Bank filtration in the sandy littoral zone of Lake Tegel (Berlin): Structure and dynamics of the biological active filter zone and clogging processes

This study focused on clogging processes and on the benthic microalgal and meiofaunal assemblage in the sandy littoral zone of Lake Tegel, which are significantly involved in bank filtration, in a long-term. Our approach combined field studies and “in situ” experiments to highlight the structure of the biological active filter zone as well as the mechanisms and effects of clogging in the interstices that influence the infiltration process.Campaigns to measure “in situ” infiltration rates and hydraulic potential were conducted monthly from March 2004 to April 2005. Meiofaunal abundances and fine particulate organic matter (FPOM) were determined every 6 weeks in freeze cores down to depths of 50 cm. In parallel, concentrations of carbon, nitrogen and chlorophyll a were measured in samples of unfrozen sediment cores, that were divided in 1-cm steps down to depths of ≥10 cm. Similar sediment profiles were generated for analysis of colloidal carbohydrates, extracellular polymeric substances (EPS) and proteins between December 2005 and June 2006. Electron microscopy was used to visualize biofilm structure. Long-term experiments with natural FPOM and melamine resin particles as fluorescent tracers were performed to study “in situ” particle retention and transport, respectively. Additionally seston input was quantified during a 1-week period in April 2005.Infiltration rates showed a high temporal and spatial variability, but were not correlated with hydraulic conductivities as hydraulic gradients changed a lot. Likewise a correlation between infiltration rates and hydraulic potentials was not observed, indicating clogging processes. These are triggered to a high extend by biological compounds. In addition, seston input and intermittent gas intrusion are considered to reduce the hydraulic conductivity considerably. No significant “in situ” transport of inert natural fluorescent tracers was observed. However, a complete and permanent clogging of the sandy sediment does not occur, and daily infiltration rates of 0.7-27 L m⁻² h⁻¹ (mean 9 L m⁻² h⁻¹) guarantee a sufficient water supply by bank filtration for decades.     

大竹蛏稚贝滤水率的研究

2008 年 10～11 月间,采用实验生态学方法对大竹蛏(Solen grandis Dunker)稚贝进行了滤水率的研究.比较了不同饵料及浓度、规格、温度对大竹蛏稚贝滤水率(R<,F>)的影响.结果表明:(1)在适宜浓度下,大竹蛏稚贝对5种单胞藻的滤水率均随着浓度的增大而增大;(2)大竹蛏稚贝的滤水率随着体质量的增...     

起始pH值对海洋混合菌群产氢量的影响

对采自天津潮间带的污泥进行热休克处理,厌氧条件下富集混合菌群进行产氢试验;设置起始pH从4．0到8．0（间隔0．5个单位）,比较混合菌群在不同pH培养条件下产氢量;利用变性梯度凝胶电泳（DGGE）分析不同起始pH培养条件下的混合菌群组成。结果表明,在起始pH为7．0时,混合菌群产氢量最高。不同起始pH对产氢量的影响,依...     

乌兰布和沙漠植物群落相异性及其影响因素北大核心CSCD

多样性反映群落间物种组成的相异性,是生态学研究的热点问题。通过对乌兰布和沙漠46个样地植物群落的调查数据进行分析,运用S?rensen相异性指数衡量该地区植物群落β多样性格局,并通过主成分分析、Mantel及Partial Mantel检验等方法来衡量各环境因子差异(包括气候和土壤)和群落地理距离对该区域植物群落β多样性格局的影响。结果表明:乌兰布和沙漠植物群落之间物种组成差异较大,物种周转(βsim)主导植物群落β多样性。气候因素、土壤因素和地理距离对植物群落β多样性及其周转组分有显著影响,物种周转对其响应与植物群落β多样性保持一致。乌兰布和沙漠植物群落物种在空间上的周转是环境限制和扩散限制综合作用的结果,环境过滤对植物群落β多样性及组分的影响超过扩散限制。     

提高鲮鱼鱼糜弹性的方法

研究了影响鲮鱼鱼糜弹性的主要因素和加工工艺条件。研究时采用漂洗鱼肉、添加谷氨酰胺转氨酶以及二段加热方法等工艺来提高鲮鱼鱼糜的弹性。结果表明 :将鲮鱼鱼肉漂洗 2次 ,添加质量分数 0 .2 %的谷氨酰胺转氨酶作为弹性增强剂 ,采用在 4 0℃温度缓慢凝胶化 3h后加热至90℃保持 30min的二段加热方式 ,可明显提高鲮鱼鱼糜的弹性。     

A comparison of instrumental dewatering methods for the separation and concentration of suspended sediment for subsequent trace element analysis

A comparison involving both field and laboratory trials was performed to evaluate the utility of two continuous-flow centrifuges and a tangential-flow filtration system for dewatering suspended sediments for subsequent trace element analysis. Although recovery efficiencies for the various devices differ, the analytical results from the separated suspended sediments indicate that any of the tested units can be used effectively and precisely for dewatering. Further, the three devices appear to concentrate and dewater suspended sediments in such a manner as to be equivalent to that which could be obtained by in-line filtration. Only the tangential-flow filtration system appears capable of providing both a dewatered sediment sample and a potentially usable effluent, which can be analysed for dissolved trace elements. The continuous-flow centrifuges can process whole water at an influent feed rate of 41 per minute; however, when suspended sediment concentrations are low (<30mg^?1), when small volumes of whole water are to be processed (30 to 401), or when suspended sediment mean grain size is very fine (<10 μm), influent feed rates of 21 per minute may be more efficient. Tangential-flow filtration can be used to process samples at the rate of 11 per minute.     

