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An investigation of underground corrosion through the use of hyperspectral remote sensing

Arril, Benjamin Robert Lewis. 2010. M.S Thesis in the Department of Geography. University of Victoria

Abstract

This thesis investigates the potential advantage of using remote sensing techniques to assess underground transmission tower corrosion. The data used in this study was collected from three electrical transmission towers in the Lower Fraser Valley, British Columbia, Canada. A comprehensive assessment of the corrosive environments have included the following factors: climate, soil pH, soil moisture content, soil resistivity, overlying plant spectral reflectance, and heavy metal content in soil and vegetation. The principal method of protection against steel tower corrosion is zinc galvanization. As zinc serves as a sacrificial coating, once corroded, it leaches into the soil, and is then absorbed by surrounding vegetation. High concentrations of heavy metals may negatively influence plant growth. Plant Root Simulator (PRS™) probes were used to assess heavy metal supply rates by continuously adsorbing charged ionic species while in soil. Heavy metal content analysis was also conducted on sampled tower vegetation using an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES). Remote sensing techniques, such as field spectroscopy, have great potential for monitoring spectral reflectance variations of various vegetation types and biophysical characteristics. The energy-matter interactions in the UV, VIS, NIR and IR wavelength regions can be used for chemical analysis of compounds and mixtures. The combination of remote sensing analysis techniques, such as NDVI, leaf structural index R110/R810, water content index R900/R970, first order derivative analysis, and continuum removal can provide non-intrusive and continuous monitoring methods for the impact and content of certain heavy metals in plants growing in contaminated soils. However, in this study, the high zinc concentrations recorded from the PRS™ probes and ICP-AES could not be correlated to the reflectance spectra measured by the field spectrometer. Although using zinc as a spectral corrosion identifier was not successful in this thesis, the presence of a chemical process in which by-products were produced and leached into the soil was evident. The integration of remote sensing techniques and underground corrosion explored in this thesis presents unique opportunities for further research in this area of study.