GENERAL PAPER Uncertainties in chemical modelling of solubility, speciation and sorption C. Ekberg • A. O ¨ degaard-Jensen Received: 20 July 2010 / Accepted: 18 October 2010 / Published online: 5 November 2010 Ó Springer-Verlag 2010 Abstract Chemical analyses become more and more expensive to perform, and more and more research is based on numerical simulation. However, all numerical models are subject to uncertainties, either in the implementation of the model towards reality or simply that the desired input data are not explicitly known without uncertainties. These uncertainties will affect the predictability of any model and thus it is of vital interest that the effect of these uncer- tainties is known. Especially if the result of the simulations is a topic upon which serious decisions are going to be made. In this paper, we outline a simple and rather straight forward approach to the effect of uncertainties on such simple chemical calculations as solubility of a solid phase in a given water and the chemical speciation of a solution. In addition, we also touch upon the much more compli- cated matter of uncertainties in sorption modelling—a subject which will be enlightened in much greater detail in an upcoming NEA publication in the matter. Keywords Uncertainty analysis Á Sensitivity analysis Á Solubility Á Speciation Á Sorption Á LJUNGSKILE Á SENVAR Introduction Chemistry is today a discipline in decline in most of the western world. In the basic schools, the practical education in chemistry is getting less and less attention and what was one taught after 8 years in school is now moved forward about 2 more years. One reason for this is that chemistry education is expensive. There is need for large laboratory facilities and comparably many teachers per number of students. As a result of this, it seems that the interest in laboratory chemistry is declining among the young ones of today. More and more focus is diverted towards computer simulations of different kinds. In general, this is a good trend in a more and more computerised society but com- puters cannot replace the need for laboratory chemistry. There is a need to see, feel and smell what is actually happening when you mix e.g. hydrochloric acid and ammoniac and that an experiment can fail. By the current trend, a lot of confidence in the predictive ability of com- puters is taught to our younger generation. This is not good. There is a distinct limit of the predictive power of any computer simulation. This limitation is called uncertainty. All computer simulations will be encumbered with uncer- tainties. They may originate from the choice of mathematical model used for the simulation, uncertainties regarding assumption of the system modelled and uncer- tainties in input data. One area where computer modelling is having a great impact is in the safety assessment of repositories for nuclear waste. The main reason is that there is a need to investigate different possible future developments in and around the repository in time spans in the range of 100000 years into the future and experiments on this time scale is impossible to do. Often the past is a good key to the future but we cannot rely only on that. There is a need to This article is part of the Topical Issue ‘‘Quality Assurance of Thermodynamic Data’’. C. Ekberg (&) Á A. O ¨ degaard-Jensen Nuclear chemistry/Industrial materials recycling, Department Chemical and Biological Engineering, Chalmers University of Technology, SE-41296 Go ¨teborg, Sweden e-mail: che@chalmers.se 123 Accred Qual Assur (2011) 16:207–214 DOI 10.1007/s00769-010-0723-4