Ville Nenonen

I am Ville Nenonen; ESR7 based in Swiss Federal Institute of Aquatic Science and Technology, Eawag. The focus of my work is on the kinetics and mechanisms of the formation and transformation of P-containing Fe(III)-precipitates in the presence of various solutes (P, Si, Ca, organic matter) with respect to impacts on the composition, structure, reactivity of the solids and on P and trace element (As, Cd) retention and solubility (I’m mostly a lab rat).

Phosphate strongly adsorbs onto Fe(III)-oxides, and for this reason the redox cycling of Fe has a major control over the fate of phosphate in natural systems. The formation of Fe(III)-precipitates by the oxidation of dissolved Fe(II) in natural waters is affected by other solutes (Ca, Na, Si, P, organic matter) that interfere with Fe(II) oxidation, precipitation and continuing transformation, and thus P-binding capability over time. In addition to Fe-solids, Ca-phosphates and Ca-carbonates are important P-binding phases that can contribute to long-term P-trapping in soils and sediments. Fe can also co-precipitate with organic matter and these Fe-organic precipitates can strongly bind cations and anions and, as colloidal carriers or immobilising sorbents. Information on the structure and reactivity of Fe-organic matter co-precipitates is therefore important for the accurate assessment of the fate of nutrients and contaminants in natural water systems. I will specifically focus on three aspects: (1) How the organic matter impacts the structure, colloidal properties and P uptake of fresh Fe oxidation products, (2) structural transformation of fresh Fe(III)-precipitates during aging and effect on P retention, and (3) how the results from my laboratory experiments can be applied to field systems (collecting samples from various field sites in Netherlands and Germany). Samples will be analyzed with state of the art analyzing techniques (for example X-ray absorption).

Figure 1: The effect of Fe-precipitate formation on P-binding. (1) Oxidation of Fe(II) into Fe(III) in presence of P, Ca, Si and organics may lead to various precipitates with differences in structures. (2) The other solutes may interfere with Fe(III) polymerization, forming mixtures of Fe, Ca, P and organics. (3) Particles grow in sizes and form colloids (solid particles that stay suspended in the solution and do not settle down). (4) If particles grow enough, they will start forming flocs (coagulation) that will eventually settle down from the suspension. (5) Fe-precipitate aging may release the bound P back into soil or water. However, this P may form Ca-phosphates if calcium is present.

A few words about me; I am from Finland and have lived most of my life on coast of the Baltic sea. Growing up on the coast of one of the most polluted water bodies, I am aware how impactful the research on Fe-oxides and associated nutrients can be in improving surface water quality. My background is in Geology; I graduated from University of Helsinki, Finland, as a MSc in geology and geophysics in 2018. I did my Master’s thesis and an internship in Institute de Radioprotection et de Sûreté Nucléaire IRSN, France. The aim of the dissertation was to gain insight on a fluid-flow potential in a clay-rich fault core in a potential host rock for deep geological repository for radioactive waste. After graduation, I worked some time in environmental consulting (contaminated soils) but decided I wanted to do something more challenging and decided to apply to the P-TRAP project.

Figure 2: Solutions containing Fe, Na, P and different organic ligands. Color differences in reaction bottles are due to different kind of precipitates forming with different organic compounds.

Most closely, I will be collaborating with ESR6 and 10. My secondments will be in KU Leuven in Belgium, Deltares in Netherlands and GEOS in Germany. Possibly collaboration will take place also with University of Wageningen with collecting aged Fe-containing water treatment residues (sludges) left to age in various field sites in Netherlands.

During my free time, I enjoy hiking, other outdoor sports like ski touring, reading, and entertaining my neighbours with my guitar playing.