VALIDATION AND IN-SITU APPLICATION OF AN AUTOMATED DISSOLVED NICKEL MONITOR FOR ESTUARINE STUDIES

The validation of a fully automated dissolved Ni monitor for in situ e stuarine studies is presented, based on adsorptive cathodic stripping voltammetry (AdCSV). Dissolved Ni concentrations were determined follo wing on-line filtration and UV digestion, and addition of an AdCSV lig and (dimethyl glyoxime) and pH buffer (N-2-hydroxyethylpiperazine-N'-2 -ethanesulphonic acid). The technique is capable of up to six fully qu antified Ni measurements per hour. The automated in situ methodology w as applied successfully during two surveys on the Tamar estuary (south west Britain). The strongly varying sample matrix encountered in the estuarine system did not present analytical interferences, and each sa mple was quantified using internal standard additions. Up to 37 Ni mea surements were performed during each survey, which involved 13 h of co ntinuous sampling and analysis. The high resolution data from the wint er and summer tidal cycle studies allowed a thorough interpretation of the biogeochemical processes in the studied estuarine system. (C) 199 8 Elsevier Science B.V. All rights reserved.