Search results for "Weathering"
showing 10 items of 138 documents
Chemical weathering of volcanic rocks at the island of Pantelleria, Italy: Information from soil profile and soil solution investigations
2007
Abstract Concentrations of major, minor and trace elements were determined in soil profiles and soil solutions from the island of Pantelleria, Sicily Channel, to evaluate the weathering extent of soils evolved on trachytic and pantelleritic rocks and the aqueous transport of elements by their soil solutions. The chemical index of alteration (CIA) indicates a low-to-moderate degree of weathering; consistently, the mineralogical and geochemical imprints of the parent rocks are generally preserved. The chemical weathering appears to be incongruent, owing to primary minerals and glass dissolving to a variable degree while secondary minerals have formed. Based on the calculated saturation state …
Over-estimation of efficiency of weathering in tropical “Red Soils”: its importance for geoecological problems
2000
Abstract Weathering and soil formation rates are regarded as the main criteria of a tolerable soil loss. The efficiency of weathering in the seasonal semiarid tropics has often been greatly over-estimated especially in the geomorphologic literature in which weathering is assumed to be as fast or even faster than surface erosion. Six selected “Red Soils” in two intramontane basins of hyperthermic SW Nepal near the border with India, with 1500–1750 mm annual rainfall (5 humid months), and a “Black Soil” near Baroda, Gujarat, India (3–4 humid months) were studied mineralogically. Two of the “Red Soils” have TL ages between 10 and 30 ka, the “Black Soil” has one of about 10 ka. The yellowish si…
Clay minerals, oxyhydroxide formation, element leaching and humus development in volcanic soils
2008
Aweathering sequence with soils developing on volcanic, trachy-basaltic parent materials with ages ranging from 100–115,000 years in the Etna region served as the basis to analyse and calculate the accumulation and stabilisation mechanisms of soil organic matter (SOM), the transformation of pedogenic Fe and Al, the formation and transformation of clay minerals, the weathering indices and, by means of mass-balance calculations, net losses of the main elements. Although the soils were influenced by ash depositions during their development and the soil on the oldest lava flow developed to a great extent under a different climate, leaching of elements and mineral formation and transformation co…
Age and mineralogy of supergene uranium minerals — Tools to unravel geomorphological and palaeohydrological processes in granitic terrains (Bohemian …
2010
Abstract Uranyl phosphates (torbernite, autunite, uranocircite, saleeite) and hydrated uranyl silicates (normal and beta-uranophane) found in various erosion levels and structures in the Late Variscan granites at the western edge of the Bohemian Massif, Germany, were the target of mineralogical investigations and age dating, using conventional and more advanced techniques such as Laser-Ablation-Inductive-Coupled-Plasma Mass Spectrometry (LA-ICP-MS). Supergene U minerals have an edge over other rock-forming minerals for such studies, because of their inherent ‘clock’ and their swift response to chemical and physical environmental changes on different scales. Uraniferous phoscretes and silcre…
Evaluation of accelerated weathering effects on the surface of two coloured sicilian building stones
2007
The dark grey Breccia di Billiemi and the Ammonitico Rosso of Piana degli Albanesi, widely employed outdoor and indoor in monuments in Sicily, undergo significant alteration processes, affecting not only the chromatic aspect but also the state of aggregation. In a previous paper [1] the effects of accelerated weathering in laboratory was compared with natural ageing in the urban environment. The study included the description of lithofacies, the characterisation by means of petrographic and physical-chemical techniques and accelerated weathering experiments on both lithotypes.
Geochemical records of limestone façades exposed to urban atmospheric contamination as monitoring tools?
2008
International audience; Magnetic susceptibility, surface rock soiling, elemental composition and lead isotope ratios were measured in surface stone samples collected at different heights of a late 19th century building in Dijon, France. We targeted four limestone facades that differ in orientation and proximity to car traffic. It seems that zinc, copper, sulphur and cadmium are present as diffuse pollutants in urban atmosphere, at least at the scale of the building studied. In contrast, lead and arsenic exhibit point sources: automotive traffic and past coal-burning fly-ash emissions; both coherent with lead isotopic composition measurements. Parameter variations primarily result from expos…
Accelerated weathering of polypropylene/wood flour composites
2008
Abstract Wood–plastic composites (WPCs) have received increasing attention during the last decades, because of many advantages related to their use. Some of their main applications are represented by outdoor furnishing and decking; therefore, it is important to assess their behaviour under UV exposure. In this work, polypropylene/wood flour composites were prepared and their resistance to photooxidation investigated. The composites were prepared by extrusion and compression moulding, and were subjected to mechanical tests, FTIR analysis and molecular weight measurements. The results showed that the composites retained a higher fraction of the original mechanical properties after accelerated…
Pore structure and water transfer in Pietra d’Aspra limestone: A neutronographic study
2020
Neutron radiography (NR) was here applied to study the effects of two different commercially available consolidants on the water absorption properties in a particular type of limestone (biocalcarenite), known as Pietra d’Aspra stone, which is one of the most extensively used lithotypes in Sicilian Baroque buildings. Our attention was mainly focused on the evaluation, using a fast and nondestructive visualization of water motion through capillarity, of the effectiveness of such layers as consolidating agents in view of preserving and maintaining both old and modern structures. The biocalcarenite was treated with nanosilica (Nano Estel®) and nanolime (CaLoSil®) by brushing it until full satur…
Inclusion of a suite of weathering tracers in the cGENIE Earth system model-muffin release v.0.9.23
2021
Abstract. The metals strontium (Sr), lithium (Li), osmium (Os) and calcium (Ca), together with their isotopes, are important tracers of weathering and volcanism – primary processes which shape the long-term cycling of carbon and other biogeochemically important elements at the Earth's surface. Traditionally, because of their long residence times in the ocean, isotopic shifts in these four elements observed in the geologic record are almost exclusively interpreted with the aid of isotope-mixing, tracer-specific box models. However, such models may lack a mechanistic description of the links between the cycling of the four metals to other geochemically relevant elements, particularly carbon, …
Mineralogical and chemical variability of fluvial sediments 2. Suspended-load silt (Ganga–Brahmaputra, Bangladesh)
2011
Sediments carried in suspension represent a fundamental part of fluvial transport. Nonetheless, largely because of technical problems, they have been hitherto widely neglected in provenance studies. In order to determine with maximum possible precision the mineralogy of suspended load collected in vertical profiles from water surface to channel bottom of Rivers Ganga and Brahmaputra, we combined Raman spectroscopy with traditional heavy-mineral and X-ray diffraction analyses, carried out separately on low-density and dense fractions of all significant size classes in each sample (multiple-window approach). Suspended load resulted to be a ternary mixture of dominant silt enriched in phyllosi…