The importance of mobile, mobilisable and pseudo total heavy metal fractions in soil for three-level risk assessment and risk management

Heavy metals which accumulate in soils may be harmful to soil and its boundary ecosystems. In this paper a unified risk assessment and risk management concept is proposed followed by a discussion on its practical implementation. To assess and manage risk, the application of a three-level evaluation system is presented, incorporating the degree of metal contamination. Levels for guide values, trigger values and clean up values are used. In order to assess exposure to heavy metals, three metal fractions like mobile, mobilisable and pseudo total metal fractions are introduced. Exceeding trigger and guide values at a site may be harmful to the risk receptors. Adequate site-specific mild remediation measures aim to diminish or eliminate risk without adversely affecting basic functions of soil. The importance of mobile and mobilisable metal concentrations is discussed in relation to the development of ecological and economical sound remediation techniques.