Simulation of a Ground Water Recirculation Well with a Dual-Column Laboratory Setup     

Suzanne Lesage  Susan Brown  Kelly Millar  Helena Steer 《Ground Water Monitoring & Remediation》2003,23(2):102-110

This paper describes a dual-column laboratory setup consisting of a glass column and a stainless-steel column filled with aquifer material. The setup was used to replicate a ground water recirculation well that serves as an in situ reactor and a combined injection/withdrawal well. The treatment solution consisted of a buffered titanium (III) citrate/vitamin B₁₂ mixture. The first column, representing the well, was made of glass, allowing for visual inspection of the mixing. The stainless-steel column was instrumented with redox (Eh) probes to monitor the changes in redox conditions. The redox measurement showed that, although the sand contained large quantities of iron oxides, the oxidation rate was relatively slow and the titanium solution would remain reduced for some time in the aquifer, continuing to react with the contaminants. This laboratory setup was used to optimize the reagent concentrations and rate of delivery for field implementation. It was found that 4 mM titanium citrate and 3 mg/L vitamin B₁₂ were sufficient to degrade 1,1,2,2-tetrachloroethane and carbon tetrachloride within one day, but not trichloroethylene, which required five days with 10 mM titanium citrate and 5 mg/L vitamin B₁₂.  相似文献   

Evidence for Late Pleistocene and Holocene sea-level,neotectonic and climate control in the coastal zone of northwest Portugal     

Granja  Helena Maria 《Geologie en Mijnbouw》1998,77(3-4):233-245

The coastal zone of northwest Portugal can be subdivided into two geomorphological sectors: Sector 1, between the Minho River and the town of Espinho, where the coastal segments consist of estuaries, sandy and shingle beaches with rocky outcrops, and Holocene dune systems (foredunes and some migrating dunes with blow-outs). The estuaries and the foredunes in particular are very degraded by human activities. Sector 2, between Espinho and the Mondego Cape, where coastal lagoons and Holocene dune systems (foredunes, parabolic and transverse dunes) occur. This study deals with the macroscale, i.e. 100–1000 years, forcing by sea-level changes and neotectonic activity on the one hand, and mesoscale, i.e. 1–100 years, forcing by climate fluctuations on the other hand, on these (palaeo-)environments. It is shown in particular that sea-level changes and neotectonic activity play a dominant role in the evolution of the coastal zone since the Late Pleistocene. Sediment starvation on the shoreface is postulated to be one of the major causes for coastal erosion since at least the 15th century. The mesoscale role of climate is difficult to assess at the present stage of knowledge, mainly because of overprinting by the macroscale evolution of the coast. However, data on estuarine saltmarsh evolution in sector 1 point towards discrete changes in storminess, while the development of Medieval dune systems in sectors 1 and 2 are attributed to the Little Ice Age or, alternatively, to human occupation of the dune areas.  相似文献   

Palaeoglaciation of Bayan Har Shan,northeastern Tibetan Plateau: glacial geology indicates maximum extents limited to ice cap and ice field scales   总被引：1，自引：0，他引：1  

Jakob Heyman  Arjen P. Stroeven  Helena Alexanderson  Clas Hättestrand  Jon Harbor  Yingkui Li  Marc W. Caffee  Liping Zhou  Daniel Veres  Feng Liu  Martin Machiedo 《第四纪科学杂志》2009,24(7):710-727

Key locations within an extensive area of the northeastern Tibetan Plateau, centred on Bayan Har Shan, have been mapped to distinguish glacial from non‐glacial deposits. Prior work suggests palaeo‐glaciers ranging from valley glaciers and local ice caps in the highest mountains to a regional or even plateau‐scale ice sheet. New field data show that glacial deposits are abundant in high mountain areas in association with large‐scale glacial landforms. In addition, glacial deposits are present in several locations outside areas with distinct glacial erosional landforms, indicating that the most extensive palaeo‐glaciers had little geomorphological impact on the landscape towards their margins. The glacial geological record does indicate extensive maximum glaciation, with local ice caps covering entire elevated mountain areas. However, absence of glacial traces in intervening lower‐lying plateau areas suggests that local ice caps did not merge to form a regional ice sheet on the northeastern Tibetan Plateau around Bayan Har Shan. No evidence exists for past ice sheet glaciation. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Geochemistry of four tropical montane watersheds,Central Panama     

Russell S. Harmon  W. Berry Lyons  David T. Long  Fred L. Ogden  Helena Mitasova  Christopher B. Gardner  Kathleen A. Welch  Rebecca A. Witherow 《Applied Geochemistry》2009

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Quality assessment of benthic macroinvertebrates under the scope of WFD using BAT, the Benthic Assessment Tool     

