基于一个年龄概念的河口污染物输运数值模拟

根据Deleersnijder定义的一个平均年龄概念,运用耦合了物质输运模式的一个三维水动力-富营养化数值模型(HEM-3D),研究了位于美国北卡罗莱纳州Pamlico河口(PRE)的污染物输运时间在不同淡水流量影响下的分布情况。模型结果表明,在正常期,污染物被输运出PRE需要大约65d的时间。而在枯水期和洪水期,污染物分别需要230d和20d时间被输运出PRE。这表明物质输运过程明显受淡水流量的影响。污染物输运时间的空间变化显著受河口中盐度入侵的影响,咸水入侵在其可以达到的最大区域形成了一个盐度锋面,而这个锋面阻碍了污染物向外的输运。盐度层化对输运时间的垂向分布影响显著,输运时间垂向梯度随着盐度层化的增强而增大。     

沂沭河流域大型水库至下游控制站河道流量演算方案研究

本文对沂沭河流域大型水库至下游控制站的河道流量演算方案进行了系统研究.文中根据马斯京根分段连续流量演算法原理.依据实测库、河中高水资料,分析确定了大型水库至下游控制站之间河段的特征河长及稳定流传播时间关系,建立了由水库泄洪最大流量和中游河道站洪峰流量推求河段代表流量的计算公式.使用本方案,可快速准确地将上游大型水库的泄洪流量过程汇流演算至下游控制站,能够有效提高下游控制站的洪水作业预报精度.     

东江三大水库联合调度下惠州河段水温变化响应研究

以东江流域控制站点博罗站为代表,通过构建一维水流水温模型,计算分析了东江三大水库不同出库流量对下游惠州河段水温的影响,探讨了该地区基于水温的鱼类生态调度目标,提出了东江三大水库3月份的水库联合生态调度方案.研究结果表明,在东江三大水库出库流量比例不变的情况下,博罗站3月份水温随着流量的增大而增大,但变化并不明显;在博罗站流量不变的情况下,东江三大水库出库流量的变化对博罗站水温有较大的影响,其中以白盆珠水库的影响最为显著.结合前人的研究成果认为,在博罗站流量320m3/s的情况下,保持白盆珠水库3月份最小出库流量为30m3/s,有利于东江下游惠州河段的生态条件改善.     

水环境容量的影响因素及分析研究

本文采用流量级频率分析和统计分析方法,对黄河下游流量及泥沙含量对水环境容量的影响进行了研究分析.分析结果:河流在平滩流量时不仅输沙能力最大[8],而且输运污染物能力也最大,黄河下游水环境容量萎缩是平滩流量降低的必然结果.     

断裂多孔岩石中的复杂反应流体动力学

:断裂多孔介质中的流体流动和组分输运过程对于理解金属成矿过程、油气运移、污染物质的输运和分布十分重要 ,近 2 0年来得到了广泛的研究。文中综述了这一领域的进展 ,涉及断裂多孔介质中的流体流动和组分输运的连续介质模型、多孔介质和断裂多孔介质的渗透率关系 ,特别是重点介绍了渗滤理论及其在断裂多孔介质中的流体流动和组分输运中的应用     

三峡水库生态调度目标研究

水库生态调度研究是当前国内外河流生态恢复研究中的热点问题。针对三峡水库具体情况,指出了现行水库调度存在的生态问题,进而以水库下游宜昌站作为分析对象,主要从维持天然河道内环境流量和有利于水库下游中华鲟和四大家鱼产卵繁殖的角度,确定了三峡水库生态调度目标,主要包括三峡水库下游河道内环境流量调度目标以及中华鲟和四大家鱼产卵繁殖期水库调度目标。三峡水库生态调度目标的确定可为三峡工程正式运行后制定合理的调度运用方案提供参考。     

雅砻江下游梯级水库生态友好型优化调度

根据雅砻江下游梯级水库水电站的布置和河道生态环境要求,分别设置了两个流量控制断面:锦屏二级电站引水闸址下减水河段、二滩电站坝址下游河段.针对这两个控制断面河道流量的要求,提出了25组生态流量控泄方案,建立了以梯级水电站群发电量最大为目标的长期优化调度模型,并采用动态规划法进行求解,获得各个方案下梯级水电站群多年平均发电量及水库调度出流过程.比较分析了减水河段生态流量及二滩水库泄流控制方案对发电量的影响,定义并计算了生态需水电能损失指标.对梯级水库调度出流过程进行了初步评价.结果表明:二滩水库出流维持天然径流模式,将限制水库调节能力和减少梯级电站发电效益.     

