Characterization of alloying components in galvanic anodes as potential environmental tracers for heavy metal emissions from offshore wind structures

Response and adaptation mechanisms of Apostichopus japonicus to single and combined anthropogenic stresses of polystyrene microplastics or cadmium

Microplastics (MPs) have become pervasive in marine ecosystems, exerting detrimental effects on marine life. The concurrent presence and interaction of MPs and heavy metals in aquatic environments could engender more insidious toxicological impacts. This study aimed to elucidate the potential impacts and underlying mechanisms of polystyrene microplastics (PS-MPs), cadmium (Cd), and their combined stress (MPs-Cd) on sea cucumbers (Apostichopus japonicus). It focused on the growth, Cd bioaccumulation, oxidative stress responses, immunoenzymatic activities, and metabolic profiles, specifically considering PS-MPs sizes preferentially ingested by these organisms. The high-dose MPs (MH) treatment group exhibited an increase in cadmium bioavailability within the sea cucumbers. Exposure to PS-MPs or Cd triggered the activation of antioxidant defenses and immune responses. PS-MPs and Cd exhibited a synergistic effect on lysozyme (LZM) activity. A total of 149, 316, 211, 197, 215, 619, 434, and 602 differentially expressed metabolites were identified, distinguishing the low-dose MPs (ML), high-dose MPs (MH), low-dose Cd (LCd), low-dose MPs and low-dose Cd (MLLCd), high-dose MPs and low-dose Cd (MHLCd), high-dose Cd (HCd), low-dose MPs and high-dose Cd (MLHCd), high-dose MPs and high-dose Cd (MHHCd) groups, respectively. Metabolomic analyses revealed disruptions in lipid metabolism, nervous system function, signal transduction, and transport and catabolism pathways following exposure to PS-MPs, Cd, and MPs-Cd. Correlation analyses among key differentially expressed metabolites (DEMs) underscored the interregulation among these metabolic pathways. These results offer new perspectives on the distinct and synergistic toxicological impacts of microplastics and cadmium on aquatic species, highlighting the complex interplay between environmental contaminants and their effects on marine life.

Ecological impacts of the expansion of offshore wind farms on trophic level species of marine food chain

The global demand for renewable energy has resulted in a rapid expansion of offshore wind farms (OWFs) and increased attention to the ecological impacts of OWFs on the marine ecosystem. Previous reviews mainly focused on the OWFs' impacts on individual species like birds, bats, or mammals. This review collected numerous field-measured data and simulated results to summarize the ecological impacts on phytoplankton, zooplankton, zoobenthos, fishes, and mammals from each trophic level and also analyze their interactions in the marine food chain. Phytoplankton and zooplankton are positively or adversely affected by the 'wave effect', 'shading effect', oxygen depletion and predation pressure, leading to a ± 10% fluctuation of primary production. Although zoobenthos are threatened transiently by habitat destruction with a reduction of around 60% in biomass in the construction stage, their abundance exhibited an over 90% increase, dominated by sessile species, due to the 'reef effect' in the operation stage. Marine fishes and mammals are to endure the interferences of noise and electromagnetic, but they are also aggregated around OWFs by the 'reef effect' and 'reserve effect'. Furthermore, the complexity of marine ecosystem would increase with a promotion of the total system biomass by 40% through trophic cascade effects strengthen and resource partitioning alternation triggered by the proliferation of filter-feeders. The suitable site selection, long-term monitoring, and life-cycle-assessment of ecological impacts of OWFs that are lacking in current literature have been described in this review, as well as the carbon emission and deposition.