Heliana Teixeira  João Magalhães Neto  Joana Patrício  Helena Veríssimo  Rute Pinto  Fuensanta Salas  João Carlos Marques 《Marine pollution bulletin》2009,58(10):1477-1486

Assessing the health of ecosystems has become a focal point among researchers worldwide. Recently, the European Water Framework Directive intensified the development of approaches to assess ecosystems’ ecological quality. The Benthic Assessment Tool (BAT) is a multimetric approach to evaluate condition of subtidal soft bottom macroinvertebrates of coastal and transitional waters. The effects of anthropogenic disturbances on benthic macroinvertebrate communities, from 1990 to 2006, allowed testing BAT performance in Mondego estuary (Portugal). The method was able to detect decrease on ecological quality, induced essentially by eutrophication and physical disturbances, and follow communities’ subsequent recovery. It evidenced, nevertheless, some limitations associated with the unstable nature of estuaries. The ecological classification of key species in the community and the balance expected between ecological groups of estuarine communities had great influence in the final ecological assessment. Shortcomings of the method were discussed in the light of its suitability for assessing transitional waters’ condition.  相似文献   

Constraints on the use of phytoplankton as a biological quality element within the Water Framework Directive in Portuguese waters   总被引：3，自引：0，他引：3  

Domingues RB  Barbosa A  Galvão H 《Marine pollution bulletin》2008,56(8):1389-1395

The European Union Water Framework Directive (WFD), a new regulation aiming to achieve and maintain a clean and well-managed water environment, refers to phytoplankton as one of the biological quality elements that should be regularly monitored, and upon which the reference conditions of water quality should be established. However, the use of phytoplankton as a biological quality element will result in several constraints, which are analyzed in this article with examples from Portuguese waters. Specifically, the establishment of reference conditions of water quality may be difficult in some water bodies for which no historical data exists. The sampling frequency proposed for phytoplankton monitoring does not seem suitable to assess phytoplankton succession, and may preclude the detection of algal blooms. Finally, the use of chlorophyll a as a proxy of phytoplankton biomass and abundance has been proposed by some authors, but it may overlook blooms of pico- and small nanophytoplankton, and overestimate the importance of large microphytoplankton. Furthermore, most studies in Portugal have used only inverted microscopy for phytoplankton observation and quantification; this method does not permit the distinction between autotrophic and heterotrophic cells, especially in samples preserved with Lugol's solution, and does not allow the observation of smaller-sized cells. Finally, some techniques, such as remote sensing and chemotaxonomic analysis, are proposed to be used as supplements in phytoplankton monitoring programs.  相似文献   

Calc-Alkaline Magmatism at the Archean Proterozoic Transition: the Caico Complex Basement (NE Brazil)     

De Souza  Zorano Sergio; Martin  Herve; Peucat  Jean-Jacques; Jardim De Sa  Emanuel Ferraz; Macedo  Maria Helena De Freitas 《Journal of Petrology》2007,48(11):2149-2185

The Paleoproterozoic metaplutonic rocks of the CaicóComplex Basement (Seridó region, NE Brazil) provide importantand crucial insights into the petrogenetic processes governingcrustal growth and may potentially be a proxy for understandingthe Archean–Proterozoic transition. These rocks consistof high-K calc-alkaline diorite to granite, with Rb–Sr,U–Pb, Pb–Pb and Sm–Nd ages of c. 2·25–2·15Ga. They are metaluminous, with high Yb_N, K₂O/Na₂O and Rb/Sr,low I_Sr ratios, and are large ion lithophile elements (LILE)enriched. Petrographic and geochemical data demonstrate thatthey belong to differentiated series that evolved by low-pressurefractionation, thus resulting in granodioritic liquids. We proposea model in which the petrogenesis of the Caicó Complexorthogneisses begins with partial melting of a metasomaticallyenriched spinel- to garnet-bearing lherzolite (with high-silicaadakite melt as the metasomatic agent), generating a basic magmathat subsequently evolved at depth through fractional crystallizationof olivine, followed by low-pressure intracrustal fractionation.A subduction zone setting is proposed for this magmatism, toaccount for both negative anomalies in high field strength elements(HFSE) and LILE enrichment. Mantle-derived juvenile magmatismwith the same age is also known in the São Franciscoand West Africa cratons, as well as in French Guyana, and thusthe Archean–Proterozoic transition marks a very importantcontinental accretion event. It also represents a transitionfrom slab-dominated (in the Archean) to wedge-dominated post-Archeanmagmatism. KEY WORDS: calc-alkaline; magmatism; NE Brazil; Paleoproterozoic; petrogenesis  相似文献   

