The understanding of pollutant transformations, sorption and transport in soils and uptake by plants is the key to controlling contaminant movement towards groundwater and accumulation in food-chains. Some of these major processes were discussed in the first International Workshop on Pollutants in Porous Media, con­ vened in Israel in 1983 (pollutants in Porous Media, Eds. Yaron, Dagan and Goldshmid, Springer-Verlag, 1984). Since that meeting, research on contaminant impact on the environment expanded considerably. New mechanisms explaining inorganic pollutant par­ titioning between solid and solution phases in soils were proposed and tested; specific elements and specific reactions were investigat­ ed, and more case studies to evaluate management practice effects on drinking water quality and accumulation of contaminants in crops were carried out. The recognition that the new knowledge needs to be discussed and evaluated, and the scientific and engineering communities be updated, led the IUPAC (Interna­ tional Union of Pure and Applied Chemistry) and IAHS (Interna­ tional Association of Hydrological Sciences) Water Quality Com­ missions to organize a second International Workshop on pollu­ tant behaviour in the vadose zone, hosted by the Institute of Soils and Water of the Agricultural Research Organization, Israel. In this workshop, taking place in June 1987, attention was focused on chemical, physico-chemical and microbial-mediated reactions of different contaminants in the vadose zone. This book contains selected works presented in the 1987 workshop by invited special­ ists from various disciplines and countries.

Inhalt

A Processes and Principles of Pollutants Behavior in Reactive Porous Media.- Organo-Metal Complexes as Mobility-Determining Factors of Inorganic Toxic Elements in Porous Media.- 1 Introduction.- 2 Organic Substances in Natural Porous Media.- 3 Experimental Procedures.- 3.1 Origin and Properties of Samples.- 3.2 Monolith Lysimeter Experiments.- 3.3 Batch and Column Experiments.- 4 Results.- 4.1 Monolith Lysimeter Experiments.- 4.2 Batch Experiments.- 4.3 Column Experiments.- 5 Conclusions.- References.- Suitability of Sorption-Desorption Models to Simulate Partitioning and Movement of Ions in Soils.- 1 Introduction.- 2 Simple Approaches.- 3 Constrained Approaches.- 4 Pragmatic Approaches.- 5 Mechanistic Approaches.- 6 Simulation of Movement.- 7 Conclusions.- References.- Oxyanion Sorption on Soil Surfaces.- 1 Introduction.- 2 Sites of Reactions of Oxyanions.- 3 Inorganic Oxyanion Adsorption.- References.- The Effects of Micro-Scale Solute Movement on Biotic Transformations in Porous Media.- 1 Introduction.- 2 Types of Model.- 3 Mechanistic Models of Soil Processes.- 4 Micro-Scale Effects on Biotic Transformations.- 5 Micro-Scale Transport Processes in Artificial Porous Media.- 6 Micro-Scale Diffusion of Oxygen in Soil.- 7 Micro-Scale Diffusion of Enzyme Substrates in Soil.- 8 Micro-Scale Diffusion of Soil Acidity in Soil.- 9 Conclusions.- References.- Effect of Gels and Coatings on Clay Mineral Chemical Properties.- 1 Introduction.- 2 Micromorphological Evidence of the Presence of Coatings on Clays.- 3 Effect of Coatings on Clay Chemical Properties.- 3.1 Surface Characteristics of Amorphous Compounds.- 3.2 Effect of Coatings on Clay Electrical Charges.- 3.3 Effect of Gels or Coatings on Clay Adsorption Properties.- 4 Conclusion.- References.- B Behaviour of Specific Elements.- Fluoride Sorption and Mobility in Reactive Porous Media.- 1 Introduction.- 2 Materials and Methods.- 2.1 F Adsorption by K-Montmorillonite.- 2.2 F Sorption by Soils.- 2.3 F Movement in Water-Saturated Soil Columns.- 3 Results.- 3.1 F Adsorption by K-Montmorillonite.- 3.2 F Sorption by Soils.- 3.3 F Movement in Water-Saturated Soil Columns.- 4 Discussion.- References.- Cu, Zn, and Cd Availability in a Sludge-Amended Soil Under Controlled pH and Redox Potential Conditions.- 1 Introduction.- 1.1 Background.