Search

Tellurium (Te) is a Technology Critical Element (TCE) and a relevant product of nuclear fission. It has an unknown environmental biogeochemical cycle, mostly related to current analytical challenges in measuring its ultra-trace dissolved concentrations in complex environmental matrices. It is therefore generally compared to its geochemical pair selenium (Se), which shows a narrow range between diet essentiality and toxicity properties. Batch experiments using isotopically-labelled stable Te and Se were performed with fresh suspended particulate matter (SPM) from the fluvial part of the Gironde Estuary, simulating both estuarine salinity (S = 0 vs S = 32) and turbidity (100 mg L−1 vs 1000 mg L−1) gradients to understand the importance of the particulate phases in Te reactivity under estuarine conditions and verify the resemblance to Se behaviour. These experiments addressed sorption kinetics, sorption isotherms and fractionation from selective extractions of final equilibrated SPM. Results showed a strong, salinity-independent affinity of Te for the particulate phases (log10 Kd ~ 4.9 L kg−1), following a Langmuir-type isotherm. Contrastingly, Se adsorbs clearly less to estuarine SPM (log10 Kd ~ 2.5 L kg−1), following a Freundlich-type isotherm. Both isotherms and selective extractions highlighted differences between Te and Se sequestration. Selective extractions suggested higher mobility of particulate Se in contrast to Te. Based on these results the paper sets a first dispersion scenario on the environmental fate of radioactive Te and Se after hypothetical nuclear power plant accidental releases in coastal aquatic systems such as the Garonne-Gironde fluvial-estuarine system.

15 pages, 1 table, 4 figures, Short-term variations of Pt concentrations and primary production indicators were compared in three contrasting coastal sites during spring bloom: (i) the Gironde Estuary mouth (SW France), (ii) the semi-enclosed Arcachon Bay (SW France), and (iii) the urbanized Genoa Harbor (NW Italy). At each site, surface seawater sampling and physical-chemical measurements were combined to study diel cycles (over 25 h) of dissolved Pt concentrations in seawater (PtD) and master variables reflecting primary production activity (chlorophyll-a, phaeopigments, and particulate organic carbon, POC concentrations). Plankton nets were used in all sites, providing for the first time plankton Pt concentrations (PtPK) over a whole diel cycle (Gironde Estuary mouth) and spot sampling (Arcachon Bay and Genoa Harbor) in the coastal zone. Bivalves (wild oysters or mussels), reflecting organisms at higher trophic levels, were also collected at all sites. The POC/Chl-a ratios in the collected particulate material suggested high contribution of phytoplankton to the particulate matter in the productive Gironde Estuary mouth. At this site, phytoplankton activity partly controlled Pt cycling and particle/dissolved Pt partitioning during daytime. During the night, zooplankton grazing may release Pt into the dissolved phase. These processes are partly masked by external factors such as tide or local Pt sources, especially in more confined and/or urbanized coastal water bodies such as the Arcachon Bay and the Genoa Harbor. Platinum levels in plankton and bivalves from these contrasting sites along the Atlantic and Mediterranean coasts tended to reflect the general Pt levels in seawater. These results clearly suggest that (i) Pt contamination of coastal waters and marine organisms has become a common feature in urbanized sites and (ii) Pt transfer to the marine food chain starts at the basic level of primary producers. By concentrating Pt (Bioconcentration Factor: BCF ~ 104), phytoplankton may serve as a biomonitor to assess Pt contamination in coastal environments, This work has benefited from the financial support of the FEDER Aquitaine-1999-Z0061, the COST Action TD1407, and the EU FP7 Ocean 2013.2 Project SCHeMA (Project-Grant Agreement 614002), which are gratefully acknowledged

Batch experiments were performed to study adsorption and desorption of 75Se and 113Sn radiotracers at environmentally representative concentrations of ~0.3 ng L−1 and ~3 ng L−1, respectively. The radiotracers were incubated with wet bulk sediments from the Gironde Estuary and the Rhone River, combining freshwater and coastal seawater salinity (S = 0, S = 32) and three different Suspended Particulate Matter (SPM) concentrations (10 mg L−1, 100 mg L−1, 1000 mg L−1) to simulate six hydrologically contrasting situations for each particle type. Results showed no measurable adsorption for 75Se under the experimental conditions, whereas >90% of 113Sn rapidly adsorbed onto the particles during the first hours of exposure. Adsorption efficiency increased with increasing SPM concentration and seemed to be slightly greater for the Rhone River sediments, potentially related to the intrinsic mineral composition. Desorption of spiked sediments exposed to filtered, unspiked freshwater and seawater only occurred for 113Sn (

