Empirical relationships for estimating stream depletion by a well pumping near a gaining stream   总被引：1，自引：0，他引：1  

Di Matteo L  Dragoni W 《Ground water》2005,43(2):242-249

Siting wells near streams requires an accurate estimate of the quantity of water derived from the river due to pumping. A number of hydrogeological and hydraulic parameters influence this value. This study estimates stream depletion under steady-state conditions for a variety of hydrogeological systems. A finite differences model was used to analyze several hydrogeological situations, and for each of these the stream depletion was estimated using an advective transport method. An empirical equation for stream depletion was obtained for the case of a stream that partially penetrates the aquifer and a pumping well that is screened over a portion of the aquifer. The derived equation, which is valid for both isotropic and anisotropic conditions, expresses stream depletion as a function of the unit inflow to the river, the discharge of the pumping well, the well screen length, the distance between the river and pumping well, the wetted perimeter, and a new parameter called "overlap," which is defined to be the distance between the riverbed and the top of well screen. The overlap parameter makes it possible to consider indirectly the vertical component of flow, which is accentuated when the well is screened below the streambed. The formula proposed here should be useful in deciding where to locate a pumping well and to decide the appropriate length of its screen.  相似文献   

Protective effect of phospholipid hydroperoxide glutathione peroxidase (PHGPx) against lipid peroxidation in mussels Perna perna exposed to different metals   总被引：2，自引：0，他引：2  

de Almeida EA  Miyamoto S  Bainy AC  de Medeiros MH  Di Mascio P 《Marine pollution bulletin》2004,49(5-6):386-392

Levels of antioxidant defenses and lipid peroxidation were evaluated in mussels exposed to lead (200 mg/l), iron (500 microg/l), cadmium (200 microg/l) and copper (40 microg/l), for 12, 24, 72 and 120 h. Glutathione S-transferase (GST) activity was unchanged with all treatments. Catalase (CAT) increased after 120 h of exposure to all metals. Mussels exposed to Cd for 12 h, and to Cu and Fe for 120 h had increased lipid peroxidation, which might be associated to decreased levels of reduced glutathione (GSH) and glutathione peroxidase (GPx) activity. Pb exposure caused GSH depletion after 12 h and increased GPx activity after 120 h. Negative correlations were observed between the enzyme phospholipid hydroperoxide glutathione peroxidase (PHGPx) and malonaldehyde (MDA) levels after Fe and Cu exposure, indicating a protective role of PHGPx against lipid peroxidation, and suggesting the use of this enzyme as a new potential biomarker of toxicity associated with contaminant exposure in mussels.  相似文献   

The effects of paraquat on microsomal oxygen reduction and antioxidant defenses in ribbed mussels (Geukensia demissa) and wedge clams (rangia cuneata)     

Richard J Wenning  Richard T Di Giulio   《Marine environmental research》1988,24(1-4)

The hepatopancreae of the ribbed mussel, Geukensia demissa, and the wedge clam, Rangia cuneata, were examined for their ability to catalyze the reduction/oxidation cycling of the bipyridyl herbicide paraquat. In vitro studies indicated a dose-dependent increase in the rate of superoxide anion (O₂⁻) generation in microsomal fractions supplemented with NADPH; the highest concentration of paraquat employed (4 mm) elicited an 81 % increase in cytochrome c reduction in G. demissa and a 135% increase in R. cuneata. In both .species, cytochrome c reduction was inhibited by the addition of exogenous superoxide dismutase (SOD). For in vivo studies, a single application of paraquat (0·5, 1·0 or 2·0 mm) was added to aerated salt-water aquaria containing G. demissa. Biochemical analyses of antioxidant enzymes, reduced glutathione (GSH) and lipid peroxidation were performed in hepatopancreatic tissue after exposures of 6, 12, 24 and 36 h. Results support the hypotheses that these bivalves can activate redox cycling compounds and demonstrate in vivo responses typical of oxidative stress as observed in other organisms.  相似文献   

Oxidative stress in two populations of killifish (Fundulus heteroclitus) with differing contaminant exposure histories     

Lisa R. Bacanskas  Julia Whitaker  Richard T. Di Giulio   《Marine environmental research》2004,58(2-5):597

A population of killifish (Fundulus heteroclitus) inhabiting a creosote-polluted inlet of the Elizabeth River demonstrates tolerance to the acute toxic effects exerted by contaminated sediments on reference site killifish. Previous data have suggested that upregulated antioxidant defenses contribute to short-term tolerance in killifish exposed to Elizabeth River sediments. This study investigated population differences in antioxidant defenses from wild caught Elizabeth River and reference population killifish in different seasons, and after being held in the laboratory. Parameters measured in the killifish were total glutathione concentrations (GSH_T), activities of glutathione reductase (GR), glutathione peroxidase (GPx), and lipid peroxidation (LPO), all in adult hepatic tissues. The Elizabeth River population exhibited greater GSH_T, higher GPx activities, and increased LPO as compared to the reference population. Sex specific population differences were also observed in GSH_T and GPx. Both populations displayed decreased GSH_T and increased GR from early to late summer, as well as after being held in the laboratory. This study indicates that there are many factors that may contribute to differences in levels of antioxidant defenses in addition to exposure to contaminants, including reproductive status and environmental conditions.  相似文献   

