New objectives regarding the improvement of water quality, as well as problems with the resuspension and land deposition of dredged materials, require a standardized assessment of sediment quality. Numerical criteria approaches, which are based on pore water concentrations, and the accumulation, solid/liquid partition, and elution properties of contaminants, usually do not imply variations of chemical interactions with solid matrices. Regarding the potential release of metals from sediments, changes in pH and redox conditions are of prime importance. To incorporate new experience with non-linear and time-delayed processes, special emphasis should be put on the characteristics of the mineral and organic solid matrices, e.g. to capacity controlling properties, and in particular, the buffer capacity against pH-depression.
