Exploring Mechanisms for the Development of Reversible Soil Hydrophobicity

150 Pages·2013·1.77 MB·English

by  Woolverton, Priscilla

AN ABSTRACT OF THE THESIS OF

Priscilla B. Woolverton for the degree of Master of Science in Soil Science
presented on June 7, 2013
Title: Exploring Mechanisms that Drive the Development of Reversible Soil
Hydrophobicity

Abstract approved:

Maria I. Dragila Markus Kleber

This study focuses on one widespread characteristic of poor soil quality:
hydrophobic soil. Previous research has produced conclusive evidence to
show that soil hydrophobicity is affected by soil organic matter (SOM) and
soil water content (WC). Hydrophobicity that responds to changes in WC
is a unique form of surface hydrophobicity and is termed “reversible
hydrophobicity” (RHP). Recent experimental results support an
amphiphilic model for SOM, which contains mechanisms for the
occurrence of RHP. What has not been directly demonstrated, however,
are conformational changes in the orientation of amphiphilic moieties as
an effect of WC that would be associated with RHP. Quincy soils, which
exhibit RHP, were investigated at varying WC using Photoacoustic Fourier
transform infrared spectroscopy (Pas-FTIR), chemical analysis of
carbon:nitrogen, and physical measurement of hydrophobicity, using the
Capillary Rise Method and the Sessile Drop Method, in order to reveal
how SOM and water interact to drive the creation of hydrophobic surfaces.
This investigation suggests that SOM and water interact at the molecular
scale to drive hydrophobic phenomena at the field-scale.
©Copyright Priscilla B. Woolverton
June 7, 2013
All Rights Reserved
Exploring Mechanisms that Drive the Development of Reversible Soil
Hydrophobicity

by
Priscilla B. Woolverton

A THESIS

submitted to

Oregon State University

in partial fulfillment of
the requirements for the
degree of

Master of Science

Presented June 7, 2013
Commencement June, 2014
Master of Science thesis of Priscilla B. Woolverton presented on June 7,
2013.

APPROVED:

Co-Major Professor representing, Soil Science

Co-Major Professor representing, Soil Science

Head of the Department of Crop and Soil Science

Dean of the Graduate School

I understand that my thesis will become part of the permanent collection of
Oregon State University libraries. My signature below authorizes release
of my thesis to any reader upon request.

Priscilla B. Woolverton, Author
AKNOWLEDGEMENTS

There are many people to whom I owe gratitude. First, I would like to
express sincere admiration to my husband and family who have made the
last few years possible. I would also like to especially thank Dr. Maria
Dragila for her enduring patience and thoughtful insight.
CONTRIBUTION OF AUTHORS

Jess Holcomb assisted with soil sampling and chemical extraction data
collection. Dr. Maria Dragila was involved with the design and writing of
Chapters 1, 2 and 3, and assisted in the interpretation of the data. Dr.
Markus Kleber was involved with the design and writing of Chapter 3 and
assisted in the interpretation of the data. Dr. Don Horneck facilitated the
oversight of all field-site activities, including soil sampling, field trial
management and grower participation.
TABLE OF CONTENTS

Page

1. Introduction: Soil hydrophobicity................................................... 1

2. Characterization of soil wettability................................................. 11

2.1. Introduction.............................................................................. 11

2.2. Background............................................................................. 14

2.2.1 Quantifying soil wettability.............................................. 14
2.2.2 Theoretical support of physical soil wettability,
and soil organic matter, measurements........................ 17

2.3. Materials and Methods........................................................... 23

2.3.1 Study site........................................................................ 23
2.3.2 Physical measurement of wettability and soil
organic matter characterization...................................... 24

2.4. Results..................................................................................... 29

2.4.1 Comparison of Capillary Rise Method (CRM),
moisture content, and carbon:nitrogen ratio................... 29
2.4.2 Sessile Drop Method (SDM) and Photoacoustic
Fourier transform infrared spectroscopy (Pas-FTIR)..... 34
TABLE OF CONTENTS (Continued)

Page

2.5. Discussion............................................................................... 41

2.5.1 Bulk-scale wettability: Comparison of results
from CA(CRM) and C:N................................................. 41
2.5.2 Surface-scale wettability: Comparison of
results from CA(SDM) and Pas-FTIR............................. 47

2.6. Conclusion............................................................................... 53

3. Photacoustic Fourier transform infrared spectroscopy to
explore mechanisms of soil water repellency............................... 55

3.1. Introduction............................................................................. 55

3.2. Background: The nature of soil organic matter and its
implications for soil hydrophobicity.......................................... 57

3.3. Materials and Methods............................................................ 64

3.3.1 Soil organic matter: Pas-FTIR and C:N......................... 64
3.3.2 Physical wettability........................................................ 68

3.4. Results..................................................................................... 69

3.5. Discussion............................................................................... 89
TABLE OF CONTENTS (Continued)

Page

3.6. Conclusion............................................................................... 94

4. Bibliography.................................................................................. 95

5. Appendices................................................................................... 105