成矿流体输运物理机制研究的关键难题与方法体系

流体的物质来源，流体活化→迁移→聚集→沉淀过程的化学机理，流体输运与定位过程的物理机制，可视为构造-流体-成矿系统这一课题研究中的主要问题。相对于前两个基本方面的研究进展而言，流体的输运与定位过程的物理机制仍然是矿床学研究中一个重要难题。流体输运物理规律的研究方法主要包括定性分析、定量模拟和相似物理实验等。定性分析主要是对大量地质现象的高度概括和科学升华，分析结果表明成矿流体，尤其是多相热流体在给定三维动态形变场中的运移趋势及定位规律是成矿流体输运物理机制研究的关键问题；但由于逻辑推理和经验判断在定性研究中扮演了重要角色，定性研究的结果显得抽象和过于概略，不能详尽地阐明流体输运的物理过程。而定量模拟难以把握成矿期介质渗透率及成矿应力场的动态变化，使其与实际地质对象在物理性质上具有一定差距。物理实验虽能处理二维动态构造形变场中流体输运问题，但由于实验条件的限制，难以处理三维空间内流体运移问题。因而，上述 3种研究手段优势互补，它们的交错应用及结论间的相互对比与验证，将有望解决流体输运与定位过程物理机制研究中的重要问题。     

河流集合预报方法(ESP)在水资源中长期预测中的应用研究

中长期径流预测是水文水资源研究领域中的一项重要内容,为水资源规划管理及可持续利用、防汛抗旱、水库调度与发电计划制作、工农业用水计划编制等提供科学依据,对国民经济发展具有十分重要的意义.但由于大气圈极其复杂,水文要素并非仅是气象强迫输入的函数.它还受流域基本特性,前期来水以及人类活动等诸多因素的影响,中长期径流预测在其计算中存在着多种不确定性.因此,中长期径流预测一直是水文预测研究中难度较大的课题之一.本文引入河流集合预报方法(ESP),以丹江口水库为应用实例,利用水文气象历史资料和新安江水文模型,预测分析水库2007年10月份每旬的平均入库流量及概率分布统计,并经与实测流量过程对比分析,满足水库运行调度需求,为水库发电计划制作提供了可靠依据.     

珠江河口区枯季咸潮入侵与盐度输运机理分析

以河口区物质平衡原理为基础,应用物质输运机理对珠江三角洲河口区盐度净输运进行分析,对比各动力因子对盐度净输运贡献的大小.结果表明:珠江三角洲各河口盐淡水混合以缓混合型为主,分层系数均在0.01～1.0之间:盐度净输运主要是由斯托克斯输运和平均流输运控制,潮抽吸作用也不容忽视,其中,斯托克斯输运是导致咸潮上溯的最主要动力因素;珠江三角洲各口门径潮流情况及动力条件各有不同,除黄金站和挂定角V6站外,盐度输运以向上游为主,咸潮上溯明显.     

Simulation of polychlorinated biphenyls transport in the vadose zone

Polychlorinated biphenyls (PCBs) are the main constituents of clophen (the liquid of the electric transformers and capacitors) and have been characterized as potential human carcinogens. PCBs can be a hazardous contaminant of soil and groundwater. We used the mathematical model variably saturated 2D flow and transport (VS2DT model) to simulate the transport of PCBs from the soil surface to groundwater for a time period of 30 years. We also used a mathematical model to simulate the colloid-facilitated PCB transport, under saturated flow conditions. The results showed that PCBs dissolved in water cannot be transported to large depths in unsaturated soils, because of their strong sorption onto soil and low solubility in water. For soils with very low or no organic matter content, PCB transport is much faster and the probability of groundwater contamination is much higher. PCBs can partition to colloids originating from dissolved organic matter in groundwater. Colloid-facilitated PCB transport is faster compared to PCB transport in aqueous solution with no colloids present.     

