Hydrogen peroxide, solute and methane released from crushing sedimentary rocks

Three sedimentary samples and a sediment sample from subglacial environments and from a previously glaciated terrain were crushed and incubated to investigate the potential for subglacial abrasion to generate H2O2 and release bio‑utilisable volatile fatty acids (VFA’s) and nutrients (N, Fe). Samples were broken up using either a pestle and mortar or mallet and plate. The 125um to 2mm fraction was then used in incubations (Coarse) or crushed further using a ball mill for 30 mins at 500rpm (Crushed). Approximately 1 g of sample was then incubated in serum vials at 4 °C with 15 ml of 18.2 MΩ water for 3 mins, 5 or 25 hours. Headspace gases were then analysed at each time point, after which the serum bottles were opened and the slurry was filtered using a 0.22 µm PES Steriflip® Vacuum Filtration System (Millipore). A 4 ml aliquot was then taken to analyse pH and H2O2 immediately after filtering, the remainder of the solution was frozen and used to analyse for SO42-, dFe, NH4+, acetate and formate.