{'fraction_non_alphanumeric': 0.028151774785801713, 'fraction_numerical': 0.02447980416156671, 'mean_word_length': 4.797872340425532, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
The CO2FieldLab project: how to adapt a geochemical monitoring strategy to complex geological environments

Under the auspices of the CO2FieldLab project, a shallow CO 2 leakage experiment was conducted during the summer in 2011 in Norway. This experiment was designed to describe the CO 2 behaviour during an induced leakage, and consisted of an injection in saturated horizons followed by physical/chemical monitoring in both saturated and unsaturated horizons. The leakage site, the Svelvik ridge, is located in the Drammen Fjord, 50 km south-west of Oslo. The injection was performed at a c.a. 20 m depth in heterogeneous glacio-fluviatile formations. We are here focusing on the results obtained from the geochemical monitoring. The point monitoring of gas species present in the unsaturated zone allowed recording strong CO 2 enrichments (up to 15% vol.) in environments naturally poor in CO 2 (concentrations often lower than 0.5%) together with flushing of other gaseous species, mainly O 2 . This was concomitant with a strong imprint of the injected CO 2 on the carbon isotope composition ( 13 C) of the gas. Monitoring points with low CO 2 concentrations had natural 13 C CO2 ratios ranging between -16 to -21‰ VPDB, with values as low as -27‰ at the leakage paroxysm, clearly highlighting the isotope influence of the injected CO 2 (heavily depleted in 13 C with 13 C=-30.4‰). Upon results obtained during this point monitoring, we were able to adapt the monitoring strategy during the leakage experiment. Indeed, the heterogeneity of the Svelvik geological formations induced shifts in the plume upwelling trajectory that