Work

Estimation of mineral saturation and CO2 partial pressure in natural waters using electrical conductivity and pH: A fast and versatile on-site tool

Year: 2025

Type: article

Abstract: Our study presents a methodology designed for estimating the saturation index (SI) of halite, gypsum, anhydrite, and calcite, as well as the partial pressure of CO2 (logPCO2), by using easily measurable water parameters: electrical conductivity, temperature, and pH.The approach eliminates the need for several chemical analyses, allowing an efficient on-site application. PHREEQC, which was also used for generating databases of water compositions for single (NaCl, CaCO3 and CaSO4) and mixed-salt systems. Multiple linear regression (MLR) equations were further developed to enhance estimations and provide practical expressions.The estimations for the NaCl and CaCO3 systems have a greater accuracy when compared to those for the CaSO4 system. MLR equations improve significantly the estimation accuracy over the theoretical equations, both in single and mixed systems. The validation against experimental and natural karst water datasets from the Rull Cave area (SE Spain) demonstrates that the theoretical equations reliably estimate SI and logPCO2 for ion proportions relative to a single-salt system below 20%, with optimal accuracy at proportions below 10%.This methodology is an efficient tool for evaluating water-mineral equilibrium, particularly in karstic systems, by identifying oversaturation states, assessing CO2 equilibrium conditions, and guiding sampling site selection. Our research offers a methodology apt for geochemical studies in natural and engineered systems, highlighting the critical role of electrical conductivity in hydrogeochemical modeling.

Source: Journal of Hydrology

DOI: 10.1016/j.jhydrol.2025.133474

Authors: D. Benavente, M.C. Ruiz, N. García-Martínez, M. Vergara, A. Fernandez-Cortes, S. Sanchez-Moral

Institutions: University of Alicante, University of Almería, Consejo Superior de Investigaciones Científicas, Museo Nacional de Ciencias Naturales

Language: English

Topic: Karst Systems and Hydrogeology

Subfield: Earth-Surface Processes

Field: Earth and Planetary Sciences

Domain: Physical Sciences

SDG: Clean water and sanitation

Open Access status: hybrid

Estimated APC paid: $4,030