Study on the concentration distribution in a trapezoidal open-channel flow with a side discharge

The number and distribution of pollutant concentration in a trapezoidal open channel flow with a side discharge is calculated and effects of the bank gradient are investigated in this paper. A sigma-coordinate water quality numerical model is used to simulate the process of both water and pollutant transportation in the trapezoidal channel open flow. The diffusion coefficient used in the prediction is determined by two methods including constant coefficient and the depth-averaged k-epsilon turbulence closure model. The change of the concentration with the bank gradient is acquired based on the simulation of cases with different bank gradients. An analytical formula is derived by using the mirror image method and related diffusion theories, ignoring the discharge momentum and the influence of the opposite bank. The formula can predict the number and distribution of pollutant concentration with some acceptable errors. The results demonstrate that the bank gradient has great influence on the concentration distribution which will decrease with the increase of the bank gradient approximately following a hyperbolic law.     

塑性混凝土渗透及渗透变形试验模型与指标测定

介绍了为堤防防渗工程设计的塑性混凝土渗透系数及渗透破坏比降试验模型及其测定方法。     

Cultivation of aerobic granular sludge in a conventional,continuous flow,completely mixed activated sludge system

Aerobic granules were formed in a conventional, continuous flow, completely mixed activated sludge system (CMAS). The reactor was inoculated with seed sludge containing few filaments and fed with synthetic municipal wastewater. The settling time of the sludge and the average dissolved oxygen (DO) of the reactor were 2 h and 4.2 mg·L^-1, respectively. The reactor was agitated by a stirrer, with a speed of 250 r·min^-1, to ensure good mixing．The granular sludge had good settleability, and the sludge volume index (SVI) was between 50 and 90 mL·g^-1. The laser particle analyzer showed the diameter of the granules to be between 0.18 and 1.25 mm. A scanning electron microscope (SEM) investigation revealed the predominance of sphere-like and rod-like bacteria, and only few filaments grew in the granules. The microbial community structure of the granules was also analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Sequencing analysis indicated the dominant species were α, β, and γ-Proteobacteria, Bacteroidetes, and Firmicutes. The data from the study suggested that aerobic granules could form, if provided with sufficient number of filaments and high shear force. It was also observed that a high height-to-diameter ratio of the reactor and short settling time were not essential for the formation of aerobic granular sludge.     

Current molecular biologic techniques for characterizing environmental microbial community

Microbes are vital to the earth because of their enormous numbers and instinct function maintaining the natural balance. Since the microbiology was applied in environmental science and engineering more than a century ago, researchers desire for more and more information concerning the microbial spatio-temporal variations in almost every fields from contaminated soil to wastewater treatment plant (WWTP). For the past 30 years, molecular biologic techniques explored for environmental microbial community (EMC) have spanned a broad range of approaches to facilitate the researches with the assistance of computer science: faster, more accurate and more sensitive. In this feature article, we outlined several current and emerging molecular biologic techniques applied in detection of EMC, and presented and assessed in detail the application of three promising tools.     

Hunting, law enforcement, and African primate conservation

Abstract: Primates are regularly hunted for bushmeat in tropical forests, and systematic ecological monitoring can help determine the effect hunting has on these and other hunted species. Monitoring can also be used to inform law enforcement and managers of where hunting is concentrated. We evaluated the effects of law enforcement informed by monitoring data on density and spatial distribution of 8 monkey species in Taï National Park, Côte d’Ivoire. We conducted intensive surveys of monkeys and looked for signs of human activity throughout the park. We also gathered information on the activities of law‐enforcement personnel related to hunting and evaluated the relative effects of hunting, forest cover and proximity to rivers, and conservation effort on primate distribution and density. The effects of hunting on monkeys varied among species. Red colobus monkeys (Procolobus badius) were most affected and Campbell's monkeys (Cercopithecus campbelli) were least affected by hunting. Density of monkeys irrespective of species was up to 100 times higher near a research station and tourism site in the southwestern section of the park, where there is little hunting, than in the southeastern part of the park. The results of our monitoring guided law‐enforcement patrols toward zones with the most hunting activity. Such systematic coordination of ecological monitoring and law enforcement may be applicable at other sites.     

旅游干扰对九寨沟原始森林岷江冷杉树干附生苔藓植物组成和结构的影响

附生苔藓植物是森林生物多样性的重要组分,对森林及其环境的质量有很好的指示作用.为了揭示旅游活动对森林及其环境的影响,调查了几寨沟原始森林景点内附近旅游活动频繁地段与未扰动地段原始林优势种岷江冷杉(Abies faxoniana)树干4个高度附生苔藓种类的组成、生物量和群落结构,采用独立样本t检验对苔藓层结构参数进行了差异性检验.结果表明:(1)冷杉树干附生苔藓物种组成在旅游活动频繁地段与未扰动地段有很大的差异.在旅游活动频繁地段,耐荫喜湿物种局部消失(重要值下降),耐干旱抗干扰的植物种群扩大;(2)旅游活动频繁地段树干附生苔藓植物的丰富度、盖度和生物量较未扰动地段小;(3)距地面较高的高度120 cm和180 cm处受到的干扰强度最大,基部的影响较小.旅游活动对附生苔藓植物的干扰主要为间接的环境影响,其机理还未充分认识,还需进一步研究.综合分析表明,旅游干扰影响了几寨沟的生态环境,需要进一步加强管理,控制游客数量和规范游客行为.图2表3参25     

