Distribution, behavior, and erosion of uranium in vineyard soils

Daniel A Campos,Sophia Blanché,Allan Philippe,Hermann F Jungkunst

doi:10.1007/s11356-021-14381-9

Daniel A Campos, Sophia Blanché + Show 2 more

Open Access

https://doi.org/10.1007/s11356-021-14381-9

Copy DOI

Abstract

Phosphate fertilization contributes to an input of uranium (U) in agricultural soils. Although its accumulation and fate in agricultural soils have been previously studied, its colloidal transport and accumulation along slopes through erosion have been studied to a lesser extent in viticulture soils. To bridge this gap, the contents and potential mobility of U were investigated in vineyard model soils in the Rhineland-Palatinate region, Germany. In addition to elevated U contents, U was expected to associate with colloids and subject to erosion, thus accumulating on slope foots and in soils with fine structure, and reflecting a greater variability. Moreover, another expectation was the favorable erosion/mobility of U in areas with greater carbonate content. This was tested in three regional locations, at different slope positions and through soil horizon depths, with a total of 57 soil samples. The results show that U concentrations (0.48–1.26 ppm) were slightly higher than proximal non-agricultural soils (0.50 ppm), quite homogenous along slope positions, and slightly higher in topsoils. Assuming a homogeneous fertilization, the vertical translocation of U in soil was most probably higher than along the slope by erosion. In addition, carbonate content and soil texture correlated with U concentrations, whereas other parameters such as organic carbon and iron contents did not. The central role of carbonate and soil texture for the prediction of U content was confirmed using decision trees and elastic net, although their limited prediction power suggests that a larger sample size with a larger range of U content is required to improve the accuracy. Overall, we did not observe neither U nor colloids accumulating on slope foots, thus suggesting that soils are aggregate-stable. Lastly, we suggested considering further soil parameters (e.g., Ca2+, phosphorus, alkali metals) in future works to improve our modelling approach. Overall, our results suggest U is fortunately immobile in the studied locations.

Highlights

Phosphate fertilizers result from the processing of phosphate rock that contains impurities such as uranium (U) mainly as uranyl (UO22+) complex (Roessler 1990; Khater 2008)
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)
EN is an integral approach that combines both ridge regression and LASSO, which allows to differentiate the effects of collinear and variables and to shrink the effects of variables with low predictive power (Tomaschek et al 2018). These results suggest that carbonate is a better predictor of U, followed by soil texture

Summary

Introduction

Phosphate fertilizers result from the processing of phosphate rock that contains impurities such as uranium (U) mainly as uranyl (UO22+) complex (Roessler 1990; Khater 2008). iES Landau, Institute for Environmental Sciences, Group of Environmental and Soil Chemistry, University of Koblenz-Landau, Fortstraße 7, 76829 Landau in der Pfalz, Germany. iES Landau, Institute for Environmental Sciences, Group of Geoecology & Physical Geography, University of Koblenz-Landau, Fortstraße 7, 76829 Landau in der Pfalz, Germany 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; 2020). Phosphate application resulted with the highest U input in agricultural land in comparison to other processes (e.g., manure application; Bigalke et al 2020). U from fertilized soils could leach into ground and surface water (Birke and Rauch 2008; Liesch and Hinrichsen 2015; Haneklaus et al 2017), which is of concern considering experimental animal studies and human epidemiology (Brugge and Buchner 2011; Schnug and Lottermoser 2013)

Objectives

Methods

Results

Conclusion