Abstract
Real-time measurements of carbonate ion concentrations in the ocean are critical to advancing marine environmental monitoring and research into deep-sea hydrothermal activity. Herein, we report the first example of deep-sea hydrothermal field exploration using a carbonate ion-selective electrode (ISE). The novel carbonate ISE was composed of a Ni wire as substrate, carbon film as transducers and carbonate-selective membrane layers. This paper describes the preparation process of the electrode and characterises its performance via scanning electron microscopy (SEM) and electrochemical analysis. The detection limit of the electrode for CO32− is 2.821 × 10−6 mol/L, the linear response range is 1.0 × 10−5–1.0 × 10−1 mol/L and the Nernst slope was −30.4 mV/decade. In April 2021, the carbonate ISE was mounted on multi-parameter sensors with pH and Eh (redox) electrodes for the search of hydrothermal activity at the Southwest Indian Ridge. The simultaneous potential anomalies appeared at this carbonate electrode with the pH and Eh electrodes when passing through the hydrothermal field. The study of the hydrothermal field was supported by the in situ camera video and the sulphide samples. Additionally, the carbonate electrode provides enhanced information of water chemistry for the study of the hydrothermal field.
Highlights
Carbon dioxide is one of the important greenhouse gases in the atmosphere, with around 28% of atmospheric CO2 being dissolved in seawater [1]
Accurate knowledge of carbonate levels in seawater is necessary to maintain the balance of marine ecosystems, while the implementation of realtime monitoring of carbonate ion concentrations in hydrothermal fluids is a major advance in the detection of hydrothermal fields [2,3,8,9,10]
A carbon film is plated on thecarbonate surface of the nickel wire by electrochemical Firstly, athen carbon film is plated on thefilm surface of the nickel by electrochemical methods, a carbonate-sensitive is applied to thewire surface of the carbon methods, plated a carbonate-sensitive film is applied to the surface of the carbon plated nickel nickel wire using the dipping method
Summary
Carbon dioxide is one of the important greenhouse gases in the atmosphere, with around 28% of atmospheric CO2 being dissolved in seawater [1]. Most of the commonly used methods for determining carbonate concentrations rely on laboratory analytical instruments such as gravimetric methods, colour change, equilibrium pressure, gas chromatography, infrared spectrophotometry and coulometric titration [11,12,13,14,15,16,17]. These analytical methods require sample pre-treatment, which is a complex, time-consuming and insensitive process, cannot
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