ROLE OF EFFLUENTS AS AFFECTING COPPER BIOAVAILABILITY IN CONTAMINATED RIVERWATER

The role of water chemistry on metal bioavailability was investigated in river water affected by effluent-originated contamination with the aim to evaluate the effect of interactions between metal and river water toxicity. Two Lambro river sites, located upstream and downstream of a highly industrialized area in Northern Italy, were selected as study area and compared for copper bioavailability. The high-sensitivity chronic test based on S. capricornutum 72h-growth inhibition was used within an experimental framework which was set-up combining TRE (Toxicity Reduction Evaluation) with WER (Water Effect Ratio) procedures. While discriminating between toxicants, the sample treatments of LiChrolut solid phase extraction (SPE) and EDTA addition proved to be effective showing the role of the dissolved organic matter on metal toxicity. In spite of the original toxicity found in the downstream water (Dw) sample, copper bioavailability was lower than expected when the metal was experimentally added, the Dw-WER being three times higher than the upstream water (Uw)-WER. Effluent-originated organic ligands are suggested to have an important role in metal complexation, thus reducing copper toxicity. The link found between effluent contribution and complexing capacity, however, suggests the risk associated to the variability over time and flow conditions of the effluent itself.