Structure of a monitoring unit (Ralf Trabitzsch, UFZ)

Project title: Steigerung des mikrobiellen Abbaus von Kohlenwasserstoffen in der ungesättigten Bodenzone durch die gezielte Injektion von Nährstoffen
(Project title – English translation: Increasing the microbial degradation of hydrocarbons in the unsaturated soil zone using the specific injection of nutrients)

Short project description:
Microorganisms can mineralise pollutants to carbon dioxide by degradation processes naturally occurring in soil. Adding nutrients and trace elements via artificial irrigation these biological processes can be supported and accelerated. Within the micro-fertilization field experiment, the stimulation of microbial degradation of residual pollutant phases, primarily BTEX, by regular fertilization applying an in situ ENA approach will be monitored, detected and quantified.

In order to measure an increase in the microbial degradation of hydrocarbons qualitatively and quantitatively, two test fields will be founded on which two monitoring units will be installed. These units consist of measuring points for groundwater and soil gas as well as monitoring technology for pore water and soil moisture. While one of the test fields serves as a reference field (irrigation with water only), the second test field will be fertilised with a nutrient and trace element solution. Soil samples from different depths can be used to track the vertical distribution of the fertiliser front within the unsaturated soil zone and to identify and characterise potential degradation processes. The installation of soil gas gauges allows the determination of the oxygen content and the isotope ratio of methane and carbon dioxide of the soil gas at different depths.

All data generated in the field experiment as well as the data from preliminary exploration and detailed field exploration is transferred to a site model. The geological and hydrogeological conditions of the project site are summarised within the context of a structural model. This structural model serves as the basis for a stationary and transient flow model, respectively, established for the simulation of the unsaturated soil zone. In parallel, based on the flow model, a mass transfer model will be compiled which, in conjunction with analytical data from pore water chemistry, will be able to determine the spatial distribution of individual nutrient groups in the subsurface. The transient flow and transport model will be extended to a reactive transport model using the program PHREEQC.

Project duration: 05/18 - 12/19

Funding organisation: Landesanstalt für Altlastenfreistellung (LAF), Mitteldeutsche Vermögensverwaltungsgesellschaft mbH (MDVV)

At the Department of Environmental Informatics, research for this project is being conducted at the workgroup Complex Groundwater Systems.

Project website: not available