Transfer of U, Al and Mn in the water–soil–plant (Solanum tuberosum L.) system near a former uranium mining area (Cunha Baixa, Portugal) and implications to human health

Knowledge about metals in crops, grown in contaminated soils around mine sites, is limited and concerns about exposure to hazardous elements through the consumption of contaminated foodstuff, are high. In this study a field experiment was carried out in two agricultural soils located near a former uranium mine area (Cunha Baixa, Portugal). The purpose of the study was to assess the effect of irrigation water quality on soil–potato (Solanum tuberosum L.) crop system and to evaluate if the consumption of the crop represents health risk to the local villagers. The soils were divided in two plots: one irrigated with contaminated water (U: 1.03–1.04 mg/L; Al: 7.5–8.00 mg/L; Mn: 4.52 mg/L) and the other with uncontaminated water (U: 14–10 μg/L; Al: 17–23 μg/L; Mn: 2.4–5.7 μg/L). After irrigation and potato growth, only soil characteristics, as salinity and total U and Mn concentrations were significantly different from those measured at the beginning of the experiment. Within the potato plants, elements were mostly translocated and concentrated in the aerial part: stems and leaves (U: 73–87%; Al: 85–96%; Mn: 85–94%), which minimize the risk of contamination of the edible tissue. In potato tubers, the highest average concentrations (121–590 μg U/kg; 25–64 mg Al/kg; 12–13 mg Mn/kg dry weight) were registered at soil plots irrigated with contaminated water. Uranium and Al were mostly concentrated in the potato peel (88–96 and 76–85%, respectively), and Mn (67–78%) in the pulp, which reinforces the importance of removing peel to minimize human exposure. The risk analysis calculated for non-cancer health effects (hazard quotient), related only to the exposure through the consumption of this basic foodstuff, revealed safety for Cunha Baixa village residents (adults and children) even when potato crop was grown on U enriched soils and irrigated with contaminated water.

► Field experiment with potato in agricultural soils near a former uranium mine site ► U, Al and Mn transfer from water irrigation to soil, potato and man ► Contaminated irrigation water did not change significantly soil characteristics ► High element accumulation in aerial tissues and tuber peel minimizes human exposure ► Potatoes from U enriched soils irrigated with contaminated water are safe for humans