Hydrogeochemical and multi-tracer investigations of arsenic-affected aquifers in semi-arid West Africa     

Anja Bretzler  Lucien Stolze  Julien Nikiema  Franck Lalanne  Elaheh Ghadiri  Matthias S.Brennwald  Massimo Rolle  Mario Schirmer 《地学前缘(英文版)》2019,10(5):1685-1699

The semi-arid Sahel regions of West Africa rely heavily on groundwater from shallow to moderately deep(100 m b.g.l.)crystalline bedrock aquifers for drinking water production.Groundwater quality may be affected by high geogenic arsenic(As)concentrations(10μg/L)stemming from the oxidation of sulphide minerals(pyrite,arsenopyrite)in mineralised zones.These aquifers are still little investigated,especially concerning groundwater residence times and the influence of the annual monsoon season on groundwater chemistry.To gain insights on the temporal aspects of As contamination,we have used isotope tracers(noble gases,~3H,stable water isotopes(~2 H,~(18)O))and performed hydrochemical analyses on groundwater abstracted from tube wells and dug wells in a small study area in southwestern Burkina Faso.Results revealed a great variability in groundwater properties(e.g.redox conditions,As concentrations,water level,residence time)over spatial scales of only a few hundred metres,characteristic of the highly heterogeneous fractured underground.Elevated As levels are found in oxic groundwater of circum-neutral pH and show little relation with any of the measured parameters.Arsenic concentrations are relatively stable over the course of the year,with little effect seen by the monsoon.Groundwater residence time does not seem to have an influence on As concentrations,as elevated As can be found both in groundwater with short(50 a)and long(10~3 a)residence times as indicated by ~3He/~4He ratios spanning three orders of magnitude.These results support the hypothesis that the proximity to mineralised zones is the most crucial factor controlling As concentrations in the observed redox/pH conditions.The existence of very old water portions with residence times10~3 years already at depths of50 m b.g.l.is a new finding for the shallow fractured bedrock aquifers of Burkina Faso,suggesting that overexploitation of these relatively low-yielding aquifers may be an issue in the future.  相似文献   

Major and trace element geochemistry of superficial sediments and suspended particulate matter of shallow saline lakes in Eastern Austria     

Anja Stojanovic  Daniel Kogelnig  Dieter Mader  Rudolf Krachler 《Chemie der Erde / Geochemistry》2009,69(3):223-234

General geochemical parameters of water, superficial sediments, and suspended particulate matter (SPM) were determined from small shallow saline lakes (soda ponds) as well as from lake Neusiedlersee in eastern Austria. Additionally, instrumental neutron activation analysis (INAA) was used to determine the distribution of major, rare earth and other trace elements in superficial sediments and SPM. Chemical results show remarkable differences in salinity and ionic strength between the investigated ponds. Anthropogenic effects, such as drawdown of ground water level and a loss of lake water due to drainage, are clearly reflected in obtained chemical and geological data. Due to a strong dependence of the complexation and scavenging behavior of the rare earth elements (REE) on ionic strength, a significant difference between REE concentrations in soda ponds with different anthropogenic impact was found. The content and composition of authigenic evaporitic minerals in superficial sediments and SPM clearly differ with a fluctuating water level and salt concentration. Furthermore, we determined the distribution of major and trace elements in superficial sediments of a nearby fluvial system. Our results show a clear correlation between REE superficial sediment concentrations in anthropogenically degraded soda ponds and fluvial system. Therefore, we assume that REE concentrations of sediments and SPM are suitable for the study of geochemical changes of inland saline lakes due to anthropogenic impacts on water balance.  相似文献   

Holocene and Pleistocene fringing reef growth and the role of accommodation space and exposure to waves and currents (Bora Bora,Society Islands,French Polynesia)     

Eberhard Gischler  J. Harold Hudson  Marc Humblet  Juan Carlos Braga  Dominik Schmitt  Anja Isaack  Anton Eisenhauer  Gilbert F. Camoin 《Sedimentology》2019,66(1):305-328

Holocene fringing reef development around Bora Bora is controlled by variations in accommodation space (as a function of sea‐level and antecedent topography) and exposure to waves and currents. Subsidence ranged from 0 to 0·11 m kyr^?1, and did not create significant accommodation space. A windward fringing reef started to grow 8·7 kyr bp , retrograded towards the coast over a Pleistocene fringing reef until ca 6·0 kyr bp , and then prograded towards the lagoon after sea‐level had reached its present level. The retrograding portion of the reef is dominated by corals, calcareous algae and microbialite frameworks; the prograding portion is largely detrital. The reef is up to 13·5 m thick and accreted vertically with an average rate of 3·12 m kyr^?1. Lateral growth amounts to 13·3 m kyr^?1. Reef corals are dominated by an inner Pocillopora assemblage and an outer Acropora assemblage. Both assemblages comprise thick crusts of coralline algae. Palaeobathymetry suggests deposition in 0 to 10 m depth. An underlying Pleistocene fringing reef formed during the sea‐level highstand of Marine Isotope Stage 5e, and is also characterized by the occurrence of corals, coralline algal crusts and microbialites. A previously investigated, leeward fringing reef started to form contemporaneously (8·78 kyr bp ), but is thicker (up to 20 m) and solely prograded throughout the Holocene. A shallow Pocillopora assemblage and a deeper water Montipora assemblage were identified, but detrital facies dominate. At the Holocene reef base, only basalt was recovered. The Holocene windward–leeward differences are a consequence of less accommodation space on the eastern island side that eventually led to a more complex reef architecture. As a result of higher rates of exposure and flushing, the reef framework on the windward island side is more abundant and experienced stronger cementation. In the Pleistocene, the environmental conditions on the leeward island side were presumably unfavourable for fringing reef growth.  相似文献   

