Autonomous sensor for in situ measurements of total alkalinity in the ocean

Schaap, Allison ORCID: https://orcid.org/0000-0001-5391-0516; Papadimitriou, Stathys; Mawji, Edward; Walk, John; Hammermeister, Emily ORCID: https://orcid.org/0000-0002-1739-761X; Mowlem, Matthew; Loucaides, Socratis ORCID: https://orcid.org/0000-0001-5285-660X. 2025 Autonomous sensor for in situ measurements of total alkalinity in the ocean. ACS Sensors, 10 (2). 795-803. 10.1021/acssensors.4c02349

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Text Copyright © 2025 The Authors. Published by American Chemical Society schaap-et-al-2025-autonomous-sensor-for-in-situ-measurements-of-total-alkalinity-in-the-ocean.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (4MB) | Preview

Abstract/Summary

Total alkalinity (TA) is one of the measurable parameters that characterize the oceanic carbonate system. A high temporal and spatial frequency in TA data can lead to better measurements, modeling, and understanding of the carbon cycle in aquatic systems, providing insights into problems from global climate change to ecosystem functioning. However, there are very few autonomous technologies for in situ TA measurements, and none with field demonstrations below 2 m depth. To meet this need in marine observing capabilities, we present a submersible sensor for autonomous in situ TA measurements to full ocean depths. This sensor uses lab-on-a-chip technology to sample seawater and perform single-point open-cell titration with an optical measurement. It can carry multiple calibration materials on board, allowing for routine recalibration and quality checks in the field. The sensor was characterized in the laboratory and in a pressure testing facility to 600 bar (equivalent to 6 km depth) and deployed in a shallow estuary, on a lander at 120 m depth, and on an autonomous underwater vehicle. With a demonstrated precision and accuracy regularly better than 5 μmol kg–1 in field deployments, this sensor has the potential to dramatically expand our ability to perform long-term autonomous measurements of the marine carbonate system.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1021/acssensors.4c02349
ISSN:	2379-3694
Additional Keywords:	total alkalinity, sensor, lab-on-chip, autonomous instruments, ocean carbonate system
Date made live:	04 Mar 2025 14:53 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/539012

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