Contamination events at Oak Creek, which runs through Oregon State University Research lands, prompted investigations into alternate transport mechanisms for moving liquid effluent from OSU Diary lands to Oak Creek. Magnetometer surveys conducted at the Diary identified magnetic signatures spatially associated with sub-surface locations of drain tiles, a 12-inch pipe, and other features. These pipes may provide alternate methods of transporting effluent to Oak Creek. Magnetometer surveys in support of the contamination study identified an interesting variability in the Earth's local magnetic field. Magnetic signatures spatially associated with drain tiles appear strong in the western portion of the site, but fade out in the eastern part of the site. The cause of this variability was investigated by examining soil iron distributions. The Field-scale soil iron distribution was determined using a colorimetric analysis of extractions obtained from soil core samples. This study shows larger concentrations of iron in the western portion of the site where the magnetic signal is strong and lower concentrations of iron where the magnetic signal is lower. Tile-scale iron distribution over the drain tiles and in control units were analyzed using the same colorimetric technique. This study identified a disturbance to the natural iron distribution over the tile in the western part of the site due to soil mixing in the back-filled tile trench resulting in a contrast in the magnetic data. In the eastern part of the site, where there is no magnetic signature associated with the tile, the iron distribution over the tile looks similar to the control unit results. Analysis of the soils determined that excavating during tile installation disturbed soil horizons, but the iron has redistributed itself to the pre-tile configuration effectively erasing the magnetic contrast that existed shortly after tile installation. This project has shown that iron redistribution can adversely affect the ability of magnetometer surveys to identify drain tiles. This project also demonstrates that soils must be looked at as dynamic systems rather than the more common static system approach when evaluating the success of magnetometer surveys. Applying a dynamic view of soils can help ground-based remote sensing surveyors avoid costly, unproductive surveys. / Graduation date: 2003

Call number: LD2668 .T4 1966 G197 / Master of Science

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