A review of the formation of tectonic veins and their microstructures

Veins are common features in rocks and extremely useful structures to determine stress, strain, pressure, temperature, fluid composition and fluid origin during their formation. Here we provide an overview of the origin and terminology of veins. Contrary to the classical tripartite division of veins into syntaxial (inward growth), antitaxial (outward growth) and stretching veins (no consistent growth direction), we emphasise a continuum between syntaxial and stretching veins that form from the crack-seal process, as opposed to antitaxial veins that grow without the presence of an open fracture during growth. Through an overview of geochemical methods that can be applied to veins we also address the potential, but so far little-investigated link between microstructure and geochemistry. There are basically four mechanisms with increasing transport rates and concomitant decreasing fluid–rock interaction: (1) diffusion of dissolved matter through stagnant pore fluid; (2) flow of fluid with dissolved matter through pores; (3) flow of fluid with dissolved matter through fractures and (4) movement of fractures together with the contained fluid and dissolved matter (mobile hydrofractures). A vein system is rarely the product of a single transport and mineral precipitation mechanism, as these vary strongly both in space and time within a single system.     

Effects of Soil Composition on Zn Speciation in Drainage Waters from Agricultural Soils

The influence of Zn speciation on Zn transport by drainage from different soils to surface water is examined in a stream catchment in an agricultural area. Drainage waters were collected from two types of soils, a mineral soil (MS) and a soil rich in organic matter (OS) by means of artificial drainage pipes. The speciation of dissolved Zn in the stream and the drainage waters was determined using ligand-exchange and voltammetry. About 50–95% of dissolved Zn is bound in strong complexes, and the free Zn²⁺ ion concentration is in the range of 1–16% of dissolved Zn. A substantial part of Zn is present in weaker organic or inorganic complexes. The simulated Zn speciation using the WHAM VI model is compared to the determined speciation. Free Zn²⁺ concentrations predicted by the WHAM VI model are generally higher than the analytically determined free Zn²⁺, but are mostly within the same order of magnitude. Effects of different soil organic matter content on Zn speciation and transport are discussed. Zn speciation in the drainage at the OS site is influenced by the distribution of organic matter between the solid and solution phase. The abundant organic Zn complexes in solution contribute to facilitate Zn transport from soil into surface waters, through the drainage at the OS site. Drainage from the OS site contributes about twice as much Zn input to the receiving water as the MS soil, as related to specific area. The mineral soil contains much lower organic matter, and a part of Zn bound with inorganic phases can hardly be released by dissolved organic ligands, leading to much higher Zn retention at the MS site.     

Interaction of dissolution,sorption and biodegradation on transport of BTEX in a saturated groundwater system: Numerical modeling and spatial moment analysis

Interaction of various physical, chemical and biological transport processes plays an important role in deciding the fate and migration of contaminants in groundwater systems. In this study, a numerical investigation on the interaction of various transport processes of BTEX in a saturated groundwater system is carried out. In addition, the multi-component dissolution from a residual BTEX source under unsteady flow conditions is incorporated in the modeling framework. The model considers Benzene, Toluene, Ethyl Benzene and Xylene dissolving from the residual BTEX source zone to undergo sorption and aerobic biodegradation within the groundwater aquifer. Spatial concentration profiles of dissolved BTEX components under the interaction of various sorption and biodegradation conditions have been studied. Subsequently, a spatial moment analysis is carried out to analyze the effect of interaction of various transport processes on the total dissolved mass and the mobility of dissolved BTEX components. Results from the present numerical study suggest that the interaction of dissolution, sorption and biodegradation significantly influence the spatial distribution of dissolved BTEX components within the saturated groundwater system. Mobility of dissolved BTEX components is also found to be affected by the interaction of these transport processes.     

