分别为1.36%、0.1%、0.03%,而芦苇/米草混合型黏质土壤中分别为2.41%、0.27%、0.07%。随着高程的增加(从光滩向高潮滩过渡),芦苇(Phragmitescommunis)型沙质湿地土壤与芦苇/米草(Phragmites communis/Spartina alterniflora)混合型黏质土壤中有机质、全氮含量平稳上升,但全磷变化并不显著。这表明芦苇/互花米草混合型黏质湿地土壤对造成沿海水域富营养化的氮、磷营养盐以及引起全球气候变化的碳排放具有更好的汇聚效应,同时高潮滩的汇聚功能总体较光滩为高。     

全球生物多样性评估方法及研究进展

评估和预测全球生物多样性丧失趋势及其对人类福祉的影响,是当前国际生物多样性研究的重要方向之一。结合全球生物多样性评估的最新研究进展,对全球生物多样性评估的内涵、方法和成果进行了阐述。驱动力-压力-状态-影响-响应(DPSIR)概念框架是当前生物多样性评估项目主要使用的评估框架。按照评估目的的不同,可将生物多样性评估方法划分为指标评估、模型模拟和情景分析3种主要方法,其中全球2010年目标评估指标框架、全球环境综合评估模型(IMAGE)/全球生物多样性评估模型(GLOBIO)组合以及政府间气候变化专门委员会(IPCC)的《排放情景特别报告》(SRES)以及千年生态系统评估(MA)、全球环境展望(GEO)和世界经济合作组织(OECD)环境展望等项目建立的情景模式是全球评估项目中主要采用的评估方法。多个全球评估项目的研究结果表明,全球生物多样性丧失趋势没有得到有效遏制,在21世纪,其速度将进一步加快。在今后的研究中,仍需在理解生物多样性、生态系统服务和人类福祉之间的关系,全球2020年评估指标框架,以及发展基于多情景、多模型和多生态系统的综合评估方法等方面进行深入探讨。中国应认真总结全球生物多样性评估理论和方法方面的研究经验,加强中国2020年目标评估指标体系和中国生物多样性监测网络建设,发展适合中国区域特点的具有自主知识产权的生物多样性综合评估模型和情景分析方法,定期对全国生物多样性进行综合评估,切实掌握全国生物多样性现状及变化趋势,为中国生物多样性保护和管理决策提供服务。     

UV-H2O2工艺对饮用水中 DMP的去除效果和影响因素

采用UV-H2O2工艺对饮用水中内分泌干扰物邻苯二甲酸二甲酯(DMP)的去除进行研究,结果表明,单独的UV或H2O2都不能有效氧化去除DMP;而UV-H2O2联用工艺对饮用水中DMP具有很好的去除效果.在原水DMP浓度为5.1496×10-3mmol·l-1(1.0mg·l-1)左右,UV光强133.9μW·cm-2,H2O2投加量20mg·l-1和反应时间60min条件下,DMP的去除率可达到97.8%.探讨了反应速率常数随影响因素变化的规律,其中H2O2浓度、pH值、DMP初始浓度和本底TOC值对该工艺去除DMP的影响较大.     

基于强度理论及虚拟仿真相结合的行星减速机构可靠性分析

基于破煤理论建立了采煤机的力学模型,采用ADAMS建立采煤机刚柔耦合模型,并解决了边界条件添加、接触法向力提取等技术问题,分析了行星轴、架的可靠性;基于行星减速机构强度校核基本原理,开发了行星齿轮强度校核软件,以虚拟仿真中的动态接触法向力为输入,对某公司两种行星减速机构设计方案中各齿轮的接触应力和弯曲应力进行研究。该方法解决了传统分析中齿轮受力无法确定以及采用有限元软件无法求解齿根弯曲应力、求解接触应力时间过长的不足。结果表明:二级行星减速机构采用4行星轮结构要优于采用3行星轮方案,传动更稳定、可靠。     

基于模糊故障树的海洋立管破坏失效风险分析

针对海洋立管破坏失效事故资料不完备及发生概率缺乏精确值的现状,提出了基于模糊故障树的海洋立管破坏失效风险分析方法。通过对现有的海洋立管破坏失效事故原因的统计分析,建立了以"海洋立管破坏失效"为顶事件的故障树。在对故障树进行定性分析的基础上,得到了引起海洋立管破坏失效的105个各阶最小割集,确定了海洋立管发生破坏失效的主要模式。采用专家判断法与模糊集理论结合的方法对故障树进行了定量分析,评估了故障树底事件的发生概率,并计算了故障树顶事件的发生概率。通过模糊故障树分析得到了海洋立管系统的薄弱环节,从而可以对其采取有效措施,以降低事故发生概率及提高系统可靠性。     

污泥回流对流化床生物膜—A/O活性污泥耦合工艺的影响研究

设计一套流化床生物膜(MBBR)—A/O活性污泥耦合装置处理城镇污水,考察了污泥回流对耦合工艺处理效率的影响,研究了系统中生物膜相和悬浮相微生物在有机物降解和脱氮反应中的活性差异。实验结果表明,当系统进水COD在200~400mg/L,进水氨氮在8.0~32.0mg/L,污泥回流比为1/8时,水力停留时间为12.4h,系统COD去除率平均值达81.4%,TN去除率平均值达70.6%,系统对较难降解城镇污水的处理具有明显的技术优势。污泥回流降低了生物膜相微生物的活性,而提高了悬浮相微生物活性,但生物膜相微生物活性速率仍高于悬浮相微生物活性。与传统活性污泥工艺相比,MBBR—A/O活性污泥耦合工艺将高活性生物膜引入,使悬浮污泥浓度极大降低,有助于减少污泥回流能耗与处理成本,具有明显应用价值。