POPab - Persistent organic pollutants in Old Mining - investigations into relevant organic groups

Country / Region: Germany / Lower Saxony

Begin of project: July 1, 2022

End of project: August 29, 2024

Status of project: August 29, 2024

Sedimentation basin Source: Selina Hering

As part of this project, the occurrence and behavior of organic pollutants within a floating iron film in the sedimentation basin of an abandoned mine were investigated. Such floating iron films have previously been documented in natural environments such as wetlands and estuaries, where they form through both microbiological and abiotic processes. However, their occurrence and contamination with organic pollutants in anthropogenically influenced systems, such as former mining sites, remain largely unexamined in the existing literature.

The aim of the project was therefore to investigate the chemical composition and structure of the iron layer, as well as the mobilization and transport of contaminants from the mining side into surrounding ecosystems.

We conducted three field campaigns in February 2023, and in February and June 2024. Analytical results demonstrated that the floating iron films contained elevated concentrations of both anthropogenic organic contaminants and geogenic inorganic substances. A passive sampling approach enabled the detection of contaminant fluxes from the floating iron film into surface waters. Furthermore, the distribution patterns (fingerprint) of polycyclic aromatic hydrocarbons (PAHs) provided insights into the sources of contamination, supporting the hypothesis of pollutant emission and transport from mining side into the aquatic environment.

Sampling Source: Selina Hering

Ongoing investigations aim to better understand the formation mechanisms and transport dynamics of these contaminated floating iron films. Preliminary laboratory experiments indicate that hydrophobic, non-polar organic compounds affect iron floatation and aggregation behavior. These substances appear to enhance the stability of the floating iron film, thereby facilitating the persistence and mobility of associated pollutants.

Vehicle for sampling Source: Selina Hering

Milestones / Aims

• (Literature) research on the use and use of organic pollutants in mining.
• Development of a suitable sampling strategy for different matrices (e.g. water, sediment and floating iron layers) and planning/organisation of underground sampling.
• Obtaining samples for analysis of both chemical composition (inorganic and organic substances) and biological and structural characteristics. Identifying the source of pollutant and detecting pollutant transport.