By looking at the color of a soil mass, a rough idea of the moisture content of the soil, drainage properties, and degree of oxidation can be obtained. Colloid particles differ from electrolytes in the fact that when electric current is passed in the colloidal suspension, all the colloidal particles are attracted towards one electrode or the other depending upon the nature of charge they carry on them. When coated with clay, these sand particles take very active part in chemical reactions. Its formation from the primitive mantle requires removal of ca. Average particle density of organic soil varies from 1. It is controlled by climate, colour of soil, slope, and altitude of the land and also by vegetational cover of the soil.
The variations in the soil colour are due to organic substances, iron compounds, silica, lime and other inorganic compounds. Coagulation or flocculation of colloidal particles: Colloidal particles in the suspension can be coagulated either by heating or by adding some substances which contain opposite charged ions. For example, there are two soil samples which have similar pH values but they require different quantities of lime for neutralization. Atmospheric composition and evolution are further constrained by noble gases in these meteorites, although Xe and Kr isotopes suggest different origins for the atmosphere. Some soils are fine, while others are coarse. Bulk density of the soil divided by density of water gives volume weight or apparent specific gravity of soil.
Dark rocks appear to be high in silica and geochemically similar to anorogenic andesites; lighter rocks are richer in sulfur and lower in silica, consistent with being coated with various amounts of dust. Soils rich in silt possess high water holding capacity. Soil Colour : Soils exhibit a variety of colours. The word colloid first coined by Grahm 1849 is derived from Greek words kolla meaning glue and eoids meaning appearance, i. Certain deviations from simple soil-rock mixing are consistent with mineralogical fractionation of detrital iron and titanium oxides during sedimentary transport. They take very active part in physicochemical reactions of the soil. As this material is mostly devoid of mineral soil material, they cannot be described in terms of soil texture.
Grade: This indicates the degree of distinctness of peds. Precise calibration curves for major and minor elements were obtained. Aminosugars : i Glucosamine ii N. Colloidal particles of one electrical charge have tendency to attract colloids of opposite charge. Mars Pathfinder successfully landed at Ares Vallis on July 4, 1997, deployed and navigated a small rover about 100 m clockwise around the lander, and collected data from three science instruments and ten technology experiments. Silicate Clay Presence The presence of silicate clay materials affects the chemical properties of soil mass. In terms of sensitivity and selectivity, data are partly redundant and partly complementary: alpha backscattering is superior for light elements C, O , while proton emission is mainly sensitive to Na, Mg, Al, Si, S, and X ray emission is more sensitive to heavier elements Na to Fe and beyond.
The five synthetic Mars analogues represent the salt-rich soils of Gusev Crater Ming et al. Temperature of soil depends upon the temperature of atmospheric air and on moisture content. Air and water movement through a soil mass directly depends upon the structure of soil mass. Bulk density is the proportion of the weight of a soil relative to its volume. The finer the clay particles the greater will be the percentage of hygroscopic moisture.
When many particles or peds are aggregated into cluster, a compound particle is formed. Permeability and Porosity of Soil The ease with which soil will allow water to pass through it is called permeability, which is a very useful value for civil engineers. Soil Temperature : The chief sources of soil heat are solar radiations and heat generated in the decomposition of dead organic matters in the soil and heat formed in the interior of earth. This might explain the dominance of sulphur and chlorine in the Viking soils. The compressibility is partly a function of elastic nature of soil particles and is directly related to settlement of structures. Information and inferences about martian geology drawn from these samples are discussed. Compressibility: It refers to the tendency of soil to consolidate or decrease in volume.
Excess sulfur abundances provide strong indicators for the presence of an exogenous component. In sandy soil, it forms minor part of colloids. Methyl Sugars: i Rhamnose ii Fucose iii 2-0, methyl D-xylose iv 2-0, methyl D-arabinose Besides these compounds locked up in the humus fraction, the soil also contains fats, oils, waxes, resins, tannin, lignin and some pigments. In suspension, particles of largest dimensions will settle first and those of smaller dimensions will settle afterwards. Although Mars is volatile element-rich, estimations of the amount of water delivered to the surface by volcanism are controversial. Structure of Soil: Sand, silt and clay are found in aggregated form.
So, they are important from the standpoint of the adsorption of large quantity of water perhaps, 5-10 layers of water molecules are held on the surface of clay colloid. Our quantum chemical investigations suggest that a multistep reaction mechanism involving purine cation, hydroxyl and amino radicals, together with water and ammonia, explains the experimentally obtained products in an independent study. Coarse materials such as gravels and sands have low compressibility and the settlement is considerably less in these materials as compared to highly compressible fine grained organic soils. Massive structures in clayey soils usually have very small pores, slow permeability, and poor aeration. These horizons exhibit obliteration of all or much of the original rock structure.
In buffer solution, acetate ions are in excess, owing to presence of well ionised sodium acetate. When pH value is less than 7, it is acidic. Sometimes living micro-organisms add sufficient amount of organic matters in soil in the form of metabolic wastes. Of all the planets, Mars is the most Earthlike, inviting geochemical comparisons. In India, international system of particle differentiation is commonly followed.