Evaluation of Discrete and Passive Sampling (Diffusive Gradients in Thin-films – DGT) Approach for the Assessment of Trace Metal Dynamics in Marine Waters – a Case Study in a Small Harbor

Two complementary approaches, based on discrete and passive samplings (diffusive gradients in thin-films DGT), supported by the speciation modeling, were evaluated for the assessment of distribution and operational speciation of trace metals (Zn, Cd, Pb, Cu, Ni and Co) within a small marine harbor (Rijeka, Croatia). Concentrations of dissolved metals were relatively low and comparable to, or slightly above those found in coastal Adriatic region. Compared to higher variability of dissolved metal concentrations due to the discrete sampling, smoother temporal distribution was recorded for DGT-labile metals. The percentages of DGT-labile metal concentrations, which reflect their affinity to organic matter, varied among metals with the following order: Cu<Zn≈Co<Ni<Cd≈Pb. DGT-labile metal concentrations predicted by speciation modeling were in a good agreement with the measured ones for Zn, Cd and Ni, while they are underestimated for Pb and Cu, and overestimated for Co. In-situ DGT technique is recommended for the assessment of the water quality status in marine environment.