Arsenic in the groundwater of Ouro Preto (Brazil): its temporal behavior as influenced by the hydric regime and hydrogeology     

José Augusto Costa Gonçalves  Jorge Carvalho de Lena  José Fernando Paiva  Hermínio Arias Nalini Jr  Janice Cardoso Pereira 《Environmental Geology》2007,53(4):785-793

In the city of Ouro Preto (MG), water catchment for public supply originates from superficial drainage, springs, old abandoned mines and some driven wells. In the rocks of the region, As is originally found in gold-enriched sulphide-bearing mineral deposits. The weathering process introduces As into the hydrological system by dissolution of this element into the leachate. Measurement of the As content in the groundwater of some catchments was carried out during 1 year and these measurements demonstrated high As content—up to 224 μg L⁻¹ of As(V)—during the rainy season (the maximum concentration limit according to World Health Organization is 10 μg L⁻¹). Lower values were observed during the dry season and in some sampling stations, As was not even detected. The As concentration variability during 1 year shows a strict and direct relationship to seasonal and hydrological conditions. For city authorities, responsible for public water supply, it is necessary to perform a complete inventory of the water sources used and constantly monitor the As content in the water.  相似文献   

An attempt to use LA-ICP-SMS to quantify enrichment of trace elements on pyrite surfaces in oxidizing mine tailings     

Björn Öhlander  Barbara Müller  Mikael Axelsson  Lena Alakangas 《Journal of Geochemical Exploration》2007

Metals released from oxidation and weathering of sulphide minerals in mine tailings are to a high degree retained at deeper levels within the tailings themselves. To be able to predict what could happen in the future with these secondarily retained metals, it is important to understand the retention mechanisms. In this study an attempt to use laser ablation high-resolution ICP-MS (LA-ICP-SMS) to quantify enrichment of trace elements on pyrite surfaces in mine tailings was performed. Pyrite grains were collected from a profile through the pyrite-rich tailings at the Kristineberg mine in northern Sweden. At each spot hit by the laser, the surface layer was analyzed in the first shot, and a second shot on the same spot gave the chemical composition of the pyrite immediately below. The crater diameter for a laser shot was known, and by estimating the crater depth and total pyrite surface, the total enrichment on pyrite grains was calculated. Results are presented for As, Cd, Co, Cu, Ni and Zn. The results clearly show that there was an enrichment of As, Cd, Cu and Zn on the pyrite surfaces below the oxidation front in the tailings, but not of Co and Ni. Arsenic was also enriched on the pyrite grains that survived in the oxidized zone. Copper has been enriched on pyrite surfaces in unoxidized tailings in the largest amount, followed by Zn and As. However, only 1.4 to 3.1% of the Cd and Zn released by sulphide oxidation in the oxidized zone have been enriched on the pyrite surfaces in the unoxidized tailings, but for As and Cu corresponding figures are about 64 and 43%, respectively. There were many uncertainties in these calculations, and the results shall not be taken too literally but allowed the conclusion that enrichment on pyrite surfaces is an important process for retention of As and Cu below the oxidation front in pyrite rich tailings. Laser ablation is not a surface analysis technique, but more of a thin layer method, and gives no information on the type of processes resulting in enrichment on the pyrite surfaces. Although only pyrite grains that appeared to be fresh and without surface coatings were used in this study, the possibility that a thin layer of Fe-hydroxides occurred must be considered. Both adsorption to the pyrite directly or to Fe-oxyhydroxides may explain the enrichment of As, Cd, Cu and Zn on the pyrite surfaces, and, in the case of Cu, also the replacement of Fe(II) by Cu(II) in pyrite.  相似文献   

Impact of Spawning Substrate Complexity on Egg Survival of Atlantic Herring (<Emphasis Type="Italic">Clupea harengus</Emphasis>, L.) in the Baltic Sea     

Lena von Nordheim  Paul Kotterba  Dorothee Moll  Patrick Polte 《Estuaries and Coasts》2018,41(2):549-559

Shallow shore zones are generally considered to provide juvenile habitats for many invertebrate and fish species and additionally serve as spawning grounds for important components of oceanic food webs and fishery resources such as herring (Clupea spp.). Herring attach their demersal eggs to benthic substrates, rendering reproduction success vulnerable to environmental changes and local habitat alterations. However, little information is available on the effects of different substrates on the survival of demersal eggs. Hypothesizing that the structural complexity of spawning substrates generally affects herring egg survival and that the effect magnitude depends on the suitability of ambient environment, field experiments were conducted on a major spawning ground of C. harengus in the Southwestern Baltic Sea. Herring eggs were artificially spawned on substrates of different structural complexities and incubated in situ under differing temperature regimes, at the beginning and the end of the natural herring spawning season, to include the full suite of stressors occurring on littoral spawning beds. Results of this study indicate a positive relation between high structural complexity of spawning substrates and herring egg survival. Mean egg mortality was three times higher on substrates of lowest complexity than on highly complex substrates. These differences became even more prominent under unfavorable conditions that appeared with rising water temperatures later in the spawning season. Although the mechanisms are still unclear, we conclude that structural complexity, particularly formed by submerged aquatic vegetation, provides a crucial prerequisite for the successful reproduction of substrate spawning marine fishes such as herring in the Baltic Sea.  相似文献   

