The geochemical dataset includes:

1. **Soil gas sampling/flux measurements:**

Soil gas surveying involves collecting gas samples from the active layer zone to measure the concentrations of various gaseous species in the soil pores. Samples were collected by inserting a steel probe vertically into the soil to a depth ranging from 0.2 m to 0.6 m, depending on the thickness of the active layer. Soil gas samples were taken from the probe using a 60 cc plastic syringe and stored in 15 ml glass vials. The collected gas samples were analyzed with a chromatograph (CP4900 by Varian) to determine the concentrations of the following gaseous species: He, Ne, H2, O2, N2, CH4, C2H2, C2H4, C2H6, CO2, H2S. Radon (222Rn) and Thoron (220Rn) were measured directly in the field using a Durridge RAD7 instrument, performing three or four measurements with a 5-minute integration time. A total of 231 samples were collected during this expedition. Measurements of exhalation flux of CO2 and CH4 from the soil into the atmosphere were conducted using the West System (West Systems TM) accumulation static closed-chamber method.

2. **Continuous monitoring of CO2 concentrations in the active layer:**

Continuous monitoring of CO2 concentrations in the bottom of the active layer was recorded. GasPro CO2 Monitoring Probes were designed to measure temperature and CO2 concentration in the unsaturated soil horizon. CO2 concentrations were measured using a Non-Dispersive Infra-Red (NDIR) sensor (model IRCA1 Alphasense). The probes collected one measurement per hour during the period 2020 - 2023 (with gaps) at strategic points within the Taylor and Wright valleys.

3. **Water samples:**

We sampled shallow waters from all streams, ponds, and lakes in the studied areas. Physical-chemical parameters such as water temperature, pH, redox potential (Eh), electrical conductivity, and alkalinity were determined in situ. Water samples were collected and stored in high-density polyethylene flasks for laboratory analysis in the following quantities:

- 2 flasks of 50 ml for major anions and cations

- 1 flask of 50 ml for minor and trace elements

- 1 flask of 100 ml for isotopic analyses

- 1 serum glass bottle of 155 ml for dissolved gases in the water.

Major anions and cations were sampled from filtered and acidified samples, respectively. Minor and trace elements were collected from filtered and acidified samples. An unfiltered sample was collected for the determination of stable isotope analyses (18O, D). The chemical composition analysis of dissolved gases (He, Ne, H2, O2, N2, CH4, CO2), extracted from water samples collected in serum glass bottles and sealed with gas-tight rubber plugs according to the method of Capasso and Inguaggiato (1998), was carried out in the Scott Base Laboratory using an Agilent 4900 CP Micro-gas chromatograph equipped with two TCDs and Ar as carrier gas. The dissolved gas composition (expressed in mmol/L at STP) was calculated from the composition of the exsolved gas phase based on the solubility coefficient of each gas compound (Whitfield, 1978). The analytical error was <5%. A total of 15 water samples were collected during this expedition.