Uptake of strontium by chamisa (Chrysothamnus nauseosus) shrub plants growing over a former liquid waste disposal site at Los Alamos National Laboratory

摘要

A major concern of managers at low-level waste burial site facilities is that plant roots may translocate contaminants up to the soil surface. This study investigates the uptake of strontium ((sup 90)Sr), a biologically mobile element, by chamisa (Chrysothamnus nauseosus), a deep-rooted shrub plant, growing in a former liquid waste disposal site (Solid Waste Management Unit (SWMU) 10-003(c)) at Los Alamos National Laboratory (LANL), Los Alamos, New Mexico. Surface soil samples were also collected from below (understory) and between (interspace) shrub canopies. Both chamisa plants growing over SWMU 10-003(c) contained significantly higher concentrations of (sup 90)Sr than a control plant--one plant, in particular, contained 3.35 x 10(sup 6) Bq kg(sup (minus)1) ash (9.05 x 10(sup 4) pCi g(sup (minus)1) ash) in top-growth material. Similarly, soil surface samples collected underneath and between plants contained (sup 90)Sr concentrations above background and LANL screening action levels (> 218 Bq kg(sup (minus)1) dry (5.90 pCi g(sup (minus)1) dry)); this probably occurred as a result of chamisa plant leaf fall contaminating the soil understory area followed by water and/or winds moving (sup 90)Sr to the soil interspace areas. Although some soil surface migration of (sup 90)Sr from SWMU 10-003(c) has occurred, the level of (sup 90)Sr in sediments collected downstream of SWMU 10-003(c) at the LANL boundary was still within regional (background) concentrations.