南海莺歌海盆地形成机制的物理模拟   总被引：2，自引：3，他引：2  

孙珍  周蒂  钟志洪  曾佐勋  胡光道  赵鹏大 《热带海洋学报》2001,20(2):35-40

莺歌海盆地位于印支板块和华南板块的拼接带，红河断裂带的海上延伸带上，构造演化十分复杂，由于盆地沉积厚度巨大，泥流体底辟发充,肝震勘探难以直接揭示盆地内部深层的构造面貌，因而对盆地形成与构造演化的认识存在明显的分歧，利用常用的三维比例沙箱模型，对盆地的形成机制进行了物理模拟，结果表明莺歌海盆地的形成可分3个阶段，自50MaB.P，或更早开始，在沿红洒断裂带带伸分量的左旋错动和印支地块的顺时针旋转的联合应力场作用下，形成了莺歌海盆地的断陷格架，大约21MaB.P.之后在纯左旋错动阶段叠加了压扭应力场，形成了盆地西北部的反转构造，约5MaB.P.之后发生右旋错动，带来了盆地内新一轮的快速沉积，根据盆地内最老和最新的沉积中心之间的距离，推测沿红河断裂带的左行位错约200km.  相似文献   

Intrinsic and forced interannual variability of the Gulf of Alaska mesoscale circulation     

Vincent Combes  Emanuele Di Lorenzo 《Progress in Oceanography》2007,75(2):266-286

The response of the Gulf of Alaska (GOA) circulation to large-scale North Pacific climate variability is explored using three high resolution (15 km) regional ocean model ensembles over the period 1950-2004. On interannual and decadal timescales the mean circulation is strongly modulated by changes in the large scale climate forcing associated with PDO and ENSO. Intensification of the model gyre scale circulation occurs after the 1976-1977 climate shift, as well as during 1965-1970 and 1993-1995. From the model dynamical budgets we find that when the GOA experiences stronger southeasterly winds, typical during the positive phase of the PDO and ENSO, there is net large-scale Ekman convergence in the central and eastern coastal boundary. The geostrophic adjustment to higher sea surface height (SSH) and lower isopycnals lead to stronger cyclonic gyre scale circulation. The opposite situation occurs during stronger northwesterly winds (negative phase of the PDO).Along the eastern side of the GOA basin, interannual changes in the surface winds also modulate the seasonal development of high amplitude anticyclonic eddies (e.g. Haïda and Sitka eddies). Large interannual eddy events during winter-spring, are phase-locked with the seasonal cycle. The initial eddy dynamics are consistent with a quasi-linear Rossby wave response to positive SSH anomalies forced by stronger downwelling favorable winds (e.g. southwesterly during El Niño). However, because of the fast growth rate of baroclinic instability and the geographical focusing associated with the coastal geometry, most of the perturbation energy in the Rossby wave is locally trapped until converted into large scale nonlinear coherent eddies. Coastally trapped waves of tropical origin may also contribute to positive SSH anomalies that lead to higher amplitude eddies. However, their presence does not appear essential. The model ensembles, which do not include the effects of equatorial coastally trapped waves, capture the large Haïda and Sitka eddy events observed during 1982 and 1997 and explain between 40% and 70% of the tidal gauges variance along the GOA coast.In the western side of the GOA basin, interannual eddy variability located south of the Alaskan Stream is not correlated with large scale forcing and appears to be intrinsic. A comparison of the three model ensembles forced by NCEP winds and a multi-century-long integration forced only with the seasonal cycle, shows that the internal variability alone explains most of the eddy variance. The asymmetry between the eddy forced regime in the eastern basin, and the intrinsic regime in the western basin, has important implications for predicting the GOA response to climate change. If future climate change results in stronger wintertime winds and increased downwelling in the eastern basin, then increased mesoscale activity (perhaps more or larger eddies) might occur in this region. Conversely, the changes in the western basin are not predictable based on environmental forcing. Eastern eddies transport important biogeochemical quantities such as iron, oxygen and chlorophyll-a into the gyre interior, therefore having potential upscale effects on the GOA high-nutrient-low-chlorophyll region.  相似文献   

