2022 Early Hearing Detection & Intervention Virtual Conference
March 13 - 15, 2022
5/26/2021 | 8:30 AM - 10:30 AM | CALCULATING FRESHWATER pCO2: COMPARING THE ACCURACY OF SPECTROPHOTOMETRIC AND ELECTROCHEMICAL pH MEASUREMENTS FOR EQUILIBRIUM CALCULATIONS IN FRESHWATER SYSTEMS | Virtual Platform
CALCULATING FRESHWATER pCO2: COMPARING THE ACCURACY OF SPECTROPHOTOMETRIC AND ELECTROCHEMICAL pH MEASUREMENTS FOR EQUILIBRIUM CALCULATIONS IN FRESHWATER SYSTEMS
Inland waters are increasingly recognized for their role in the global carbon cycle, yet uncertainties involved in freshwater carbonate system calculations, i.e., the partial pressure of CO2 (pCO2), remain. This study compares spectrophotometric (indicator based) and electrochemical pH measurements and their application for calculation of pCO2. The accuracy and uncertainty of calculated pCO2 was determined from three different pH measurements (spectrophotometric pH, a laboratory grade pH electrode, and a field-ready pH electrode) along with total alkalinity (AT), temperature, and ionic strength. Our study found that, compared to an infrared reference method, pCO2 was overestimated with pH electrodes (+193 ± 200 µatm) but found good agreement with measured pCO2 values calculated from spectrophotometric pH (+10 ± 39 µatm). To further validate these results, a field study using autonomous sensors was undertaken. During this deployment, we found an average error in calculated pCO2 of 15 ± 75 µatm. This study highlights the need for more accurate pH measurements for pCO2 calculations. These findings will improve future freshwater pCO2 calculations and thus better quantify inland waters’ role in the global carbon budget.
- Greenhouse gases
- Biogeochemistry
- Global change
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Presenters/Authors
Fischer Young
(), University of Montana, Department of Chemistry and Biochemistry, fischer.young@umconnect.umt.edu;
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Qipei Shangguan
(), University of Montana, qipei.shangguan@umontana.edu;
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Cory Beatty
(), University of Montana, Department of Chemistry and Biochemistry, cory.beatty@mso.umt.edu;
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Michael DeGrandpre
(), University of Montana, michael.degrandpre@umontana.edu;
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