Short-term bacterial community composition dynamics in response to accumulation and breakdown of Microcystis blooms

Short-term bacterial community composition (BCC) dynamics in response to accumulation and breakdown of Microcystis blooms were examined by conducting in situ mesocosm experiments with varying levels of Microcystis sp. biomass, ranging from 15 to 3217 μg/L as measured by chlorophyll-a concentration in the freshwater water column. The BCC was assessed by means of terminal restriction fragment length polymorphism (T-RFLP) of 16S ribosomal RNA genes followed by cloning and sequencing of selected samples. The results showed that the composition of both free-living and particle-attached bacterial communities changed during the accumulation and breakdown phases of a Microcystis bloom, and differences were also evident with different levels of Microcystis biomass. The relative abundance of bacteria affiliated with Micrococcineae and Legionellales increased in general after amendment with Microcystis. Significant correlation between the relative abundance of Micrococcineae and breakdown of Microcystis biomass was also observed. Canonical correspondence analysis (CCA) showed that the changes in the free-living and particle-attached bacterial community were mostly related to the changes in the concentrations of chlorophyll-a, dissolved organic carbon (DOC), dissolved oxygen (DO) and pH, which were mainly induced by the breakdown of Microcystis biomass. Overall, our study revealed the following: i) accumulation of Microcystis blooms and their breakdown have strong impacts on bacterial community composition; ii) there might be saprophytic association between Micrococcineae and decomposition of Microcystis biomass; iii) it is necessary to reveal potential associations between Legionellales organisms and Microcystis blooms in eutrophic freshwater lakes.     

伊犁盆地南缘蒙其古尔铀矿床东部黏土矿物分布特征

伊犁盆地南缘蒙其古尔铀矿床是近年来探寻出的储量可观的铀矿床之一,含矿岩系主要为下侏罗统三工河组上、下段及中侏罗统西山窑组上、下段。本文通过X射线衍射、扫描电镜等分析测试手段,初步探讨含矿岩层砂体黏土矿物分布特征及转化关系。研究发现蒙其古尔铀矿床东部地区黏土矿物以高岭石为主,其次为伊利石、伊利石/蒙脱石混层,少量绿泥石及蒙脱石。黏土矿物种类及含量随地层埋深增加及地下水运移方向存在一定的变化规律:随深度增加高岭石含量呈递增趋势,伊利石/蒙脱石混层呈递减趋势,伊利石呈微弱递增趋势;沿地下水运移方向高岭土含量持续递减,伊利石/蒙脱石混层含量呈递增趋势,伊利石呈微弱递减趋势。高岭石一部分为陆源碎屑成因,另一部分为成岩初期的次生产物;伊利石大部分是成岩前期的自生矿物,另一部分则是由蒙脱石最终转换而成;伊利石/蒙脱石混层则是蒙脱石向伊利石过渡转化的中间产物。高岭石和伊利石/蒙脱石混层含量呈明显负相关性;伊利石和伊利石/蒙脱石混层表现为微弱负相关,高岭石和伊利石二者相关性较差,表明由原生矿物长石、云母等转变成伊利石与高岭石,并且存在高岭石向蒙脱石及绿泥石的转化,而蒙脱石经伊利石/蒙脱石混层中间产物后向伊利石转化的过程。     

鄂尔多斯盆地Y66井区延9油层组砂体连通性评价

鄂尔多斯盆地Y66井区延9油层组属于低孔-低渗储层,注水见效差异显著。为实现该油层组高效开发,利用静态和动态连通性组合分析方法系统评价延9油层组的砂体连通性。基于单砂体叠置类型确定砂体静态连通性,并引入连通厚度与连通系数对砂体连通性进行定量表征。依据开发过程中产能变化和注水响应定量描述井间砂体的动态连通性。综合钻井岩心、分析测试资料,结果表明,整个Y66井区延9油层组中部的砂体连通性较好,相对而言,西南部和东北部的砂体连通性较差;从各小层来看,延911小层和延921小层砂体具有良好的垂向叠置及横向叠置关系,连通厚度大多在6～10 m内,连通系数大多在80%以上。综合动静态资料,对油层组的连通关系进行了判别,为油气田生产开发提供理论基础。     