Determination of technology-critical elements in seafood reference materials by inductively coupled plasma-tandem mass spectrometry

The certified reference materials (CRMs) BCR-668 (mussel tissue), NCS ZC73034 (prawn), NIST SRM 1566a (oyster tissue) and NIST SRM 2976 (mussel tissue) were analyzed for their mass fractions of 23 elements using inductively coupled plasma tandem-mass spectrometry (ICP-MS/MS). This study focused on the quantification of selected technology-critical elements (TCEs), specifically rare earth elements (REE) and the less studied TCEs Ga, Ge, Nb, In and Ta. Microwave assisted closed vessel digestion using an acid mixture of HNO3, HCl and H2O2 was applied to varying sample masses and two different microwave systems. Recoveries of 76% (Gd, NCS ZC73034) to 129% (Lu, BCR-668) were obtained for the REE and 83% (Ge, NCS ZC73034) to 127% (Nb, NCS ZC73034) for the less studied TCEs across all analyzed CRMs (compared to certified values) using the best-performing parameters. Mass fractions for all analyzed, non-certified elements are suggested and given with a combined uncertainty U (k = 2), including mass fractions for Ga (11 µg kg-1 ± 9 µg kg-1 to 67 µg kg-1 ± 8 µg kg-1) and In (0.4 µg kg-1 ± 0.3 µg kg-1 to 0.8 µg kg-1 ± 0.7 µg kg-1). This study provides mass fractions of possible new emerging contaminants and addresses the relevant challenges in quantification of less studied TCEs, thus allowing the application of existing CRMs for method validation in studies dealing with the determination of TCEs in seafood or other biota.

The energy park of the future: Modelling the combination of wave-, wind- and solar energy in offshore multi-source parks

To mitigate the effects of climate change, a significant percentage of future energy generation is set to come from renewable energy sources. This has led to a substantial increase of installed offshore wind in the North Sea in the last years (28 GW in 2021) and is projected to further accelerate to an installed capacity of 212 GW by 2050. Increasing the renewable energy grid penetration brings challenges, including 1) limitations in space availability and 2) the reliability of renewable energy systems in terms of grid balancing. In the North Sea, maritime space is getting scarce and the projected upscaling of offshore wind is putting pressure on the chemical-, biological, and physical balance of the marine ecosystem. Without economically viable large-scale storage systems, a renewable energy system focused on one intermittent source does not provide reliable baseload- and energy demand compliance. By integrating different supplementary offshore renewable energy sources into multi-source parks output becomes smoother, while the energy yield per area increases. Despite multiple studies stating the benefits of multi-source energy parks of either wind and wave energy or wind and PV energy, no study has been conducted on the co-location of all three offshore renewables. This study combines and analyzes the three offshore renewable energy sources: wave-, offshore PV- and wind energy in the example of Ten Noorden van de Waddeneilanden, a future wind farm north of the Dutch Wadden Islands. The additional renewables are allocated within the wind turbine spacing, taking into account safety zones and maintenance corridors. Co-location of these renewables increases the extracted energy density by 22%, making more efficient use of the limited available marine space. Moreover, the park output becomes smoother as the yearly-averaged coefficient of variation decreases by 13%, the capacity factor with respect to the export cable increases by 19%, and the hours where the output of the park is below 20% of the export cable capacity decreases by 86.5%.

Enabling Al sacrificial anodes in tetrahydrofuran electrolytes for reductive electrosynthesis

Al0 is widely used as a sacrificial anode in organic electrosynthesis. However, there remains a notable knowledge gap in the understanding of Al anode interface chemistry under electrolysis conditions. We hypothesize that Al interfacial chemistry plays a pivotal role in the discernible bias observed in solvent selections for reductive electrosynthesis. The majority of existing methodologies that employ an Al sacrificial anode use N,N-dimethylformamide (DMF) as the preferred solvent, with only isolated examples of ethereal solvents such as tetrahydrofuran (THF). Given the crucial role of the solvent in determining the efficiency and selectivity of an organic reaction, limitations on solvent choice could significantly hinder substrate reactivity and impede the desired transformations. In this study, we aim to understand the Al metal interfaces and manipulate them to improve the performance of an Al sacrificial anode in THF-based electrolytes. We have discovered that the presence of halide ions (Cl-, Br-, I-) in the electrolyte is crucial for efficient Al stripping. By incorporating halide additive, we achieve bulk Al stripping in THF-based electrolytes and successfully improve the cell potentials of electrochemically driven reductive methodologies. This study will encourage the use of ethereal solvents in systems using Al sacrificial anodes and guide future endeavors in optimizing electrolytes for reductive electrosynthesis.

