THE EFFECTS OF DIURNAL MIXING ON THERMAL STRATIFICATION OF STATIC IMPOUNDMENTS1

ABSTRACT: The time variation in the temperature distribution of a static water impoundment is predicted. The body of water is modeled as a discrete number of horizontally isothermal layers and the energy equation is solved using an implicit numerical scheme. Vertical energy transport mechanisms included are solar absorption, molecular diffusion, and convective mixing due to nocturnal turnover. The latter mechanism, called diurnal mixing, is found to have a profound effect on the stratification, particularly in the eplimnion patterns for a typical deep static impoundment.     

多极涡流管式混合器的设计与混合效能

本文主要论述了依据絮凝动力学中涡旋理论设计的多极涡流管式混合器及其絮凝试验的研究结果，同时讨论了影响多极涡流管式混合器混合效能的管径及流量等因素，结果证实，该混合器适合于无机高分子絮凝剂的絮凝动力学反应特点，具有较高的工程推广和应用价值。     

旋转流厌氧附着膜膨胀床运行及水力流态研究

试验以树脂为载体,用自行设计的旋转流厌氧附着膜嘭胀床处理高浓度有机废水.经过启动、中等负荷稳定运行及高负荷稳定运行等阶段,成功地培养出高效生物膜颗粒,最高有机负荷达46.4 kg/(m3·d).相应的COD去除率大于80%.在反应器运行过程中采用脉冲示踪法,以LiCl作示踪剂,对反应器的水力流态规律进行了系统的试验研究.研究表明,水力上升流速及气体负荷是影响反应器容积利用率及反应器内固液两相混合程度的重要因素.     

Arrived in the light: diel and seasonal activity patterns in wild Verreaux’s sifakas (<Emphasis Type="Italic">Propithecus v. verreauxi</Emphasis>; Primates: Indriidae)

Madagascar is characterised by pronounced annual climatic and ecological seasonality and harbours a radiation of closely related sympatric primates (Lemuriformes) that exhibit diurnal, nocturnal and cathemeral activity patterns. We collected continuous activity data over a complete annual cycle from wild diurnal Verreauxs sifakas (Propithecus v. verreauxi) to contribute detailed and comparative data: (1) to characterise their diel and seasonal activity rhythms, (2) to identify factors shaping variation in activity rhythms, and (3) to help reconstruct the evolutionary transition from nocturnal to diurnal activity. We fitted eight adult sifakas from seven different groups living in Kirindy forest with an accelerometer/data logger device and recorded their activity in 5-min bins for a total of 12 months. We characterise P. verreauxi as a strictly diurnal species with a pronounced bimodal activity pattern that briefly changed to a more unimodal pattern during their annual mating season (January to March). We documented significant annual variation in total daily activity, activity time, and activity level, as well as in most parameters characterising their bimodal activity pattern. Despite a significant positive correlation of the animals activity time with day length, pronounced annual variation in the phase position of onset and end of activity in relation to sunrise and sunset times could also be discerned. Minor enhancing effects of moonlight on nocturnal activity were only found for the first 3 h of the inactivity period. Bimodality of the activity pattern and the additional reduction of activity time during the cold and dry winter months associated with reduced food availability can be interpreted as flexible behavioural adaptations to reduce energy expenditure. We therefore propose that energetic and thermoregulatory benefits are important factors shaping these primates activity pattern.Communicated by C. Nunn     

北京市土壤重金属形态分析

采用Tessier连续提取法对北京市朝阳、通州、石景山、海淀、顺义等地土壤进行重金属元素锌、铅、铬的形态分析,并用原子吸收分光光度法测定了重金属元素的含量。研究结果表明,在所测区土壤中,铬主要以可交换态和残渣态存在,说明元素铬较活泼,具有潜在的环境影响能力;锌元素主要以有机结合态和残渣态存在,说明元素锌相对比较稳定;而铅则主要以可交换态形式存在,说明铅最为活泼,应该给予更多的关注。     

