engleski

Evaluation of Diffusive Gradients in Thin films technique for short-term and long-term assessment of trace metals at potentially polluted costal sites

Despite low concentrations of trace metals (TM) in natural waters, some of them are listed as priority pollutants - Hg, Cd, Pb, Ni, Cu. One of the major pollution sources to coastal waters are nautical marinas and harbours. Besides characterized by elevated levels of TMs, a high variability in TM concentrations occurs in these regions. Consequently, a classical discrete sampling is not adequate sampling methodology and passive sampling, such is diffusive gradients in thin films (DGT) is preferred. In this study we examined the applicability of DGT technique for short-term and long-term study of TM in marine/estuarine environments. A small marine harbour in Rijeka town was examined for 5-months period, with sequential DGT deployment over 2-weeks period. Two estuarine locations specified as “clean” and “polluted” ones within Šibenik bay were examined during different seasons, applying 5-days deployment period. Discrete samples were also taken: each 2 weeks at Rijeka harbour, and once or twice each day at Šibenik bay resulting in 6 composite samples. In addition, a speciation modelling was performed for comparison purposes, whereas labile Cu was also measured by anodic stripping voltammetry (ASV) for study performed in Šibenik bay. No correlation between dissolved and DGT-labile concentrations was obtained in Rijeka harbour due to rare discrete sampling, indicating high temporal variability of TM. The percentages of DGT-labile metal concentrations varied among metals with the following order: Cu<Zn~Co<Ni<Cd~Pb. Thanks to frequent discrete sampling, a very good agreement between vertical profiles of DGT- labile and dissolved TM concentrations at both sites in Šibenik bay were obtained. The fraction of DGT- labile TM, that reflects their binding to natural organic ligands, ranged from <20% for Cu to >90% for Cd. A linear relationship between ASV-labile and DGT-labile Cu concentrations was obtained, with slightly lower concentrations measured by ASV. Measured and predicted DGT-labile concentrations of TM agreed well if partial accumulation of organic complexes is considered by the model. DGT technique can be successfully used to determine potentially bioavailable TM concentrations in estuarine conditions and is preferable for monitoring purposes. Acknowledgement: This research was realized within MEBTRACE project (IP-2014- 09-7530), financially supported by the Croatian Science Foundation.

trace metals ; estuary ; DGT

nije evidentirano