Loose programming of GIS workflows with geo‐analytical concepts     

Johannes F. Kruiger  Vedran Kasalica  Rogier Meerlo  Anna‐Lena Lamprecht  Enkhbold Nyamsuren  Simon Scheider 《Transactions in GIS》2021,25(1):424-449

Loose programming enables analysts to program with concepts instead of procedural code. Data transformations are left underspecified, leaving out procedural details and exploiting knowledge about the applicability of functions to data types. To synthesize workflows of high quality for a geo‐analytical task, the semantic type system needs to reflect knowledge of geographic information systems (GIS) at a level that is deep enough to capture geo‐analytical concepts and intentions, yet shallow enough to generalize over GIS implementations. Recently, core concepts of spatial information and related geo‐analytical concepts were proposed as a way to add the required abstraction level to current geodata models. The core concept data types (CCD) ontology is a semantic type system that can be used to constrain GIS functions for workflow synthesis. However, to date, it is unknown what gain in precision and workflow quality can be expected. In this article we synthesize workflows by annotating GIS tools with these types, specifying a range of common analytical tasks taken from an urban livability scenario. We measure the quality of automatically synthesized workflows against a benchmark generated from common data types. Results show that CCD concepts significantly improve the precision of workflow synthesis.  相似文献   

Evaluation of the similarity between drought indices by correlation analysis and Cohen's Kappa test in a Mediterranean area     

Vergni  L.  Todisco  F.  Di Lena  B. 《Natural Hazards》2021,105(2):2187-2201

Natural Hazards - Forest fire hazard is a major problem in the Mediterranean region of Turkey and has a significant effect on both the climate system and ecosystems. During the last century, many...  相似文献   

Gottfried Konecny:the influence in the global development of the three geosciences     

Lena Halounová 《地球空间信息科学学报》2021,24(1):22-26

PREFACE The paper contains a brief overview of the professional activities of Professor Gottfried Konecny,Professor Emeritus at the Institute of Photogrammetry and GeoInformation,Leibniz University Hannover,Germany,and his influence on photogrammetry,remote sensing and geospatial infor-mation science during his time at the University of New Brunswick,Canada,and at the Leibniz University.His work can be divided into educational,scientific,application,organizational,and work in international societies.Additional activities comprised of giving courses in various languages,consultancy activities,and various other cooperations which took place in many South American countries,in Africa and Asia,for organizations such as the World Bank,United Nations,German Space Agency DLR,to name only a few.Activities in connection with international societies mainly took place during Prof.Konecny's engagement in the Council of the International Society for Photogrammetry(ISP),renamed the International Society for Photogrammetry and Remote Sensing(ISPRS),and the European Association of Remote Sensing Laboratories(EARSeL)Bureau.He was a key figure in bringing many countries and organizations to ISPRS as Ordinary and Sustaining Members.Professor Konecny has always been aware of the importance of international cooperation at various levels,also with sister societies such as the International Cartographic Association and the United Nations-Global Geospatial Information Management(UN-GGIM).His application activities span from the photogrammetry-oriented projects he was awarded in Canada,to remote sensing topics and geospatial sciences,combined with cartography during his Hannover period.His vision and endless effort are exemplary for a person who has always been devoted to the three geosciences mentioned above.Professor Konecny is the author of a number of books,journal papers and papers presented at international and national conferences.He has been a recognized keynote speaker at many conferences throughout the world due to his vast experience.This paper describes 75 years of a man who is an expert in fields which arose during his academic life.  相似文献   

Benthic Phosphorus Dynamics in the Gulf of Finland, Baltic Sea     

Lena Viktorsson  Elin Almroth-Rosell  Anders Tengberg  Roman Vankevich  Ivan Neelov  Alexey Isaev  Victor Kravtsov  Per O. J. Hall 《Aquatic Geochemistry》2012,18(6):543-564

Benthic fluxes of soluble reactive phosphorus (SRP) and dissolved inorganic carbon (DIC) were measured in situ using autonomous landers in the Gulf of Finland in the Baltic Sea, on four expeditions between 2002 and 2005. These measurements together with model estimates of bottom water oxygen conditions were used to compute the magnitude of the yearly integrated benthic SRP flux (also called internal phosphorus load). The yearly integrated benthic SRP flux was found to be almost 10 times larger than the external (river and land sources) phosphorus load. The average SRP flux was 1.25?±?0.56?mmol?m^?2?d^?1 on anoxic bottoms, and ?0.01?±?0.08?mmol?m^?2?d^?1 on oxic bottoms. The bottom water oxygen conditions determined whether the SRP flux was in a high or low regime, and degradation of organic matter (as estimated from benthic DIC fluxes) correlated positively with SRP fluxes on anoxic bottoms. From this correlation, we estimated a potential increase in phosphorus flux of 0.69?±?0.26?mmol?m^?2?d^?1 from presently oxic bottoms, if they would turn anoxic. An almost full annual data set of in situ bottom water oxygen measurements showed high variability of oxygen concentration. Because of this, an estimate of the time which the sediments were exposed to oxygenated overlying bottom water was computed using a coupled thermohydrodynamic ocean?Csea and ecosystem model. Total phosphorus burial rates were calculated from vertical profiles of total phosphorus in sediment and sediment accumulation rates. Recycling and burial efficiencies for phosphorus of 97 and 3%, respectively, were estimated for anoxic accumulation bottoms from a benthic mass balance, which was based on the measured effluxes and burial rates.  相似文献   

