Incorporating layer- and local-scale heterogeneities in numerical simulation of unsaturated flow and tracer transport

This study characterizes layer- and local-scale heterogeneities in hydraulic parameters (i.e., matrix permeability and porosity) and investigates the relative effect of layer- and local-scale heterogeneities on the uncertainty assessment of unsaturated flow and tracer transport in the unsaturated zone of Yucca Mountain, USA. The layer-scale heterogeneity is specific to hydrogeologic layers with layerwise properties, while the local-scale heterogeneity refers to the spatial variation of hydraulic properties within a layer. A Monte Carlo method is used to estimate mean, variance, and 5th, and 95th percentiles for the quantities of interest (e.g., matrix saturation and normalized cumulative mass arrival). Model simulations of unsaturated flow are evaluated by comparing the simulated and observed matrix saturations. Local-scale heterogeneity is examined by comparing the results of this study with those of the previous study that only considers layer-scale heterogeneity. We find that local-scale heterogeneity significantly increases predictive uncertainty in the percolation fluxes and tracer plumes, whereas the mean predictions are only slightly affected by the local-scale heterogeneity. The mean travel time of the conservative and reactive tracers to the water table in the early stage increases significantly due to the local-scale heterogeneity, while the influence of local-scale heterogeneity on travel time gradually decreases over time. Layer-scale heterogeneity is more important than local-scale heterogeneity for simulating overall tracer travel time, suggesting that it would be more cost-effective to reduce the layer-scale parameter uncertainty in order to reduce predictive uncertainty in tracer transport.     

Development of a Quantitative Pasture Phosphorus Management Tool Using the SWAT Model1

Abstract: Assessment tools to evaluate phosphorus loss from agricultural lands allow conservation planners to evaluate the impact of management decisions on water quality. Available tools to predict phosphorus loss from agricultural fields are either: (1) qualitative indices with limited applicability to address offsite water quality standards, or (2) models which are prohibitively complex for application by most conservation planners. The purpose of this research was to develop a simple interface for a comprehensive hydrologic/water quality model to allow its usage by farmers and conservation planners. The Pasture Phosphorus Management (PPM) Calculator was developed to predict average annual phosphorus (P) losses from pastures under a variety of field conditions and management options. PPM Calculator is a vastly simplified interface for the Soil and Water Assessment Tool (SWAT) model that requires no knowledge of SWAT by the user. PPM Calculator was validated using 33 months of data on four pasture fields in northwestern Arkansas. This tool has been extensively applied in the Lake Eucha/Spavinaw Basin in northeastern Oklahoma and northwestern Arkansas. PPM Calculator allows conservation planners to take advantage of the predictive capacity of a comprehensive hydrologic water quality model typically reserved for use by hydrologists and engineers. This research demonstrates the applicability of existing water quality models in the development of user friendly P management tools.     

三峡库区腹地规模农地空间分布规律

山区农业转型对于我国山区耕地可持续利用效率、土地整治方向以及生态建设方向具有一定的指导意义,渝东北生态涵养发展区是重庆市农用地整治项目的主要分区,通过定义作为农业转型产物的"规模农地"相关概念及其判读标准,旨在提出一种新的研究路径对重庆市典型山区地貌的耕地利用现状给予指导和改善意见。首先选取三峡库区腹地5个区县为研究区,并结合研究区实际对"规模农地"进行等级划分,利用Arc GIS10.2等软件通过景观格局指数、核密度测算、空间自相关等方法从斑块特征、数量分布、空间格局三方面对研究区内规模农地的空间分布规律进行探讨。研究表明:(1)不同类型规模农地斑块特征呈现一定的规律性,小规模农地斑块密度最大为6.004,大规模农地平均最近指数MNN值最低为643.401,且农地规模越大,面积加权平均斑块分维数AWMPFD值和聚集度AI值越高;(2)中、大规模农地数量多集中在奉节县,微、小规模则多集中在巫山县,且规模农地自身及其相互之间存在固定的邻接性规律,即同类斑块之间的邻接性与其斑块大小成反比,不同类型斑块之间则与之相反;(3)研究区规模农地整体空间分布主要集中在奉节县中部以及巫溪县东部,沿江流域的平坝地区分布相对密集,且不同类型规模农地在空间上存在明显的自相关性。     

Application of Forensic Techniques for Age Dating and Source Identification in Environmental Litigation

A multitude of forensic techniques are available for age dating and source identification, including corrosion models for underground storage tanks, the commercial availability of a compound, chemical associations with discrete types of manufacturing processes, chemical profiling, proprietary additives, stable isotope analysis, degradation models, biomarkers and contaminant transport models. The selection and use of these techniques in environmental litigation must be thoroughly understood and applied to be effective as forensic evidence. When introduced as scientific evidence, the governing assumptions and quality of the data are critically evaluated and frequently successfully challenged. The purpose of this paper is to present an overview of commonly used environmental forensic techniques and their possible applications so that a user can decide which technique or combination of methods is most appropriate for their case.     

