SEA-TRIALS OF 3 DIFFERENT METHODS FOR MEASURING NONVOLATILE DISSOLVED ORGANIC-CARBON IN SEAWATER DURING THE JGOFS NORTH-ATLANTIC PILOT-STUDY

In 1989 the shipboard comparison of three different methods for measuring concentrations of dissolved organic carbon (DOC) resulted in reasonable agreement, with differences likely as a result of a combination of calibration offsets and general instability of the instruments at sea. Typical concentrations were about 80-140 mumol in the upper 1000 m of the water column, with a tendency towards higher values (100-150 mumol) in the surface waters. These elevated surface water levels are below the 200-300 mumol values recently reported for the Atlantic and the Pacific Oceans. In 1990 the small dataset obtained with a further modified High Temperature Combustion instrument showed similar trends. Within the analytical error there is no significant offset between two HTCO methods and one wet oxidation technique.