The Emerging Role of Soil Physics in Environmental Engineering

Abstract

Historically, soil physics research in Japan and worldwide has focused on soil-water physics with a majority of studies on cultivated surface soils, and with the objective of optimizing water supply to plants and minimize leaching of pesticides and nutrients below the root zone. Recently, transport, fate and emissions of greenhouse gases such as carbon dioxide and methane is an area where rapidly growing environmental concerns about global warming and climate effects has provided new challenges for soil physicists. Another important challenge originates from the increasing problems in most urban areas with contaminated sites, where soil and groundwater have been polluted with EICs (Environmental Impact Chemicals) including gasoline and chlorinated compounds. To respond to these challenges, a broader focus in soil physics research and more emphasis on soil physical properties and processes in an environmental engineering perspective is needed. Improved understanding and better predictive models together with reliable in-situ measurement methods for a larger variety of soil physical parameters can give soil physicists a major role within the rapidly emerging research field that combines environmental engineering and polluted soil science ; soil environmental engineering. Detailed knowledge of soil physical processes in all three soil compartments (the soil-air, water and particle phases) is the platform for soil environmental engineering, including : -Realistic calculations of transport and fate of EICs at contaminated soil sites -Risk assessments concerning indoor and outdoor air and groundwater pollution -Development and optimization of remediation methods for soil and groundwater In this perspective, future soil physics research should focus on chemical diffusion, sorption, release, and convective transport in both the soil-water and soil-air phases and, also, evaluate the significance of particle-facilitated chemical transport through soil. As examples of less investigated soil physical parameters that are key parameters in soil environmental engineering, we advocate the importance of gas and solute diffusivity, air permeability, and vapor sorption coefficients in relation to both risk assessment and to remediation by soil vapor extraction and pump and treat methods. For soil environmental engineering purposes, not only the surface soil but the entire vadose zone between the soil surface and the groundwater table should be considered during studies of soil physical parameters. The dominating role of soil-physical processes in controlling and optimizing biodegradation of pollutants during soil remediation should be investigated and highlighted. With this emerging role of soil physics in environmental engineering combined with the rapid developments in process understanding and non-destructive measurement equipments, we are on the brink of an exciting new era in soil physics.