Methods for Measurement of Dissolved Inorganic Carbon in Natural Waters.

Abstract

Knowing the concentrations of dissolved inorganic carbon (DIC) in natural waters is often important in studies of ecology and biogeochemistry. However, the available measurement methods remain relatively difficult and imprecise. Here we demonstrate that a commercially available, non-dispersive infrared (ND-IR) organic carbon analyzer can provide relatively accurate and precise (±2-3, μmol dm-3) DIC measurements. This precision, though less than the 0.5-1 umol dm-3 for the state-of-the-art instrument (CO2 coulometer), is adequate for many applications and the ND-IR instrument is easier to use. For transects and profiles of DIC in systems with moderate to large DIC variations or for discrete DIC productivity measurements, the TOC-5000's precision is generally sufficient. However, the precision of the coulometer remains necessary for marine DIC surveys.