Cadmium kinetics in freshwater clams (Unionidae) under field and laboratory conditions.

Cadmium dosing experiments were carried out with the freshwater clam Unio pictorum in flow-through micro-streams in order to obtain additional information on the kinetics of cadmium accumulation and elimination. Accumulation of cadmium in the kidney was rapid and within 3 weeks a concentration factor of 6000 was found. During elimination (29 weeks), the organs lose about one-third of their cadmium content rather rapidly, but no further elimination occurs. It can be concluded that the process of Cd accumulation is rapid and almost irreversible.     

中国国情下的绿色建筑

1绿色建筑必须考虑中国国情 "绿色"概念,也就是可持续发展概念本身就强调实事求是和因地制宜.中国是一个发展中的大国,人口数量巨大,国土与资源有限,按温家宝总理的数学:再小的消耗乘上13亿人就是巨大的量,再大的产量和储量被13亿人除就是很小的量.所以在中国发展绿色建筑、制订标准和进行评估必须考虑中国国情.     

Soil-pipe-atmosphere interaction under field conditions

Bulletin of Engineering Geology and the Environment - Unsaturated clay deposits swell and shrink as a result of seasonal variations in climatic conditions and affect the performance of underground...     

Wind field simulation of large horizontal‐axis wind turbine system under different operating conditions

This paper proposes a technique of generating turbulent wind velocities on large horizontal‐axis wind turbine systems under different operating conditions. The rotational sampling effect, vertical wind shear and coherence between wind velocities at blades and on the tower were taken into account. Coordinate system of wind time series at certain discrete sampling points on the vertical plane of the wind turbine is generated by the hybrid weighted amplitude wave superposition and proper orthogonal decomposition (POD) methods. The POD eigenmodes on the blades after updating locations were calculated subsequently using B‐spline surface interpolation method, and the rotationally sampled wind velocities are reconstructed by taking advantage of POD method again. Examples are subsequently presented to validate this proposed technique and demonstrate the generation of wind velocities under different operating conditions. The results show that the simulated spectrum of turbulent wind velocities at blades corresponds well to the measured data and that on the tower agrees well with the fixed point Kaimal spectrum. The reasonable sampling points spacing is suggested to be about 10 m for the wind field simulation of wind turbine system. The proposed method is of great advantage in accuracy and efficiency, which is greatly significant for the fine analysis of multi‐megawatt wind turbines. Copyright © 2015 John Wiley & Sons, Ltd.     

Electro-dewatering of wastewater sludge: influence of the operating conditions and their interactions effects

Electric field-assisted dewatering, also called electro-dewatering (EDW), is a technology in which a conventional dewatering mechanism such a pressure dewatering is combined with electrokinetic effects to realize an improved liquid/solids separation, to increase the final dry solids content and to accelerate the dewatering process with low energy consumption compared to thermal drying. The application of these additional fields can be applied to either or both dewatering stages (filtration and/or compression), or as a pre-or post-treatment of the dewatering process. In this study, the performance of the EDW on wastewater sludge was investigated. Experiments were carried out on a laboratory filtration/compression cell, provided with electrodes, in order to apply an electrical field. The chosen operating conditions pressure (200-1200 kPa) and voltage (10-50 V) are sufficient to remove a significant proportion of the water that cannot be removed using mechanical dewatering technologies alone. A response surface methodology (RSM) was used to evaluate the effects of the processing parameters of EDW on (i) the final dry solids content, which is a fundamental dewatering parameter and an excellent indicator of the extent of EDW and (ii) the energy consumption calculated for each additional mass of water removed. A two-factor central composite design was used to establish the optimum conditions for the EDW of wastewater sludge. Experiments showed that the use of an electric field combined with mechanical compression requires less than 10 and 25% of the theoretical thermal drying energy for the low and moderate voltages cases, respectively.     

