Scale effects of hydrostratigraphy and recharge zonation on base flow   总被引：2，自引：0，他引：2  

Juckem PF  Hunt RJ  Anderson MP 《Ground water》2006,44(3):362-370

Uncertainty regarding spatial variations of model parameters often results in the simplifying assumption that parameters are spatially uniform. However, spatial variability may be important in resource assessment and model calibration. In this paper, a methodology is presented for estimating a critical basin size, above which base flows appear to be relatively less sensitive to the spatial distribution of recharge and hydraulic conductivity, and below which base flows are relatively more sensitive to this spatial variability. Application of the method is illustrated for a watershed that exhibits distinct infiltration patterns and hydrostratigraphic layering. A ground water flow model (MODFLOW) and a parameter estimation code (UCODE) were used to evaluate the influence of recharge zonation and hydrostratigraphic layering on base flow distribution. Optimization after removing spatial recharge variability from the calibrated model altered base flow simulations up to 53% in watersheds smaller than 40 km(2). Merging six hydrostratigraphic units into one unit with average properties increased base flow residuals up to 83% in basins smaller than 50 km(2). Base flow residuals changed <5% in watersheds larger than 40 and 50 km(2) when recharge and hydrostratigraphy were simplified, respectively; thus, the critical basin size for the example area is approximately 40 to 50 km(2). Once identified for an area, a critical basin size could be used to guide the scale of future investigations. By ensuring that parameter discretization needed to capture base flow distribution is commensurate with the scope of the investigation, uncertainty caused by overextending uniform parameterization or by estimating extra parameter values is reduced.  相似文献   

铼—锇同位素体系的研究现状及其在地质学中的应用   总被引：8，自引：0，他引：8  

殷宁万  黄典豪 《国外矿床地质》1994,(1):1-11

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加拿大安大略萨德伯里镍矿石中铂族元素地壳成因的锇同位素证据     

Dick.  AP 黄典豪 《国外矿床地质》1994,(1):44-52

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城市物探—综述     

亨德.  RJ  吴其斌 《国土资源信息化》1994,(5):38-42

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Investigation of recreational boats as a source of copper at anchorage sites using time-integrated diffusive gradients in thin film and sediment measurements   总被引：1，自引：0，他引：1  

Warnken J  Dunn RJ  Teasdale PR 《Marine pollution bulletin》2004,49(9-10):833-843

Antifouling paints on small to medium recreational vessels were first recognized as an important source of pollution in the 1970s. One of the principle biocides in these paints is Cu. Results from a field program in the Gold Coast Broadwater, Queensland, demonstrate a clear correlation between recreational boat numbers at anchorage sites and water column Cu concentrations, for both time-integrated 24 h DGT measurements (n=14, r=0.815, p<0.001) and measurements on composite 0.45 mum-filtered grab samples (n=14, r=0.698, p<0.01) collected every 4 h over 24 h. At boat numbers above 30 the 0.45 microm-filterable Cu concentrations were mostly above the relevant guideline value (1.3 microgl(-1)) but the DGT-reactive Cu concentrations were well below this value at all boat numbers studied. For three-day DGT deployments in Moreton Bay, Queensland, correlations between Cu levels and vessel numbers were not observed, possibly because of uncertain estimates of boat numbers. However, using a multi-factorial ANOVA, DGT-reactive Cu concentrations showed a significant effect for 'sites with vessels vs. sites without vessels' (alpha=0.10, p=0.077) and for 'sampling period' (non-holiday weekdays, weekends, holiday weekdays, holiday weekends) at alpha=0.10, p=0.02. Cu levels in sediments at the same sites were strongly influenced by fraction of clay (<63 microm) material but also by whether the samples were collected at an anchorage or control site. Results from this study further support the view that Cu emissions from antifouling paints may become an important source in waters with high boat numbers and should be taken into account when designing management instruments for coastal waterways.  相似文献   

Stepwise use of GFLOW and MODFLOW to determine relative importance of shallow and deep receptors   总被引：1，自引：0，他引：1  

Feinstein D  Dunning C  Hunt RJ  Krohelski J 《Ground water》2003,41(2):190-199

A stepwise modeling approach is implemented in which a regional one-layer analytic element model is used to simulate the flow system and to furnish boundary conditions for an extracted local three-dimensional model. In this case study the stepwise approach is used to evaluate the fate of recharge in the Menomonee Valley adjacent to Lake Michigan. Two major receptors exist for recharge that flows through contaminated valley fill: the surface water estuary and a tunnel system constructed approximately 75 to 110 m below land surface to store storm runoff. The primary objective of the modeling is to delineate the contributing areas of recharge to each receptor. Of interest is the ability of the one-layer regional model to furnish flux boundary conditions to the local three-dimensional model despite the presence of vertical flow conditions at the boundaries of the local model. Sensitivity analysis suggests that the local model was insensitive to the vertical distribution of the flux. Each step of the modeling approach demonstrates that both receptors play an important role in capturing valley recharge. The pattern of capture of the one-layer model differed in shape from that delineated by the multi-layer local model in the presence of a flow system with pronounced vertical anisotropy and with sinks drawing water from different elevations.  相似文献   

