地下水NO3^-氮与氧同位素研究进展     

邓林曹玉清  王文科 《地球科学进展》2007,22(7):716-724

人为活动通常是地下水硝酸盐污染的主要原因。不同来源的NO3^-具有不同的氮、氧同位素组成,利用地下水NO3^-中的δ15N和δ18O值可有效识别地下水硝酸盐污染的来源。引起地下水中NO3^-含量显著减少的不同物理、化学和生物过程,所产生的氮、氧同位素分馏效应有明显差别。地下水系统中反硝化作用发生时,NO3^-中氮和氧同位素分馏系数呈一定比例。因此NO3^-中δ15N和δ18O值也是示踪地下水硝酸盐循环,尤其是反硝化作用的有效手段。利用NO3^-中氮和氧双同位素,并与其他环境同位素及化学分析技术相结合,示踪NO3^-来源及其循环是地下水硝酸盐污染研究的重要方向之一。综述了利用地下水硝酸盐中氮和氧同位素识别NO3^-污染源与循环的研究进展,简述了近年迅速发展的阴离子交换树脂取样法,概述了此方面研究存在的主要问题,并展望了今后的研究方向。  相似文献   

Simulating conservative tracers in fractured till under realistic timescales     

Helmke MF  Simpkins WW  Horton R 《Ground water》2005,43(6):877-889

Discrete-fracture and dual-porosity models are infrequently used to simulate solute transport through fractured unconsolidated deposits, despite their more common application in fractured rock where distinct flow regimes are hypothesized. In this study, we apply four fracture transport models--the mobile-immobile model (MIM), parallel-plate discrete-fracture model (PDFM), and stochastic and deterministic discrete-fracture models (DFMs)--to demonstrate their utility for simulating solute transport through fractured till. Model results were compared to breakthrough curves (BTCs) for the conservative tracers potassium bromide (KBr), pentafluorobenzoic acid (PFBA), and 1,4-piperazinediethanesulfonic acid (PIPES) in a large-diameter column of fractured till. Input parameters were determined from independent field and laboratory methods. Predictions of Br BTCs were not significantly different among models; however, the stochastic and deterministic DFMs were more accurate than the MIM or PDFM when predicting PFBA and PIPES BTCs. DFMs may be more applicable than the MIM for tracers with small effective diffusion coefficients (De) or for short timescales due to differences in how these models simulate diffusion or incorporate heterogeneities by their fracture networks. At large scales of investigation, the more computationally efficient MIM and PDFM may be more practical to implement than the three-dimensional DFMs, or a combination of model approaches could be employed. Regardless of the modeling approach used, fractures should be incorporated routinely into solute transport models in glaciated terrain.  相似文献   

水文地质蓄水构造级、区带划分及其水资源分布特点     

胡宽瑢  曹玉清  胡忠毅 《吉林大学学报(地球科学版)》2000,30(3):246-250

为研究水资源对生态环境的影响 ,和寻求供排水的最佳勘察地段 ,根据我国地质构造、地貌规模和特点 ,提出蓄水构造的Ⅳ级划分 ;划分指标按具体地区的地质、含水层富 (透、导 )水性、水文地球化学资料统计确定 ;Ⅰ、Ⅱ级蓄水构造属区域性分区 ,Ⅲ、Ⅳ级水文地质区带属水文地质单元内部具体分级。巨厚含水层富 (透、导 )水性随垂向深度呈负指数 (y =Ax-B)变化 ,水平方向上随埋深标高呈幂函数 (y =AH±B)变化 ;饱和指数 (βj)与埋深标高呈负指数 (H =Aβ-Bj )变化 ;为建立水资源—生态环境多重耦合模型奠定基础 ;为确定供水和矿区防治水最佳勘察地带、点和深度指明方向。  相似文献   

Error control of iterative linear solvers for integrated groundwater models     

Dixon MF  Bai Z  Brush CF  Chung FI  Dogrul EC  Kadir TN 《Ground water》2011,49(6):859-865

An open problem that arises when using modern iterative linear solvers, such as the preconditioned conjugate gradient method or Generalized Minimum RESidual (GMRES) method, is how to choose the residual tolerance in the linear solver to be consistent with the tolerance on the solution error. This problem is especially acute for integrated groundwater models, which are implicitly coupled to another model, such as surface water models, and resolve both multiple scales of flow and temporal interaction terms, giving rise to linear systems with variable scaling. This article uses the theory of "forward error bound estimation" to explain the correspondence between the residual error in the preconditioned linear system and the solution error. Using examples of linear systems from models developed by the US Geological Survey and the California State Department of Water Resources, we observe that this error bound guides the choice of a practical measure for controlling the error in linear systems. We implemented a preconditioned GMRES algorithm and benchmarked it against the Successive Over-Relaxation (SOR) method, the most widely known iterative solver for nonsymmetric coefficient matrices. With forward error control, GMRES can easily replace the SOR method in legacy groundwater modeling packages, resulting in the overall simulation speedups as large as 7.74×. This research is expected to broadly impact groundwater modelers through the demonstration of a practical and general approach for setting the residual tolerance in line with the solution error tolerance and presentation of GMRES performance benchmarking results.  相似文献   

时域电磁测量中的激发极化效应     

Flis.  MF 蒋邦远 《物探化探译丛》1990,(2):19-28

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Spatio-temporal variation of suspended and sedimentary organic matter quality in the Bay of Marseilles (NW Mediterranean) assessed by biochemical and isotopic analyses     

