Suchergebnisse

8 páginas, 3 tablas, 5 figuras ; The concentrations of Pt in sediments, water and suspended particulate matter (SPM) were determined in the Lérez River estuary (Pontevedra Ria, NW Iberian Peninsula) on two sampling dates in 2008 and 2011, by means of catalytic adsorptive stripping voltammetry. Average concentrations in sediments (1.2 ± 0.5 ng g− 1; n = 13) corresponded to an enrichment factor of 2–4 compared to background values, and were in the range of those found in the SPM during the 2011 sampling (2.1 ± 2.4 ng g− 1; n = 15), but significantly lower than those in 2008 SPM (8.0 ± 4.4 ng g− 1; n = 15). Higher dissolved Pt concentrations were also found in 2008 (0.21 and 0.62 pM in the freshwater and seawater end-member) compared to the 2011 campaign (0.03 — freshwater and 0.40 pM — seawater end-member). Concentrations in the seawater end-members exceed those of typical North Atlantic waters, suggesting inputs of this element within the estuary. The extremely low value for the freshwater end-member in 2011 appears to be among the lowest Pt concentrations ever reported in the literature. Non-conservative behavior of Pt during estuarine mixing was observed on both sampling dates. Particle–water distribution coefficients (KD) show a decrease with salinity, in agreement with speciation calculations, which predict a transfer from neutral Pt(II) (as Pt(OH)2) in freshwater to negatively charged Pt(IV) (as PtCl5(OH)2 −) species in seawater. Such behavior during estuarine mixing can play an important role in Pt mobilization from contaminated particles discharged into estuaries and coasts. ; This work was funded by the Galician Government (Xunta de Galicia) through the project ref. 08MDS036000PR, and the Spanish Ministry of Science and Innovation through the project P.I. 200830I150 ; Peer reviewed

8 páginas, 9 figuras, 1 tabla ; The cycling of nutrients (silicate, nitrate, ammonium and phosphate) in a quasi-pristine barrierelagoon complex (Louro Lagoon, NW Iberian Peninsula) was studied both in a diel and temporal timescale covering different seasonal conditions. Hydrographical and meteorological conditions exert a major control on the nutrient cycling in the lagoon. From late autumn to early spring the lagoon is characterized by oxic conditions due to significant freshwater inputs and sporadic communication with the sea. In summer, elevated primary production coupled with water stagnancy leads to bottomwaters hypoxia and marked diel variation of pH, oxygen and redox potentials. Diel variation of nutrients was only evident when mixing of surface and bottom waters during the night was observed. Temporal changes in nutrients concentrations and their relative abundance were found to induce a clear shift in the phytoplankton composition. In winter, during silicate and nitrate abundance and low phosphate, diatoms predominate. In summer, under hypoxic conditions, sediments take control on the supply of nutrients leading to increased phosphate availability relative to nitrate/ammonium or silicate. Diatoms are then replaced during the summer blooms e linked to low atomic N:P ratios (typically <2) e by flagellates and green algae with minor contributions of cyanophytes and dinoflagellates. ; This work was funded by the Galician Government (Xunta de Galicia) through the project ref.08MDS036000 PR. The C.S.I.C., under the program JAE-PreDoc (Junta para la Ampliación de Estudios) cofunded by the Fondo Social Europeo (FSE), is greatly acknowledged for the predoctoral fellowship to D.E. López-Sánchez. ; Peer reviewed