Diffusion of mercury through concrete and bentonite -enhanced sand - proposed container and backfill materials in a repository for permanent disposal of mercury

摘要

The objective of this study was to measure the transport by diffusion of Hg(II) and elemental Hg through a barrier of concrete or bentonite-enhanced sand. Sand was used as a reference system parallel to the two systems. Break-through within 33 months was observed in the sand system in contact with Hg(II) and in none of the other systems. Mercury concentration profiles were analysed for the systems of sand/Hg(II) and sand/ Hg°. For elemental mercury in sand, the apparent diffusivity was 6.9xlO~(-12) m~2/s. For mercury oxide (Hg(II)) two apparent diffusivities l.lxl0~(-12) m~2/s and l.lxl0~(-12) m~2/s were indicated. The concrete is an efficient barrier for both Hg~0 and Hg(II). The higher diffusivity for Hg(II) than for Hg~0 is unexpected, since uncharged mercury was supposed to diffuse faster than charged species.