Cresson P  Ruitton S  Fontaine MF  Harmelin-Vivien M 《Marine pollution bulletin》2012,64(6):1112-1121

Isotopic and biochemical features of suspended particulate organic matter (POM) in the water column and of sedimentary organic matter (SOM) were investigated seasonally in the Bay of Marseilles. Biochemical compounds (carbohydrates, lipids and proteins) were consistently more concentrated in POM than in SOM, with SOM mainly composed of insoluble carbohydrates. POM displayed lower δ(13)C and higher δ(15)N values than SOM. Phytoplanktonic production represented the major contributor of POM year-round with spatial and seasonal variations. Climatic parameters and wind-induced currents created differences in POM contributions, with more important inputs of terrestrial OM at one sampling site. Spatial and seasonal variations were lower for SOM. The composition of this pool appeared to be linked with the permanent inputs of phytoplankton and Posidonia oceanica detritus. The combined use of biochemical and isotopic analyses was a useful tool to characterize OM pools and would help understanding the trophic functioning of this coastal environment.  相似文献   

Oil spill treatment products approval: the UK approach and potential application to the Gulf region     

Kirby MF  Law RJ 《Marine pollution bulletin》2008,56(7):1243-1247

The environmental threat from oil spills remains significant across the globe and particularly in regions of high oil production and transport such as the Gulf. The ultimate damage caused can be limited by mitigation actions that responders deploy. The responsible and appropriate use of oil spill treatment products (e.g. dispersants, sorbents etc.) can offer response options that can result in substantial net environmental benefit. However, the approval and choice of what products to use needs careful consideration. The United Kingdom has had in place a statutory approval scheme for oil spill treatment products for 30 years. It is based on measures of efficiency and environmental acceptability. Two toxicity tests form an integral part of the assessment, the Sea test and the Rocky Shore test, and work on the premise that approved products will not make the situation significantly worse when added to spilled oil. This paper outlines the UK approach and how its rationale might be applied to the approval of products specific for the Gulf region. Issues such as species choice, higher temperatures and salinity and regional environmental conditions are considered.  相似文献   

岩溶水系统溶蚀速度的多重耦合模型——以山西太原东山水文地质系统为例   总被引：1，自引：1，他引：0  

曹玉清  胡宽王容  李彦斌  张文兵 《中国岩溶》1997,16(3):199-208

本文运用化学热力学与水文地质系统耦合理论,将太原东山水文地质系统划分成矿物溶解、沉淀各异的区带;通过各区带内的化学—数学与相关分析法的耦合模型,计算出各区带碳酸、硫酸盐岩的综合溶蚀模量;再将综合溶蚀模量和用化学动力学理论确定地下水实际速度的解析解公式与有限单元法耦合,计算确定出各节点的溶蚀速度。从而不仅有效地评价了水文地质系统内的溶蚀特点,还可反映区内地质构造和水文地质条件,以及含水层在倾向方向随埋深增大呈幂函数变化的规律;进而可确定出区内供水、矿井防治水的最佳勘探地段。这些不仅具有一定理论意义,也具有一定的社会和经济效益   相似文献   

济南泉域地下水年龄计算   总被引：1，自引：1，他引：0  

房佩贤  曹玉清  唐克旺  李祥之  王绍文 《中国岩溶》1989,8(1):47-52

本文应用环境同位素分析,估算了济南泉域地下水的年龄;根据碳酸盐矿物溶解动力学理论,又计算了泉水的化学年龄;并与同位素求出的年龄作出比较。   相似文献   

Can PAHs influence Cu accumulation by salt marsh plants?     

Almeida CM  Mucha AP  Delgado MF  Caçador MI  Bordalo AA  Vasconcelos MT 《Marine environmental research》2008,66(3):311-318

The presence of polycyclic aromatic hydrocarbons (PAHs) may change the mechanisms of metal uptake, thus influencing kinetics and extent of metal phytoextraction. Studies on the subject are scarce, particularly for salt marsh plants. The aim of this work was to investigate the effect of PAHs on the uptake of Cu by Halimione portulacoides, a plant commonly found in salt marshes. Experiments were carried out in the laboratory, either in hydroponics (sediment elutriate) or in sediment soaked in elutriate, which were prepared with sediment and water from a salt marsh of the Cavado river estuary (NW Portugal). Groups of H. portulacoides (grown in a greenhouse) were exposed to those media during six days. Cu(2+) (as Cu(NO(3))(2)), 10(2) and 10(4)mugl(-1), was added to the media as well as 1.6mugl(-1) of the sixteen EPA priority PAHs (0.1mugl(-1) of each PAHs). Cu was assayed in solutions, sediments and different plant tissues before and after experiments. After exposure, photosynthetic efficiency and levels of chlorophylls were also measured, indicating that plant stress indicators were identical in all plants independently of the media to which the plants were exposed. PAHs influenced both the soluble Cu fraction and Cu uptake by plants. The amounts of metal accumulated in both roots and stems were significantly higher when the 10(4)mugl(-1) of Cu enriched elutriate was amended with PAHs. Thus, results suggest that PAHs may modify Cu solubility, the Cu sorption by plants and/or the passive penetration of Cu into the root cells. Therefore, the combined effects of different types of pollutants should be taken in consideration when studying the remediation potential of plants, namely in terms of phytoextraction.  相似文献