Calculation of site specific characterisation factors for metal ecotoxicity using decoupled multi species fate and exposure modelling

Calculation of characterisation factors (CF’s) for metal ecotoxicity typically involves fate and exposure modelling of metals in multi-media models developed for assessment of organic compounds. Metals do not follow the fate patterns of organic chemicals, and the results will therefore most likely misrepresent the exposure concentration of metals. However, using multiple versions of such models for individual metal species within each model region and linking these to databases containing information on speciation pattern and fate properties of the individual metal species enables the assessment of metals taking into account the speciation pattern under e.g. specific pH, DOM and salinity conditions. The study presented here indicates that CF’s calculated using the traditional assessment method known as single species assessment of metals, under realistic conditions differs significantly, due to the part of the metal species present as complexes which is very hard to account for in single species assessment. Preliminary results on the CF’s based on single species assessment and decoupled multi species assessment will be presented for 4 common metals.