Effects of the nuisance algae, Cladophora, on Escherichia coli at recreational beaches in Wisconsin

Recreational beaches constitute a large part of the 12 billion dollar per year tourism industry in Wisconsin. Beach closures due to microbial contamination are costly in terms of lost tourism revenue and adverse publicity for an area. Escherichia coli (E. coli), is used as an indicator of microbial contamination, as high concentrations of this organism should indicate a recent fecal contamination event that may contain other, more pathogenic, bacteria. An additional problem at many beaches in the state is the nuisance algae, Cladophora. It has been hypothesized that mats of Cladophora may harbor high concentrations of E. coli. Three beaches in Door County, WI were selected for study, based on tourist activity and amounts of algae present. Concentrations of E. coli were higher within Cladophora mats than in surrounding water. Beaches displayed an E. coli concentration gradient in water extending away from the Cladophora mats, although this was not statistically significant. Likewise, the amount of Cladophora observed on a beach did not correlate with E. coli concentrations found in routine beach monitoring samples. More work is needed to determine the impact of mats of Cladophora on beach water quality, as well as likely sources of E. coli found within the mats.     

Efficacy of monitoring and empirical predictive modeling at improving public health protection at Chicago beaches

Efforts to improve public health protection in recreational swimming waters have focused on obtaining real-time estimates of water quality. Current monitoring techniques rely on the time-intensive culturing of fecal indicator bacteria (FIB) from water samples, but rapidly changing FIB concentrations result in management errors that lead to the public being exposed to high FIB concentrations (type II error) or beaches being closed despite acceptable water quality (type I error). Empirical predictive models may provide a rapid solution, but their effectiveness at improving health protection has not been adequately assessed. We sought to determine if emerging monitoring approaches could effectively reduce risk of illness exposure by minimizing management errors. We examined four monitoring approaches (inactive, current protocol, a single predictive model for all beaches, and individual models for each beach) with increasing refinement at 14 Chicago beaches using historical monitoring and hydrometeorological data and compared management outcomes using different standards for decision-making. Predictability (R²) of FIB concentration improved with model refinement at all beaches but one. Predictive models did not always reduce the number of management errors and therefore the overall illness burden. Use of a Chicago-specific single-sample standard—rather than the default 235 E. coli CFU/100 ml widely used—together with predictive modeling resulted in the greatest number of open beach days without any increase in public health risk. These results emphasize that emerging monitoring approaches such as empirical models are not equally applicable at all beaches, and combining monitoring approaches may expand beach access.     

A systematic study on spatial and seasonal patterns of eight taste and odor compounds with relation to various biotic and abiotic parameters in Gonghu Bay of Lake Taihu, China

A systematic study was conducted on seasonal and spatial patterns of taste and odor (T&O) compounds with relation to biotic and abiotic parameters at fifteen sites in Gonghu Bay of Lake Taihu in 2008. We developed a sensitive and automated method to simultaneously analyze eight T&O compounds (boiling points ranging from 38 °C to 239 °C) by using Purge-and-Trap (P&T) coupled with GC/MS. Maximum particulate dimethyl trisulfide (DMTS, 69.6 ng/L) exceeded its odor threshold concentrations (OTC, 10 ng/L) and maximum dissolved DMTS was 6.1 ng/L, but still far below concentration in the drinking water pollution incident of Wuxi City in 2007 when DMTS reached 1768-11,399 ng/L. Geosmin (GEO), 2-methylisoborneol (MIB), β-cyclocitral, β-ionone and 2-isobutyl-3-methoxypyrazine (IBMP) occasionally or frequently exceeded their OTCs, whereas 2-isopropyl-3-methoxypyrazine (IPMP) and dimethyl sulfide (DMS) did not. We found for the first time significant correlations between particulate β-cyclocitral and β-ionon concentrations and intracellular and extracellular microcystin concentrations. Spatially, Nanquan Waterworks faced more risk by T&O contamination than Xidong Waterworks. High concentrations of NO₃-N, TDN and TN could be risky signs of taste and odor events by DMS, DMTS, IPMP, IBMP and GEO.     

