A multi-directional tracer test in the fractured Chalk aquifer of E. Yorkshire, UK

A multi-borehole radial tracer test has been conducted in the confined Chalk aquifer of E. Yorkshire, UK. Three different tracer dyes were injected into three injection boreholes and a central borehole, 25 m from the injection boreholes, was pumped at 330 m(3)/d for 8 days. The breakthrough curves show that initial breakthrough and peak times were fairly similar for all dyes but that recoveries varied markedly from 9 to 57%. The breakthrough curves show a steep rise to a peak and long tail, typical of dual porosity aquifers. The breakthrough curves were simulated using a 1D dual porosity model. Model input parameters were constrained to acceptable ranges determined from estimations of matrix porosity and diffusion coefficient, fracture spacing, initial breakthrough times and bulk transmissivity of the aquifer. The model gave equivalent hydraulic apertures for fractures in the range 363-384 microm, dispersivities of 1 to 5 m and matrix block sizes of 6 to 9 cm. Modelling suggests that matrix block size is the primary controlling parameter for solute transport in the aquifer, particularly for recovery. The observed breakthrough curves suggest results from single injection-borehole tracer tests in the Chalk may give initial breakthrough and peak times reasonably representative of the aquifer but that recovery is highly variable and sensitive to injection and abstraction borehole location. Consideration of aquifer heterogeneity suggests that high recoveries may be indicative of a high flow pathway adjacent, but not necessarily connected, to the injection and abstraction boreholes whereas low recoveries may indicate more distributed flow through many fractures of similar aperture.     

Evaluation of the Impact of Long-range Transport and Aerosol Concentration Temporal Variations at the Eastern Coast of the Baltic Sea

Ambient particles vary greatly in their ability to affect visibility, climate and human health. The fine fraction of aerosol is responsible for greater and wider effects on human health; thus, investigation of this fraction is very important. Continuous measurements of PM2.5 (particulate matter below 2.5 μm in size) concentrations at the Preila monitoring station started in 2003. During a period of 2 years, the episodes of high daily and semi-hourly concentrations of PM2.5 were measured. These episodes did not depend on the season or time of day. The substantial role of long-range transport of pollutants to these increases in concentration was shown using chemical and statistical analysis. It was found that most of the severe episodes occurred when air masses came from a specific site besides it was established that air masses of different origin were characterized by different mixing layer depth. Lower mixing depth was observed in air masses characterized by higher observed concentrations at the measuring site and vice versa. PM2.5 concentrations showed diurnal and seasonal variations whose pattern reflected the regional origin of the aerosol. The regional pollution level was evaluated by the statistical analysis of PM2.5 concentrations. The background annual average of PM2.5 mass concentration for the eastern coast of the Baltic Sea was 15.1 ± 0.8 μg m⁻³.     

上海市地表灰尘中PAHs季节变化与功能区差异

研究了上海市中心城区地表灰尘中多环芳烃（PAHs）的季节变化与功能区差异,并探讨了这种变化特征的原因.结果表明,上海市中心城区地表灰尘中PAHs累积水平具有显著的季节变化,PAHs总量和组分均表现出冬季含量高于夏季的特征.冬季样品中PAHs含量为9 176～32?573 ng·g^-1,平均值为20 648 ng·g^-1;而夏季PAHs含量为6?875～27?766 ng·g^-1,平均值仅为14?098 ng·g^-1.PAHs组分也表现出相似特征,冬季含量为50(二氢苊)～3 162 ng·g^-1 (茚并［1,2,3-c,d ］芘),夏季含量为3(苊)～1 485 ng·g^-1 (茚并［1,2,3-c,d ］芘).各个功能区地表灰尘PAHs含量的差异明显.冬季最高值出现在工业区（31 163 ng·g^-1）、商业区（24 932 ng·g^-1）和交通要道（18 815 ng·g^-1）,最低值出现在公园（7 885 ng·g^-1）和绿地（8 036 ng·g^-1）;夏季最低值出现在公园（7 942 ng·g^-1）,最高值出现在交通要道（14 528 ng·g^-1）、工业区（14 247 ng·g^-1）和商业区（11 523 ng·g^-1）.所有功能区样品中PAHs组分含量呈现出按环数或分子量的增加而逐渐升高的趋势.大城市地表灰尘中PAHs的季节变化与功能区差异与其来源密切相关,也受到各组分理化性质的影响.     

河道污染质垂向迁移对地下水影响的研究

包气带是连接地表水和地下水的重要通道,对地下水资源有很好的"屏障"功能,而近年来工农业废水及生活污水的大量排放已影响到了地下水的"安全".为此,在渭河河漫滩进行了模拟河流的垂向入渗试验,并通过建立数学模型对水分和六价铬在具有弱透水层的多层介质中的迁移进行了模拟运算.试验和模拟结果一致表明,弱透水层虽对地下水有很好的保护作用,但在上部土壤层易形成面状污染带,而且由于大的浓度梯度作用,一旦污染质穿透该层将很快污染到地下水.     