Similarity theory and parameterization of mixing in the upper ocean

Boundary layers with small thermal and mechanical inertia are close to steady-state conditions. This underlies the Monin-Obukhov similarity theory and explains why the surface values of the fluxes can be chosen as external parameters. For fluids with large thermal inertia, such as the ocean, the thermal time scale is relatively large, and the density flux is a complex function of depth; thus, the external thermal forcing is no longer a governing parameter. However, the mechanical inertia of the upper ocean is about three orders of magnitude smaller than the thermal inertia. Consequently, the upper ocean can be considered as steady-state in the dynamic sense, to any dynamic property depends primarily on the depth, the surface momentum flux, and the vertical density structure. This property allows us to suggest an alternative formulation of the similarity theory for the stratified boundary layers through specification of a new stratification parameter which characterizes the internal density structure instead of the external density flux. The turbulent mixing coefficient is derived as dependent on the stratification parameter. The latter includes the surface stress and the integral density deficit for the entire layer above. The general form and the asymptotic behavior of the nondimensional turbulent mixing coefficient as a function of the stratification parameter are obtained using dimensional considerations. Determination of numerical parameters is based on 8 years of temperature profiles acquired at the Ocean Weather Ship (OWS) PAPA. Finally, a method for calculating the profile of the turbulent mixing coefficient is obtained. This approach reproduces the 8-year evolution of the upper ocean with the maximum rms difference of approximately 1C and the bias of 1C over the depth range 0–150 m. Additional 1-year simulation of the upper ocean at OWS CHARLEY and 9-year simulation at OWS NOVEMBER confirms reasonable applicability of this approach. The proposed simple turbulent mixing scheme reproduces the evolution of the upper ocean with accuracies similar to those obtained using much more complicated models.     

Upstream Turbulence Effect on Pollution Dispersion

Experiments have been carried out to investigate turbulence at and above roof-level in an urban environment, and to predict the behaviour of street pollution from experiments using dye dispersion, for different roughness conditions and bed geometries. The flow in the boundary layer above an idealised urban environment has been simulated in a laboratory water flume. Comparisons have been made for the same model street canyon with and without the presence of upstream roughness. In the tests reported here, model street canyons were aligned perpendicular to the flow direction, and velocity measurements made within and above the model street canyons using a laser Doppler velocimeter (LDV). Flow visualisation techniques have also been used to confirm the gross flow features from streak images. Turbulence generated from the upstream roughness has a significant effect on the turbulence production and dispersion behaviour of the dye simulating pollution in street canyons.     

深圳市盐田区植被格局分析

运用景观生态学的方法 ,选取斑块形状指数、斑块形状破碎化指数、分维数、景观多样性指数、均匀度、相对丰富度、优势度等指标 ,对深圳盐田区的植被格局进行分析。结果显示 :在城乡发展过程中 ,盐田区植被景观保存较好 ,类型丰富 ;植被景观总体上呈现出符合其生境特征的规则分布 ;群落景观异质性较高 ,拥有南亚热带的沟谷雨林、山地常绿阔叶林、红树林等特色植被景观 ;沟谷雨林和季风常绿林是本区较脆弱的生态系统 ,应积极加以保护和发展     

Boundary Layer Evolution and its Influence on Ground-Level Ozone Concentrations

Accurate determination of the planetary boundary layer (PBL) height (i.e., mixing height (MH)) is critical to properly simulating pollutant levels with the grid-based photochemical models. In this study, the daytime mixing heights based on the parcel and bulk Richardson number methods are compared with those obtained directly from a numerical mesoscale meteorological model in an effort to evaluate the uncertainties in the estimation of the PBL evolution. Mixing heights are estimated from hourly outputs of meteorological variables of the Penn State/NCAR Mesoscale Model Version 3.3 (MM5V3) with two PBL schemes (Blackadar and Gayno-Seaman) during July 1999 over Philadelphia, PA. An analysis of the diurnal variation in the urban PBL and its influence on ground-level ozone (O₃) levels is presented in this paper. The results indicate that on average, the MHs determined from the bulk Richardson number were larger than those estimated from the parcel method. The MHs from the MM5V3 output were much smaller than those derived from the parcel and bulk Richardson number methods, especially for the Gayno-Seaman scheme that is based on turbulent kinetic energy. The MH and ground-level O₃ concentration have been found to be twice as much on episode days than on non-episode days. The average hourly MH growth rate and O₃ tendency (i.e. rate of change in O₃) were largest during the morning hours (0700 to 1000 eastern standard time (EST)), suggesting that vertical mixing contributes significantly to the accumulation of ground-level O₃ in urban areas in the morning hours.     

浙西山区水库小流域放逸短沟蜷的空间格局

放逸短沟蜷(Semisulcospira libertina)是浙西山区水库小流域底栖螺类的优势种，定量采集不同环境条件的9个样点的标本，分别采用Taylor幂法则、Iwao聚集格局回归分析法及Morisita指数公式计算和统计分析，结果显示，所调查流域的放逸短沟蜷种群密度差异极显著，其种群空间格局理论上属于聚集型负二项分布，主要是由环境污染和流域底质所致。图2表3参10