Uranium Budget and Leaching in Swiss Agricultural Systems

Abstract

Many mineral P fertilizers contain toxic uranium (U) in high concentrations. When the fertilizers are applied to agricultural sites, U can either accumulate in the soil or leach to ground and surface waters. We analyzed the U fluxes at three arable and three grassland agricultural sites on the Swiss plateau for 1 year. We calculated all inputs and outputs to the soils, modeled the speciation of U in the soil solution and investigated the possible leaching of U along preferential flow paths. We found that all sites showed positive U budgets (+0.9-6.6 g ha −1 y −1 ), indicating an accumulation of U. However, the accumulation of U was low and a doubling of U concentration in the surface soil would need 850-2,660 years assuming today's U fluxes. Mineral P fertilizers were the quantitatively most important input, followed by manure application and mineral weathering (only important in the soils developed on limestone). While at sites with slightly acidic pH only little U (<0.01 µg L −1 ) was leached, the U leaching increased at neutral pH values, because of the formation of carbonato-U complexes. In all soil solutions, the U concentrations (≤0.8 µg L −1 ) were below legal threshold values and comparable to local drinking and surface waters. We found no indication for enhanced U leaching along preferential flow paths.

Distribution, behavior, and erosion of uranium in vineyard soils

“…HSD tests revealed that comparisons between groups within each location resulted in non-significant U concentration differences (p>0.05). In addition, it was observed that U concentrations were generally slightly higher in the uppermost profile layers, which was similarly observed in other studies (e.g., Takeda et al 2006;Wetterlind et al 2012;Steinmetz et al 2017;Bigalke et al 2020). However, it is possible that effects on leaching and accumulation of U (i.e., in respect to greater carbonate, clay, and/or C org contents) are masked due to thorough mixing by deep tillage practices during preparation of new fields (Ziegler 2012).…”

“…Previous studies have shown relationships between U and the abundance of finer particles (Blanco-Rodríguez et al 2008;Scheffer et al 2010;Kumar et al 2015), and with Al and Fe in agricultural soils (Yamaguchi et al 2009). However, other studies have pointed out the importance of carbonates to determine U mobility (e.g., Echevarria et al 2001;Bigalke et al 2020). Therefore, in order to obtain a closer insight in the parameters influencing U concentrations, predictive models were built and analyzed.…”

“…The continuous application of these fertilizers introduces large amounts of U, thus leading to its accumulation in soils (Takeda et al 2006;Rogasik et al 2008;Yamaguchi et al 2009;Schipper et al 2011;Wetterlind et al 2012;Schnug and Haneklaus 2014;Bigalke et al 2017;. Recently, phosphate application resulted with the highest U input in agricultural land in comparison to other processes (e.g., manure application; Bigalke et al 2020). Although there is currently limited information on U concentrations in viticulture soils, it has been reported that conventionally fertilized agricultural soils contain more U than organically cultivated vineyard soils (Steinmetz et al 2017).…”

Trace metal accumulation in agricultural soils from mineral phosphate fertiliser applications in European long‐term field trials

“…In New Zealand, Schipper et al observed a steady linear increase of U in the soil at fertiliser application rates of 30 kg P ha −1 y −1 when applying either SSP or TSP, contrasting the abovementioned decline in Cd concentration when shifting from SSP to TSP at rates below 50 kg P ha −1 y −1 (Schipper et al, 2011). In Switzerland, positive U budgets were calculated for three arable fields (2 to 6 g U ha −1 y −1 ), while negative Cd budgets were calculated for the same field when growing wheat (−0.49 to −0.01 g Cd ha −1 y −1 ) and small positive Cd budgets when growing barley (0.18–0.71 g Cd ha −1 y −1 ) (Bigalke et al, 2020; Imseng et al, 2018). Importantly, the study of Schipper et al (2011) used aqua regia for soil analysis as is commonly used for the Cd analyses.…”

Sewage Sludge Treatment by Hydrothermal Carbonization: Feasibility Study for Sustainable Nutrient Recovery and Fuel Production

“…In addition to huge mining areas, the production of phosphoric acid from phosphate ore leaves behind hundreds of millions of tons of phosphogypsum, some of which is radioactive [6]. Radioactive material such as uranium as well as heavy metals (HM) like cadmium can be transferred from the ore to the mineral P fertilizer [7][8][9][10][11][12]. A study by the Braunschweig Federal Research Center for Cultivated Plants JKI (Julius Kühn-Institute) found in triple superphosphate 52-232 mg/kg of uranium [6].…”