Autonomous monitoring results at the AXH2-10 location (33°0′33″S, 115°51′5″E) from the 4th of May 2022 to the 17th of May 2022 and at the AXH2-13 location (33°0′18″S, 115°50′59″E) from the 18th of May 2022 to the 31st of May 2022 a) AXH2-10 atmospheric pressure (hPa). b) AXH2-10 temperature (°C). c) AXH2-10 carbon dioxide concentration (ppm). d) AXH2-10 hydrogen concentration (ppm – temperature corrected). e) AXH2-13 atmospheric pressure (hPa). f) AXH2-13 temperature (°C). g) AXH2-13 carbon dioxide concentration (ppm). h) AXH2-13 hydrogen concentration (ppm- temperature corrected) shown with restricted range 0–120 ppmin the main image and with full range 0–600 ppm cH₂ in the inset, demonstrating the scale of the spike observed on 19th May 2022. Blue dashed lines indicate periods of precipitation measured at the Bunbury Weather Station, Western Australia.