Are teachers and students ready for the new middle school geography syllabus in Sweden? Traditions in geography teaching,current teacher practices,and student achievement     

Lena Molin  Ann Grubbström 《Norsk geografisk tidsskrift. Norwegian journal of geography》2013,67(3):142-147

The article examines the relationship between selective traditions in geographical education, what middle school teachers choose to emphasise in geographical education, and student achievement. The study, conducted in Sweden, is based on observations made by students in teacher training programmes, interviews with teachers, and analyses of a test administered to middle school students. It shows that selective traditions in geographical education are strong, resulting in a focus on country-related knowledge and map-reading skills. Both teachers and students seem unclear about what other subject-specific skills geography teaching provides. Furthermore, students have difficulty achieving a high level of geographic reasoning. The authors argue that a subject-specific language in geography is important in both teaching and assessment. They stress that students need more practice in geographic reasoning, since this is required by the new curriculum and in the national test in geography for Year 6 (i.e. pupils in the age range 12–13 years). The study adds to earlier research by highlighting Swedish middle school teaching, which is a neglected field within curriculum studies, and by using a combination of methods to analyse the impact of selective traditions.  相似文献   

Investigating the last deglaciation of the Scandinavian Ice Sheet in southwest Sweden with 10Be exposure dating     

Nicolaj Krog Larsen  Henriette Linge  Lena Håkansson  Derek Fabel 《第四纪科学杂志》2012,27(2):211-220

In this study we have obtained 17 cosmogenic exposure ages from three well‐developed moraine systems – Halland Coastal Moraines (HCM), Göteborg Moraine (GM) and Levene Moraine (LM) – which were formed during the last deglaciation in southwest Sweden by the Scandinavian Ice Sheet (SIS). The inferred ages of the inner HCM, GM and LM are 16.7 ± 1.6, 16.1 ± 1.4 and 13.6 ± 1.4 ka, respectively, which is slightly older than previous estimates of the deglaciation based on the minimum limiting radiocarbon ages and pollen stratigraphy. During this short interval from 16.7 ± 1.6 to 13.6 ± 1.4 ka a large part (100–125 km) of the marine‐based sector of the SIS in southwest Sweden was deglaciated, giving an average ice margin retreat between 20 to 50 m a^?1. The inception of the deglaciation pre‐dated the Bølling/Allerød warming, the rapid sea level rise at 14.6 cal. ka BP and the first inflow of warm Atlantic waters into Skagerrak. We suggest that ice retreat in southwest Sweden is mainly a dynamical response governed by the disintegration of the Norwegian Channel Ice Stream and not primarily driven by climatic changes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Regional frequency analysis of rainfall extremes in Southern Malawi using the index rainfall and L-moments approaches   总被引：3，自引：1，他引：2  

Cosmo S. Ngongondo  Chong-Yu Xu  Lena M. Tallaksen  Berhanu Alemaw  Tobias Chirwa 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(7):939-955

Rainfall extremes often result in the occurrence of flood events with associated loss of life and infrastructure in Malawi. However, an understanding of the frequency of occurrence of such extreme events either for design or disaster planning purposes is often limited by data availability at the desired temporal and spatial scales. Regionalisation, which involves “trading time for space” by pooling together observations for stations with similar behavior, is an alternative approach for more accurate determination of extreme events even at ungauged areas or sites with short records. In this study, regional frequency analysis of rainfall extremes in Southern Malawi, large parts of which are flood prone, was undertaken. Observed 1-, 3-, 5- and 7-day annual maximum rainfall series for the period 1978–2007 at 23 selected rainfall stations in Southern Malawi were analysed. Cluster analysis using scaled at-site characteristics was used to determine homogeneous rainfall regions. L-moments were applied to derive regional index rainfall quantiles. The procedure also validated the three rainfall regions identified through homogeneity and heterogeneity tests based on Monte Carlo simulations with regional average L-moment ratios fitted to the Kappa distribution. Based on assessments of the accuracy of the derived index rainfall quantiles, it was concluded that the performance of this regional approach was satisfactory when validated for sites not included in the sample data. The study provides an estimate of the regional characteristics of rainfall extremes that can be useful in among others flood mitigation and engineering design.  相似文献