Cadmium and zinc in soil solution extracts following the application of phosphate fertilizers

This study investigated the solubility of cadmium and zinc in soils after the application of phosphate fertilizers containing those two metals. The solubility of cadmium and zinc was assessed by measuring their concentration in soil water extracts. Three monoammonium phosphate fertilizers containing various amounts of metals were applied on cultivated fields for 3 years at three different rates. In order to investigate the effects of long-term applications of fertilizers on the solubility of Cd and Zn, a similar design was used to apply contaminated fertilizers to soils in a laboratory experiment using a single fertilizer addition equivalent to 15 years of application. Phosphate fertilizers increased the concentration of Cd in soil extracts compared to control in 87% and 80% of the treatments in field and laboratory experiments respectively. Both increasing the rate of application and using fertilizer containing more Cd lead to higher Cd concentrations in extracts for the field and the laboratory experiments. The addition of the equivalent of 15 years of fertilizer application in the laboratory results in higher Cd concentration in extracts compared to the field experiment. For Zn, the fertilizer treatments enhanced the metal solution concentration in 83% of field treatments, but no significant correlations could be found between Zn inputs and its concentration in solution. In the laboratory, fertilizer additions increase the Zn concentrations in 53% of the treatments and decrease it in most of the other treatments. The decrease in Zn concentrations in the laboratory trial is attributed to the higher phosphate concentrations in the soil solution; which is presumed to have contributed to the precipitation of Zn-phosphates. For both trials, the metal concentrations in soil extracts cannot be related to the Zn concentration in the fertilizer or the rate of application. The high Zn to Cd ratio is presumably responsible for the Cd increase in the soil extracts due to competitive displacement by Zn. Finally, the observed acidification of soils with fertilizer application will also contribute to metal solubilisation.     

Loss of infectivity of poliovirus 1 in river water under simulated field conditions

The effects of light, virus concentration, and turbidity on the rate of loss of infectivity (LOI) of poliovirus 1 were investigated in two test systems, which utilized flowing river water. Two levels of each variable were used in a 2³ confounded factorial design. The seeded systems were sampled at regular intervals to establish LOI rates. Virus infectivity was measured by plaque assay. Loss of infectivity followed a two-component curve; an initial, rapid phase followed by a second, slower component. The slopes of the two components were examined by the analysis of variance to determine the potential influence of each variable. Both light and turbidity exerted a significant influence on the LOI rate in the second component of the LOI curve and also in the transition period between the two components; however, during the initial, rapid phase none of the variables influenced the LOI rate (at the 0.05 significance level). This research demonstrates the significance of light as a virucidal component in the aquatic environment.     

Cadmium and zinc concentrations in drinking water supplies of Dhaka City, Bangladesh

The cadmium concentration in different drinking water supplies of Dhaka City is reported. In this study, cadmium was extracted from water into chloroform after chelation with sodium diethyldithiocarbamate and then back extracted into water for determination by atomic absorption spectrophotometry (AAS). The concentration of cadmium in source water is below the detection limit (51 micrograms l-1) and that in supply water (tap water) and tube-well water ranges from 1.03 to 1.58 and 1.71 to 2.24 ppb, respectively. The corresponding zinc content ranges from 0.013 to 0.30, 0.018 to 3.8 and 0.042 to 0.37 ppm. The implications of these findings are discussed.     

Imaging of engineered nanoparticles and their aggregates under fully liquid conditions in environmental matrices

The increasing industrial production of engineered nanoparticles (ENPs) raises concern over their safety to humans and the environment. There is a lack of knowledge regarding the environmental fate and impact of ENPs and in situ methods are needed to investigate e.g. nanoparticle aggregation and adsorption in the media of concern such as water, sediment and soil. In this study, the application of wet scanning electron microscopy (WetSEM™) technology in combination with energy dispersive x-ray spectroscopy (EDS) to visualise and elementally identify metal and metal oxide nanoparticles (Au, TiO₂, ZnO and Fe₂O₃) under fully liquid conditions in distilled and lake water as well as in a soil suspension has been investigated. WetSEM™ capsules comprise an electron transparent membrane enabling the imaging and EDS analysis of liquid samples. Results are compared with conventional SEM images and show that WetSEM™/EDS is a promising complementary tool for the in situ investigation of ENPs and their aggregates in natural matrices. In combination with other analytical tools (e.g. HDC- or FFF-ICP-MS, DLS), WetSEM™ could help to provide a better understanding of the fate and behaviour of ENPs in the environment.     

