Search results for "Epos"

Carbonate deposits from the ancient aqueduct of Béziers, France — A high-resolution palaeoenvironmental archive for the Roman Empire

2016

Abstract Carbonate deposits from a Roman aqueduct in Beziers, southern France, record environmental conditions during the late first century C.E. These deposits formed in a steep section of the aqueduct with a high flow velocity, which caused rapid deposition of up to 11 mm of calcite per year over a period of 22–24 years. The microstructure, trace element and stable isotope composition show that regular deposition was interrupted by high-discharge events, probably in response to heavy rainfall during autumn and winter, transporting colloidally- and particle-bound elements and depositing calcite with elevated δ 18 O values. Individual autumn high-discharge events coincide with abrupt decrea…

Bulk composition of northern African dust and its source sediments — A compilation

2013

Abstract This paper presents a review of bulk compositional data of northern African dust and its potential source sediments and includes elemental, isotope and mineralogical data. Northern African dust represents about one half of the total global atmospheric mineral dust burden, and its uplift, transport and deposition have strong impacts on climate and various terrestrial and marine ecosystems. The chemical data set shows, that an ‘average northern African dust’ exhibits comparable Si, Fe and Mn contents with respect to the average composition of the upper continental crust, is slightly depleted in the alkali metals K and Na, and enriched in Ti and P. However, the complete data set yield…

2016

AbstractAn inscription on the supporting wall of the inverted siphon of the aqueduct of the ancient Roman city of Patara, SW Turkey, explains how the wall collapsed during an earthquake and was subsequently restored. Carbonate deposits formed inside the aqueduct channel show cyclic stable isotope changes representing 17 years of deposition. This sequence, together with the text of the inscription, allows dating the earthquake to 68 AD and the original inauguration of the aqueduct to the winter of 51/52 AD. Thus, the carbonate deposits represent a high-resolution record of palaeotemperature and precipitation for SW Turkey covering the complete reign of the Emperor Nero. The period shows a co…

Deposition order controls the first stages of a metal-organic coordination network on an insulator surface

2016

| openaire: EC/FP7/610446/EU//PAMS We report on first stages toward the formation of a surface-confined metal-organic coordination network (MOCN) by sequential deposition of biphenyl-4,4′-dicarboxylic acid and iron atoms on the surface of a bulk insulator, calcite (10.4). The influence of the deposition order on the structure formation is studied by noncontact atomic force microscopy operated in ultrahigh vacuum at room temperature. It is found that sequential deposition facilitates MOCN formation when the organic linker molecules are first adsorbed on the surface, followed by iron deposition. This observation is explained by first-principles computations, indicating that the metal-molecule…

Textural features and isotope geochemistry of the Scillato travertine (north-central Sicily): genetic implications.

2015

The travertine deposit, outcropping near the Scillato town (north-central Sicily), was originated by precipitation of calcium carbonate from the Scillato springs, documented as bicarbonate-enriched waters due to dissolution of the Madonie mountains carbonate rocks. This deposit is today well represented by the Travertine Cave, essentially constituted by stalactites and stalagmites in which travertine typically appears laminated with alternation of light and dark laminae. Mineralogical analysis have revealed the almost exclusive presence of calcite and observation under the polarized-light microscope showed different textural features, like presence of debris and porous portions, micritic po…

Deep-water stromatolites andFrutexites Maslov from the early and Middle Jurassic of S-Germany and Austria

1993

Despite extensive discussions during the last 20 years stromatolites are still used by many geologists as unequivocal indicators of very shallow-water conditions. We investigated four stratigraphic units from the Lower and Middle Jurassic of southern Germany (Posidonien-Schiefer, Amaltheen-Ton) and of the Northern Calcareous Alps (Adneter Kalk, Klauskalk), which were formerly interpreted as shallow marine sediments by some authors due to the occurrence of stromatolites. Our interpretations of the macro-, micro- and ultrafacies of these sediments are not compatible with shallow-water settings. We therefore propose a deep-marine, aphotic origin of these stromatolites. Former interpretations o…

Galvanic deposition and characterization of brushite/hydroxyapatite coatings on 316L stainless steel

2016

In this work, brushite and brushite/hydroxyapatite (BS, CaHPO4·H2O; HA, Ca10(PO4)6(OH)2) coatings were deposited on 316L stainless steel (316LSS) from a solution containing Ca(NO3)2·4H2O and NH4H2PO4 by a displacement reaction based on a galvanic contact, where zinc acts as sacrificial anode. Driving force for the cementation reaction arises from the difference in the electrochemical standard potentials of two different metallic materials (316LSS and Zn) immersed in an electrolyte, so forming a galvanic contact leading to the deposition of BS/HA on nobler metal. We found that temperature and deposition time affect coating features (morphology, structure, and composition). Deposits were char…

Short-term response of the Ca cycle of a montane forest in Ecuador to low experimental CaCl2 additions

2013

The tropical montane forests of the E Andean cordillera in Ecuador receive episodic Sahara-dust inputs particularly increasing Ca deposition. We added CaCl2 to isolate the effect of Ca deposition by Sahara dust to tropical montane forest from the simultaneously occurring pH effect. We examined components of the Ca cycle at four control plots and four plots with added Ca (2 x 5kg ha(-1) Ca annually as CaCl2) in a random arrangement. Between August 2007 and December 2009 (four applications of Ca), we determined Ca concentrations and fluxes in litter leachate, mineral soil solution (0.15 and 0.30 m depths), throughfall, and fine litterfall and Al concentrations and speciation in soil solutions…

Amazonian biomass burning-derived acid and nutrient deposition in the north Andean montane forest of Ecuador

2008

[1] We explored the influence of biomass burning in Amazonia and northeastern Latin America on N, C, P, S, K, Ca, Mg, Al, Mn, and Zn cycles of an Andean montane forest in south Ecuador exposed to the Amazon basin between May 1998 and April 2003. We assessed the response of the element budget of three microcatchments (8–13 ha) to the variations in atmospheric deposition between the intensive burning season and outside the burning season in Amazonia. There were significantly elevated H, N, and Mn depositions during biomass burning. Elevated H deposition during biomass burning caused elevated base metal loss from the canopy and the organic horizon and deteriorated already low base metal supply…

Nitrogen and phosphorus budgets in experimental grasslands of variable diversity.

2007

Previous research has shown that plant diversity influences N and P cycles. However, the effect of plant diversity on complete ecosystem N and P budgets has not yet been assessed. For 20 plots of artificially established grassland mixtures differing in plant diversity, we determined N and P inputs by bulk and dry deposition and N and P losses by mowing (and subsequent removal of the biomass) and leaching from April 2003 to March 2004. Total deposition of N and P was 2.3 +/- 0.1 and 0.2 +/- 0.01 g m(-2) yr(-1), respectively. Mowing was the main N and P loss. The net N and P budgets were negative (-6.3 +/- 1.1 g N and -1.9 +/- 0.2 g P m(-2) yr(-1)). For N, this included a conservative estimat…