Experimental Study of the Criteria of Flow Laminarization in Two-Dimensional Dense Gas Plumes

Laminarization of flow in a two-dimensional dense gas plume was experimentally investigated in this study. The plume was created by releasing CO₂ through a ground-level line source into a simulated turbulent boundary layer over an aerodynamically rough surface in a meteorological wind tunnel. The bulk Richardson number (Ri_*), based on negative plume buoyancy, plume thickness, and friction velocity, was varied over a wide range so that the effects of stable stratification on plume laminarization could be observed. A variety of ambient wind speeds as well as three different sizes of roughness arrays were used so that possible effects of roughness Reynolds number (Re_*) on plume laminarization could also be identified. Both flow visualization methods and quantitative measurements of velocity and intermittency of turbulence were used to provide quantitative assessments of plume laminarization.Flow visualization provided an overall picture of how the plume was affected by the negative buoyancy. With increasing Ri_*, both the plume depth and the vertical mixing were significantly suppressed, while upstream propagation of the plume from the source was enhanced. The most important feature of the flow revealed by visualization was the laminarization of flow in the lower part of the plume, which appeared to be closely related to both Ri_* and Re_*.Measurements within the simulated dense gas plumes revealed the influence of the stable stratification on mean velocity and turbulence intensity profiles. Both the mean velocity and turbulence intensity were significantly reduced near the surface; and these reductions systematically depended on Ri_*. The roughness Reynolds number also had considerable influence on the mean flow and turbulence structure of the dense gas plumes.An intermittency analysis technique was developed and applied to the digitized instantaneous velocity signals. It not only confirmed the general flow picture within the dense plume indicated by the flow visualization, but also clearly demonstrated the changes of flow regime with variations in Ri_* and Re_*. Most importantly, based on this intermittency analysis, simple criteria for characterizing different flow regimes are formulated; these may be useful in predicting when plume laminarization might occur.     

无线传感器网络在环境监测中的应用

介绍了一种基于无线传感器网络的环境监测系统组成及架构,讨论了系统网络节点、网关的硬件设计,并对基于TinyOS的应用程序组件结构和节点工作流程做了说明。     

环境气体标准样品量值的计算及不确定度分析

依据《气体分析校准气体混合物的制备重量法》（1SO6142—2001）和《气体分析气体标准样品组成的测定和校验比较法》（ISO6143—2001）,阐述了环境气体标准样品不同定值方法的量值计算及不确定度来源,并比较了同一气体标准样品采用不同定值方法得到的不同量值结果及不确定度：     

IFTCIP: An Integrated Optimization Model for Environmental Management under Uncertainty

In this study, an interval-fuzzy two-stage chance-constrained integer programming (IFTCIP) method is developed for supporting environmental management under uncertainty. The IFTCIP improves upon the existing interval, fuzzy, and two-stage programming approaches by allowing uncertainties expressed as probability distributions, fuzzy sets, and discrete intervals to be directly incorporated within a general mixed integer linear programming framework. It has advantages in uncertainty reflection, policy investigation, risk assessment, and capacity-expansion analysis in comparison to the other optimization methods. Moreover, it can help examine the risk of violating system constraints and the associated consequences. The developed method is applied to the planning for facility expansion and waste-flow allocation within a municipal solid waste management system. Violations of capacity constraints are allowed under a range of significance levels, which reflects tradeoffs between the system cost and the constraint-violation risk. The results indicate that reasonable solutions for both binary and continuous variables have been generated under different risk levels. They are useful for generating desired decision alternatives with minimized system cost and constraint-violation risk under various environmental, economic, and system-reliability conditions. Generally, willingness to take a higher risk of constraint violation will guarantee a lower system cost; a strong desire to acquire a lower risk will run into a higher system cost.     

高效液相色谱-原子荧光光谱联用分析土壤中形态砷

采用高效液相色谱(HPLC)-原子荧光光谱(AFS)联用技术分析土壤中亚砷酸盐[As(Ⅲ)]、二甲基砷(DMA)、一甲基砷(MMA)和砷酸盐[As(Ⅴ)]等4种形态砷,以磷酸为提取剂、抗坏血酸为还原剂,优化了水浴提取条件。As(Ⅲ)、DMA、MMA和As(Ⅴ)在7 min之内实现了完全分离,在1.00μg/L～100μg/L范围内线性良好,实验室检出限分别为0.25μg/L、0.36μg/L、0.39μg/L和0.51μg/L,土壤标准样品平行测定的RSD≤7.4%,加标回收率为79.5%～95.0%,提取率为74.6%～90.4%。     

