engleski

Electrochemical determination of copper complexing capacity in the surface layer of the coastal central Adriatic Sea

We studied the effect of atmospheric organic matter deposition on the Cu2+ complexing capacity (CuCC) in the surface seawater layer of the Middle coastal Adriatic, especially evident in the sea- surface microlayer (SML) during the period of retrieval of the oligotrophic conditions (February-July 2019). We applied differential pulse anodic stripping voltammetry (DPASV) in conjunction with static mercury drop working electrode. The obtained experimental data were fitted into the Langmuir/Gerringa nonlinear mathematical model built in the ProMCC software to determine CuCC parameters (organic ligand class, its concentration and apparent stability constant). We defined the optimal experimental conditions: Ea = -0.6 V, ta = 120 s, Ed = -1.4 V for 1 s, [Triton-X-100] = 1 mg/L. The presence of L2 class ligands ([L2] = 28 – 392 nM) was determined in all SML samples, while L1 class ligands were found only in four samples, with concentrations ranging from 41 – 76 nM. The determined concentrations of L2 class ligands in the underlying water (ULW) ranged from 20 – 70 nM, while no ligands belonging to L1 class were determined. Values of conditional stability constants for the SML samples were in the range log KCuL1 = 10.34 – 11.11 and log KCuL2 = 8.32 – 10.02, and for the ULW samples log KCuL2 = 9.51 – 10.18. The SML showed enrichment with organic ligands by a factor of 0.9 – 9.1 relative to ULW, with the highest concentrations of organic ligands present in SML originating from the specific atmospheric deposition of pollen in April 2019. The deposition of open fires and Saharan dust aerosols in the study period did not have a significant effect on CuCC parameters. The free Cu concentrations (2 – 46 pM) were in the range of the estimated toxic Cu concentration limits.

Aerosol ; Anodic stripping voltammetry ; Atmospheric deposition ; Copper speciation ; Sea-surface microlayer

nije evidentirano