A TEST OF LONG-TERM, PREDICTIVE, GEOCHEMICAL TRANSPORT MODELING AT THE AKROTIRI ARCHAEOLOGICAL SITE

A study of elemental transport at the Akrotiri archeological site on t he island of Santorini, Greece, has been conducted to evaluate the use of natural analog data in support of long-term predictive modeling of the performance of a proposed geologic repository for nuclear waste a t Yucca Mountain, Nevada. Akrotiri and Yucca Mountain have many analog ous features including silicic volcanic rocks, relatively dry climates , and oxidizing, hydrologically unsaturated subsurface conditions. Tra nsport of trace elements from artifacts buried in volcanic ash 3600 ye ars ago at Akrotiri is analogous to transport of radioactive wastes in the proposed repository. Subtle evidence for a plume of Cu, Zn, and P b has been detected by selective leaching of packed earth and bedrock samples collected immediately beneath the site where bronze and lead a rtifacts were excavated. The geologic setting of the artifacts and the hydraulic properties of the enclosing media were characterized. A num erical model of the type used in repository performance assessments wa s developed for elemental transport at the site. Site characterization data were used to build the model but no prior information on the nat ure of the contaminant plume was provided to the modelers, Some model results are qualitatively consistent with field data, including the sm all amount of material transported, limited amounts of sorbed material , and relatively elevated sorption on a packed earth layer. However, d iscrepancies result from incomplete representation of heterogeneity an d complexity and poorly constrained model parameters. Identification o f such system characteristics and model limitations in relevant system s is a major contribution that analog studies can contribute in suppor t of repository modeling. (C) 1998 Elsevier Science B.V.