Tracing platinum accumulation kinetics in oyster Crassostrea gigas, a sentinel species in coastal marine environments

Reactivity and bioconcentration of stable cesium in a hyperturbid fluvial-estuarine continuum: A combination of field observations and geochemical modeling

Effective, post-accidental management needs an accurate understanding of the biogeochemical behavior of radionuclides in surface environments at a regional scale. Studies on stable isotopes (element homologs) can improve this knowledge. This work focuses on the biogeochemical behavior of stable cesium (Cs) along a major European fluvial-estuarine system, the Gironde Estuary (SW France). We present results obtained from (i) a long-term monitoring (2014-2017) of dissolved (Csd) and particulate (Csp) Cs concentrations at five sites along the freshwater continuum of the Garonne watershed, (ii) Csd and Csp concentrations during four oceanographic campaigns at contrasting hydrological conditions along longitudinal profiles of the estuarine system, (iii) a 24 h cycle of Csp at the estuary mouth, and (iv) a historical trend of Cs bioconcentration in wild oysters at the estuary mouth (RNO/ROCCH, 1984-2017). In addition, we model the partitioning of Cs within the estuarine environment for clay mineral interactions via PhreeqC. At fluvial sites, we observe a geogenic dependence of the Csp and a seasonal variability of Csd, with a downstream increase of the solid-liquid partitioning (log10 Kd values from 3.64 to 6.75 L kg-1) for suspended particulate matter (SPM) < 200 mg L-1. Along the estuarine salinity gradients, Cs shows a non-conservative behavior where fresh SPM (defined as Cs-depleted particles recently put in contact with Csd) act as a Cs sink during both flood and low discharge (drought) conditions. This sorption behavior was explained by the geochemical model, highlighting the relevance of ionic strength, water and SPM residence times. However, at high salinities, the overall log10 Kd value decreases from 6.02 to 5.20 for SPM ∼300-350 mg L-1 due to the Csd oceanic endmember. Despite wild oysters showing low bioconcentration factors (∼1220 L kg-1) at the estuary mouth, they are sensitive organisms to Cs fluxes.

Platinum Group Element distribution in water and marine biota from two impacted estuarine environments (Douro and Ave estuaries, Portugal)

Platinum Group Elements (PGEs) are contaminants of emerging environmental concern considering their continuous increasing use and subsequent release in the environment. While recent field studies provided PGE levels in seawater, scarce knowledge still exists regarding PGE contamination in marine organisms, especially for rhodium (Rh). Water, macroalgae and mussels were sampled along two representative urbanized estuarine systems and adjacent coastal areas (Douro and Ave estuaries, Portugal). Rhodium and platinum (Pt) concentrations were quantified through both stripping voltammetry and mass spectrometry in collected samples. Spatial mapping of PGE contamination was, to a certain extent, correlated with proxies of urban effluents. The use of Pt/Rh ratios reflected the dominant influence of PGE traffic emissions along the Douro and inputs from various sources (including industries) on the Ave Estuary. Macroalgae and mussels PGE concentrations reflected urban pressure, amplifying environmental signals, and supporting their relevant use as bioindicators of PGE contamination in estuarine/coastal systems.

Metabolomics for in situ monitoring of attached Crassostrea gigas and Mytilus edulis: Effects of offshore wind farms on aquatic organisms

While offshore wind power has support from countries around the world, studies show that offshore wind farms (OWFs) may affect marine organisms. Environmental metabolomics is a high-throughput method that provides a snapshot of an organism's metabolic state. To elucidate the effects of OWFs on aquatic organisms, we studied, in situ, Crassostrea gigas and Mytilus edulis attached within and outside of OWFs and their reef areas. Our results show that epinephrine, sulphaniline, and inosine 5'-monophosphate were significantly increased and L-carnitine was significantly reduced in both Crassostrea and Mytilus species from the OWFs. This may be related to immune response, oxidative stress, energy metabolism and osmotic pressure regulation of aquatic organisms. Our study shows that active selection of biological monitoring methods for risk assessment is necessary and that metabolomics of attached shellfish is useful in elucidating the metabolic pathways of aquatic organisms in OWFs.

