Project properties

Title Cadmium binding to manganese oxides: an overlooked process in quantifying its bioavailability
Group Soil Chemistry and Chemical Soil Quality
Project type thesis
Credits 24-39
Supervisor(s) Wietse Wiersma, Liping Weng, Bert-Jan Groenenberg
Examiner(s) Rob Comans
Contact info wietse.wiersma@wur.nl
Begin date 2021/08/01
End date
Description Cadmium (Cd) is a heavy metal that is toxic for humans and that regularly exceeds limits in agricultural products around the world, such as rice, potatoes and cacao. Understanding Cd behaviour in soils and uptake by crops is thus essential for sustainable farming systems. To achieve this, adsorption of metals to soil surfaces needs to be quantified under various soil chemical conditions. In addition to organic matter and clay, metal hydroxides are important surfaces. Iron (Fe) and aluminium (Al) oxides are generally present in larger concentrations, and are more widely studied, than manganese (Mn) oxides. Despite their smaller presence, Mn oxides (e.g. birnessites) are often present as fine-grained nanoparticles and are known to be ‘scavengers’ of heavy metals due to their structure and strong negative charge. Part of the puzzle is to consider the more complex structure of Mn oxides compared to Fe and Al oxides. Hence, fundamental work needs to be done to quantitatively and qualitatively describe heavy metal adsorption to Mn oxides.

Besides the clear scientific knowledge gap, understanding Mn oxides is also crucial to address a wide range of societal issues related to sustainable food production. For example, some empirical studies have shown that the content of Mn oxides in the soil is related to the concentration of heavy metals in edible above-ground plant parts. This has been observed for cadmium taken up by cacao beans. Therefore, your work would in general improve our understanding of metal sorption in soils, and also contribute specifically to solutions for the cadmium-in-cacao issue. The latter is a major threat to the livelihood of smallholder farmers in Latin America and the Caribbean, where Cd is naturally present in high concentrations (https://climaloca.org/).
Used skills • Literature review
• Writing proposal and thesis
• Chemical laboratory experiments and analyses
• Data processing and statistics, with option of geochemical modeling
• Presentation skills
Requirements Required courses for MSc thesis Soil Chemistry and Chemical Soil Quality