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Title: Soil water repellency : comparison between individual particles and bulk properties
Author: Bayer, Julia
Awarding Body: Swansea University
Current Institution: Swansea University
Date of Award: 2009
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Two different methods for probing soil particle surfaces were tested and applied to particles from natural soils to examine soil water repellency arising from organic coatings on their surfaces. The applicability of laser scanning confocal microscopy to the characterisation of organic soil particle surface coatings was examined. Individual particle fluorescence showed a correlation with organic matter present in the corresponding soil, although not all organic material in soil fluoresces. This indicates that fluorescence could be used to probe soil particle surfaces. Other parameters such as the extent of coverage with fluorescent material, number of fluorescent areas and their size gave no consistent results, but seemed to be strongly dependent on sample origin and possibly factors such as the surface roughness of the particles. Another new method for investigating soil particle surfaces involved measurement of the height of a water lamella pulled up by an individual particle. Good agreement was found between lamella height and the contact angle of bulk soil materials of various but known water repellencies. Soil samples generally contained particles with a wide distribution of individual water repellencies. However, particles from water repellent soils showed more variation in lamella height than those from wettable soils, indicating a non-uniform distribution of hydrophobic surfaces within soil. The influence of pH on soil water repellency was examined by changing soil pH using gases rather than liquid reagents. Addition of base led to a decrease in water repellency confirming observations that soils of high pH are seldom water repellent. Using these methods it was not possible to unravel all the characteristics and effects of organic particle coatings on soil water repellency. However, the results indicate that these coatings, and their chemistry, may not be the only factor involved. Physical properties, such as surface roughness, may interact with the chemistry.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available