Rice Husk Biochar and Radionuclide Activity in Contrasting Soils

This descriptive 90-day study examined 137Cs, 90Sr and 238U activity concentrations in recovered <2 mm fractions of three artificially contaminated soils amended with rice husk biochar (RHB; 500 °C, 8 h) at nominal 0, 15, 25 and 35 t ha−1. Four independent reactors per soil–rate combination provided 48 endpoint observations per radionuclide. At nominal 35 t ha−1, concentrations were lower than those of the final unamended controls by 41.6%, 37.3% and 34.3% in black soil; 33.5%, 28.5% and 25.6% in light brown soil; and 25.7%, 23.7% and 21.7% in light gray soil for Cs, Sr and U, respectively. Sample standard deviations describe endpoint dispersion. Initial-loading, compartment and counting data support activity calculations and partial analytical uncertainty estimates. These data lack complete reactor matching and measurement uncertainty budgets, limiting assessment of initial-to-final changes and treatment contrasts. Summary activity recovery at the highest nominal rate was 80.6–89.2%, leaving an unresolved deficit. Biochar doses are geometry-based targets; the available weighing entry lacks a reactor identifier. The observed patterns support descriptive endpoint comparisons and further investigation, but do not establish radionuclide removal, immobilization, reduced mobility, reduced plant transfer or an optimal rate.