AquaDiva
Retroaction of geochemical perturbations and critical zone media reactivity on trace elements speciation and transport parameters (C07)
DFG grant 218627073
Duration: July 2021 - June 2025
Project leader: Prof. Dr. Thorsten Schäfer
Personnel in charge: Ruth Ewouame, Dr. Dirk Merten
Coordinating/Cooperation: Collaborative Research Centre 1076 AquaDiva.
Project webpage: https://www.aquadiva.uni-jena.de/
key words: Clay nanoparticles, engineered nanoparticles, trace metal transport, crititcal zone
Description:
Groundwaters represent on average, a third of the fresh water consumed by humans, even in some parts of the world, this percentage can reach up to 100%.(2) Despite their importance, they are threatened by different events such as lands use and extreme weather events (heavy rains, snow melt), especially with the climate change.
Accordingly, the Collaborative Research Center 1076 AquaDiva aims to globally understand the link between surface and subsurface biogeosphere called Earth’s Critical Zone.
Two different sites in Germany with a contrast in geological settings have been selected for our research. The first one is the so-called Hainich Critical Zone Exploratory (Hainich CZE) in Northwestern Thuringia with a carbonate / siliciclastic bedrock (alkaline geological setting) and a fractured aquifer. (3) And the second one is the so-called Saale-Elster-Sandsteinplatte Observatory (SESO) in Southeastern Thuringia with a siliciclastic bedrock-dominated (acidic geological setting) and a fractured/porous aquifer. (4)
Our subproject C07’ s main goals are to understand the dynamics, controls, and feedbacks of fluid flow on colloid-associated Traces Metals transport and speciation from the surface to the subsurface by using Engineered Clay Nanoparticles (ECNs) as tracers and to generalize the role of the local geology / weather events for the subsurface microbiome on the two AquaDiva sites.
The fluid infiltration during weather events is an important way for the transport of solutes, colloids, and nanoparticles from the surface to the subsurface (groundwater). This is of high importance since clay nanoparticles are known as great adsorbers of metallic pollutants due to their negative surface charge and their large specific surface.
Indeed, a condition for colloids and nanoparticles migration is their stability against aggregation. (5) This stability and the associated trace metals speciation can be influenced by the seepages and groundwater physico-chemical parameters (pH, Ionic strength, Natural Organic Matter), defined by the local geology and nutrients inputs. Therefore, we are investigating the stability (aggregation kinetics) of the Engineered Clay Nanoparticles (Ni/Zn-Montmorillonite) in synthetic water and well waters from Hainich CZE and SESO by using e.g. Nanoparticles Tracking Analysis (NTA) and Dynamic Light Scattering (DLS) as methods.
Furthermore, the dissolution of the rock material in contact with the rainwater can modify the aquifer structure (modification of pores and fractures) and so change the fluid flow paths. This can also release some trace metals incorporated in the rock matrix (6) and by this increase the concentration of pollutants coming from surface to subsurface. We will investigate the dissolution experiments with the rock materials from SESO and Hainich sites and assess trace metals repartition with LA-ICP-MS.
The mobility of the stable or aggregated nanoparticles depends on the fluid flow rate and the fluid flow paths depending on the aquifer structure (fractures, porosity). We will then investigate the role of extreme weather events (heavy rains, snow melt) and fluid flow paths in this transport and the mobility of this particles. On one hand, the aquifer pores will be determined by XRay Microscopy (XRM) and on the other hand, column experiments will be set up to monitor the mobility of the clay nanoparticles.
For further information please have a look on this poster.pdf, 850 kb · de