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The uptake and translocation of contaminants from uranium mill tailings piles and other similar wastes (such as uranium mine spoils and phosphate mine tailings) could be an important transport mechanism of these contaminants into the environment. Kadium-226 is of particular concern due to its long half-life and its ability to be accumulated in bone. This work is the study of the content of radium-226 in plants growing on inactive uranium mill Sailings sites in the Four Corners Region of the southwestern I'nited States and in plants grown under greenhouse conditions with minimal surficial contamination. Field plant samples and associated substrates were analyzed from two carbonate tailings sites in the (irants Mineral Belt of New Mexico. Radium activities in air-cleaned samples ranjjed from ?•> to ^68 pCi/g (dry weight) depending on species and location: activities in plants growing on local soils averaged 1.0 pCi/g. The tailings and local soils contain 14()-14(M) p<"i/g and 2.1 pCi/g. respectively. An evaluation of cleaning methods on selected samples showed that from 17 to 79% of the radium activity measured in air-cleaned samples was due to surficial contamination, which varied with species and location. A survey of IH inactive uranium mill sites in the Four Corners Region was performed. Radium activity in plant tissut irom nine species ranged from 2 to 210 pCi/g on bare tailings and from ().•' < to 'M) pCi/g on covered tailings. The radium content in most of the soil overburdens on the covered tailings piles was 10 to 17 pCi/g. An experiment was performed to measure radium-226 uptake by two species grown on tailings covered with a shallow (5 cm) soil layer. A grass, Sporobolus airoides (alkali sacatonl and a shrub. Atriplex canescens (four-wing salt bush), were studied. The tailings were a mixture of sands and slimes from a carbonate pile. The tailings treatments were plants grown in a soil cover over tailings; the controls were plants grown only in soil. Three soil types, dune sand, clay loam, and loam, were used. The radium activity of the plant tissue from the tailings treatment compared to that of the appropriate control was 1 to 19 times greater for the grass and 4 to 27 times greater for the shrub. ix 'Results of one measurement ± analytical uncertainty given. •Three size fractions of substrates: (1) bulk-all fractions; (2) wet fines-fraction <53pm produced by sieving after dispersal in sodium hypophosphate solution; and (3) dry fines-fraction <53pm produced by sonically sieving dry samples.

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