Wind-blown material

Coarse Mechanically produced From soil, plants, sea salt, volcanoes, wind blown material, abrasion... 

There are circumstances where the drainage sample does not represent material derived from the basin upstream of the site, and these should be dealt with at the orientation phase of the project. Such circumstances would include wind-blown material collecting in the drainage channel or exotic materials introduced to the drainage basin through anthropogenic activity. 

The red clays and silts in the upper level of the cave probably represent wind-blown material washed into the cave from the ground surface. They presumably represent the effects of one of the major periods of aridity that affected the landscape of southeastern Australia in the early Pleistocene, prior to 780 ka. 

A second serious consideration is whether one wishes to collect a bulk sample as opposed to a wet-only sample. A bulk sample is one which is directly exposed to the atmosphere and remains open throughout a prescribed interval of time. This is not a very satisfactory way of collecting precipitation samples because of the natural tendency of birds to perch on the rim of the collector always f cing outward contributing to the debris deposited inside the container. Equally important, dust, leaves, and other natural wind-blown materials are likely to enter the sampler and contaminate the precipitation in an unpredictable manner. 

The total mineral content of peats is dependent primarily upon the extent to which the residues of the peat-forming plants are diluted with sand, silt, clay and calcium carbonate transported from surrounding areas. Where no such washed-in or wind-blown materials are present the minerals are largely limited to those originally assimilated by the plants from the soil or waters where they grew. 

Some identified modes are evaporation through a stack emission through a vent (a vent is not designed to elevate the emitted material—a stack is) leaks in plumbing or storage containers and wind-blown dust. 

Wind transport. Wind-blown components are carried away over a more or less important distance as a function of wind velocity and particle size of the material. Wind speeds up till 6.5 m/sec transport dust and fine sand with a diameter of less than 0.25 mm sand grains up to 1 mm diameter are uplifted at wind speeds of 10 m/sec. At 20 m/sec also particles of 4-5 mm may be removed. Based on these physical laws, the transportation of coarse fragments, in casu the sand fraction, occurs over-relatively short distances from the deflation zones. These sand grains settle then in more or less continuous layers and either become progressively mixed with the underlying soil layers, or concentrate in dune formations. 

It is seen that the distribution is bimodal, with the coarse mode dominating the aerosol volume concentrations. The 1979 average volume concentration of aerosol less than 10 ym diameter was 32.4 ymVcm. From its large standard deviation, it is clear that the coarse particle mode exhibited considerable variation throughout the year. Records show that high coarse mode volume concentrations accompanied moderate-to-high wind speeds. The coarse material was very likely wind-blown dust of crustal composition. 

BENTONITE. The term applied to alteied fine-grained volcanic ashes which have been blown considerable distance from their origin and deposited m marine waters. The resulting material is usually a white, but sometimes a colored, clay-like sediment which may contain bits of volcanic glass but is composed mainly of colloidal silica which will absorb large quantities of water. Since bentonites are wind-blown deposits they are useful as definite datum planes in stratigraphy, especially in helping to determine the contemporaneity of the different facies of marine sediments. 

Any of a number of insoluble materials laid down in a cooling system by a variety of mechanisms, such as scales and wind-blown minerals. Modem applied chemical technology has blurred the traditional notions of scales, corrosion debris, and inorganic mineral foulants as being separate problems, requiring individual chemical treatment, and now any of these may be referred to as a deposit. 

Loess refers to deposits of fine-grained wind-blown (eolian) sediments, which may accumulate up to 100 m thick. The material mostly consists of silt grains with perhaps 5-30% clay-sized particles and 5-10% sand (Benn and Evans, 1998), 291. Like other sediments, loess may contain considerable arsenic depending on the chemistry of its source rocks (Table 3.15). 

Mortar/membrane mixed with foreign material, such as wind-blown dust, or sand. (2)... 