Simulating ground water-lake interactions: approaches and insights   总被引：4，自引：0，他引：4  

Hunt RJ  Haitjema HM  Krohelski JT  Feinstein DT 《Ground water》2003,41(2):227-237

Approaches for modeling lake-ground water interactions have evolved significantly from early simulations that used fixed lake stages specified as constant head to sophisticated LAK packages for MODFLOW. Although model input can be complex, the LAK package capabilities and output are superior to methods that rely on a fixed lake stage and compare well to other simple methods where lake stage can be calculated. Regardless of the approach, guidelines presented here for model grid size, location of three-dimensional flow, and extent of vertical capture can facilitate the construction of appropriately detailed models that simulate important lake-ground water interactions without adding unnecessary complexity. In addition to MODFLOW approaches, lake simulation has been formulated in terms of analytic elements. The analytic element lake package had acceptable agreement with a published LAKI problem, even though there were differences in the total lake conductance and number of layers used in the two models. The grid size used in the original LAKI problem, however, violated a grid size guideline presented in this paper. Grid sensitivity analyses demonstrated that an appreciable discrepancy in the distribution of stream and lake flux was related to the large grid size used in the original LAKI problem. This artifact is expected regardless of MODFLOW LAK package used. When the grid size was reduced, a finite-difference formulation approached the analytic element results. These insights and guidelines can help ensure that the proper lake simulation tool is being selected and applied.  相似文献   

The loss of the chemical tanker Ievoli Sun in the English Channel,October 2000     

Law RJ  Kelly C  Matthiessen P  Aldridge J 《Marine pollution bulletin》2003,46(2):254-257

A chemical product tanker, The Ievoli Sun, was abandoned and later sank approximately 11 miles NW of Alderney in the English Channel in October 2000. The vessel carried a mixed cargo comprising 4000 tonnes of styrene, and 1000 tonnes each of methyl ethyl ketone and isopropyl alcohol. These chemicals are of low to moderate toxicity to aquatic life, are not persistent and have a low potential for bio-accumulation. Both of the solvents are miscible in water, whilst styrene is practically insoluble and, following release, it will rise to the sea surface and rapidly evaporate. More than 1000 tonnes of styrene are believed to have been lost to sea during the incident, resulting in an aerial plume of vapour which crossed Alderney and episodic contamination of air and water in the immediate vicinity of the wreck site. Analysis of edible tissues using coupled gas chromatography/mass spectrometry demonstrated low-level styrene contamination of crabs recovered from pots laid very close to the wreck site prior to the incident. These concentrations posed no risks to human consumers, and no fishery controls were implemented. The remainder of the styrene and the ship's main bunker fuel were recovered from the wreck on the seabed, whilst the two chemical solvents were released to the water column in a slow, controlled manner.  相似文献   

三江地区义敦岛弧造山带演化和成矿系统   总被引：80，自引：12，他引：80       下载免费PDF全文

侯增谦杨岳清  曲晓明黄典豪吕庆田  王海平余金杰 唐绍华 《地质学报》2004,78(1):109-120

义敦岛弧是喜马拉雅巨型造山带中的一个复合造山带,它经历了印支期洋壳俯冲造山、燕山湖弧-陆碰撞和喜马拉雅期陆内走滑作用诸演化历史。可能由于洋壳板片俯冲角度不同,义敦晚三叠世古岛弧带(206～237 Ma)南北两段具有不同的发育历史,北段昌台弧以发育孤间裂谷为特色,具张性弧特征,发育扩张环境流体聚敛成矿系统,形成VMS型Zn-Pb-Cu矿床和浅成低温热液型Ag-Au-Hg矿床;南段中甸弧不发育弧后盆地,但广泛发育钙碱性弧火山岩-玢岩-斑岩杂岩系和挤压环境岩浆-流体成矿系统,形成斑岩型-夕卡岩型铜多金属矿床。在三叠纪-侏罗纪之交的弧-陆碰撞作用中,早期大陆板片俯冲形成同碰撞花岗岩带(约200 Ma),晚期造山后伸展作用,形成A型花岗岩带(75～138 Ma),伴随扬子大陆板片俯冲而发生的强烈剪切和推覆,在甘孜-理塘蛇绿混杂带发育挤压剪切环境流体聚敛成矿系统,形成剪切带型金矿。伴随造山后伸展和A型花岗岩侵位,发育伸张环境岩浆-流体聚敛成矿系统,主要形成夕卡岩型锡矿和构造破碎带热浪脉型银多金属矿床。印度-亚洲大陆碰撞在义敦造山带主要表现为陆内走滑作用,并控制碱性花岗岩和花岗斑岩的发育(50～30 Ma),伴随斑岩型金矿的形成。  相似文献   

香港中生代同源深成岩和火山岩套的地球化学     

Sewe.  RJ 《广东地质》1998,13(4):1-12

香港中朱罗世一早白垩世中酸性深成岩和火山岩的组分,随着时间的移从钙碱性向高钾钙碱性及过渡型橄榄粗玄质演化。同源的火山岩－深成岩在空间和时间上的密切关系表明,岩浆作用呈不连续的动脉式发生,每次脉动幼大部分少于１００万ａ。  相似文献