Soil Liquid Phase Composition

V.V. Snakin,A.A. Prisyazhnaya,E. Kovács-Láng

• Publisher: Elsevier Science
• Year: 2001
• ISBN:
  9780080541389
• Topic: Technology & Engineering
• Subtopic: Agronomy
• Index: Technology & Engineering

The liquid phase of soil (soil solution) is a very thin, penetrating and all-embracing water layer. It has the most extensive surface among the biosphere components and interacts with all these components. Presented in this work is a new complex approach developed for soil liquid phase investigation that is based on in situ measurements. Investigation of the soil liquid phase can be of great significance in environmental research.

This volume sums up the vast experience of the authors' research into soil liquid phase composition in various ecosystems of Central and Eastern Europe. It describes the methodological basics of soil liquid phase research: methods of soil solution extraction, the main problems of application of ion-selective electrodes for immediate in situ assessment of ionic activity in soil liquid phase and redox potential, and ways to overcome those problems. Data are presented on soil liquid phase composition in natural and agricultural ecosystems, their redox, pH, carbonate and other regimes as well as the relations between the composition of the soil liquid phase and different ecological properties.

This work is devoted to the pursuit of new approaches to soil liquid phase analysis with a goal of discovering the role of soil liquid phase in the functioning of natural and agricultural ecosystems in recent soil-formation, formation of primary biological production, and in bio-geochemical turnover of elements. It includes new field investigation data as well as all data generalization carried out by means of a special complex database (developed by the authors) on soil liquid phase composition and other soil-ecological properties in various ecosystems in Central and Eastern Europe.

This book is the first English edition that integrally considers both methodological aspects and results of investigation of composition, formation, dynamics, spatial heterogeneity, and interrelations of soil liquid phase with other components of ecosystems. Soil scientists, agricultural chemists and ecologists will find this title of great interest.

Chapter 1

Soil Liquid Phase as a Structural Element of an Ecosystem

The subject of this work is the liquid phase of the soil. Normally, soil liquid phase is considered a part of soil and is not distinguished as an independent component of ecosystem. In this respect, soil samples analysis used to be the approach to investigate the soil liquid phase (water extracts, suspensions, and insulation of soil solution, non-destructive methods). This approach is characteristic for the soil investigations and the relation between the composition of soil solution and solid soil phase can be elucidated only. However, soil liquid phase is an element of an ecosystem, situated at the boundary between the living matter, solid soil part, the atmosphere (soil air) and sometimes ground water. The properties of soil liquid phase reflect the overall impact of all these components and a range of environmental factors, which determine the chemical conditions in ecosystem and plant nutrition. Therefore, as far as the properties of soil liquid phase are concerned, it should be recognised as a separate structural element of ecosystem. The presented results provide support for this approach (see part 4.6).

Traditionally, soil science has viewed soil as a three-phase system (solid, gaseous, liquid phases) and organic (including living) matter. The notion of “phase” is only used in a conventional sense, and in the strict sense, and does not correlate with the thermodynamic definition. According to this definition, a phase is a sum of system components, identical by their chemical composition and thermodynamic properties in the state of thermodynamic equilibrium (Chemical Encyclopaedic Dictionary, 1983). Although it has been suggested to use more precise notions of “solid, liquid and gaseous parts” instead of “phase” notion (Orlov, 1985), the conventional terminology has sustained, so we prefer to use the term “soil liquid phase”.

1.1 TYPES OF SOIL WATER

Soil liquid phase is a complicated subject, this may be explained by the diversity of water forms in soil and the characteristics of water itself, in which we often come across the term "anomalous". Kovda (1973) distinguished a range of basic water forms in soil: vaporous, chemically hard bonded, crystallizational water, physically bonded (hygroscopic) and slightly bonded (pellicular), capillary, gravitational, ground, surface and that in form of ice. He also said that the nature of the boundaries between them is conventional. At present many scientists think that these soil water forms differ in their energetic status (water potential).

Three forms have a bearing on soil liquid phase: layer, capillary and gravitational (Fig. 1). We shall consider their properties and formation later.

Fig. 1 Water forms in the soil

1.1.1 PELLICULAR WATER

Pellicular water in soil is usually associated with the concept of ‘non-solvent volume’ (NV) and ‘negative ion adsorption’, elaborated by the works of A.V. Trofimov (1925, 1927a, b). It is based on the fact that water surrounding solid soil particles is under the direct impact of surface charge and adsorption force. This results in differences between the energetic status and properties of water contained in soil liquid phase and those of water at standard conditions (potential = 0). Experiments have shown that within this water-layer the anion concentration is lower than in the other of soil moisture; this was the basis for the experimental techniques of non-solvent volume measurement (Trofimov, 1925; Dumansky & Dumanskaya, 1934). With this technique a solution of known concentration is added to an air-dry or fresh soil sample, and via concentration increase in supernatant after thorough mixing and centrifugation, non-solvent volume is estimated according to the:

$X=\frac{C_2-C_1}{C_2}\cdot V\text{,}$

where X –non-solvent volume value, C₁ - initial reagent (tested substance) concentration, V - solution volume, C₂ - reagent concentration after mixing with soil.

In the estimation of non-solvent volume it is necessary to remember that this is an abstract concept. It is difficult to imagine the well-defined moisture boundaries, close to solid phase surface, not containing dissolved substances. This is proved by the absence of specific points in the curves of negative suction pressure dependence of residual soil moisture (Kriukov & Komarova, 1956). However, it has been experimen...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Introduction
• Acknowledgments
• Chapter 1: Soil Liquid Phase as a Structural Element of an Ecosystem
• Chapter 2: Soil Liquid Phase Investigation
• Chapter 3: Study Areas
• Chapter 4: Environmental Impact on the Soil Liquid Phase
• Chapter 5: Spatial and Temporal Properties of Soil Liquid Phase
• Chapter 6: Material and Energy Exchange in Ecosystems
• Chapter 7: Environmental Processes and Soil Liquid Phase
• Summary
• Glossary
• References
• Correlation Between Soil Names*
• Subject Index
• Author Index