Late Holocene tsunami traces on the western and southern coastlines of the Peloponnesus (Greece)   总被引：1，自引：0，他引：1  

Anja Scheffers  Dieter Kelletat  Andreas Vtt  Simon Matthias May  Sander Scheffers 《Earth and Planetary Science Letters》2008,269(1-2):271-279

Greece, in particular the western and southern parts close to the subduction zone of the Hellenic Trench, experiences strong earthquakes and subsequent tsunamis. Nevertheless, field evidence of tsunamis from the late Holocene is extremely rare. Our research along the coastlines of the western and southern Peloponnesus resulted in new findings of tsunami impacts in the form of clusters and ridges of large boulders and thick tsunamigenic sand layers encountered in vibracores. Many boulders contained attached marine organisms, which prove that they were transported from the foreshore environment against gravity by extreme wave events. The attached organisms, which have been dated by ¹⁴C-AMS, suggest that historical tsunami events of great energy occurred around 1300 cal AD. A wood fragment found at the base of tsunami deposits in a vibracore from Cape Punta was dated to ~ 250 cal AD.  相似文献   

Effects of current exposure on habitat preference of mobile 0-group epibenthos for intertidal seagrass beds (Zostera noltii) in the northern Wadden Sea     

Patrick Polte  Anja Schanz  Harald Asmus 《Estuarine, Coastal and Shelf Science》2005,62(4):627-635

In the northern Wadden Sea, the extent of intertidal seagrass beds, their plant biomass and shoot density highly depends on local current regimes. This study deals with the role of intertidal Zostera noltii beds as nursery for mobile epibenthic macrofauna and the impact of seagrass bed characteristics on their abundance and distribution patterns. According to their exposure to the main tidal gullies, sampling sites were separated into exposed, semi-exposed and sheltered. Dominant species of crustaceans and demersal fish were studied in respect of their abundances within seagrass beds and adjacent unvegetated areas. Quantitative sampling was performed at day and night high tide using a portable drop trap. In general, species composition varied little between seagrass beds and bare sand. However, the presence of vegetation had a quantitative effect increasing individual numbers of common epifaunal species. Abundances of 0-group shore crabs (Carcinus maenas), common gobies (Pomatoschistus microps) and brown shrimps (Crangon crangon) were highest within sheltered seagrass beds. With decreasing plant density habitat preference of epibenthos changed on species level. By regulating the habitat complexity the currents regime is profoundly influencing the nursery function of intertidal seagrass beds in the Wadden Sea.  相似文献   

Chemical and isotopic characteristics of groundwater-dominated Radovna River (NW Slovenia)     

Anja Torkar  Mihael Brenčič  Polona Vreča 《Environmental Earth Sciences》2016,75(18):1296

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Reply to Comment on: Coarse clast ridge sequences as suitable archives for past storm events? Case study on the Houtman Abrolhos,Western Australia     

Anja M. Scheffers  Sander R. Scheffers  Dieter H. Kelletat  Peter Squire  Lindsay Collins  Yuexing Feng  Jian‐Xin Zhao  Renaud Joannes‐Boyau  Simon Matthias May  Gerhard Schellmann  Heather Freeman 《第四纪科学杂志》2013,28(2):213-215

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Comment on “The beginnings of hydrous mantle wedge melting”, CB Till, TL Grove, AC Withers, Contributions to Mineralogy and Petrology, DOI 10.1007/s00410-011-0692-6     

David H. Green  Anja Rosenthal  István Kovács 《Contributions to Mineralogy and Petrology》2012,164(6):1069-1071

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The dependence of organohalogen compound concentrations on herring age and size in the Bothnian Sea, northern Baltic     

Parmanne R  Hallikainen A  Isosaari P  Kiviranta H  Koistinen J  Laine O  Rantakokko P  Vuorinen PJ  Vartiainen T 《Marine pollution bulletin》2006,52(2):149-161

The concentrations and composition profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls, polybrominated diphenyl ethers and polychlorinated naphthalenes were determined in herring individuals collected from the commercial catches of the Bothnian Sea, northern Baltic. The median age of herring was 5.0 years and in the muscle the median toxic equivalent concentration of PCDD/Fs was 5.6 WHO(PCDD/F)-TEQ pg/g fresh weight (fw) and that of PCBs 2.7 WHO(PCB)-TEQ pg/g fw. The median sum concentration of PBDEs was 1.4 ng/g fw and that of PCNs 0.1 ng/g fw. Differences in age-dependent accumulation between the organohalogen groups and individual congeners were major. In the Bothnian Sea the content of organohalogen compounds in herring is obviously elevated due to the availability and large proportion of Mysis crustaceans in their diet. More intensive fishing could reduce the concentrations of organohalogens, including the abundant, accumulative and toxic 2,3,4,7,8-PeCDF congener in the Baltic herring catch.  相似文献   

The build-up of the colour–magnitude relation in galaxy clusters since z∼ 0.8     

Gabriella De Lucia  Bianca M. Poggianti  Alfonso Aragón-Salamanca  Simon D. M. White  Dennis Zaritsky  Douglas Clowe  Claire Halliday  Pascale Jablonka  Anja von der Linden  Bo Milvang-Jensen  Roser Pelló  Gregory Rudnick  Roberto P. Saglia  Luc Simard 《Monthly notices of the Royal Astronomical Society》2007,374(3):809-822

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