Potential for the formation and migration of colloidal material from a near-surface waste disposal site

Organic material typically constitutes a substantial volume (∼ 90%) of the low-level radioactive wastes (LLRW) intended for near-surface disposal at Chalk River Laboratories (CRL), Ontario, Canada. These wastes can contain a large variety of organic materials, including paper, cardboard, plastic bags, used clothing, and mop heads. After emplacement in a disposal facility, leaching of the LLRW by water can mobilize inorganic and organic substances, ranging from small molecules such as acetic acid to unidentifiable material of colloidal size range. This study determined the potential for colloid formation produced by LLRW degradation, because colloid-facilitated transport of contaminants could affect the safety performance of a disposal facility.The decomposition of compacted LLRW was simulated by recirculating water in a closed system over several compacted bales of waste to determine the potential composition and colloid content of leachates. Size fractionation of organic matter was performed on leachate samples that had been aged for 18 months to simulate the microbial degradation of organic matter within leachates during migration out of the LLRW disposal facility. The aged leachates contained high concentrations of dissolved organic matter, ranging between 74 and 5074 mg/l as C. In most of the leachates, volatile fatty acids accounted for a significant fraction (up to 81%) of the dissolved organic carbon. Although 5–110 mg/l of organic colloids were observed in leachates, in most cases, the organic colloids made up a very small fraction of the total leached organic carbon. Therefore, since the complexation properties of dissolved and colloidal organics are probably similar, contaminants complexed to organics are most likely to be dissolved and not affected by colloid transport. The leachates also contained significant quantities of Fe and Al, which could potentially precipitate Fe and Al as colloids after oxidation. Although a significant portion of the dissolved Fe may have been produced by the corrosion of the ☐es used to contain the bales, the high Fe concentrations could be representative of leachates from LLRW that contain metallic Fe components. If Fe and Al colloids are stable, stable concentrations in LLRW leachates could be high enough to affect contaminant transport. Therefore, the Fe and Al content of LLRW should be minimized. The concentrations of natural colloids in sandy aquifers, such as those found at CRL are too low to affect contaminant migration significantly.     

Mobilization of trace metals in a tropical turbid estuary influenced by a monsoon season

The selective removal of trace metals by suspended matter in high turbidity zones plays a major role in the fluvial transport of terrigenous metals to the marine environment. The seasonal longitudinal variability of trace elements (Cu, Zn, Cd, Ni, Pb, Fe, and Mn) in Cochin estuary, a tropical positive estuary, was studied and the results were compared with the prevailing situation in other subtropical waterways. The hydrodynamical features showed increasing turbidity downstream with increasing salinities during both the seasons. In contrast with the temperate estuaries where the development of turbidity maxima causes the removal of metals, the estuaries of tropics modify the fluvial transport of metals by the way of redistribution between the dissolved and particulate fractions in the intermediate salinities. In Cochin estuary, the distributional features of trace metals are primarily influenced by the variations in salinities and river discharges. Consequently, this gives rise to two different types of distributional patterns: (1) during premonsoon, the estuarine reactivity is more pronounced and hence, mid-estuarine solubilization of the particulate metal appears to play a prominent role in controlling the fluxes of trace metals studied and (2) but during monsoon, the hydrological conditions influence the downstream transport of the metals more by physical dilution than chemical reactivity.     

Adsorption of dissolved organic matter on clay minerals as assessed by infra-red, CPMAS C NMR spectroscopy and low field T1 NMR relaxometry

Dissolved organic matter (DOM) is a very important environmental constituent due to its role in controlling factors for soil formation, mineral weathering and pollutant transport in the environment. Prediction of DOM physical-chemical properties is achieved by studying its chemical structure and spatial conformation. In the present study, dissolved organic matter extracted from compost obtained from the organic fraction of urban wastes (DOM-P) has been analysed by FT-IR, CPMAS ¹³C NMR spectroscopy and ¹H T₁ NMR relaxometry with fast field cycling (FFC) setup. While the first two spectroscopic techniques revealed the chemical changes of dissolved organic matter after adsorption either on kaolinite (DOM-K) or montmorillonite (DOM-S), the latter permitted the evaluation of the conformational variations as assessed by longitudinal relaxation time (T₁) distribution at the fixed magnetic field of 500 mT. Alterations of T₁ distributions from DOM-P to DOM-K and DOM-S were attributed to a decreasing molecular complexity following DOM-P adsorption on the clay minerals. This study applied for the first time solid state ¹H T₁ NMR relaxometry to dissolved organic matter from compost obtained from the organic fraction of urban wastes and revealed that this technique is very promising for studying environmentally relevant natural organic systems.     

