Role of Soil Properties in Phytoaccumulation of Uranium

Abstract

Thirty four plant species were screened for uranium (U) accumulation from U contaminated soil. There was a significant difference in U accumulation among plant species. Sunflower (Helianthus annuus) and Indian mustard (Brassica juncea) accumulated more U than other plant species. Sunflower and Indian mustard were selected as potential U accumulators for further study in one U mine tailing soil and eight cultivated soils (pH range4.7 to 8.1) contaminated with different rates (100 to 600 mg U(VI) kg-1) of uranyl nitrate (UO2(NO3)2⋅6H2O). Uranium fractions of contaminated soils [(exchangeable, carbonate, manganese (Mn), iron (Fe), organic, and residual)] were determined periodically over an 8-week incubation period. Uranium accumulated mainly in the roots of plant species. The highest concentration of U was 102 mg U kg-1 in plant shoots and 6200 mg U kg-1 in plant roots. Plant performance was affected by U contamination rates, especially in calcareous soils. Plants grown in soils with high carbonate-U fractions accumulated the most U in shoot sand roots. The lowest plant U occurred in clayey acid soils with high Fe, Mn and organic U-fractions. The effectiveness of U remediation of soils by plants was strongly influenced by soil type. Soil properties determined the tolerance and accumulation of U in plants.