The long-term accumulation of bioavailable uranium in soil due to the use of mineral phosphate fertilizers

Uranium (U) is an ubiquitous radioactive and toxic trace metal present in soils. It is now well accepted that the continuous application of phosphate fertilizers has caused accumulation of U in agricultural soils above background levels. This enrichment is of concern, as U may be absorbed by crops or leached to groundwater and thereby enter the human food chain. Uranium is an unwanted impurity present in phosphate fertilizers but currently its levels are not monitored nor regulated at EU level. The goal of this study is to measure the long-term accumulation of bioavailable U in soil and plants due to the use of mineral phosphate fertilizers and to make future trends in soil and plant U exposure at EU-wide scale. We propose that bioavailable U is likely to be better indicated by the acid soluble fraction (aqua regia U) compared to real total concentrations and hence of environmental relevance. This project is probably first in assessing an EU mass balance of U in soils to identify exposure at a large scale which can be the base for the implementation of future regulations on U in fertilizers.