锰资源开发利用中存在的问题和对策——以秀山锰矿为例

针对秀山锰矿开采秩序混乱、效率偏低、矸石处理、电解锰渣堆存和生产废水、锰深加工路线不健全等特点,结合其他地区锰资源的开发利用情况,提出了秀山锰矿应扩大开采规模,规范管理,矸石用于充填安全柱,加高加固锰渣尾矿库,锰渣的资源化利用等措施;提取生产废水中的金属元素,减少废水产生量,废水达标处理和循环利用降低污染;依靠发展和扩大锰产业链,加大科技投入,促进秀山的可持续发展.     

辉县市城区环境空气质量现状及污染防治对策

对辉县市城区2006—2011年间环境空气质量监测数据进行了评价,并对城区污染物浓度时空变化进行了分析。结果表明,辉县市城区大气污染主要表现为可吸入颗粒物污染严重,主要是能源结构不合理、锅炉废气污染严重、城区道路保洁方式落后等原因造成的,由此提出了合理规划城市布局、减少结构性污染等对策。     

曝气沉砂池除砂机理分析

针对曝气沉砂池小试装置模型,通过配砂实验对沉砂池除砂率进行统计分析,研究曝气强度与HRT对沉砂池除砂率的影响。实验结果表明,不同曝气强度下,随着HRT变化,除砂率逐渐上升,并最终趋于平衡状态;不同HRT下,曝气强度与除砂率近似呈现一定的线性关系,且随着曝气强度的增大,除砂率降低;在HRT小于1min时,砂粒的运行路径和沉降时间缩短,不利于砂粒的去除;在HRT大于1min时,其中1、3和4min,随着气水比的增加除砂率降低幅度相对较小,曝气所引起的横向环流在一定程度上有利于砂粒的沉降,而HRT为2min时,除砂率降幅却很大,这与砂粒在曝气沉砂池池体断面分布有关,即断面处旋转流速和水平流速的大小变化将影响砂粒的运动;相比曝气强度,HRT对除砂率的影响较大。     

Risk assessment and prioritisation of contaminated sites on the catchment scale

Contaminated sites pose a significant threat to groundwater resources worldwide. Due to limited available resources a risk-based prioritisation of the remediation efforts is essential. Existing risk assessment tools are unsuitable for this purpose, because they consider each contaminated site separately and on a local scale, which makes it difficult to compare the impact from different sites. Hence a modelling tool for risk assessment of contaminated sites on the catchment scale has been developed. The CatchRisk screening tool evaluates the risk associated with each site in terms of its ability to contaminate abstracted groundwater in the catchment. The tool considers both the local scale and the catchment scale. At the local scale, a flexible, site specific leaching model that can be adjusted to the actual data availability is used to estimate the mass flux over time from identified sites. At the catchment scale, a transport model that utilises the source flux and a groundwater model covering the catchment is used to estimate the transient impact on the supply well. The CatchRisk model was tested on a groundwater catchment for a waterworks north of Copenhagen, Denmark. Even though data scarcity limited the application of the model, the sites that most likely caused the observed contamination at the waterworks were identified. The method was found to be valuable as a basis for prioritising point sources according to their impact on groundwater quality. The tool can also be used as a framework for testing hypotheses on the origin of contamination in the catchment and for identification of unknown contaminant sources.     

企业安全文化评估与企业安全行为的质化研究

通过总结国内外各种不同的安全文化概念,归纳分析了国内外较为流行的近10种安全文化建立模式。在研讨文献的基础上,通过深入访谈、焦点小组与参与观察,归纳构造了一套共11个维度,总题项为152题的安全文化评估量表。通过对选定企业的实证问卷调查,进行统计分析,采用多元逐步回归分析等方法对安全文化各评核因素及整体安全文化进行预测,并以百分数呈现其整体的安全文化现状水平。通过基于扎根理论的各种质化研究方法,对案例企业的安全文化建设和企业安全行为进行研究,得到了7点关于企业安全行为的研究发现,并提出了相应的改进建议。     

电厂循环冷却水处理方案试验

实验研究了阻垢剂HEDP、EDTMPS、PBTCA、DTPMPA、ATMP、PAPEMP在电厂循环水中的应用.通过实验筛选出具有良好处理功效的复合配方:ATMP6mg/L、DTPMPA 4 mg/L、PBTCA 3 mg/L,相应的阻垢率达到92.42%.该复合配方在阻垢性能方面存在协同效应,使得复配处理剂具有良好的阻垢效果.