نتایج جستجو برای: smectite
تعداد نتایج: 982 فیلتر نتایج به سال:
Although clay mineral reduction is thought to occur primarily as a result of the activity of indigenous microorganisms in soil, most research has focused on chemical mechanisms of Fe reduction within clay minerals. Here we show that bacteria isolated from soils and sediments catalyze the rapid reduction of structural Fe(III) in the smectite clay minerals. The extent of Fe(III) reduction is larg...
The influence of clay preparation methods on the sorption and hydrolysis of carbaryl (1-naphthyl, N-methyl carbamate) by K+-saturated reference smectite SWy-2 was studied. Four methods were utilized: (1) The reference (or specimen) clay used as received was K+-saturated (hereafter referred to as whole clay). (2) High-speed centrifugation (3295g) of whole clay resulted in a pellet with three dis...
Clay minerals deserve special attention as they play a crucial role in many soils. The clay mineralogy of five gypsiferous soils from different landforms in eastern Isfahan was investigated using X-ray diffraction (XRD). In addition, soil aggregates and wind-deposited sediments were examined by scanning electron microscope (SEM) and analyzed by energy dispersive X-ray analyzer (EDX). The resul...
Recent studies have focused on the formation of authigenic clays in an alkaline soil system surrounding lakes of the Nhecolândia region, Pantanal wetland. The presence of trioctahedral Mg-smectites (stevensite and saponite types), which requires low Al and Fe contents in the soil solution for its formation, contrasts with the neoformation of dioctahedral Fe-mica (glauconite, and Fe-illite), whi...
Sorption of carbaryl (1-naphthyl-N-methyl-carbamate) from aqueous suspension to smectite was studied using Fourier transform infrared (FTIR), high-performance liquid chromatography (HPLC) (for batch sorption), and quantum chemical methods. The amount of carbaryl sorbed was strongly dependent on the surface-charge density of the smectite with more sorption occurring on the two "low" surface-char...
Expansive soils owe their characteristics to the presence of swelling clay minerals. As they get wet, the clay minerals absorb water molecules and expand; conversely, as they dry they shrink, leaving large voids in the soil. Swelling clays can control the behavior of virtually any type of soil if the percentage of clay is more than about 5 percent by weight. Soils with smectite clay minerals, s...
The mineralogy and geochemistry of the bulk rock and clay fraction of sediments deposited at the CretaceousTertiary transition and in the KTB layer have been investigated by various methods in two sections from the Betic Cordilleras (Agost, Caravaca) and five sections from the Basque-Cantabrian Basin (Monte Urko, Sopelana, Zumaya, Hendaye, Biarritz). Active terrigenous supply prevailed in both ...
Mars atmosphere. The imprint of atmospheric evolution in the D/H of Hesperian clay minerals on Mars.
The deuterium-to-hydrogen (D/H) ratio in strongly bound water or hydroxyl groups in ancient martian clays retains the imprint of the water of formation of these minerals. Curiosity's Sample Analysis at Mars (SAM) experiment measured thermally evolved water and hydrogen gas released between 550° and 950°C from samples of Hesperian-era Gale crater smectite to determine this isotope ratio. The D/H...
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