Uranium in agricultural soils and drinking water wells on the Swiss Plateau

Mineral phosphorus fertilizers are regularly applied to agricultural sites, but their uranium (U) content is potentially hazardous to humans and the environment. Fertilizer-derived U can accumulate in the soil, but might also leach to ground-, spring and surface waters. We sampled 19 mineral fertilizers from the canton of Bern and soils of three arable and one forest reference sites at each of four locations with elevated U concentrations (7–28 μg L−1) in nearby drinking water wells. The total U concentrations of the fertilizers were measured. The soils were analysed at three depth intervals down to 1 m for general soil parameters, total Cd, P, U and NaHCO3-extractable U concentrations, and 234/238U activity ratios (AR). The U concentrations and AR values of the drinking water samples were also measured. A theoretical assessment showed that fertilizer-derived U may cause high U concentrations in leaching waters (up to approx. 25 μg L−1), but normally contributes only a small amount (approx. 0–3 μg L−1). The arable soils investigated showed no significant U accumulation compared to the forest sites. The close positive correlation of AR with NaHCO3-extractable U (R = 0.7, p