Lab-on-Chip Total Alkalinity Sensor for Highly Resolved, Efficient, and Long-Term Monitoring, Reporting, and Verification of Ocean Alkalinity Enhancement

Increasing atmospheric CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> from human activities is causing shifts in marine chemical and biological cycles. Ocean Alkalinity Enhancement (OAE) shows promise as a potential carbon dioxide removal (CDR) solution. However, comprehensive measurement, reporting, and verification (MRV) of OAE is required for the development and deployment of OAE as a CDR technology. The current observational approaches are not yet standardized or readily available to assess early-stage field trials. In this study, we report using a microfluidic lab-on-a-chip total alkalinity sensor in an OAE field experiment conducted in Tuft's Cove, Halifax, Canada to monitor seawater alkalinity during and after the addition of an alkaline mineral. To the authors knowledge, this is the first reported lab-on-chip sensor used in support of OAE mCDR. Over a 40-day period, our sensor collected 374 measurements along with 60 on-board standard measurements with the measurement frequency of one measurement per three hours. We report a precision of 9.2 μmol/kg which is the standard deviation of the CRM measurements. The data obtained during this trial demonstrates the capability of our technology for total alkalinity monitoring at OAE sites for long periods.