Vegetation composition and 226Ra uptake by native plant species at a uranium mill tailings impoundment in South China

Abstract

A field investigation was conducted for the vegetation composition and 226Ra uptake by native plant species at a uranium mill tailings impoundment in South China. 80 species belonging to 67 genera in 32 families were recorded in the sampling sites. The Poaceae and Asteraceae were the dominant families colonizing the impoundment. The number of the plant species and vegetation community composition in the sampling sites seemed most closely related to the activities of 226Ra and the pH value of the uranium tailings. The plant species in the sampling sites with relatively low activities of 226Ra and relatively high pH value formed a relatively stable vegetation community. The plant species in the sampling sites with medium activities of 226Ra and medium pH value formed the transitional vegetation community. The plant species in the sampling sites with relatively high activities of 226Ra and relatively low pH value formed a simple unstable vegetation community that was similar to that on the unused grassland. The activities of 226Ra and transfer factors (TFs) varied greatly with the plant species. The high activities of 226Ra and TFs were found in the leaves of Pteris multifida (150.6 Bq/g of AW; 9.131), Pteridium aquilinum (122.2 Bq/g of AW; 7.409), and Dryopteris scottii (105.7 Bq/g of AW; 6.408). They satisfied the criteria for a hyperaccumulator for 226Ra. They may be the candidates for phytoremediation of 226Ra in the uranium mill tailings impoundment areas and the contaminated soils around.