New insights into trace metal speciation and interaction with phytoplankton in estuarine coastal waters

In coastal productive zones, phytoplankton activity may influence trace metal speciation and partitioning at short temporal scale. We coupled hourly in situ voltammetry quantification of the lead (Pb), cadmium (Cd), and copper (Cu) potentially bioavailable fractions, using an innovative submersible sensing probe (the TracMetal), to surface water sampling for the quantification of the targeted trace metals in the dissolved <0.2 μm and <0.02 μm fractions, suspended particles, and phytoplankton nets in the Gironde Estuary mouth. The in situ TracMetal monitoring reflected real-time dynamic Cd and Cu regeneration related to algal cells under post-bloom conditions as well as Pb remobilization due to photoreduction of colloids. The potentially bioavailable fraction consisted in 30, 30-50 and <10 % of the total dissolved fraction for Pb, Cd, and Cu, respectively, representing crucial ecotoxicological information. Metal bioconcentration factors using the dynamic fraction concentrations showed levels up to 10⁷ for Cu in phytoplankton.

Implications of kinetically-hindered metals in ecotoxicological studies: Effect of platinum spike aging on its toxicity to Dunaliella salina

Platinum (Pt) is considered an emerging environmental micro-contaminant due to its increasing use in anthropogenic activities during the past decades. However, there are still important gaps in the understanding of its biogeochemical behavior in the aquatic environment - e.g. its speciation, reactivity and fate - mainly as a result of the analytical challenge of the determination of its typical ultra-trace environmental concentrations. Also, Pt is a kinetically-hindered metal displaying slow reaction kinetics, which has important implications regarding eco-toxicological studies. That is, investigation of its toxicity under laboratory-controlled conditions may therefore require ensuring that equilibrium speciation conditions are reached before starting the experiments. In order to shed further light on this issue, in this study we have monitored the speciation changes during aging of the Pt(IV) spikes in controlled media (seawater) using an UV-Vis spectrophotometry. Platinum toxicity to the green microalgae Dunaliella salina was then compared, using standardized tests, with fresh and aged Pt(IV) spikes at the mg L^-1 concentration range. Following 96-hour exposure, ecotoxicological assays consisting in spectrometric measurements of chlorophyll-a concentrations and Effective Concentrations (EC) of Pt resulting in the inhibition of 10% and 50% of algae growth rate were calculated (EC₁₀ and EC₅₀, respectively). Daily monitoring of Pt speciation reflected the transition from PtCl₆^2- (spike) to hydrolyzed species, probably in the form [PtCl_3-n(OH)_3+n]^2-, n = 0-3. Exposure experiments showed that after a short period of aging (10 days), Pt(IV) toxicity increased one order of magnitude compared to freshly spiked media. These results confirm the relevance of considering spike aging to ensure that speciation equilibrium conditions are attained in order to produce environmental realistic eco-toxicological data.

Development and validation of DGT passive samplers for the quantification of Ir, Pd, Pt, Rh and Ru: A challenging application in waters impacted by urban activities

Platinum group elements (PGEs) are among the least abundant in the continental crust. They have become excellent tracers of anthropogenic activities, particularly due to their use in catalytic converters or in the medical industry. However, their quantification in environmental matrices is still problematic because of their low concentrations combined with the presence of interfering elements. Preconcentration methods are therefore necessary to measure accurate concentrations. In this study, the quantification of Ir, Rh, Ru, Pd and Pt was studied in depth by focusing on two resins: AG MP-1 (anion exchange) and Purolite® S-920 (chelating) with the aim of developing passive Diffusive Gradients in Thin films (DGT) samplers as in-situ pre-concentration tools. The characteristics of both resins (e.g. adsorption, elution, selectivity, etc.) were studied and the diffusion coefficients of PGEs in different matrices were determined. For the first time, carcinostatic platinum-based drugs were also studied. Better rates and percentages of adsorption were observed for S-920 while AG MP-1 was more selective with regard to spectral interferents and easier to elute. The diffusion coefficients of PGEs were resin-dependent, particularly for carcinostatic platinum-based drugs. For the first time, the applicability of these DGT samplers dedicated to PGEs was demonstrated in the field after their deployment in two wastewater treatment plants in Northern France for which concentrations were found to range from few pg L^-1 (Ir, Ru) to few ng L^-1 (Pt).

Search for effective eluent for Pd separation on ion-exchange sorbent before voltammetric determination

Determination of Pd traces in environmental samples is still a challenging analytical task. The aim of this study was to propose an efficient system (i.e. ion-exchange resin and eluent) for Pd elution from SPE column after the analyte preconcentration. Moreover, the search was focused on solvents that would not interfere voltammetric determination of Pd, as well as ICP-MS analysis. Five ion-exchange sorbents were compared in terms of effective Pd separation from matrix components when using different eluents. The highest recovery (up to 91%) of palladium was obtained for Dowex 1 and ammonium buffer as the eluent. This solution not only provides relatively high palladium elution efficiency but also allows both voltammetric and ICP-MS determinations, without any additional sample preparation. It was proven that the proposed procedure including SPE separation and determination with AdSV and/or ICP-MS could be used for quantitative Pd measurement in environmental samples, such as quartz sand used for the monitoring of Pd emission in the areas of high traffic density.

