PRELIMINARY-STUDY OF DOC IN THE TAMAR ESTUARY, UK, USING UV-PERSULFATE AND HTCO TECHNIQUES

A comparative study of techniques for the determination of dissolved organic carbon was conducted on estuarine waters. High-temperature catalytic oxidation was performed using the home-built system-of Sugimura and Suzuki (Mar. Chem., 24: 105-131 (1988)) and a commercially available Shimadzu TOC-500, and wet-chemical oxidation was carried out with a UV-persulphate system. Interpretation of relative oxidation efficiencies is discussed in light of the procedures adopted for instrument calibration and determination of appropriate blank values. Data from UV-persulphate are generally lower than from both HTCO techniques. Large differences are observed in low-salinity waters, where colloidal concentrations are highest. Contrasting behaviour between HTCO systems is possibly due to compositional differences in dissolved organic matter with varying susceptibility to each oxidation technique. UV-persulphate derived data appear to demonstrate conservative behaviour whereas both sets of HTCO values are non-conservative; this finding confirms previous reports from the Severn and Delaware Estuaries, respectively.