LYCOS RETRIEVER 
Electrical Conductivity: Water
built 633 days ago
Electrical conductivity is an important soil property related to salinity, and is often used for delineating other soil properties. The purpose of this study was to examine the influence of smectite properties on the complex electrical conductivity spectra of hydrated smectitic clays. Four smectites were saturated with Ca, Mg, Na or K and equilibrated at four relative humidities ranging from 56 to 99%. X-ray diffraction was used to determine fractions of the various smectite layer hydrates (0 to 4 layers of interlayer water molecules) in each sample. A vector network analyzer was used to determine the real component of the complex electrical conductivity spectra (') for frequencies (f) ranging from 300 kHz to 3 GHz. Values of the dc electrical conductivity (0), the frequency where the slope changes in the spectra (fr), and the slope at the high-frequency end of the spectra (n) were determined by fitting ' to '(f) = 0(1 + f/fr)n. Both 0 and fr increased with the total amount of water, the amount of interlayer water, and, for saturating cations in the order K < Mg < Ca < Na.
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Summary: Magnetotellurics and geomagnetic depth sounding have revealed zones of anomalously high electrical conductivity in a variety of crustal and mantle environments. Crustal and shallow mantle high conductivity zones are observed beneath continental collision zones, mid ocean ridges and the ocean floor, and continental shields, among other areas, and mantle transition zone high-conductivity zones are generally observed at depths of 300-400 km. A variety of explanations for these high conductivity features have been invoked including the presence of partial melt, hydrogen in minerals, aqueous fluids, and the presence of interconnected or oriented metals or other highly conducting minerals (with different explanations for different areas). In order to properly invert and interpret magnetotelluric response functions, the electrical response of Earth materials in the low frequency range must be determined. This proposal outlines an experimental effort to determine the electrical conductivity and the complex electrical impedance of relevant geological materials at elevated temperatures and pressures over the frequency range 0.0001 to 100,000 Hz. In particular, 1) the influence of melt composition and texture at low melt fraction on the bulk electrical properties of partially molten systems and 2) the influence of hydrogen in hydrous minerals (amphibole, serpentine) and nominally anhydrous minerals (olivine and pyroxene) on electrical properties will be examined. The electrical properties of texturally equilibrated partially molten olivine-basalt systems will be studied at one bar total pressure and at elevated temperatures and pressures (up to 2000 degrees C and 20 GPa) in a multiple anvil device. The electrical properties of hydrous minerals and hydrogen-containing nominally anhydrous minerals will be examined at temperatures up to 1200 degrees C and .8 - 1 GPa in an internally heated device under appropriate water fugacity conditions.
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Contamination discharges can change the water's electrical conductivity in various ways. For example, a failing sewage system raises the conductivity because of its chloride, phosphate, and nitrate content, but an oil spill would lower the conductivity. The discharge of heavy metals into a waterbody can raise the conductivity as metallic ions are introduced into the waterway.
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You can estimate the total dissolved salt concentration of a water sample by multiplying its temperature normalized electrical conductivity by a factor of between 0.5 and 1.0 for natural waters. The value of this factor depends upon the type of dissolved solids. A widely accepted value to use for a ballpark guestimate is 0.67.
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The electrical conductivity of water samples should be measured on the spot at the waterbody. Measurement can be delayed by up to 1 month if the sample is refrigerated (but NOT frozen) immediately on being taken, and if the sample bottle is filled completely, with no air gap at the top.
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