Bioaccumulation of microplastics and its in vivo interactions with trace metals in edible oysters

Microplastics have been an emerging threat to marine environments and marine life. Oysters as seafood are popular worldwide, yet also a high-risk group to accumulate pollutants due to their filter-feeding nature. In this study, edible oysters were collected from Yantai, a coastal city in China, to study the uptake, accumulation and translocation of microplastics in marine life, as well as their in vivo interactions with other persistent pollutants. Microplastics were found in all of the studied oyster tissue samples with an average concentration around 4.53 items/g wet weight (24.49 items/g dry weight). Microplastics were mainly translocated and distributed in the gills and mantle of the studied oysters in the form of fibers. The detected microplastics in the oysters were mostly cellophane and polyester as identified by the micro-Fourier transform infrared spectroscope. Cellophane tends to accumulate in gills, mantle and muscle while polyester tends to accumulate in digestive glands of the studied oysters. Excessive concentrations of trace metals (30.484, 4.415, 0.395 and 181.044 μg/g dry weight of Cr, Cd, Pb and Cu, respectively) were detected in the studied oysters using inductively coupled plasma mass spectrometry. Trace metals of Cr, Mn, Ni, Cu, Zn, Cd and Pb were found to be adsorbed on the surface of microplastics isolated from the oysters. There was a correlation between the in vivo concentration of microplastics and the in vivo concentration of four trace metals: Cd, Cr, Cu and Pb, which suggests potential in vivo interactions between microplastics and trace metals. This study can help to understand the impacts of microplastics and their joint toxicity with other pollutants on marine life, especially on aquaculture seafood. This study will be an important reference for the assessment of health risks associated with consumption of edible coastal oysters in China.

Organotropism and biomarker response in oyster Crassostrea gigas exposed to platinum in seawater

Platinum (Pt) is a technology critical element (TCE) for which biogeochemical cycles are still poorly understood. This lack of knowledge includes Pt effects on marine organisms, which proved to be able to bioconcentrate this trace element. Oysters Crassostrea gigas were exposed to stable Pt isotope spiked daily in seawater for 35 days. Seawater was renewed daily and spiked (with Pt(IV)) to three nominal Pt concentrations (50, 100, and 10,000 ng L^-1) for two replicate series. Organotropism study revealed that gills, and to a lesser extent mantle, are the key organs regarding Pt accumulation, although a time- and concentration-dependent linear increase in Pt levels occurred in all the organs investigated (i.e., digestive gland, gonads, gills, mantle, and muscle). In oysters exposed to Pt concentrations of 10,000 ng L^-1, significant biomarker impairments occurred, especially at cellular levels. They reflect altered lipofuscin and neutral lipid contents, as well as intralysosomal metal accumulation. These observations were attributed to activation of excretion/detoxification mechanisms, including Pt elimination through feces and clearly support the importance of the digestive gland in the response to direct Pt exposure. Despite relatively constant condition index, the integrative biological response (IBR) index suggests a generally decreasing health status of oysters.

Platinum in sediments and mussels from the northwestern Mediterranean coast: Temporal and spatial aspects

Platinum (Pt) is considered a Technology Critical Element (TCE) and an emerging metallic contaminant with increasing release into the environment. Gaps in knowledge and understanding of environmental levels, fate and effects of Pt still exist, especially in the marine environment. This work presents Pt concentrations in the northwestern Mediterranean coast including: (i) temporal variability from sediment cores and farmed mussels in the Toulon Bay (historically affected by intense human activities) and (ii) spatial distribution from recent wild mussels collected along ∼ 700 km coastline with contrasting ecosystems (including natural reserves), quantified using voltammetry and inductively coupled plasma-mass spectrometry. The historical (>100 years) record of Pt in sediments from the Toulon Bay suggests the existence of non-negligible Pt sources older than those related to vehicle emission devices, such as petrol industry and coal-fired activities. A strong Pt increase in more recent sediments (from ∼12 to 16 ng g^-1) and mussels (8-fold increase from ∼0.12 to 0.80 ng g^-1) covering the past 25 years reflect the overall evolution of Pt demand in Europe (∼20-fold increase for vehicle catalysts in 20 years). Spatial biomonitoring of Pt in mussels along the northwestern Mediterranean coast is assumed to reflect inter-site differences of Pt exposure (0.09-0.66 ng g^-1) despite seasonal effect on tissue development. This study highlights the need for thorough and regular monitoring of Pt levels in sediments and biota from urbanized coastal areas in order to better assess the environmental impact of this TCE, including potential risks for marine organisms.