Transported clay

Secondary clay, also known as sedimentary clay, transported clay, or potter s clay, is a mixture of clay and nonclay particles. After it is formed, much clay is... 

Rivers transport clay minerals primarily as part of their suspended load (silts and clays). The silt-size fraction is composed of quartz, feldspars, carbonates, and polycrystalline rocks. The clay-sized fraction is dominated by the clay minerals illite, kaolinite, chlorite, and montmorillonite. In addition to suspended particles, rivers carry as a bed load larger size fractions. The bed load constitutes only 10% of the total river load of particles and is predominantly quartz and feldspar sands. 

During the Tertiary period continental movements resulted in the opening of the North Atlantic. Scandinavia rose to become a pronounced highland, where rivers transported clay and sand out to the sea. These deposits created floody plains and delta plains that led to the Danish area being above the sea level. 

The clay minerals are basically described as hydrous silicates and can be divided into two types on the basis of their natural locations, i.e., (i) residual clay, which is produced during surface weathering of rock by various means and is generally found in the place of origin, (ii) transported clay (or) sedimentary clay, which is produced by the chemical decomposition of rock and could be separated out from the original deposit through erosion... 

The composition of transported clays varies because these materials consist mainly of abrasion products (usually silty particles) and transported residual clay material. 

Lessivage. Lessivage involves the vertical transport of particles and colloids of clay minerals. The downward horizons where the accumulation of the transported clays occurs are called argillic (denoted B,) horizons. Usually, due to the swelling of clay minerals with water, the plugging of argillic horizons ensures an impermeabilization of lower horizons. 

The research of hydraulically transported clay balls dates back to 1949 when Casa-grande studied the hydraulic reclamation of 30 million m of clay balls for the construction of the Boston airport (Casagrande, 1949). 

Leshchinsky, D. and Richter, S.D. Dredging research program/US army corps of engineers. Hydraulically transported clay balls, 1994. 

Certain grades of siUca gel or selected clay minerals are often used. The buffeting material is preconditioned under the selected relative humidity and, after equihbration, installed in the case. This method of microclimate control has proven to be very efficient, not only in exhibition cases and storage spaces, but also in packing crates used for the transportation of sensitive objects. 

Many factors affect the mechanisms and kinetics of sorption and transport processes. For instance, differences in the chemical stmcture and properties, ie, ionizahility, solubiUty in water, vapor pressure, and polarity, between pesticides affect their behavior in the environment through effects on sorption and transport processes. Differences in soil properties, ie, pH and percentage of organic carbon and clay contents, and soil conditions, ie, moisture content and landscape position climatic conditions, ie, temperature, precipitation, and radiation and cultural practices, ie, crop and tillage, can all modify the behavior of the pesticide in soils. Persistence of a pesticide in soil is a consequence of a complex interaction of processes. Because the persistence of a pesticide can govern its availabiUty and efficacy for pest control, as weU as its potential for adverse environmental impacts, knowledge of the basic processes is necessary if the benefits of the pesticide ate to be maximized. 

Preferential flow through root-mediated soil pores has been demonstrated for chloride, nitrate, and other ions that are not sorbed onto soil organic matter and clays. However, pesticide sorption onto soil affects both mobiUty of the pesticide as well as its residual life in the soil. Pesticide sorption onto root organic matter or organic linings of worm burrows may also slow transport of pesticides relative to water (72), thus countering the effects of increased permeabihty caused by roots. 

Electroultrafiltration (EUF) combines forced-flow electrophoresis (see Electroseparations,electrophoresis) with ultrafiltration to control or eliminate the gel-polarization layer (45—47). Suspended colloidal particles have electrophoretic mobilities measured by a zeta potential (see Colloids Elotation). Most naturally occurring suspensoids (eg, clay, PVC latex, and biological systems), emulsions, and protein solutes are negatively charged. Placing an electric field across an ultrafiltration membrane faciUtates transport of retained species away from the membrane surface. Thus, the retention of partially rejected solutes can be dramatically improved (see Electrodialysis). 

Clays or shales that may be utilized ia the manufacture of bricks, tiles, and other heavy clay products exist ia every state ia the United States. (See Building materials, survey). Some blending of materials is often necessary to control shrinkage of the product, and the economics of manufacture are governed by the demands of fuel, labor, transportation costs, and the market. 

The commercial value of a clay deposit depends on market trends, competitive materials, transportation faciflties, new machinery and processes, and labor and fuel costs. Naturally exposed outcrops, geological area and stmcture maps, aerial photographs, hand and power auger drills, core drills, earth resistivity, and shallow seismic methods are used ia exploration for clays (32). Clays are mined primarily by open-pit operation, including hydraulic extraction however, underground mining is also practiced. 

Clays vary in price from only a few doUars per ton for common clay to > 0.25/kg for some of the specialty surface treated clays. For clays that are used in large quantities such as kaolins for paper coatings, transportation to the point of use may be the primary cost component. 

Seawater muds are commonly used on offshore locations, which eliminate the necessity of transporting large quantities of freshwater to the drilling location. The other advantage of seawater muds is their inhibition to the hydration and dispersion of clays, because of the salt concentration in seawater. The typical composition of seawater is presented in Table 4-48 most of the hardness of seawater is due to magnesium. 

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