景观规划设计中的城市湖泊保护

城市湖泊作为城市中最重要的自然要素,开发利用过程中的保护问题至关重要。结合《玄武湖景观区总体规划》的实践,从环境生态层面,就湖泊水体本身保护、湖泊流域的宏观保护,结合国外对于城市湖泊流域的相关规划设计条目、准则,确定了湖泊流域范围内的水质保护原则方法;从视觉景观层面,就高度的保护控制、风格风貌保护控制、景观时间变化控制提出了原则方法;从人文活动层面,就历史人类文遗产的保护、人类景观活动的保存延伸进行了探讨。     

Mercury distribution and speciation in Lake Balaton, Hungary

The distribution and speciation of mercury in air, rain, lake water, sediment, and zooplankton in Lake Balaton (Hungary) were investigated between 1999 and 2002. In air, total gaseous mercury (TGM) ranged from 0.4 to 5.9 ng m(-3) and particulate phase mercury (PPM) from 0.01 to 0.39 ng m(-3). Higher concentrations of both TGM and PPM occurred during daytime. Higher concentrations of PPM occurred in winter. In rain and snow, total mercury ranged from 10.8 to 36.7 ng L(-1) in summer but levels up to 191 ng L(-1) in winter. Monomethylmercury (MMHg) concentrations ranged from 0.09 to 1.26 ng L(-1) and showed no seasonal variations. Total Hg in the unfiltered lake water varied spatially, with concentrations ranging from 1.4 to 6.5 ng L(-1). Approximately 70% of the total Hg is dissolved. MMHg levels ranged from 0.08 to 0.44 ng L(-1) as total and from 0.05 to 0.37 ng L(-1) in the dissolved form. Lower Hg concentrations in the water column occurred in winter. In suspended particulate matter and in sediment, total mercury ranged from 9 to 160 ng g(-1) dw, and MMHg ranged from 0.07 to 0.84 ng g(-1) dw. In zooplankton, an average mercury level of 31.0+/-6.8 ng g(-1) dw occurred, with MMHg accounting for approximately 17%. In sediments, suspended-matter- and zooplankton-high Hg and MMHg levels occurred at the mouth of the River Zala, but, in the lake, higher concentrations occurred on the Northern side, and an increasing trend from north-west to north-east was observed. In general, regarding Hg, Lake Balaton can be considered as a relatively uncontaminated site. The high-pH and well-oxygenated water as well as the low organic matter content of the sediment does not favour the methylation of Hg. In addition, bioconcentration and bioaccumulation factors are relatively low compared to other aquatic systems.     

历史公共园林的价值探讨——以北京内城最大的水系公共园林什刹海地区为例

公共园林在中国古典园林体系中占有重要的地位。随着城市化进程的加快,大型公共园林与城市公共空间和社会生活的联系也越来越紧密。什刹海地区是北京城中轴线上典型的城市公共空间,是首都居民最为喜爱的公共游览区。同时,这里也是北京内城最大的一处水系公共园林,以什刹海为例,从生态、审美、文化和社会等方面来思考历史公共园林的价值,将对今后城市公共空间建设、生态文明建设以及和谐社会的构建具有启发意义。     

游船旅游活动对洱海水环境的影响分析

根据洱海现有游船的特点和数量,基于游船产生的含油废水、固体废弃物、生活污水,分析了游船旅游活动对洱海环境的影响及其特点,并在此基础上提出了洱海游船污染防治措施。