- 1.2 Literature Review: Soil Redox Effects on Plant Uptake of Metals.- 1.3 Objectives and Experimental Approach.- 2 Materials and Methods.- 2.1 Sludge and Soil Sources.- 2.2 Preliminary Study-Effect of Air or N2 Purging on Extractable Cu, Zn, and Cd in Soil/Sludge Mixtures of Various Ratios.- 2.3 Incubation of Sludge: Soil Suspensions Under Controlled pH and Redox Potential Conditions.- 2.4 Extraction Procedures for Chemical Availability Studies.- 2.5 Plant Uptake Studies.- 2.6 Experimental Incubations.- 2.7 Effect of Aerobic or Anaerobic Sewage Digestion Method on Plant Availability of Metals.- 3 Results and Discussion.- 3.1 Chemical Availability Studies - Preliminary Study with Air and N2 Purged Sludge/Soil Suspensions.- 3.2 Chemical Availability Studies - Controlled pH and Redox Potential.- 3.3 Plant Uptake Studies.- 3.4 Effect of Aerobic or Anaerobic Sewage Digestion Method on Plant Availability of Metals.- 4 Summary and Conclusions.- References.- Microbiological Aspects of Heavy Metal and Toxic Chemical Behaviour in Porous Media.- 1 Introduction.- 2 Microbiological Aspects.- 2.1 Influence on Microbial Communities.- 2.2 Influence on Microbial Functions.- 2.3 Influence on Microbial Interactions.- 3 Chemical Behaviour.- 3.1 Microbial Contributions to Availability.- 3.2 Relative Toxicity of Chemicals.- 3.3 Relative Stability of Chemicals.- 4 Environmental Influences on Chemical Behaviour.- 4.1 Biotic Influences on Degradation.- 4.2 Abiotic Influences on Degradation.- 5 Conclusions.- References.- C Management of Inorganic Pollutants.- Municipal Sludges and Utility Ashes in California and Their Effects on Soils.- 1 Introduction.- 2 Inorganic Chemical Composition of Fly Ash and Municipal Sludge in California.- 2.1 Fly Ash.- 2.2 Municipal Sewage Sludges.- 3 Movement of Toxic Chemical Constituents in Solid Waste Treated Soils.- 4 Physical Properties of Waste Treated Soils.- 4.1 Particle Size Analysis and Consistency Limits.- 4.2 Bulk Density, Hydraulic Conductivity, Water-Holding Capacity, and Modulus of Rupture.- 5 Summary and Conclusions.- References.- Toxic Element Accumulation in Soils and Crops: Protecting Soil Fertility and Agricultural Food-Chains.- 1 Introduction.- 2 Transfer of Sludge-Applied Trace Elements to Animals by Direct Ingestion of Sludge or Sludge-Amended Soil.- 2.1 Bioavailability of Elements in Ingested Sludge.- 3 "Soil-Plant Barrier" Protects the Food-Chain Against Most Toxic Elements.- 4 Interactions Among Dietary and Sludge Constituents Influence Microelement Impact on the Food-Chain.- 5 Assessing Potential Risk from Sludge-Applied Cadmium.- 5.1 Cd Bioavailability.- 5.2 Crop Cd Relationship with Soil Cd.- 5.3 Long Term Availability of Sludge-Applied Cd to Crops.- 6 Estimating Cd Transfer from Sludge-Amended Soils to Human Diets.- 7 Estimating Maximum Allowable Soil Cd Loading Based on Predicted Increase in Dietary Cd.- 7.1 The Revised "Worst-Case" Cd Transfer Estimate.- References.- Sources and Distribution of Pollutant Elements in the Environment, with Particular Reference to Sewage Sludges.- 1 Introduction.- 2 Sources of Inorganic Pollutants.- 3 Transformations Among the Pollutant Elements.- 4 Assessments of the Toxicity of Pollutant Elements in Soils, or Sludge Treated Soils.- 5 Conclusion.- References.- D Case Studies.- Advances in Management of Fertilizer Application and the Resulting Effect on the Pollutant Load in Soil.- 1 Introduction.- 2 Methodology.- 3 Results.- 3.1 Nitrogen Fertilizer Use.- 3.2 Nitrogen Application Rate.- 3.3 Irrigation and Fertilizer Application Techniques.- 3.4 N-Fertilizer Efficiency.- 3.5 N-Removal in Harvested Crops and N-Residues in Soil.- 3.6 Relative Contribution of N-Fertilizer to the Pollution Load.- 4 Discussion.- References.- Water and Anion Transport in the Unsaturated Zone Traced by Environmental Tritium.- 1 Introduction.- 2 Methods.- 3 Results and Discussion.- 3.1 Simultaneous Transport of Water and Anions.- 3.2 Mobile and Immobile Water Domains.- 3.3 Matrix and Fissure Water Tra…