Résumé
Concentrations of total dissolved arsenic and selenium were determined in the well-stratified Krka estuarine system (Yugoslavia) during low and high water flow periods (March 1987 and May 1988, respectively). In addition, arsenite was measured during the May 1988 survey. The river concentrations of As (1.7 nM) and Se (2.45 nM) reflect the karst lithology of the drainage area and the absence of significant sources of contamination. Dissolved arsenic and selenium behave conservatively in the river surface plume, whereas arsenite appears to be reactive and correlates well with chlorophyll
a. In the bottom layer, dissolved As and Se concentrations generally increase from the downstream young seawater to the upstream old saline water. An enrichment of arsenite, total dissolved arsenic and selenium is observed at the freshwater-seawater interface. This could be attributed to the ‘regeneration’ of As and Se from the degradation of plankton-derived organic matter which accumulates at the halocline.