Dissolved Trace Metal–Organic Complexes in the Lot–Garonne River System Determined Using the C18 Sep-Pak System

An 11-month observation of dissolved and particulate organic matter, chlorophyll a(Chl a), C18 Sep-Pak extractable hydrophobic dissolved organic matter (hDOM) fraction and associated dissolved trace metals (Cd, Cu, V, Co, Ni, Mo, U) was performed in the Lot–Garonne River system. This system includes the Riou Mort, the Lot River and the downstream reaches of the Garonne River and represents the fluvial transport path of trace metals between the major point source of polymetallic pollution, located in the Riou Mort watershed and the Gironde estuary. Spatial and temporal variations of dissolved and particulate organic carbon and Chl areflect the presence of different types of organic matter and their relation with the hDOM fraction. Maximum Chl a/POC ratios (up to 0.03), indicate intense phytoplankton production from March to May. In the Lot River (Temple), DOC and POC concentrations were clearly higher and mean Chl a concentration (2.8 mg g⁻¹) was about three times higher than those of the other sites. High Chl a/POC ratios suggest high phytoplankton activity with maxima in spring and late summer. In the Riou Mort River, very high POC concentrations of up to 40 (mean: 20) occurred, whereas Chl a concentrations were relatively low indicating low phytoplankton activity. High, strongly variable DOC and POC concentrations suggest important natural (Carboniferous soils, forests) or anthropogenic (e.g., former coal mines, waste areas, agriculture, sewage) carbon sources within the small Riou Mort watershed. Despite high DOC concentrations in the Riou Mort River, hDOM metal fractions were generally lower than those at the other sites. The general order of decreasing binding strength between metals and the organic hydrophobic phase (Cu, U > Co, Ni > V, Mo > Cd) at all four sites was in good agreement with the Irving–William series of transition element affinity towards organic ligands. Accordingly, the role of the hydrophobic phase in dissolved Cd transport appeared to be negligible, whereas the hDOM–Cu fraction strongly contributed to dissolved Cu transport.     

Effect of organic matter on DOM sorption on lake sediments

The effect of organic matter on the sorption of dissolved organic matter (DOM) on lake sediments is critical to understanding the fate and transport of contaminants at the sediment–water interface in lake ecosystems. Results indicate that DOM sorption on sediment is largely due to ligand exchange between the DOM and hydroxyl groups, and the amount of DOC sorbed is a linear function of added DOC. With increasing organic matter content the sediment has lower binding strength, higher releasing ability for DOM, and the higher amount of DOM sorbed by sediment naturally. There was no clear difference before and after the sediment was treated with H₂O₂, but the constant b implied that after the sediments were treated DOC release was promoted. Organic matter in the sediment tends to impede the sorption of DOC and results in a remarkable decrease in DOC sorption rates.     

Reactive Transport Modeling of Subaqueous Sediment Caps and Implications for the Long-Term Fate of Arsenic, Mercury, and Methylmercury

A 1-D biogeochemical reactive transport model with a full set of equilibrium and kinetic biogeochemical reactions was developed to simulate the fate and transport of arsenic and mercury in subaqueous sediment caps. Model simulations (50?years) were performed for freshwater and estuarine scenarios with an anaerobic porewater and either a diffusion-only or a diffusion plus 0.1-m/year upward advective flux through the cap. A biological habitat layer in the top 0.15?m of the cap was simulated with the addition of organic carbon. For arsenic, the generation of sulfate-reducing conditions limits the formation of iron oxide phases available for adsorption. As a result, subaqueous sediment caps may be relatively ineffective for mitigating contaminant arsenic migration when influent concentrations are high and sorption capacity is insufficient. For mercury, sulfate reduction promotes the precipitation of metacinnabar (HgS) below the habitat layer, and associated fluxes across the sediment–water interface are low. As such, cap thickness is a key design parameter that can be adjusted to control the depth below the sediment–water interface at which mercury sulfide precipitates. The highest dissolved methylmercury concentrations occur in the habitat layer in estuarine environments under conditions of advecting porewater, but the highest sediment concentrations are predicted to occur in freshwater environments due to sorption on sediment organic matter. Site-specific reactive transport simulations are a powerful tool for identifying the major controls on sediment- and porewater-contaminant arsenic and mercury concentrations that result from coupling between physical conditions and biologically mediated chemical reactions.