黄土隧道特殊地质条件下的换拱技术总结

结合山西吕梁环城高速公路磨湾2号隧道换拱施工经验,重点阐述了特殊地形条件下,黄土隧道换拱的施工工艺及具体施工流程,较好地解决了施工中的诸多难题,坚持以人为本、安全第一的原则,保证了隧道换拱的施工安全。     

Protecting fire fighters exposed in room fires,part 2: Performance of turnout coat materials under actual fire conditions

Seven experimental fires varying in fire load were conducted in a simulated townhouse. Specimens of various current fire fighters turnout coat materials were exposed in the room of fire origin. The time at which conditions would become untenable for the fire fighter due to pain, as well as the time to second degree burn, were calculated. These times ranked the coat specimens in roughly the same order as the Thermal Protection Performance measured according to NFPA 1971–1986, especially if the heat in the room developed rapidly.This paper is a contribution of the National Institute of Standards and Technology (formerly National Bureau of Standards) and is not subject to copyright.     

冬季无霜工况下闭式热源塔的动态换热特性

为研究闭式热源塔冬季无霜工况下的传热过程,利用有限差分法建立了闭式热源塔冬季无霜工况下的动态传热传质模型。将实验数据与数值计算结果进行对比,验证了模型的有效性。误差分析结果表明：溶液出口温度的均方根误差为0.201℃。通过实验与模拟方法分析了机组变负荷运行时闭式热源塔的动态换热特性,结果表明：当热泵机组变工况运行时,闭式热源塔作为取热装置,可为机组蒸发器提供温度相对稳定的热源;此外,与传统空气源热泵相比,闭式热源塔在低温高湿环境下的结霜风险更小,节能潜力更大。     

沥青转运车温度场无线测试系统设计

选用新型的数字温度传感器结合无线数传模块,实现对沥青转运车温度场数据的高速巡检和数据管理,并结合软件上采取一定的措施,从而使巡检速度明显得到提高。     

寒流降温作用下混凝土温度场传递特性分析

根据冬季某温度场试验现场的实测数据,用数值分析方法研究了在寒流降温作用下混凝土温度场传递的波动幅度衰减性和时间滞后性,提出了求解混凝土板件一维热传导温度场的函数表达式,并用ANSYS热分析[2]的方法对结论进行了验证,得出有限元计算结果与实测数据规律一致的结论。     

Predicting psychrometric conditions in biocontaminant microenvironments with a microclimate heat and moisture transfer model -- description and field comparison

A numerical model is described that is designed to model psychrometric conditions in biocontaminant microenvironments, such as in bedding and the base of carpets for dust-mites, and on the surface of linings for molds. The model is very general and can include room air, other room components, other zones including the outdoors, other rooms and any subfloor space. Mechanical plant can be modeled. Good agreement between modeled and field results are reported for the complex case of an occupied bed and for the microclimate in the base of a carpet, before and after its timber floor above a crawl space was retrofitted with insulation. PRACTICAL IMPLICATIONS: Biocontaminants such as dust-mites and molds can pose serious health problems. Understanding microclimates in biocontaminant microhabitats, when coupled with biologic models, will make it possible to predict how the life cycles of these biocontaminants are affected as these conditions change. In turn, this will suggest which interventions that modify indoor climate and microclimate are likely to control these biocontaminants. Furthermore such interventions might include indoor humidity control, changing building insulation and ventilation levels, covering mattresses, use of electric blankets, use of carpet heating, etc. Such models will provide a fast way for screening for interventions that are likely to be effective in the control of biocontaminants.     

变温入流条件下的U形地埋管换热能效

针对变温入流工况下地埋管换热能效系数的变化特征,将其表示为最大埋管换热温差比φ与热泵机组出口水温差比σ的乘积,利用基于多极理论的U形地埋管三维传热模型,模拟分析了建筑负荷、埋管流量、主机性能对地埋管换热能效的影响规律,为优化地埋管地源热泵系统的设计提供技术支持。     

Membrane gas transfer under conditions of creeping flow: modeling gas composition effects

A computational model was developed to predict gas transfer and gas composition changes in membrane modules designed for addition of gases to groundwater. The model was verified using pilot-scale gas transfer experiments. The modeling and experimental results suggest that back diffusion of dissolved gases into the membrane has a significant effect on gas transfer via hollow-fiber membrane. In the experimental study, N(2) back-diffusion reduced the partial pressure of O(2) within the membrane and decreased the concentration gradient for gas transfer. The model was able to simulate both the dynamic and steady-state gas transfer behavior of the membranes under a variety of operating conditions. This model can be used to estimate gas transfer as a function of different membrane module design and operating conditions.