Exploring organo-mineral associations in ripening sediments

In this thesis the organo-mineral interaction will be studied in ripening dredged harbour sediments. These interactions are vital for soil functions including contaminant availability, aggregate formation and soil carbon sequestration.

Metal hydroxides and organic matter are vital reactive surfaces for geochemical processes in a wide variety of natural and anthropogenic environments. For example, these mineral and organic interfaces are capable of adsorbing contaminants. Metal hydroxides and organic matter also interact with each other (organo-mineral association). This interaction plays a large role in aggregate formation and organic matter stabilisation (Regelink et al., 2015; Kleber et al., 2021). Because of their relevance for chemical processes in soils and sediments, several analytical techniques have been developed for characterisation of metal hydroxides and organic matter. For iron- and aluminium hydroxides extraction protocols using dithionite, ammonium-oxalate and ascorbate are often used to compare different levels of hydroxide crystallinity (Kostka and Luther, 1994). Organic matter is frequently characterised by humic substance fractionation (Van Zomeren and Comans, 2007).

Mineral associated organic matter is dissolved during extraction of metal hydroxides. The coextracted dissolved organic matter is often ignored in these solutions, however, it could give insight in the nature of the organo-mineral interaction. By quantification and chemical characterisation of the organic matter that is extracted when dissolving metal hydroxides, the properties and mechanisms of organo-mineral association are assessed.

The study will focus on a chronosequence of dredged harbour sediments that have ripened on land. During ripening transition from anaerobic and unstructured sediment to aerobic and structured soil occurs and metal hydroxides and organic matter are (trans)formed. By working with these samples the development of organo-mineral associations can be evaluated. Additionally, other soil samples could be included to put the findings in a broader perspective.

The aim of this MSc thesis is to characterise organo-mineral interaction by extending traditional characterisation approaches for metal hydroxides and organic matter. These results can potentially be compared to other analyses (to be determined), models and literature. The findings from this thesis can ultimately improve understanding of contaminant availability, aggregate formation and soil carbon sequestration in developing soils.

Used skills

• Laboratory work
• Method development
• Data analyses
• Literature review
• Modelling
• Proposal and thesis writing

Requirements

You can find the requirements for this MSc thesis topic in the Study Handbook.

Supervisors