Ecosystem health: an overview. Molecular structure-reactivity- toxicity relationships. Metal ion speciation and its significance in ecosystem health. Dynamics and transforamtions of radionuclides in soils and ecosystem health. Adsorption of dissolved organic ligands onto (hydr)oxide minerals. Organophosphorus ester hydrolysis catalyzed by dissolved metals and metal-containing surfaces. Impact of chemical and biochemical reactions on transport of environmental pollutants in porous media. Soil-root interface: biological and biochemical processes. Soil-root interface: physicochemical processes. Soil-root interface: ecosystem health and human food-chain protection. Nontarget ecological effects of plant, microbial, and chemical introductions to terrestrial systems. Ecosystem health and its relationship to the health of the soil subsystem. Role of soil chemistry in soil remediation and ecosystem conservation.