Dynamics of groundwater ecosystem services

Groundwater has long been considered a static environment. For that reason, the potential impact of environmental drivers like water level fluctuation, pulses of substrate in- and export, and transient hydraulics has mostly been neglected. The three work packages (WP) of this IP tackle this important research gap by focusing on the physical, biological and chemical dynamics of groundwater ecosystem services.

WP 1: The soil/groundwater interface - a natural barrier under dynamic hydraulic conditions

The focus of this WP lies on the unsaturated/saturated water interface as well as the transition zone between surface water and groundwater. These zones are natural barriers for dissolved organic matter (DOM), nutrients and contaminants which keeps the groundwater free from these substances. However, common water table fluctuations as well as extreme events like floods and droughts impact the transport of substances within these zones. Work in WP 1 focuses on the identification and quantification of physical, chemical, and biological processes in the transition zones which control transport of substances. Of particular interest is the development of monitorin tools, i. e. stable isotope techniques, to follow the irregular dynamics in a high spatial and temporal resolution. Currently, we study the influence of fluctuating water tables on solute and reactive transport as well as on microbial communities at the soil/groundwater interface in controlled lab experiments. Further, we developed a new field monitoring system for high-resolution sampling in the unsaturated and saturated zone. This system was installed in the riparian zone to study the impact of dynamic hydraulic conditions on nutrient dynamics.

WP 2: Effects of hydrogeochemical dynamics on the natural attenuation of point sources

The transition between contaminated areas and the surrounding non-contaminated zones are "hot spots" of microbial degradation. The activity of bacteria within these zones is, however, strongly driven by the geochemical gradients, substrate supply, electron acceptor availability, and contaminant concentration. Main objective of WP 2 is to examine how sensitive microbial communities respond to dynamics in environmental conditions and how this affects their degradation efficiency.
In various projects we examine the effect of groundwater fluctuations on sessile biodegrader populations. A current focus of research lies on the role of phages steering and the composition and functions of bacterial communities.

WP 3: Dynamic transformation and elimination pathways for diffuse and emerging contaminants

Diffuse contaminants like nitrate, pesticides, personal care products, pharmaceuticals or pathogens enter groundwater from waste water and the application of manure, fertilizers and pesticides. While they are of primary concern for human and environmental health, our knowledge about their distribution, transformation and elimination pathways still remains fragmentary. The fate of these substances and the governing elimination pathways as controlled by microbial activity, hydrodynamics, spatial heterogeneity and redox processes are therefore the focus of this WP. Our particular contribution lies in the development of specific and innovative tools in order to improve existing monitorin schemes: sensitive isotope analysis of micropollutants, development of biomarkers, bioindicators and bioassays.