Diffusion experiments for estimating radiocesium and radiostrontium sorption in unsaturated soils from Spain:...

Area of Science:

• Environmental Science
• Soil Science
• Radiochemistry

Background:

• Sorption data from batch tests are crucial for estimating pollutant transport in unsaturated soils.
• Accurate risk assessment requires comparing sorption data from batch tests and unsaturated soil conditions.

Purpose of the Study:

• To quantify apparent diffusion coefficients (D(a)) for radiostrontium (Sr) and radiocesium (Cs) in nine unsaturated soils.
• To compare derived distribution coefficients (K(d)) from diffusion experiments with K(d) data from batch experiments.
• To evaluate the reliability of batch test data for predicting radionuclide transport in unsaturated soils.

Main Methods:

• Quantification of apparent diffusion coefficients (D(a)) for radiostrontium and radiocesium in nine unsaturated soils using batch tests.
• Calculation of distribution coefficients (K(d)) from diffusion data.
• Comparison of K(d) values obtained from diffusion experiments and traditional batch experiments.

Main Results:

• Apparent diffusion coefficients for Sr (D(a)(Sr)) ranged from 1.8x10(-11) to 1.5x10(-10) m(2) s(-1) and for Cs (D(a)(Cs)) from 1.0x10(-13) to 5.9x10(-11) m(2) s(-1).
• D(a)(Sr) variation was linked to soil packing and Sr interaction properties, while D(a)(Cs) variation was explained by soil sorption properties.
• K(d) values derived from diffusion were generally lower than those from batch tests, suggesting batch data may overestimate transport.

Conclusions:

• Batch test K(d) values may overestimate radionuclide transport in unsaturated soils.
• Despite differences, K(d) values from diffusion and batch tests show good correlation.
• Batch tests offer a faster alternative for estimating radionuclide transport, despite potential overestimation.