水深梯度对苦草生长和生物量的影响

将采用沙壤土培育的苦草幼苗（Vallisneria natans）放置于60-170 cm的水深范围内,每10 cm一个处理,使用光照计测定不同水深的光照强度并用 Skalar 水质流动分析仪测定试验水体的理化指标,观测苦草在不同的水深梯度下形态及叶片、叶绿素含量的变化,以研究水深梯度对沉水植物的个体生长发育及生物量的影响。试验结果表明：（1）试验30 d后,在60-130 cm的水深范围内,苦草株高随水深的增加而增高,在130-170 cm的水深范围内,随水深增加而降低,130 cm处苦草的平均高度最大,达67.9 cm;试验60 d,苦草的叶片长度、宽度、面积都随着水深的增加而减小,且在150-170 cm水深范围内叶片长度明显变小,苦草的生长速率随水深的增加显著下降;（2）不同试验组苦草的叶片长度、宽度、面积以及生长速率与水深呈明显的负相关（P＜0.01）,而叶绿素含量与水深呈明显的正相关（P＜0.01）,叶片面积在140-150 cm水深范围内减小最明显,且在140-160 cm水深范围内苦草各叶绿素指标较高,尤其是chl a＋b在水深160 cm处高达1.876 mg·g^-1;（3）苦草叶片叶绿素含量随着水深的增加（光强降低）而升高,其变化幅度为0.369-1.876 mg·g^-1,其中叶片叶绿素a随着水深的增加呈波动递增的趋势,且在水深80 cm处较低（0.268 mg·g^-1）,而叶绿素b在60-170 cm水深范围内总体较平稳,在水深160 cm处达到最高（0.505 mg·g^-1）,chl a/b变化幅度较小,仅在2.49-2.84 mg·g^-1之间;（4）试验60 d后,各试验组总生物量的较大值主要集中在100-140 cm水深范围内,其中地上部分生物量平均占全株生物量的89.5%,地下部分生物量只占10.5%,生物量的分配随水深梯度变化不明显。说明水深梯度的变化对苦草的叶片生长及叶绿素含量有影响,但对生物量的分配作用不明显。研究表明在100-140 cm的水深范围内?     

北京都市区土地价格梯度估算与解析

文章简要梳理了国内外地产价格梯度案例研究的脉络,采用特征价格模型、非参数估计方法研究了北京都市区住宅、商业土地出让价格梯度与土地开发强度的变化,解析了新时期城市空间发展的特征。研究表明:住宅和商业土地出让价格梯度随时间呈现扁平化倾向,从土地价格视角说明了北京城市空间持续的郊区化扩展趋势。2009年以来住宅土地价格梯度为正,表明北京住宅空间结构特征不完全符合单中心城市假设,商业地块则较好地体现出市场机制下价格梯度的变化规律。线性模型在刻画住宅土地开发强度的空间变化方面不典型,但却较好地揭示了商业土地随到城市中心距离的增加,开发强度逐步降低的特征,2005年以来这种特征有所缓和。非参数估计方法由于不需要预设函数形式,有效避免了城市中心预设和模型选取引致的估计偏误,应用非参数方法中的核估计拟合北京住宅土地出让价格、开发强度与距离之间的曲线,能够描绘出变量之间的复杂关系,更符合北京都市区的实际。     

Urban forest landscape patterns in Ma'anshan City,China

The landscape pattern of Ma'anshan City was analyzed based on theories and methodologies of landscape ecology, remote sensing, global positioning, and a geographic information system (GIS). The study area encompassed the entire built-up area of 63.88 km²; a north–south transect 3-km wide and 13-km long was established along the long axis of the city. Five major landscape elements were assessed: urban land, urban forest, agriculture, water, and grass. Urban land was the dominant land cover type, and occupied 67% of total land area; while patches of urban forest occupied 16%, with a landscape element dominance of 0.42. Urban forest was classified according to land-use category and location into six types: scenic forest, yard forest, recreational forest, roadside forest, shelter forest, and nurseries. There were 2464 urban forest patches, the largest being 185.1 ha, with an average of 0.43 ha. The low nearest neighbor index and high patch density indicated that urban forest patches tend to be aggregated and have a high degree of fragmentation. This study also demonstrated that the spatial pattern of urbanization could be quantified using a combination of landscape metrics and gradient analysis. Urban forest has distinct spatial characters that are dependent on specific landscape metrics along the urbanization gradient.