Predictions by the multimedia environmental fate model SimpleBox compared to field data: Intermedia concentration ratios of two phthalate esters

This report describes the last phase of the validation exersize, i.e. validation of the model as a whole. Specific model output with respect to a model compound is compared with field observations. Di(2-ethylhexyl) phthalate (DEHP) and di n-butyl phthalate (DBP), two high volume production chemicals, were monitored in the environmental compartments air, water, fish, sediment, soil and vegetation in the period 1997- 2001. Concentration ratios as measured between the compartments, displayed a considerable spread. Probabilistic techniques were used to obtain steady state concentration ratios. In stead of a deterministic output a distribution is calculated. The width of the distribution is largely determined by very uncertain emission rates of both phthalates. The 50th percentile differed less than a factor of 10 with respect to concentration rates obtained from monitoring. From this report it is tentatively concluded that application of SimpleBox to harmonize environmental quality objectives should be retained.</p>