Volcanogenic acid deposition enhances weathering of Andisols in Nicaragua

Introduction Sulphur and halogen-rich gas emissions from passively degassing volcanoes can generate important dry- and wet-deposited fluxes of SO2, H2SO4, HCl and HF locally and regionally. Such volcanogenic depositions may represent significant inputs of acids to soils located downwind.. Here we investigate the influence of a persistent tropospheric volcanic gas plume on the weathering degree and acidification of Vitric and Eutric Andisols developed on basaltic parent materials. We contrast soils collected from the same sites in 2001 and 2017

Quantification of distinct phytolith pools in a perhydrated Andosol

Silicon (Si) is the second most abundant element of the earth crust. The Si cycle strongly depends on the bio-cycling of Si by plants. Plants roots absorb the dissolved silicon (DSi) present in the soil solution and accumulate it into amorphous silica bodies called phytoliths (PhSi). Once plant debris return to soil, PhSi may constitute an important silica pool in soil. PhSi strongly contributes to the DSi pool; especially in desilicated weathered soils. To understand the soil-plant Si cycle it is thus primordial to quantify the PhSi pool in the soil. However, quantification methods are still not very well defined especially in soils in which pedogenic amorphous silica pools are abundant. The studied soil comes from the Basse-Terre island in Guadeloupe (16°N, 61°W). MAP is 4270 mm. The soil is a perhydrated Andosol with high organic matter content and secondary minerals typical of Andosol. DRX analyses allowed to identify pyroxene and plagioclase as the main primary minerals while halloysite and gibbsite are the main crystalline secondary minerals. Volcanic glasses are absent in the studied soil. Allophane and imogolite content is 8.0 % and ferrihydrite content is 2.6%

Stock and stabilisation of organic carbon in tephra-buried volcanic soils: a case study in the northen EcuadorianAndes

Introduction : Major uncertainties in estimates of organic C trapped in soils and the mechanisms that stabilise it may impede accurate climate predictions for the future. Recent studies suggest that buried soil C represents a large and poorly constrained reservoir. In volcanic active regions, soils are repeatedly buried by tephra from explosive eruptions

Seasonal variations of dissolved Ge:Si ratios in streams from the Aso caldera, Kyùshù, Japan

Volcanic island arcs display the highest silicate weathering rates on Earth. In these environments, hydrothermal fluids act as an additional source of acids for weathering reactions. The hydrothermal influence on riverine dissolved weathering fluxes remains poorly constrained. High Ge:Si ratio values in rivers have been attributed to hydrothermal inputs to rivers. Here we assess the seasonal variability of the dissolved Ge:Si ratio in a volcanic hydrothermal region. We analysed hydrothermal spring, groundwater, river water and rainwater samples from the Aso caldera, Japan, collected in 2014-16 across five seasons. The hydrothermal springs exhibited high Ge:Si ratios (0.219.5 µmol/mol). Similar values (0.2-25.5 µmol/mol) were found in rivers with low Cl:SO4 and high SO4:Na ratios, arguing for hydrothermal inputs. In contrast, lower Ge:Si values were measured in groundwater (0.11.3 µmol/mol) and rainwater (0.2 µmol/mol). The Ge:Si ratio in hydrothermal springs, groundwater and rainwater did not vary significantly between sampling seasons and years. In contrast, the Ge:Si ratio of hydrothermally-impacted rivers was systematically lower in the wet seasons. This suggests dilution of the hydrothermal signal. Our results demonstrate a seasonal influence on the Ge:Si ratio in rivers receiving hydrothermal inputs. Estimates of the hydrothermal input to weathering fluxes which does not account for this variability may be biased

Soil weathering degree controls silicon bioavailability by increased pH after biochar application

Applying phytolith-rich biochar in agricultural soils increases soil pH, and the contents of plant nutrients and bioavailable silicon (Si). These increase induce positive impacts on plant growth, but hide the ones generated by Si uptake. Here we compare the effects of wollastonite (CaSiO3) and two biochars on Si bioavailability and mineralomass of plants in a young Cambisol and a highly weathered Nitisol. The biochars were produced from rice straws respectively enriched and depleted in Si. They had identical pH and nutrient contents, but largely differed in Si content (respectively 51.3 g Si kg-1 and 0.3 g Si kg-1). The contents of soil bioavailable and phytolithic Si were assessed through CaCl2 kinetic extraction and NaOH alkaline dissolution, respectively. Adding biochar markedly increased pH in the Nitisol, from 5 to 7. Phytoliths from phytolithic biochar provide bioavailable Si that increases plant Si uptake, biomass and Si mineralomass. At identical phytolith supply, the mobility of Si in the soil-plant system depends on soil pH and buffering capacity, hence soil weathering degree

CONCERTO POUR TROIS PIANOS EN UT MAJEUR / Jean-Sébastien BACH ; l'Orchestre du Théâtre des Champs-Elysées, dir. Arthur GOLDSCHMIDT ; aux pianos : Gisèle KUHN, Georgette ASTORG, Livia REV. CONCERTO POUR QUATRE PIANOS EN LA MINEUR / Jean-Sébastien BACH ; l'Orchestre du Théâtre des Champs-Elysées, dir. Arthur GOLDSCHMIDT ; aux pianos : Gisèle KUHN, Georgette ASTORG, Livia REV ; Monique MERCIER. FUGUE EN SOL MINEUR / Jean-Sébastien BACH ; l'Orchestre du Théâtre des Champs-Elysées, dir. Arthur GOLDSCHMIDT

Titre uniforme : [Concertos. Claviers (4), orchestre à cordes, basse continue. BWV 1065. La mineur]Titre uniforme : [Concertos. Claviers (3), orchestre à cordes, basse continue. BWV 1064. Do majeur]BnF-Partenariats, Collection sonore - BelieveContient une table des matière