Naslov
Distribution and speciation of trace metals in the Krka River estuary (Croatia) accessed by DGT and voltammetry

Autori
Cindrić, Ana-Marija ; Garnier, Cedric ; Oursel, Benjamin ; Salaun, Pascal ; Pižeta, Ivanka ; Omanović, Dario

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Conference on DGT and the Environment : abstracts / Belzunce, M.J. ; Jolley, D. ; Luo, J. ; McLaughlin, M. ; Zhang, Hao - Lancaster, 2013, 17-17

Skup
DGT conference 2013

Mjesto i datum
Lancaster, Ujedinjeno Kraljevstvo, 08.07.2013. - 11.07.2013

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
DGT

Sažetak
The Krka estuary is linking the unpolluted karstic Krka river to Šibenik bay (Croatia) in the East of the Adriatic Sea. The estuary is oligotrophic with low organic matter and low naturally occurring trace metals content. It is permanently vertically stratified along its total 22 km length, with strong salinity gradient of more than 20 salinity units within 1 meter, usually located at ca. 2 m depth. Hydrological conditions (Krka river flow) are the main factors that controls the thickness and the salinity of the upper brackish layer (at a seasonal scale), while weather (wind, precipitation) has an influence on shorter time scale (days to weeks). To gain insights into the chemical distribution and behavior of trace metals in the estuary, several surveys were undertaken between 2008 and 2012 (winter and summer periods). The distribution of trace metals along estuarine transect was studied at 15 sites (3 depths per site) during 2 contrasted seasons. A high- resolution surface mapping (40 sites) of Šibenik bay was done in summer to identify the main sources of trace metals. Finally, two sites (considered as “clean” and “polluted”, respectively) were selected in Šibenik bay for detailed study of trace metals dynamic using diffusive gradient in thin film (DGT) and anodic (ASV) and cathodic (CSV) stripping voltammetry. DGT devices with open and restrictive pores were deployed at six depths for 5 days (during a total of 5 separate campaigns). Discrete samples were daily collected (once or twice a day) at each depth to make up composite samples in which dissolved and total metal concentrations (Zn, Cd, Pb, Cu, Ni, Co), were determined by voltammetry in addition of Cu complexation parameters (ligand concentration and stability constants). DGT-labile metal concentrations were measured by HR ICP-MS and compared to voltammetric results (Thermo Element 2). In summer periods, a significant increase of metal (especially Cu) concentrations was occurring in surface (brackish) layer which is attributed to an increased nautical traffic releasing metals from anti-fouling paints. In the bottom seawater layer, which has countercurrent comparing to surface layer, an upstream increase of metal content was recorded due to the progressive enrichment of that layer by metals scavenged from the more polluted upper (surface) layer. As expected, highest concentrations of metals were found in nautical marinas and Šibenik harbor. Vertical distribution of DGT labile metals displayed the same decreasing trend with depth as the one observed for total dissolved metals. The percentage of DGT-labile metal was >90% for Cd, ~60% for Ni, ~50% for Pb and >20% for Cu but varied due to the different affinity of metals to dissolved organic matter (DOM), as well as different metal/DOM ratios. Although expected to be markedly lower, DGT-labile metal concentrations measured using restrictive pore devices were only slightly lower (<10 %) than those obtained using open pore probes. In some cases, higher concentrations were even obtained at restricted pore devices. In addition, a performance of DGT devices for measurement of Mo, V and U in estuary conditions was also examined. Voltammetricaly- labile metals were determined at natural pH and compared to DGT-labile ones. Good agreement was obtained and similar labile concentrations found by both techniques, despite different accumulation periods and different characteristic times.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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