DEVELOPMENT OF A BACTERIAL TRANSPORT MODEL FOR COARSE SOILS1

ABSTRACT: A bacterial transport model, developed to analyze bacterial translocation in coarse-grained soils, is presented. The complex governing equation is presented first, followed by analyses of each of the major processes influencing bacterial transport. These analyses suggest simplification of the governing equation is feasible when input data on specific processes are limited or unavailable. Model parameters, including bacterial die-off, bacterial distribution, input bacterial concentration, and saturated hydraulic conductivity, were randomly generated using a procedure known to produce either a normal or log-normal distribution of random numbers. Monte Carlo simulations were completed, and the resulting output was used to generate cumulative frequency distributions showing the probability of bacterial transport beyond various soil depths. Results from these simulations indicate that bacteria have a high probability of traveling through coarse-grained soils when low clay content and soil water temperatures limit bacterial retention and die-off.     

黑龙江省公路雪冰基本特征与灾害防治对策

黑龙江省冬季降雪不多,但在寒冷和强风条件下,容易产生风吹雪,使某些地点形成较深的积雪,阻塞交通.风吹堆积下的积雪在低温下形成密实坚硬的硬深霜.涎流冰是冬季影响山区交通的另一个主要因素,它的各个部位呈现出间歇性增厚的特征,是涌出水在各处反复交替流动、冻结的结果.随着经济发展,交通流量增加,正常降雪将会产生越来越大的影响和危害,必须给予足够的重视.因此,在雪冰减灾战略对策上,应逐步推广使用防滑汽车轮胎,建立较为完善的公路雪冰清除服务体系,并辅以必要的工程措施.     

公路隧道事故预防分析

探讨了公路隧道交通事故的特点和主要影响因素,采用事故树分析法对可能导致隧道火灾事故的因素进行了分析,得出在隧道内减少可燃烧物品数量和采用阻燃或不燃物品做内装饰是降低隧道火灾发生概率的有效措施,并提出了预防公路隧道交通事故和火灾的具体对策.     

Ecological Linkages Between Headwaters and Downstream Ecosystems: Transport of Organic Matter,Invertebrates, and Wood Down Headwater Channels1

Abstract: Headwater streams make up a large proportion of the total length and watershed area of fluvial networks, and are partially characterized by the large volume of organic matter (large wood, detritus, and dissolved organic matter) and invertebrate inputs from the riparian forest, relative to stream size. Much of those inputs are exported to downstream reaches through time where they potentially subsidize river communities. The relative rates, timing, and conversion processes that carry inputs from small streams to downstream reaches are reasonably well quantified. For example, larger particles are converted to smaller particles, which are more easily exported. Also, dissolved organic matter and surface biofilms are converted to larger particles which can be more easily intercepted by consumers. However, the quality of these materials as it affects biological activity downstream is not well known, nor is the extent to which timing permits biological use of those particles. These ecological unknowns need to be resolved. Further, land uses may disrupt and diminish material transport to downstream reaches by removing sources (e.g., forest harvest), by affecting transport and decomposition processes (e.g., flow regulation, irrigation, changes in biotic communities), and by altering mechanisms of storage within headwaters (e.g., channelization). We present conceptual models of energy and nutrient fluxes that outline small stream processes and pathways important to downstream communities, and we identify informational gaps that, if filled, could significantly advance the understanding of linkages between headwater streams and larger rivers. The models, based on empirical evidence and best professional judgment, suggest that navigable waters are significantly influenced by headwater streams through hydrological and ecological connectivities, and land use can dramatically influence these natural connectivities, impacting downstream riverine ecosystems.     

Evaluation of Three Watershed‐Scale Pesticide Environmental Transport and Fate Models1

Abstract: The U.S. Environmental Protection Agency (USEPA) Office of Pesticide Programs (OPP) has completed an evaluation of three watershed‐scale simulation models for potential use in Food Quality Protection Act pesticide drinking water exposure assessments. The evaluation may also guide OPP in identifying computer simulation tools that can be used in performing aquatic ecological exposure assessments. Models selected for evaluation were the Soil Water Assessment Tool (SWAT), the Nonpoint Source Model (NPSM), a modified version of the Hydrologic Simulation Program‐Fortran (HSPF), and the Pesticide Root Zone Model‐Riverine Water Quality (PRZM‐RIVWQ) model. Simulated concentrations of the pesticides atrazine, metolachlor, and trifluralin in surface water were compared with field data monitored in the Sugar Creek watershed of Indiana’s White River basin by the National Water Quality Assessment (NAWQA) program. The evaluation not only provided USEPA with experience in using watershed models for estimating pesticide concentration in flowing water but also led to the development of improved statistical techniques for assessing model accuracy. Further, it demonstrated the difficulty of representing spatially and temporally variable soil, weather, and pesticide applications with relatively infrequent, spatially fixed, point estimates. It also demonstrated the value of using monitoring and modeling as mutually supporting tools and pointed to the need to design monitoring programs that support modeling.     

危险货物道路运输事故统计分析

为掌握危险货物道路运输事故的发生规律,预防事故与灾害发生,笔者收集、整理了2000年9月至2007年3月间的609起危险货物道路运输事故案例,并对案例进行详细分解和统计分析,获得了危险货物道路运输事故的时间分布、地域分布、路段分布、事故形态分布、事故原因分布等统计特征。研究结果表明,危险货物道路运输事故具有如下规律:早晨和上午(4时至12时)是事故多发时段;事故形态以单车事故为主,特别是车辆倾斜或侧翻事故为数最多;驾驶员处置不当和违法驾驶行为以及运输车辆机件失效是导致事故的最主要的两类原因。针对案例分析结果,提出预防危险货物道路运输事故、保障危险货物道路运输安全的对策与建议。