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Copper complexing capacity in Krka river estuary, Eastern Aadriatic, Croatia

The copper complexing capacities (CuCC), were measured in the Krka river estuary. Krka river estuary is a carstic, salt wedge estuary situated on the Eastern coast of middle Adriatic area. The measurements have been done on the sampling stations along the estuary on different depths, i.e.in salt and fresh water layer.The measurements were done with electrochemical method of differential pulse anodic stripping voltammetry (DPASV). It has been found that the copper complexing capacity of the fresh water layer is several times higher (from 100 up to 270 nM) than of the saline layer beneath it (from 10 up to 130nM). The average result for CuCC measured in 2008, of 103 nM is not different from the average value measured by the same technique 25 years ago ( the average value of all measurements in 80-ties is 105 nM). The speciation modelling have shown that more than 99% of copper is present as organic complexes while free(hydrated) copper ion concentration is below the toxicity threshold of 10 -11 M, although in some situations total free (hydrated) + inorganically complexed copper could be above this threshold level.

copper ; estuary ; complexing capacity

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