Reaction path modelling framework for hydrochemical processes during Pumped Hydropower Storage in open-pit lignite mines – a new software to quantify the impact of pyrite weathering

The need for the modelling framework is based on being able to make a statement as to whether the operation of a Pumped Hydropower Storage (PHS) facility in a former open-pit lignite mine can have a negative impact on the water quality in the lower reservoir and associated aquifers. The research question arises since flooded lignite mines are often associated with acidification and/or increased sulphate and metal concentrations [1-2]. Thus, the software package allows for modelling geochemical processes during the PHS operation in open-pit lignite mines.

A new software has been set-up [3]: The reaction path modelling framework comprises a Python framework for data management and a solver for geochemical reactions (PHREEQC/PhreeqPy, [4-5]). The software is based on a conceptual geochemical model that includes the main geochemical processes that are expected to influence the hydrochemistry. It integrates different non-dimensional batch reactors, each representing the water composition of the reservoirs, and water sources or sinks in the PHS system (groundwater, rainwater, surface run-off, mine dump water). These waters are cyclically mixed with ratios deducted from flow rates and time-dependent influxes of a hypothetical PHS system. A strong focus is taken on pyrite weathering reactions. The implemented parallel processing of all chemical reactions enables minimum computational times.

[1] Schnepper, T., Kühn, M., Kempka, T.: Reaction path modeling of water pollution implications of pumped hydropower storage in closed open-pit lignite mines. Mine Water and the Environment, in review.

[2] Schnepper, T., Kapusta, K., Strugala-Wilczek, A., Roumpos, C., Louloudis, G., Mertiri, E., Pyrgaki, K., Orkisz, D., Najgebauer, D., Kowalczyk, D., Kempka, T.: Potential hydrochemical impacts of Pumped Hydropower Storage operation in two European coal regions in transition - the Szczerców-Bełchatów mining complex, Poland, and the Kardia Mine, Greece. Environmental Earth Sciences, in review.

[3] Schnepper, T., Kempka, T. (2024): Reaction path modelling framework for hydrochemical processes during Pumped Hydropower Storage in open-pit lignite mines. GFZ Data Services. https://doi.org/10.5880/GFZ.3.4.2024.002

[4] Parkhurst, David L.; Appelo, C.A.J. (2013): Techniques and Methods. https://doi.org/10.3133/tm6A43

[5] Müller, M., Parkhurst, D. L., Charlton, S. R. (2011). Programming PHREEQC calculations with C++ and Python a comparative study. EXCHANGE, 1(40), 632-636.