南沙岛礁区中西部海底岩石拖网和发现早第三纪半深海沉积的地质意义   总被引：2，自引：0，他引：2  

周蒂  施小斌  陈汉宗  钟石兰 《热带海洋学报》2002,21(2):32-42

在南沙岛礁区中西部实施海底岩石拖网,有3个站获得海底岩石样品。其中在巽它陆架东北缘水深200多米的NS99－17站见深灰色淤泥中有大量铁褐色含泥钙质结核,说明该区（可能在末次冰期时）处于滨海或海滩氧化环境形成结核,之后海平面上升了至少150m。在南威岛西北方康泰滩的NS99－57站1360m水深的海底获强溶蚀的白垩多孔灰岩,含底栖有孔虫化石,指示康泰滩是从早－中中新世或更早开始生长的生物礁。在永暑礁东北约55km处的NS99－52站新命名了“东生海山”,其西北坡获含第四纪钙质超微化石的礁灰岩,以及由抱球虫类等生物碎屑和胶磷矿组成的钙质磷块岩和含磷生物屑灰岩滚石,指示半深海环境,其中的钙质超微化石大部分时代为中始新世－渐新世,以始新世可能较大,小部分属第四纪。这次海底岩石拖网为研究南沙岛礁区中部写信为和油气资源评价提供了重要的“硬证据”,尤其是发现早第三纪半深海相钙质磷块岩离南海西南次海盆很近,不但证实了南沙海域广布下第三系海相沉积的推断,而且为判断南海的张开时间提供了补充依据。  相似文献   

台西南盆地和北港隆起的中生界及其沉积环境   总被引：28，自引：4，他引：28  

周蒂 《热带海洋学报》2002,21(2):50-57

我国南海海域广泛存在中生代沉积地层，在南海寻找中生界油气藏潜力极大。台西南盆地和北港隆起有数十口井钻遇中生界，经过详细生物地层学工作确定了下白垩统（阿普特阶和下阿尔必阶）和侏罗系（？）两套中生代地层，是迄今南海北部中生界地层研究最为深入的地区，可作为对比的样板。介绍了台西南盆地和台湾西部中生界的岩性、岩相和生物地层学特征，指出晚侏罗世（？）与早白垩世之间沉积环境发生了显著变化，台西南盆地由深海至半深海变为内陆，而北港隆起由内陆变为海陆交互和浅海环境。  相似文献   

几何与语义统一的区域地质构造GIS数据模型     

何撼东  胡迪  闾国年  李安波  李军利 《测绘学报》2017,46(8):1058-1068

随着GIS在地质中的应用,地质GIS数据模型在几何描述与表达方面日趋完善,但是对地质构造现象的语义描述与表达却较为有限,制约了地质研究者对地质GIS地理解与应用。为了增强地质GIS数据模型中的语义信息,本文采用面向对象的方法,通过地质对象来统一描述和表达地质构造现象的几何与语义特征,设计了几何与语义统一的区域地质构造GIS数据模型。本文设计了基于"词汇概念-名词解释-几何图例"的地质构造现象的语义三角描述方法。依据区域地质构造的语义特征,采用线性分类法将区域地质构造现象划分为3个大类、10个中类和33个小类,在此基础上定义了地质构造现象的基本要素集和要素类,并基于地质对象之间的几何和语义关系,建立了区域地质构造现象要素的基本几何网络。采用ArcGIS Diagrammer Geodatabase建模工具,构建了几何与语义统一的地质GIS数据模型。最后,以宁镇山脉区域地质构造现象为例对该数据模型进行了试验验证,结果表明该模型具有较好的实用性。  相似文献   

基于方差分量估计的不同截止高度角下的组合单点定位     

冯彪  柴洪洲  王敏  潘宗鹏  李迪 《测绘工程》2017,26(4)

BDS/GPS/GLONASS组合系统定位时,由于系统间卫星测距精度的差异性,需要合理确定卫星间权比,Helmert方差分量估计常被用于确定不同类观测值间权比;而当观测值含有粗差时,Helmert方差分量估计定位结果容易被粗差污染或收敛失真,出现大的偏差。文中基于Helmert方差分量估计,引入等价权因子IGGIII函数,建立抗差Helmert方差分量估计权函数模型,对比分析其在低截止高度角10°、15°和20°下,在BDS/GPS/GLONASS组合系统定位中的应用及定位精度,并讨论分析在高截止高度角30°和40°下,组合系统和单系统BDS的定位精度。实验结果表明:当观测值无明显粗差时,Helmert方差分量估计和抗差分量估计的定位精度相当,略低于高度角权函数的定位结果,点位精度RMS优于2.5m;含粗差时,抗差解定位精度最高;当截止高度角为30°时,BDS单系统定位精度RMS优于5m,而组合系统RMS接近3m;为40°时,组合系统平面精度RMS优于2m,三维精度RMS优于6m,而单系统不能定位。  相似文献