Wind-blown sand dunes are accumulations of sediment laid down by aeolian processes and fashioned into bedforms by deflation and deposition (Livingstone and Warren, 1996). A supply of sand grains, either marine carbonate material or terrigenous lithoclasts that can be entrained by the... 

As much of the potential riverwater input of dissolved iron is rapidly stripped out of water during estuarine mixing, the main external source of iron to the open oceans is from the (very limited) dissolution of wind-blown soil and dust. This is material derived primarily from the great Asian, African and Middle Eastern deserts (Plate 6.2, facing p. 138) of the northern hemisphere. Dust has an atmospheric residence time of only a few days, much shorter than hemispheric atmospheric mixing times. This means that the southern hemisphere oceans receive much lower atmospheric dust inputs than those in the northern hemisphere. For example, dust inputs to the North Pacific are 11 times greater than those to the South Pacific. 

Aridisols Soils of dry climates and deserts. Often contain wind-blown dust. A and B horizons thin with little organic material. Calcium carbonate (caliche) accumulations generally present, sometimes with gypsiferous or saline horizons. 

Wind-blown dust transports zinc bound to soil particulates into the atmosphere (EPA 1980d). The particulates may also contain other materials (Pacyna et al. 1989 Saltzman et al. 1985). Zincbearing particles in the atmosphere are transported to soil and water by wet deposition (rain and snow) and dry deposition (gravitational settling and deposition on water and soil surfaces). The detection of zinc in rainwaters (at concentrations higher than atmospheric particles) confirms the importance of wet precipitation in the removal of zinc particles from the atmosphere (Aten et al. 

The beach profile (Figure 2.9) is the product of the oscillatory onshore and offshore motions of its constituent materials affected by the waves and the wave-induced currents. Granular particles on the seabed can be dislodged and suspended in the water column by a combination of drag and lift forces. These forces on the particles are exerted by bott-tom shear stresses developed by either the wave velocity exceeding a threshold value or the occurrence of turbulence. Once the particles are in the water column, they are kept in suspension longer than in subaerially wind-blown conditions because of a combination... 

The climate controls broad latitudinal sediment distribution on the shelf. In tropical, rainy climates, mud that contains high proportion of clay minerals or biogenic carbonate sediment in areas not diluted by mud deposition predominates. By contrast, in hot, dry climates, wind-blown sand and silt accumulate, and in polar climates sediment containing few clay minerals and much coarse-grained material (gravel) prevails. 

Wet deposition is linked with atmospheric water droplets and combines the effects of rain and snow as well as the impaction of wind-blown contaminated cloud or fog droplets on to vegetation when the cloud or fog extends down to the surface. The removal by rain or snow is particularly efficient just 1 mm of rain can remove more material than can be deposited by dry deposition operating over 24 h. 

At various times in the geological past, large areas of the sea were apparently cut off from the rest, and evaporation first made the water too salty to support life and then resnlted in deposits of salt and/or gypsum and anhydrite. Many other deposits are also recognized and inclnde wind-blown deposits and deposits in river valleys and lakes. However, somewhat nniqne in character among the sedimentary rocks are the vast accumnlations of plant material that formed at many different times to produce coal seams. 

If a hill, killed by progressive Verticillium wilt, is allowed to disintegrate, the dead infected plant material will rapidly transfer the disease to the adjacent hills and so through the garden. Wind-blown fragments and infected soil on boots and wheels may well be responsible for introducing the disease to other gardens. 

Silts are clastic sediments derived from pre-existing rocks, chiefly by mechanical breakdown processes. They are composed mainly of fine quartz material. Silts may occur in residual soils, but they are not important in such instances. However, silts are commonly found in alluvial, lacustrine, fluvio-glacial and marine deposits. These silts tend to interdigitate with deposits of sand and clay. Silts are also present with sands and clays in estuarine and deltaic sediments. Lacustrine silts are often banded. Marine silts may also be banded. Wind-blown silts are generally uniformly sorted. 

---