一个解析的面源浓度计算公式

利用级数展开的方法得到一个实用的解析面源公式,它不仅包括了显式源高项,还能计算面源烟羽横风向非轴线浓度,其精度远远高于其它有关模式。此外,利用该公式,研究了面源烟羽的半宽度,并证明,难以用一个固定的后退点源来描述整个面源烟羽,提出可用一移动点源来代替。     

Evaluating and structuring indicators for wetland assessment

Wetland assessment has been a popular field of research worldwide. However, various indicators have been used in wetland assessment for different purposes and backgrounds and also because of the research limitations. Therefore, a more comprehensive, sound, and efficient indicator system is needed for researchers’ referencing to evaluate wetlands. After an extensive review of wetland assessment literatures, the reported indicators were evaluated using the developed assessment system, based on the Analytical Hierarchy Process (AHP) with three main goals: nature protection, function utilization, and sustainable development. Each indicator was evaluated using two methods. The first method was to study the percentage of the indicator application, and the second was to assess the weighted ratios assigned to the indicators according to principles of comparability, typicality, sensibility, and availability. The results of these two methods were compared to study the commonalities and specialties of the indicators. They also showed that some indicators were widely used, including biodiversity, weather and climate, hydrological change, and the output of wetland. On the other hand, other sustainable indicators were easily ignored, such as environmental carrying capacity and wetland planning. Furthermore, an indicator system for wetland assessment was structured and strategized to discuss how to choose indicators for wetland assessment under different conditions. The proposed approach can be used to guide the process of wetland assessments in the future.     

Priority analysis for risk factors of equipment in a hydraulic turbine generator unit

Ensuring the safe operation of hydropower stations is one of the key challenges for electric generation. Clearly the safe operation of such systems can only be archived with proper and effective maintenance scheduling. The objective of this study is to analyze, rank and prioritize the risk factors responsible for equipment failures of a hydraulic turbine generator unit (HTGU) based on operating data and expert elicitation. Here a simple qualitative risk evaluation model is proposed able to consider seven typical failures in HTGU. The proposed tool is applied for the risk prioritization of equipment failures, e.g. shaft torsion, misalignment, rotating fault, axis bend, runner fault, water guide, and wicket gate of a hydropower station in China. The obtained results have been compared against the actual statistics of equipment failures of a hydropower station in China, considered showing good agreement. All of these results provide theoretical guidance for digitalization realization of equipment failures.     

污染场地土壤通用评估基准建立的理论和常用模型

污染场地土壤通用评估基准的建立与每个国家的经济水准及社会发展紧密相关.从国际相关领域的发展趋势来看,场地基准的建立基于风险基础之上.我国正在颁布污染场地风险评估技术导则(C-RAG),表明我国已选择风险基础上的污染场地管理模式.文章回顾了污染场地土壤通用评估基准建立的理论、方法及通用模型,并推荐污染场地评估的模型框架,...     

生态文明建设评价指标体系构建与实证分析——以黑龙江省为例

在深刻解读生态文明建设的本质、总结梳理已有生态文明指标体系的基础上,通过专家咨询,系统地构建了一套完整的符合我国国情的生态文明评价指标体系。该指标体系以生态文明建设水平为目标层,下设生态社会、生态经济、生态环境、资源保障、制度建设5个准则层,构建出包含26项指标的生态文明建设评价指标体系。以黑龙江省为例,运用层次分析法对指标赋予权重,收集黑龙江省2006~2013年最新相关统计数据,对黑龙江省生态文明建设进行实证分析与评价,表明黑龙江省生态文明建设进展较为顺利,但在生态文明建设过程中各层面发展不均衡,为此提出应着重加强完善相关制度建设、进一步提高生态资源节约水平、更加全方位保护生态环境的策略。     

Simulation of the effect of remediation on EDB and 1,2-DCA plumes at sites contaminated by leaded gasoline