Environmental contextEmerging contaminants such as platinum are continuously released into aquatic environments. Analytical challenges, however, have restricted information on their geochemical cycles. We examine the potential use of platinum as a tracer of anthropogenic inputs in a model industrial/urban site (Genoa Harbor, Italy), and provide a first estimate of dissolved platinum baseline concentrations in the northern Mediterranean coast. AbstractBiogeochemical cycles that include processes to control platinum (Pt) distribution remain widely unknown in aquatic environments, especially in coastal systems. Dissolved Pt concentrations in coastal seawater (PtD) and in suspended particulate matter (SPM, PtP) were measured, together with master variables comprising dissolved oxygen, dissolved and particulate organic carbon, chlorophyll-a, turbidity, and ammonium levels, along two longitudinal profiles in the industrial Genoa Harbor (north-west Italy). Concentrations and spatial distribution of PtD and PtP levels reflect distinct concentration gradients that were attributed to different Pt sources such as hospital, domestic and industrial wastewater, atmospheric deposition, and/or road runoff. Concentrations reaching up to 0.18ngL−1 PtD and 14ngg−1 PtP reflect the impact of Pt urban inputs to coastal sites. These first data highlight considerable anthropogenic contamination in a confined harbor compared with the proposed reference value for the western Mediterranean surface seawater measured at external sites. Identified correlations between Pt levels and human pollution signals suggest the potential use of Pt as a new tracer of anthropogenic inputs that can be applied to other urbanised coastal systems. Biogeochemical processes that induce changes in the partitioning and fate of Pt in coastal seawater reflect a spatial variability and highlight the need for comprehensive environmental monitoring at an appropriate spatial scale.

12 páginas, 4 figuras, 2 tablas.-- Melina Abdou ... et al., Platinum Group Elements (PGEs) are extremely scarce in the Earth's Crust and of strong interest for high-end technologies due to their specific properties. They belong to the Technology Critical Elements (TCEs) for which use is forecast to increase, implying growing emissions into the environment in the following years. In particular, with the intensive use of platinum (Pt) in car catalytic converters, the anthropogenic geochemical cycle of this element has surpassed the natural cycle. Yet, environmental Pt levels are still in the sub picomolar range, making its analytical detection a challenge. Few studies cover the behavior of Pt in marine waters in terms of speciation, reactivity and possible transfer to the biota. In this study, oysters (Crassostrea gigas) from an unpolluted estuary were exposed to the stable isotope 194Pt in seawater at a range of concentrations during 35 days. Seawater was renewed daily and spiked to three nominal Pt concentrations (50, 100, and 10,000 ng·L− 1) for two replicate series. In addition, control conditions were monitored. Five oysters from each tank were dissected after 3, 7, 14, 21, 28, 35 days of Pt exposure, and analyzed by ICP-MS. Accuracy of this analytical method applied to biological matrix was checked by an inter-method comparison with a voltammetrical technique. A concentration-dependent accumulation of Pt in oysters increasing with exposure time occurred. After 28 days, oyster Pt accumulation from low and intermediate exposure conditions reached a plateau. This was not the case of the highest exposure condition for which oyster tissues showed increasing concentrations until the last day of the experiment. A linear correlation exists between seawater concentrations and Pt content in oysters for low and intermediate exposure concentrations i.e. closer to environmental concentrations. By showing high Pt accumulation potential, oysters may serve as sentinels, ensuring biomonitoring of Pt concentrations in marine coastal waters, This work has benefited from the support by the FEDER Aquitaine-1999-Z0061, the Agence de l'Eau Adour-Garonne32022123 and 31033111, the COST Action TD1407, and the EU FP7 Ocean 2013.2 Project SCHeMA (Project-Grant Agreement 614002), which is gratefully acknowledged. M. Abdou has benefited of an IdEx University of Bordeaux mobility grant

International audience; Antimony (Sb) is a highly toxic trace element for which environmental biogeochemical cycles are still relatively poorly known, especially in coastal aquatic systems. In addition, Sb is a fission product in nuclear power plants (NPPs), presenting non-negligible decay and consecutive exposition rates over short to mean terms (i.e., 125Sb isotope half-life of 2.76 years). Understanding the environmental behaviour and fate of natural stable isotopes and combining this with intrinsic properties of the respective radionuclides (e.g. half-life) is essential to predict the environmental fate and potential dispersion of radioisotopes before accidental NPP events. In the present work, the distribution and geochemical behaviour of stable Sb are determined for the first time in the highly turbid Gironde Estuary. Both dissolved and particulate concentrations along the estuarine salinity and turbidity gradients were quantified during low, intermediate and high freshwater discharges. Results clearly suggest that long residence times within the salinity and turbidity gradients favour the observed non-conservative, additive behaviour of Sb. Distribution coefficients (log10 Kd ≈ 3.5–4.4 l kg− 1) indicate that in the Maximum Turbidity Zone (MTZ; SPM ~ 1000 mg l− 1) ~ 90% of total Sb occurs in the particulate phase, compared to only ~ 10% in the less turbid portions of the estuary (SPM ≤ 100 mg l− 1). We propose a first/broad qualitative approximation (scenarios) to possible behaviour and dispersion of Sb radionuclides in case of accidental release from the Blayais NPP located on the Gironde Estuary. Our results suggest that the hydrological situation and the position of the MTZ during a potential accident can be primordial to residence time and distribution pathways in the estuary. We estimate that (i) high river discharge and a downstream position of the MTZ may favour Sb radionuclide adsorption onto particles, implying long (months to years) residence times in the estuary and a high risk of seasonal upstream transport into the city of Bordeaux, whereas (ii) under low discharge conditions, dissolved Sb species will predominate implying rapid transport and higher dispersion along the coast. © 2016 Elsevier B.V.