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Past U mining near the village of Cunha Baixa in Portugal resulted in the contamination of subsurface waters used for agricultural irrigation. High radionuclide concentrations are currently found in the mine water as well as in solid mining waste and the sludge from mine water treatment. Nuclide transfer to plants was investigated using two side-by-side parcels of land, each divided into four replicate lots, which were used for the growth of the potato species Solanum tuberosum L. One parcel was irrigated with water with a high U concentration of 13.7 Bq/l and the other with water with a low U concentration of 0.3 Bq/l. The potato crop was collected and samples with or without peel were analysed for the U isotopes 238-U, 235-U and 234-U, 238-U daughters and the alpha-emitting radionuclides 230-Th, 226-Ra, 210-Po. The results showed a significant uptake of Ra and minor uptake of other radionuclides by the potatoes. Ra transfer was enhanced in the parcel of land irrigated with water with high Ra concentrations, but radionuclide concentrations in irrigation water had a minor effect on the transfer of U, Th and Po. Radionuclides were largely accumulated in the peel and in general peeling removed most of the radioactivity. Since the Ra may be transferred to man through the food chain it should be monitored in agricultural zones near U mine areas., Past U mining near the village of Cunha Baixa in Portugal resulted in the contamination of subsurface waters used for agricultural irrigation. High radionuclide concentrations are currently found in the mine water as well as in solid mining waste and the sludge from mine water treatment. Nuclide transfer to plants was investigated using two side-by-side parcels of land, each divided into four replicate lots, which were used for the growth of the potato species Solanum tuberosum L. One parcel was irrigated with water with a high U concentration of 13.7 Bq/l and the other with water with a low U concentration of 0.3 Bq/l. The potato crop was collected and samples with or without peel were analysed for the U isotopes 238-U, 235-U and 234-U, 238-U daughters and the alpha-emitting radionuclides 230-Th, 226-Ra, 210-Po. The results showed a significant uptake of Ra and minor uptake of other radionuclides by the potatoes. Ra transfer was enhanced in the parcel of land irrigated with water with high Ra concentrations, but radionuclide concentrations in irrigation water had a minor effect on the transfer of U, Th and Po. Radionuclides were largely accumulated in the peel and in general peeling removed most of the radioactivity. Since the Ra may be transferred to man through the food chain it should be monitored in agricultural zones near U mine areas.