徐州市辐射环境质量现状分析

按照江苏省辐射环境质量监测实施方案,徐州市对大气、水、土壤进行了布点监测,通过分析2007—2011年辐射环境监测数据,得出结论为:徐州市辐射环境整体质量为良好,且相对稳定,在未来几年内,仍将保持良好的状态。     

乌鲁木齐市土地利用景观格局变化研究

运用GIS、RS技术及景观生态学理论和方法,基于乌鲁木齐市2006年和2010年遥感影像解译数据,对乌鲁木齐市5年间土地利用景观格局变化特征进行分析,分别从斑块类型和景观水平2个方面对研究区土地利用景观类型进行动态分析。揭示其变化原因和内在规律,为研究区生态治理提供数据支撑,对景观的规划与管理、资源的有效利用和生物多样性保护具有重要意义。     

北京地区冬季典型PM2.5重污染案例分析

对2013年1月10—14日发生的持续性PM2.5重污染过程从污染过程演变、气象条件影响、与气态污染物关系、区域污染背景、PM2.5浓度空间分布演变及其与地面风场的关系、PM2.5组分特征等多个方面进行全面的分析,较为完整地还原了该次重污染案例的形成原因以及主要影响因素。主要结论包括:该次重污染过程是稳定气象条件下导致的局地污染物积累,再叠加华北区域性污染的影响共同造成,其中10、12日北京地区PM2.5浓度的快速增长反映了周边污染传输的显著影响;逆温不但造成污染物难以扩散,且不同的逆温类型对PM2.5浓度水平有显著影响,同时还发现逆温的破坏导致近地面高浓度污染物向上扩散,造成百花山出现峰值高污染浓度现象;NO2与PM2.5浓度水平的高相关性反映交通污染二次转化对PM2.5浓度水平的影响,在较高湿度条件下,SO2浓度水平对湿度敏感且表现为负相关性;该次污染过程中OM、SO2-4、NO-3、NH+4等组分在PM2.5质量浓度中的占比超过70%,说明燃煤、机动车等仍是北京地区最主要的污染来源,同时SO2-4占比最高也说明区域污染传输对该次重污染的显著贡献。     

高效液相色谱-电感耦合等离子体质谱法测水中不同形态砷

采用高效液相色谱(HPLC)分离水中两种常见的砷形态As(III)、As(V),电感耦合等离子体质谱系统进行检测鉴定,利用C8色谱柱,探讨了甲醇含量、磷酸二氢钾浓度、四丁基氢氧化铵浓度、p H等测试条件,由此建立了水中砷形态的分析方法。结果表明,以1.5 mmol/L磷酸二氢钾、2 mmol/L四丁基氢氧化铵(TBAOH)、5%甲醇作为流动相,调节流动相为p H 5.5,流速为1.4 m L/min,上述两种不同形态的砷可在5.5 min内得以有效分离,As(III)、As(V)检出限分别为0.001、0.01μg/L,定量下限分别为0.005、0.03μg/L。该方法实现了对水中常见的不同形态砷(As(III)、As(V))的同时分析,具有灵敏度高、选择性好、检测速度快的特点,在水质分析领域具有重要意义与应用价值。     

Multi-Criteria and Multi-Perspective Analysis of Contaminated Land Management Methods

Errors in environmental resource management over the years have created pollution problems in some areas which are difficult to handle, regardless of the development of knowledge and technologies. This is particularly true in the case of soil pollution. The negative effects of persistent pollutants have been observed for a long time. For instance, lead and cadmium remain in the soil for centuries, during which time they are absorbed by plants and simultaneously cause secondary air pollution. The authors made an attempt to describe and assess the possible options of dealing with the problem of contaminated land in Katowice District. Considering the necessity of a multilateral approach, a pairwise comparison technique has been chosen as the most suitable to show the complexity of the problem. The different variants of actions aimed at preventing the pollutants from getting into the food chain were analyzed against a set of criteria, consisting of the following issues: time, cost, effectiveness, social acceptance, feasibility. The relative importance of actions were judged by the team of experts using the Saaty method. Also, a two-perspective assessment (the two different stakeholders), which involves considering the perspective of an owner of a piece of contaminated land and an ecologist has been performed. The results of comparative, multicriteria and multi-perspective assessment indicate the following:- the best method for contaminated agricultural land management is willful and controlled cultivation,- other recommended actions are deep ploughing and phytoremediation,- there is not much acceptance for the other methods.