The unsaturated zone is the medium through which pollutants move from the soil surface to groundwater. Polluting substances are subjected to complex physical, chemical and biological transformations while moving through the unsaturated zone and their displacement depends on the transport properties of the water-air porous medium system. Pollution caused by human activities, agriculture, and industry, has brought about a growing interest in the role of the unsaturated zone in groundwater pollution. Due to the complexity and the multidisciplinary nature of the subject, it is being investigated by specialists from various scientific disciplines, such as soil physicists, chemists, biologists, and environmental engineers. This state of affairs has motivated the initiative taken by the Water Quality Commissions of IUPAC (the International Union of Pure and Applied Chemistry) and IAHS (the International Association of Hydrological Sciences) to convene an international workshop, which was organized and hosted by the Institute of Soils and Water of the Agricultural Research Organization in Bet Dagan, Israel in March 1983. The lecturers at the workshop were an invited group of specialists who are engaged in studying the many facets of the unsaturated zone, and the present book is a selection of their presentations. Each chapter of the book relates to a different aspect of the unsaturated zone.

Inhalt
A. Modeling of Pollutants Transport.- Introductory Comments.- 1. Tracing Parcels of Water and Solutes in Unsaturated Zones.- 2. Solute Transport in Soil at Field Scale.- 3. Migration of Organic Fluids Immiscible with Water in the Unsaturated Zone.- B. Behavior of Inorganic Chemicals.- Introductory Comments.- 4. Pollution of the Unsaturated Zone with Nitrate.- 5. Behavior of Phosphates in the Unsaturated Zone.- 6. Unsaturated Zone Pollution by Heavy Metals.- 7. Effect of Acid Rain on Soil and Groundwater in Sweden.- 8. Heavy Metal Pollution of Natural Surface Soils Due to Long-Distance Atmospheric Transport.- C. Behavior of Organic Compounds.- Introductory Comments.- 9. Chemical Nature and Reactivities of Soil Organic Polymers.- 10. Behavior of Pesticides in the Unsaturated Zone. Adsorption and Transport Phenomena.- 11. Nonbiological Degradation of Pesticides in the Unsaturated Zone.- 12. The Effect of Solid Organic Components of Sewage on Some Properties of the Unsaturated Zones.- D. Biological Processes.- Introductory Comments.- 13. Biochemical Processes in Unsaturated Zones.- 14. Pathogenic Bacteria and Viruses in the Unsaturated Zone.- E. Unsaturated Zone and Groundwater: Pollution Sources.- Introductory Comments.- 15. Agricultural Pollutants and Groundwater Quality.- 16. Nitrogen Presence in Groundwater as Affected by the Unsaturated Zone.- 17. Prevention of Groundwater Pollution on a National Scale: Israel as a Case Study.- F. Unsaturated Zone and Groundwater: Pollution Control.- Introductory Comments.- 18. Wastewater Renovation in Rapid Infiltration Systems.- 19. Use of Soil-Aquifer System for Effluent Purification and Reuse.- 20. Utilization of the Buffering Properties of the Unsaturated Zone in Groundwater Quality Management on a Regional Scale: The Coastal Aquifer of Israel as a Case Study.