Towards better risk assessment of cadmium in agricultural soil for sustainable nutrient management

This PhD project aims to determine sustainable application rates of recycled nutrient sources like biogas digestates, biofuel ashes, and beachcast seaweed. These sources can replace N and P from mineral fertilizers, contributing to sustainable agriculture. However, these materials may contain high levels of cadmium, which poses risks to humans and the environment.

The current knowledge on cadmium in soils is insufficient to determine safe application rates of different nutrient sources and fertilizers in relation to cadmium.

The project will provide new data on how cadmium sorption to soil depends on pH and soil solution composition, and will study its binding mode using XANES spectroscopy.

These data will be used to calibrate an improved process-based model to predict cadmium leaching, which will be verified by column experiments.

The project will also review published data on how cadmium uptake to crops depends on environmental conditions and will perform gap-filling experiments to develop an improved model for soil-crop transfer.

Finally, the content and relative solubility of Cd will be determined in a large number of ashes, digestates, and beachcast seaweed samples.

The results will be synthesized to produce a web-based tool capable of predicting sustainable application rates of recycled nutrient sources and fertilizers that will not pose risks to humans and the environment.