(459d) Recovery of Dissolved Organic Carbon (DOC) From Seawater Using Coupled Reverse Osmosis and Electrodialysis (RO/ED)

The study of dissolved organic carbon (DOC) in seawater offers insight into processes that occur in the global carbon cycle. The amount of DOC in seawater (1 mg/L) is very small compared to the amount of salt (35,000 mg/L) and therefore desalting of large sample volumes is necessary to recover the amount needed for analysis (up to 500 mg). Techniques for recovering the DOC from seawater include ultrafiltration, solid phase extraction onto adsorbents, and more recently coupled reverse osmosis and electrodialysis (RO/ED). The first two techniques have typically yielded less than a third of the DOC in seawater, whereas RO/ED has yielded ≈75% of the DOC in seawater. In the present work, the hybrid RO/ED technique was used to desalt and concentrate four 400 L seawater samples, including two surface and one deep ocean sample, to recover DOC. On average, 99.998% of the conductivity and 98.5% of the water volume were removed. Yields of the DOC for the surface samples are 74.9%. The analysis of DOC promises not only molecular and structural information of the DOC, but also of the original biomolecules and its changes, which can be utilized in global carbon models.