Induced Polarization as a Proxy for CO2-Rich Groundwater Detection—Evidences from the Ardennes, South-East of Belgium

Agathe Defourny,Arnaud Collignon,Alain Dassargues,Patrick Jobé,Thomas Kremer,Frédéric Nguyen

doi:10.3390/w12051394

Abstract

CO 2 -rich mineral groundwaters are of great economic and touristic interest but their origin and circulation paths in the underground are often poorly understood. A deeper understanding of the system plumbery and the development of non—to minimally—invasive near-surface geophysical methods for the prospection of potential productive areas is therefore of great interest to manage future supply. The objective of this contribution is to assess the ability of the time-domain induced polarization (TDIP) method, combined with the electrical resistivity tomography (ERT) method, to make the distinction between CO 2 -rich groundwater from non-gaseous groundwater. Three combined ERT/TDIP tomographies were performed above known uplift zones in the south-east of Belgium where thousands of CO 2 -rich groundwater springs exist. On all profiles, important contrasts in both electrical resistivity and chargeability distributions were observed in the vicinity of the upflow zone, also reflected in the normalized chargeability sections computed from the measured data. Low resistivity vertical anomalies extending in depth were interpreted as a saturated fracture network enabling the upflow of deep groundwater to the surface. High chargeability anomalies appearing directly close to the CO 2 -rich groundwater springs were inferred to metallic oxides and hydroxides precipitation in the upper part of the aquifer, linked to pressure decrease and changing redox conditions in the up-flowing groundwater approaching the land surface. The combined interpretation of electrical resistivity and induced polarization datasets provides a very promising method for a robust prospection of CO 2 -rich groundwater.

Highlights

Sparkling mineral waters or CO2 -rich mineral waters occur in many places around the world, in various geological context most often associated to volcanic or mantellic activity
We investigate the use of another geo-electrical method called the time-domain induced polarization (TDIP) technique as a complementary method to electrical resistivity tomography (ERT) to detect, characterise and discriminate CO2 -rich groundwater springs from other springs [18]
Our objective is to investigate the ERT and TDIP signals produced by CO2 -rich groundwater in the Ardennes region, where numerous springs of CO2 -rich groundwater exist and to assess the interest of combining these two methods for a better exploration and characterization of those specific hydrogeological systems

Summary

Introduction

Sparkling mineral waters or CO2 -rich mineral waters occur in many places around the world, in various geological context most often associated to volcanic or mantellic activity. In Europe, CO2 -rich groundwater are observed in many regions of France [1,2], Germany [3], Poland [4], Italy [5], Portugal [6], for instance, and overseas in Morocco [7], Australia [8] and South Korea [9], among others They often trigger an intense economic and touristic activity (bottling, balneotherapy, spa and wellness), the detailed ’plumbery’ of the system, the gas origin and its interactions with groundwater often remain unclear and constitute an active research topic. Any network of deep fractures may create a preferential pathway for CO2 -enriched groundwater to upflow towards the surface

Objectives

Methods

Results

Discussion

Conclusion