Comparison of the RIVM models: CATS-1, METRAS, NMPCulty, SimpleBox and SOACAS for modelling the behaviour of trace metals in soil

Modelling of the behaviour of trace metals in soil is relevant in various projects at the RIVM ; eg. projects related to the prediction of accumulation and leaching in soil, risk analysis on effects on human health and organisms, derivation of environmental standards and critical loads and assessment of metal mobility in waste materials. The model approaches used are: CATS-1, METRAS, NMPCulty, SimpleBox and SOACAS. Although these models have different application aims, they show significant resemblance in their concepts related to sorption, transport and plant uptake of trace metals. To make similarities and differences explicit, the results of the above-mentioned models were compared using four well-defined, simple cases for cadmium and copper. Predicted accumulation and leaching compared very well, while the largest differences were found in predicted plant uptake. The resemblance in model results was partly due to forcing model parameterisations into agreement with the SOACAS application. Differences in predicted plant uptake would have been larger if default parameterisations of the individual models had been used. The fair resemblance of model results should not lead to the conclusion that the complete models or modules for transport and accumulation can be easily exchanged. For easy exchange, linkage to other model components, model languages and procedures for presentation of results differ too much. However, in the longer term harmonisation of concepts and parameters for sorption, transport and plant uptake of trace metals is possible and meaningful. Initiatives to realize the harmonisation in the description of sorption are already ongoing.