Suchergebnisse

14 páginas, 4 tablas, 10 figuras ; The Water Framework Directives aims a reduction in concentration of hazardous substances in the marine environment. Consequently, there is a need to distinguish between anthropogenically influenced metal concentrations from natural background levels. To better achieve this goal in the Portuguese coast, dissolved and particulate trace metal (TM) concentrations along the Portuguese coast were determined in 46 sites distance 1–3 km from the shoreline. Dissolved values ranged within the following intervals: 0.01–0.89 nM for Cd, 0.01–3.37 nM for Co, 0.90–45.4 nM for Cu, 3.30–140 pM for Hg, 1.88–15.1 nM for Ni, 0.01–0.15 nM for Pb and 1.40–62.0 nM for Zn. Whereas Cd, Co, Cu, Ni and Zn were enhanced in the southern coast, while Pb values were higher in the central part of the western coast. Mercury concentrations showed punctual increases all along the coast. Values of trace metals in suspended particulate matter varied in a broad range: 36–2902 μmol g−1 for Al, 0.10–15.1 nmol g−1 for Cd, 1.50–165 nmol g−1 for Co, 50.0–990 nmol g−1 for Cu, 2.80–76.4 nmol g−1 for Hg, 22–1471 nmol g−1 for Ni, 10.0–347 nmol g−1 for Pb and 416–10,981 nmol g−1 for Zn. Higher values for Al, Ni and Co were found in the central part of the western coast. However, Cd, Cu, Pb and Zn increased their levels from the north coast towards the central and south areas. The variability of both dissolved and particulate metals appears to be mainly associated with oceanographic conditions and continental inputs at North and central areas of the coast, and in the south coast to geological features rather than to anthropogenic pressures. On the basis of these results, regional baseline concentrations are proposed for the three typologies in Portuguese coastal waters defined under the Water Framework Directive ; Dr. Santos-Echeandia would like to thank the Basque Government for financial support (post-doctoral contract). ; Peer reviewed

11 páginas, 3 tablas, 7 figuras ; Oceans constitute one of the most important reservoirs for mercury. In order to provide a first insight into the concentrations of Hg species in the Atlantic sector of the Southern Ocean a sampling campaign was carried out south of the Polar Front. Water samples taken at discrete depths from the surface down to 300 m at six stations were analysed for total Hg (HgT), methylmercury (MeHg) and other interpretative parameters such as salinity, temperature, dissolved and particulate organic carbon, dissolved oxygen, chlorophyll and inorganic nutrients. Results showed a high spatial variability in the concentrations of HgT and MeHg. HgT (0.93±0.69 ng L−1) and MeHg (0.26±0.12 ng L−1) levels were similar or higher than those reported in previous works in high latitude studies. The highest values were found at a location (−53°, 10°E) south of the South Polar Front, an area of strong gradients caused by the mixing of different water masses. Vertical profiles showed a great variability even for those stations sampled at the same location or an area dominated by the same oceanographic features. A decrease of HgT and a consequent increase in MeHg with depth was observed in some sites, suggesting the occurrence of Hg-methylation process, while at other stations, a concurrent decrease or increase of both mercury species was observed. In spite of these differences, an overall positive correlation between HgT and MeHg was observed. Differences between vertical profiles of Hg species were attributed to favourable environmental conditions for Hg methylation. The highest proportion of MeHg (% of HgT) was observed in sites with low dissolved oxygen or highest estimated remineralization rates. The results obtained in this study show that the Hg distribution and speciation in the Atlantic sector of the SO is comparable (or in some sites higher) to the ones published for the other open ocean regions. However, the concentrations of MeHg in this area are more dependent on the environmental conditions than on the total concentration of Hg present in the water ; JC, AP and EA acknowledge Fundação para a Ciência e Tecnologia for project UID/QUI/00100/2013 and for the InvFCT2013 grant. LML and JSE were funded by the MINECO of Spain (Grant CGL2010-11846-E) and the Government of the Balearic Islands (AAEE083/09, co-funded by FEDER) ; Peer reviewed