An analytical model is used to simulate the effects of partial source removal and plume remediation on ethylene dibromide (EDB) and 1,2-dichloroethane (1,2-DCA) plumes at contaminated underground storage tank (UST) sites. The risk posed by EDB, 1,2-DCA, and commingled gasoline hydrocarbons varies throughout the plume over time. Dissolution from the light nonaqueous phase liquid (LNAPL) determines the concentration of each contaminant near the source, but biological decay in the plume has a greater influence as distance downgradient from the source increases. For this reason, compounds that exceed regulatory standards near the source may not in downgradient plume zones. At UST sites, partial removal of a residual LNAPL source mass may serve as a stand alone remedial technique if dissolved concentrations in the source zone are within several orders of magnitude of the applicable government or remedial standards. This may be the case with 1,2-DCA; however, EDB is likely to be found at concentrations that are orders of magnitude higher than its low Maximum Contaminant Level (MCL) of 0.05 μg/L (micrograms per liter). For sites with significant EDB contamination, even when plume remediation is combined with source depletion, significant timeframes may be required to mitigate the impact of this compound. Benzene and MTBE are commonly the focus of remedial efforts at UST sites, but simulations presented here suggest that EDB, and to a lesser extent 1,2-DCA, could be the critical contaminants to consider in the remediation design process at many sites.     

Analytical solution to evaluate salt precipitation during CO2 injection in saline aquifers

Carbon dioxide sequestration in deep saline aquifers is a means of reducing anthropogenic atmospheric emissions of CO₂. Among various mechanisms, CO₂ can be trapped in saline aquifers by dissolution in the formation water. Vaporization of water occurs along with the dissolution of CO₂. Vaporization can cause salt precipitation, which reduces porosity and impairs permeability of the reservoir in the vicinity of the wellbore, and can lead to reduction in injectivity. The amount of salt precipitation and the region in which it occurs may be important in CO₂ storage operations if salt precipitation significantly reduces injectivity. Here we develop an analytical model, as a simple and efficient tool to predict the amount of salt precipitation over time and space. This model is particularly useful at high injection velocities, when viscous forces dominate.First, we develop a model which treats the vaporization of water and dissolution of CO₂ in radial geometry. Next, the model is used to predict salt precipitation. The combined model is then extended to evaluate the effect of salt precipitation on permeability in terms of a time-dependent skin factor. Finally, the analytical model is corroborated by application to a specific problem with an available numerical solution, where a close agreement between the solutions is observed. We use the results to examine the effect of assumptions and approximations made in the development of the analytical solution. For cases studied, salt saturation was a few percent. The loss in injectivity depends on the degree of reduction of formation permeability with increased salt saturation. For permeability-reduction models considered in this work, the loss in injectivity was not severe. However, one limitation of the model is that it neglects capillary and gravity forces, and these forces might increase salt precipitation at the bottom of formation particularly when injection rate is low.     

离子色谱技术在环境监测中的应用

详细介绍了离子色谱仪的构造，功能，以及离子色谱技术的发展状况，离子色谱作为一种新的分析方法以其独特的优点可广泛应用于水，气，土壤，生物等环境监测领域。     

水和废水中亚硝酸盐氮的现场快速分析方法研究

在现行水中亚硝酸盐氮分析方法的基础上,通过试验研究,采用便携式分光光度计建立了水体中亚硝酸盐氮的分析方法。该法与GB7493-87[N-(1-萘基)-乙二胺光度法]具有良好的可比性,分析结果的精密度和准确度均为良好,该方法可在现场简便快速测定水和废水中的亚硝酸盐氮。     

An analytical model for the interpretation of pulse injection experiments performed for testing the spatial variability of clay formations

This paper presents an analytical model to describe pulse injection experiments. This model solves the advection-diffusion equation while taking into account back diffusion from the clay core to the inlet and from the outlet to the clay core. In most analytical models, back diffusion is neglected. For sufficiently high Péclet numbers, this is a good approximation. However, in experiments where the Péclet number is low, back diffusion is important and must be taken into account. An additional advantage of the present model is that both concentration and flux are conserved at the inlet and at the outlet of the clay core. This model is used to fit pulse injection experiments with iodide and tritiated water (HTO) in clay cores. The (new) model is required for fitting the experimental results since in clay layers advection is very slow leading to a low Péclet number. The experiments are performed on clay cores taken from different depths from the Boom Clay and the Ypres Clay layer under the site of the nuclear power plant of Doel (Belgium). The quality of all fits is excellent and the obtained parameter values are coherent. For HTO, the fitted value for the diffusion accessible porosity is consistent with measurements of the water content in Ypres Clay cores. In both types of clays, the apparent diffusion coefficient at zero flow is between 10(-10) and 2 x 10(-10) m(2)/s for iodide and between 2 x 10(-10) and 3 x 10(-10) m(2)/s for HTO. The dispersion length is in the order of 10(-3) m. The average value for the diffusion accessible porosity is between 0.35 and 0.4 for HTO and between 0.2 and 0.25 for iodide.