硝态氮在河床垂向渗滤系统中环境行为的模拟实验

采用自行设计的室内土柱实验装置模拟硝态氮在河床中的垂向渗滤过程,以阶梯状加大浓度的硝酸钾溶液为淋滤液,研究了硝态氮在河床垂向渗滤系统中的环境行为,借以了解河床渗滤系统对硝态氮污染的净化机理。实验表明,硝态氮在河床渗滤过程中分别参与了异化还原作用及反硝化作用。在以上两种作用的影响下,河床渗滤系统对硝态氮的去除率高达100%。但是,异化还原作用却导致了地下水中氨氮浓度的上升,这是值得注意的不利因素。     

Analysis of community structure of a microbial consortium capable of degrading benzo(a)pyrene by DGGE

A microbial consortium was obtained by enrichment culture of sea water samples collected from Botan oil port in Xiamen, China, using the persistent high concentration of a mixture of polycyclic aromatic hydrocarbons enrichment strategy. Denaturing gradient gel electrophoresis (DGGE) was used to investigate the bacterial composition and community dynamic changes based on PCR amplification of 16S rRNA genes during batch culture enrichment. Using the spray-plate method, three bacteria, designated as BL01, BL02 and BL03, which corresponded to the dominant bands in the DGGE profiles, were isolated from the consortium. Sequence analysis showed that BL01, BL02 and BL03 were phylogenetically close to Ochrobactrum sp., Stenotrophomonas maltophilia and Pseudomonas fluorescens, respectively. The degradation of benzo(a)pyrene (BaP), a model high-molecular-weight polycyclic aromatic hydrocarbon (HMW PAH) compound was investigated using individual isolates, a mixture of the three isolates, and the microbial consortium (BL) originally isolated from the oil port sea water. Results showed that the order of degradative ability was BL > the mixture of the three isolates > individual isolates. BL degraded 44.07% of the 10 ppm BaP after 14 days incubation, which showed the highest capability for HMW PAH compound degradation.Our results revealed that this high selective pressure strategy was feasible and effective in enriching the HMW PAH-degraders from the original sea water samples.     

魁蚶(Scapharca broughtonii)等位基因酶遗传变异研究

采用水平淀粉凝胶电泳技术研究了秦皇岛、大连、青岛和韩国釜山４个魁蚶群体样本的等位基因酶遗传变异。在四个群体的１０～１２种等位基因酶中分别检测到了２２、２６、２２和２７个基因位点,４个群体的多态位点比例（Ｐ０．９９）分别为５０．００、５７．６９、４５．５０和６２．９６％,平均杂合度（观察值）则分别为０．０８７±０．０２４、０．１２３±０．０３８、０．１０５±０．０２３和０．０９１±０．０３１;平均位点有效等位基因数分别是１．２３０、１．３９８、１．４１５和１．２５３。另外,计算４个群体之间的遗传相似度（Ⅰ）和遗传距离（ＤＮｅｉ）,表明遗传同一性以秦皇岛和大连群体之间最大,其次为秦皇岛与青岛及大连与青岛群体之间,韩国釜山与其它３个群体之间存在一定的遗传分岐。４个群体在多个位点上都存在明显的杂合子缺失现象。文中初步探讨了引起杂合子缺失的可能原因     

Groutability of cement‐based grout with consideration of viscosity and filtration phenomenon

The groutability depends on the properties of the grout, its injection processes, and on the mechanical properties of the soil formation. During the process of pouring cement‐based grouting into a porous medium, a variation with time occurs in the viscosity of grout suspension. In addition, the particle filtration phenomenon will limit the expansion of the grouted zone because cement particles are progressively stagnant within the soil matrix. In this paper, a closed‐form solution was derived by implementing the mass balance equations and the generalized phenomenological filtration law, which can be used to evaluate the deposition of cement‐based grout in the soil matrix. The closed‐form solution relevant to a particular spherical flow was modified by a step‐wise numerical calculation, considering the variable viscosity caused by a chemical reaction, and the decrease in porosity resulting from grout particle deposition in the soil pores. A series of pilot‐scale chamber injection tests was performed to verify that the developed step‐wise numerical calculation is able to evaluate the injectable volume of grout and the deposition of grout particles. The results of the chamber injection tests concurred well with that of the step‐wise numerical calculation. Based on the filtration phenomenon, a viable approach for estimating the groutability of cement‐based grout in a porous medium was also suggested, which might facilitate a new insight in the design of the grouting process. Copyright © 2009 John Wiley & Sons, Ltd.