Limnology and Oceanography: Methods
An analytical system was developed to determine photochemically produced carbon dioxide in marine waters. Our system was designed to measure low levels of carbon dioxide by maintaining a closed system to prevent atmospheric contamination during sample preparation, irradiation, and analysis. To detect low levels of photoproduced carbon dioxide in seawater, background dissolved inorganic carbon (DIC) was removed before irradiation. To strip out DIC, samples were acidified to pH 3.0 (converting DIC to carbon dioxide) and bubbled with low carbon dioxide air. The pH was then readjusted back to the original value, and the resulting low-DIC seawater samples were transferred pneumatically to air-tight quartz tubes for irradiation. During analysis, samples were pneumatically transferred to a sample loop, injected, and acidified. Carbon dioxide was then stripped out, dried, and carried to a nondispersive infrared carbon dioxide analyzer. Calibration was done with a series of low concentration aqueous carbonate standards (0.05 to 3 μmol L-1). The detection limit, defined as the concentration corresponding to three times the standard deviation of the experimental blank (i.e., DIC-stripped seawater), was similar to ~60 nmol L-1. Method precision was largely dependent on the agreement between multiple injections from the same tube (< ± 2% relative standard deviation [RSD]) and the reproducibility between different tubes (±3% RSD). This method was used to measure carbon dioxide photoproduction in a variety of waters (e.g., estuarine, lake) including the first direct measurements in marine waters.
Original Publication Citation
White, E. M., Kieber, D. J., & Mopper, K. (2008). Determination of photochemically produced carbon dioxide in seawater. Limnology and Oceanography: Methods, 6, 441-453. doi:10.4319/lom.2008.6.441
White, Emily M.; Kieber, David J.; and Mopper, Kenneth, "Determination of Photochemically Produced Carbon Dioxide in Seawater" (2008). Chemistry & Biochemistry Faculty Publications. 118.