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University of Texas at El Paso (2002)

Reflectance spectra of common salts in arid soils (320—2500 nm) : Application of remote sensing

Howari, Fares Mohd

Titre : Reflectance spectra of common salts in arid soils (320—2500 nm) : Application of remote sensing

Auteur : Howari, Fares Mohd

Université de soutenance : University of Texas at El Paso

Grade : Doctor of Philosophy (PhD) 2002

Résumé
This study examines the high spectral resolution data of the hand-held spectrometer as a means of providing spectral information on the properties and conditions of surface soil salinity. ^ The materials examined include : (1) common pure and mixed salts of the soils of arid and semi-arid regions (gypsum (CaSO4·2H 2O), halite (NaCl), calcium carbonate (CaCO3), sodium bicarbonate (NaHCO3) sodium sulphate (Na2SO4) and their mixtures), (2) surface salt crusts formed on Harkey silty clay loam, and (3) surface salt crusts formed on Vinton fine sandy loam. The study was approached from the point of view of testing variables ; crystal (grain) size, quantities of salt crystals present per unit area, and mixing ratios of the evaporites (chemical and physical mixtures of salts) were the variables of major concern in this study. Spectral reflectance was measured with a GER 3700 spectroradiometer in the visible and near infrared region (400–2500 nm). Data from United States Geological Survey (USGS) and National Aeronautics and Space Administration (NASA) spectral libraries were used and integrated into the study. ^ The positions of the absorption bands of the evaporite and salt crusts were not affected significantly by the crystal (grain size) or with their quantities per unit area. However, the reflectivity increased with reduced particle sizes or with increasing the weight fraction of evaporites and salt presents. The spectral effect of the salt crusts on the absorption features of the organic matter content of the soils has been investigated and presented in this study. The results reported here indicated that (1) spectroscopy can differentiate between the tested salts and soils under different conditions of mixing, (2) the spectral behaviour of the salt crust cover the spectra of the other soil minerals such as the iron rich and clay minerals. Therefore it is expected that spectroscopy become a basic and cost effective tool for rapid point by point measurements of the soil environment.

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Page publiée le 27 août 2010, mise à jour le 30 janvier 2018