Soil Pollution : Processes and Dynamics

The soil is the medium through which pollutants originating from human activities, both in agriculture and industry, move from the land surfaces to groundwater. Polluting substances are subject to complex physical, chemical and biological transformations during their movement through the soil. Their displacement depends on the transport properties of the water-air-soil system and on the molecular properties of the pollutants. Prediction of soil pollution and restoration of polluted soils requires an under­ standing of the processes controlling the fate of pollutants in the soil medium and of the dynamics of the contaminants in the un­ saturated zone. Our book was conceived· as a basic overview of the processes governing the behavior of pollutants as affected by soil constituents and environmental factors. It was written for the use of specialists working on soil and unsaturated zone pollution and restoration, as well as for graduate students starting research in this field. Since many specialists working on soil restoration lack a back­ ground in soil science or a knowledge of the properties of soil pollutants, we have included this information which forms the first part of the book. In the second part, we discuss the partitioning of pollutants between the aqueous, solid and gaseous phase of the soil medium. The retention, transformation and transport of pollutants in the soils form the third section.

I The Interacting Materials.- 1 The Soil as a Porous Medium.- 1.1 The Solid Phase.- 1.1.1 Clay Materials.- 1.1.2 Minerals Other Than Clays.- 1.1.3 Soil Organic Matter.- 1.1.4 Interactions Between Components of the Solid Phase.- 1.1.5 The Electrified Surface of the Solid Phase.- 1.2 The Liquid Phase.- 1.2.1 Water Near Soil Solid Phase.- 1.2.2 The Aqueous Solution.- 1.3 The Soil Gaseous Phase.- 1.4 The Soil as Biological System.- 1.4.1 Soil Biota: Components and Distribution.- 1.4.2 Microorganism Bioactivity.- 1.5 Soil Heterogeneity.- References.- 2 The Soil Pollutants.- 2.1 Inorganic and Inorganic-Organically Combined Pollutants.- 2.1.1 Nitrogen Forms.- 2.1.2 Phosphorus Forms.- 2.1.3 Salts.- 2.1.4 Potentially Toxic Trace Elements.- 2.2 Toxic Organic Residues.- 2.2.1 Small Organic Molecules.- 2.2.2 Organic Macromolecules.- References.- II Pollutants Partitioning Among Soil Phases.- 3 Pollutants-Soil Solution Interactions.- 3.1 Acid-Base Equilibria.- 3.2 Precipitation-Dissolution.- 3.3 Ligand Effect.- 3.4 Oxidation-Reduction Equilibrium.- 3.5 Effects of Mixed Solvents and Surfactants.- 3.6 Temperature Effect on Solubility.- 3.7 Examples.- 3.7.1 Acid Rains and A1 Dissolution.- 3.7.2 Alkaline Soils and Gypsum Dissolution.- 3.7.3 Sludge Effect on Potentially Toxic Inorganic Trace Element Solubility.- 3.7.4 Redox Processes and Metal Solubility.- 3.7.5 Solubility of Organic Solvents Under a Waste-Disposal Site.- References.- 4 Volatilization into the Soil Atmosphere.- 4.1 The Volatilization Process.- 4.2 Vapor Pressure and Vaporization Relationship..- 4.3 Volatilization of Multicomponent Pollutants...- 4.4 Examples.- 4.4.1 Ammonia Volatilization.- 4.4.2 Pesticide Volatilization.- 4.4.3 Petroleum Products Volatilization.- References.- 5 Retention of Pollutants on and Within the Soil Solid Phase.- 5.1 Surface Adsorption.- 5.1.1 Adsorption of Ionic Pollutants.- 5.1.2 Adsorption of Nonionic Pollutants.- 5.1.3 Adsorption of Complex Mixtures..- 5.1.4 Adsorption Isotherms.- 5.1.5 Kinetics of Adsorption.- 5.1.6 Factors Affecting Adsorption.- 5.2 Nonadsorptive Retention.- 5.2.1 Pollutant Precipitation.- 5.2.2 Trapping.- 5.3 Examples.- 5.3.1 Pollutants Adsorption.- 5.3.2 Nonadsorptive Retention.- References.- III Pollutant Behavior in Soils.- 6 Reversible and Irreversible Retention - Release and Bound Residues.- 6.1 Retention Hysteresis.- 6.1.1 True Hysteresis.- 6.1.2 Apparent Hysteresis.- 6.1.3 Method-Created Hysteresis.- 6.2 Bound Residues.- 6.2.1 Experimental Definition..- 6.2.2 Mechanisms.- 6.3 Examples.- 6.3.1 Inorganic Pollutants.- 6.3.2 Organic Pollutants.- 6.3.3 Organo-Clays.- References.- 7 Transformation and Metabolite Formation.- 7.1 Decomposition Rate.- 7.2 Abiotically Induced Transformation.- 7.2.1 Transformation in Soil Water.- 7.2.2 Transformation at the Solid-Liquid Interface.- 7.3 Biologically Mediated Transformations.- 7.3.1 Microbial Reactions.- 7.3.2 Transformation of Inorganic Compounds.- 7.3.3 Transformation of Organic Toxic Chemicals.- 7.4 Examples.- 7.4.1 Hydrolysis.- 7.4.2 The Redox Process.- 7.4.3 Photolytic Degradation.- 7.4.4 Coordinative Transformations.- 7.4.5 Liquid Mixture Transformations.- References.- 8 Pollutants Transport in the Soil Medium.- 8.1 Solute Transport.- 8.1.1 Transport Mechanisms.- 8.1.2 Preferential Flow of Solute.- 8.2 Transport of Nonaqueous-Phase Liquid.- 8.3 Vapor Flux.- 8.4 Transport on Suspended Particles.- 8.4.1 Transport on Eroded Sediments.- 8.4.2 Transport in Association with Dispersed Colloidal Material.- 8.5 Factors Affecting Transport Processes.- 8.5.1 Field and Climate Variability..- 8.5.2 Heterogeneity of the Pollutant.- 8.6 Examples.- 8.6.1 Diffusion of a Degradable Pesticide..- 8.6.2 Miscible Displacement.- 8.6.3 Transport of Nonaqueous Pollutant Liquids (NAPL).- 8.6.4 Vertical Transport of Pesticides Adsorbed on Colloids.- 8.6.5 Preferential Flow.- 8.6.6 Transport of Pathogenic Microorganisms.- References.- IV Prediction and Remediation.- 9 Modeling the Fate of Pollutants in the Soil.- 9.1 Overview of Models.- 9.2 Description of Models.- 9.2.1 Deterministic Models.- 9.2.2 Stochastic Models.- 9.3 Examples of Models Describing the Fate of Pesticides in Soils.- 9.3.1 Transport Phenomena.- 9.3.2 Sink/Source Phenomena.- 9.4 Some Problems Connected with Modeling.- 9.4.1 The Scale of Modeling.- 9.4.2 Model Sensitivity.- 9.4.3 Model Validation.- References.- 10 Risks and Remedies.- 10.1 Risk Assessment.- 10.1.1 Diagnosis.- 10.1.2 Prognosis.- 10.2 Selection of Remedies.- 10.2.1 There Is No Pollution Risk in the Land Under Consideration.- 10.2.2 There Is No Risk Around the Contaminated Site.- 10.2.3 There Is a Risk for the Environment.- 10.3 Remediation Technologies.- 10.3.1 Hard Techniques with Excavation (Surgical Operation).- 10.3.2 Soft Techniques Without Excavation (Chemotherapy).- 10.3.3 Control and Cost.- References.