Geostatistical Interplay Between Geophysical and Geochemical Data: Mapping Litho-Structural Assemblages of Mesozoic Igneous Activities in the Parnaíba Basin (NE Brazil)     

David L. de Castro  Diógenes C. Oliveira  Maria Helena B. M. Hollanda 《Surveys in Geophysics》2018,39(4):683-713

Two widespread magmatic events are recorded in the Parnaíba basin (NE Brazil) during the Jurassic/Cretaceous opening of the Central and South Atlantic Oceans. The Early Jurassic (~ 200 Ma) lava flows of the Mosquito Formation occur essentially in the western and southern basin segments, representing one of the largest expressions of the Central Atlantic Magmatic Province in the South American Plate. In contrast, sill complexes and dike swarms of the Early Cretaceous (129–124 Ma) Sardinha Formation occur in the eastern part of the basin and are chrono-correlated to the large Paraná–Etendeka igneous province and to the Rio Ceará–Mirim Dike Swarm. We gathered geophysical, well logging, outcrop analogs and geochemical data to recognize geometrical shapes and areal distribution patterns of igneous-related constructions. Seismic and well data reveal hundreds of km wide multilayered sill complexes and dikes, which are widespread across vast regions of the basin without evident structural control from either the Precambrian basement grain or the basin internal architecture. Anomaly enhancement techniques and self-organizing maps (SOM) procedure were applied on airborne magnetic data, unraveling near-surface magmatic features in four distinct magnetic domains. Using SOM analysis, the basaltic rocks were divided into six groups based on magnetic susceptibility and major elements composition. These results suggest common origin for both magmatic episodes, probably a combination of effects of edge-driven convection and large-scale mantle warming under the westward moving West Gondwana during the Central and South Atlantic opening, which caused a shifted emplacement to the east of the igneous rocks in the Parnaíba basin.  相似文献   

Fluorescence as a Tool for Tracing the Organic Contamination from Pulp Mill Effluents in Surface Waters     

Eduarda B. H. Santos  Olga M. S. Filipe  Regina M. B. O. Duarte  Helena Pinto  Armando C. Duarte 《洁净——土壤、空气、水》2001,28(7):364-371

Three‐dimensional fluorescence spectra of water samples from an eucalyptus bleached kraft pulp mill and from a river, upstream and downstream of the discharge of the effluent, revealed the existence of a peak at δ_exc = 280 nm and δ_em = 340 nm Δδ = 60 nm), characteristic of effluentπs organic matter. Humic substances were isolated from the effluent by sequential adsorption onto resins XAD‐8 and XAD‐4 in series. Their synchronous fluorescence spectra with Δδ = 60 nm do also exhibit an intense signal at δ_exc = 280 nm (≈ 300 nm in the humic acid fraction). The peak is absent in the spectra of humic substances isolated from a non‐polluted site of the river, but it is clearly seen in the spectra of the humic substances from a site downstream of the discharge of the effluent. Synchronous fluorescence spectra (Δδ = 60 nm) of water samples from the river and its lagoon were recorded and revealed to be an easy and fast way of tracing the organic contamination from the effluent.  相似文献   

Ecological indices tracking distinct impacts along disturbance-recovery gradients in a temperate NE Atlantic Estuary – Guidance on reference values     

Heliana Teixeira  Fuensanta Salas  João M. Neto  Joana Patrício  Rute Pinto  Helena Veríssimo  José A. García-Charton  Concepción Marcos  Angél Pérez-Ruzafa  João C. Marques 《Estuarine, Coastal and Shelf Science》2008

Results gathered from a monitoring programme on the Mondego Estuary (Western Coast of Portugal) were compliant with findings drawn from other studies, which pointed out that unstable environments, namely estuarine systems, constitute a great challenge for the use of environmental tools such as ecological indices. The Margalef Index, the Shannon–Wiener Index and AMBI were proposed to evaluate the ecological status of benthic communities in the scope of the European Water Framework Directive (WFD) in Portugal and other European member states. In this system these indices were not equally effective in tracking changes in benthic communities that expressed obvious responses to anthropogenic disturbances (eutrophic situations and severe physical disturbance) and to subsequent impacts' cessation. Natural variability played an important role on the indices' response, with estuarine gradient and habitat heterogeneity affecting the ranges of values obtained, and with extreme climate events slowing down the ongoing recovery process. Nonetheless, both natural and anthropogenic variability during the study period could be satisfactorily detected if we accounted for the information provided by all three indices. Based on the whole range of variation observed (a) as a response to different kinds of impacts, and (b) along recovery gradients, as well as accounting for the natural driving forces acting upon estuarine benthic invertebrate communities, we propose a set of reference values for these three indices. This proposal aims at contributing to the implementation of classification tools within the scope of the European WFD.  相似文献