This project compares the microbial community and geochemistry of groundwater in an open-loop Ground Source Heat Pump (GSHP) system to two local boreholes. GSHPs are a low carbon alternative to gas boilers however little is known on the effect on the biogeochemistry of the groundwater they interact. This project addresses the lack of knowledge using an open-loop GSHP in Cardiff, UK. Geochemical metadata can be found at the following link: https://webapps.bgs.ac.uk/services/ngdc/accessions/index.html#item177272