Tuesday, 8 November 2005
15

Evaluation of Field Methods for Hydrophobicity Assessment.

Joshua Boxell and Patrick Drohan. University of Nevada, Las Vegas, Department of Geoscience, 4505 Maryland Pkwy Box 454010, Las Vegas, NV 89135

The pre-fire assessment of hydrophobicity conditions in soils prone to frequent fire, can help guide future Burned Area Emergency Response (BARE) plans since field testing for hydrophobicity conditions is a common BARE assessment technique following severe fires. Currently, NRCS soil scientists in Nevada are conducting hydrophobicity measurements of soils from all horizons in characterization areas using a modified water drop method. We assess the current method used by NV soil scientists and compare it to laboratory methods in order to develop an approach that improves field values. To develop an improved field method, soil horizons were characterized according to their percent organic matter, mineralogy, pH, and chemistry. Samples were also measured for hydrophobicity in the laboratory using the water drop penetration test and the critical surface tension test. These tests were chosen because of their relative ease and acceptance as accurate measures of quantifying the degree to which a soil is hydrophobic. The development of the field method took into consideration the laboratory standards and adapted these measures to applications outside the lab. It was also deemed important to set guidelines for field methods so that the results could be repeated. A statistical comparison was then made between the results obtained in the laboratory and field to show the feasibility of using the new method to characterize the extent of hydrophobicity.

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