The SENECA project aims to provide first evaluations of gas concentrations and emissions from permafrost and/or thawing shallow strata and to derive a first estimate of the CO2 and CH4 emission at Southern Polar Hemisphere. The obtained results can also be used to assess uncovered new problems and opportunities, such as how the Antarctica environment can increase to permanent and temporal scale the global temperatures. The project is organized in four major tasks: (1) soil gas content and origin; (2) CO2 and CH4 degassing output; (3) geophysics exploration and petrographic characterization of the soils; (4) seasonal trend of CO2 soil concentration.

Geochemical data:

The geochemical dataset includes:

Soil gas sampling/flux measurements and GasPRO CO2 monitoring probes

Soil gas surveying consists in collecting gas samples from the active layer zone to measure the concentrations of some gaseous species in the soil pores. To avoid the major influence of meteorological variables, samples are collected inserting a steel probe vertically in the soil to a depth from 0.2 m to 0.6 m, depending by the thickness of the active layer. Soil gas samples are taken from the probe by using a 60 cc plastic syringe and stored in a 15 ml glass vials. The collected gas samples have been analyzed in Scott Base lab with a chromatographer (CP 4900 by Varian) to define the concentrations of the following gaseous species: He, Ne, H2, O2, N2, CH4, C2H2, C2H4, C2H6, CO2, H2S. Radon (222Rn) and Thoron (220Rn) have been measured directly in the field using Durridge RAD7 instrument performing three/four measurements with 5-minute integration time. A total number of 226 samples were collected in this first expedition.

Measurements of exhalation flux of CO2 and CH4 from the soil into the atmosphere have been conducted using the West System (West Systems TM) accumulation static closed-chamber method.

Continuous monitoring of CO2 concentrations in active layer bottom was started with the deployment of GasPro CO2 Monitoring Probe designed to measure temperature, pressure and CO2 concentration in the unsaturated soil horizon. CO2 concentration is measured via a Non-Dispersive Infra-Red (NDIR) sensor (model IRC‐A1 Alphasense). The probes are equipped with four batteries and a small solar panel that should last for 10 to 12 months (depending on the outside temperature), collecting 1 measurement/hour.

Water and permafrost sampling

We sampled shallow waters among 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 polyethene flacons for laboratory analysis in the following amount:

2 flacons of 50ml for major anions and cations

1 flacon of 50ml for minor and trace elements

1 flacon of 100ml for isotopic analyses

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

Major anions and cations were sampled on filtered and filtered and acidified samples, respectively. Minor and trace elements were collected on filtered and acidified samples. An unfiltered sample was collected for the determination of stable isotope analyses (δ18O, δD).

The analysis of the chemical composition of dissolved gases (He, Ne, H2, O2, N2, CH4, CO2), extracted from water samples collected in serum glass bottles and sealed by gas-tight rubber plugs according to the method of Capasso and Inguaggiato (1998), was carried out in the Scott Base Laboratory by using a Agilent 4900 CP Micro-gas chromatograph equipped with two TCDs and Ar as carrier gas. 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). Analytical error was <5%. A total number of 31 water samples were collected in this expedition.

In addition, 33 permafrost samples were collected. These samples were sampled by hitting the permafrost with a hammer and chisel and collecting the small pieces of still frozen permafrost in a serum glass bottles of 155 ml. The bottle was sealed and vacuum-packed by removing the air inside it using a needle and syringe. Once the permafrost samples were defrosted, the gas content in the bottles were measured (He, Ne, H2, O2, N2, CH4, CO2). These measurements were performed directly at Scott Base using the Agilent 4900 CP Micro-gas chromatograph.