Investigation of potential metal emissions from galvanic anodes in offshore wind farms into North Sea sediments

To evaluate potential metal emissions from offshore wind farms (OWFs), 215 surface sediment samples from different German North Sea OWFs taken between 2016 and 2022 were analyzed for their mass fractions of metals and their isotopic composition of Sr. For the first time, this study provides large-scale elemental data from OWFs of the previously proposed galvanic anode tracers Cd, Pb, Zn, Ga and In. Results show that mass fractions of the legacy pollutants Cd, Pb and Zn were mostly within the known variability of North Sea sediments. At the current stage the analyzed Ga and In mass fractions as well as Ga/In ratios do not point towards an accumulation in sediments caused by galvanic anodes used in OWFs. However, further investigations are advisable to evaluate long-term effects over the expected lifetime of OWFs, especially with regard to the current intensification of offshore wind energy development.

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.

Impact assessment of metals realeased by aluminium-based galvanic anode on the physiology of the abalone Haliotis tuberculata in controlled conditions

To protect metal structures immersed in the sea from corrosion, the galvanic anode cathodic protection system (GACP) is often applied. However, this association leads to continuous oxidation of the galvanic anode and therefore to a release of a metal cocktail in the forms of ions or oxy-hydroxides. Therefore, the main objective of our study was to investigate the toxicity of elements released from the dissolution of an aluminium-based galvanic anode (∼95% Al, ∼5% Zn, <0.1% for In, Cu, Cd, Mn, Fe) on a grazing gastropod, the abalone Haliotis tuberculata. The present study was carried out in complement to other research currently in submission. Gastropods were exposed for 16 weeks (12 weeks of exposure and 4 weeks of decontamination phase) to 6 conditions including a control, 4 concentrations based on total aluminium level (86, 425, 1096 and 3549 µg L^-1) and a trophic control, corresponding to abalones placed in non-contaminated natural seawater but fed with contaminated algae. The effects of metals on growth, glycogen levels, brix index of hemolymph, MDA levels in digestive gland and gills, hemocyte phagocytic activity, ROS production, lysosomal system and the progress of gametogenesis were investigated throughout the entire exposure allowing the realization of kinetics. The results revealed that the aluminium-based anode does not seem to have an effect on the health status of the individuals for environmentally realistic concentrations. However, in extreme conditions strong effects were reported on the growth, immune system and reproduction of abalone.

Aluminium-based galvanic anode impacts the photosynthesis of microphytobenthos and supports the bioaccumulation of metals released

Very few studies have looked at the potential biological effects of degradation products of galvanic anodes particularly on primary producers which are central to food webs in marine ecosystems. The galvanic anode cathodic protection system (GACP) is widely used to protect submerged metallic structures from corrosion. Aluminium (Al) and zinc (Zn) are the main constituents of galvanic anodes and are therefore released in the marine environment by oxidation process to form ions or oxy-hydroxides. The main objective of our study was to evaluate the effects of the metals released from an aluminium-based galvanic anode on microphytobenthos performance in term of biofilm growing through the analysis of photosynthetic parameters, the determination of chlorophyll and extracellular polymeric substances (EPS). The bioaccumulation of Al and Zn were measured in the microphytobenthic compartment collected at the surface of polyvinyl chloride (PVC) plates exposed during 13 days to seawaters enriched in different concentrations of metals released from dissolution of one anode. Determination of bioconcentration factors confirmed that the microphytobenthos has incorporated Al. A significative effect was observed on the Chl a concentration for the higher tested concentration ([Al] = 210.1 ± 60.2 µg L ^- 1; [Zn] = 20.2 ± 1.4 µg L ^- 1). The seawater exposed to the anode affected the MPB productivity (ETRII_max) with consequences on acclimatation light (Ek), absorption cross section of PSII (σ_PII), F_v/F_m and NPQ. Regarding the EPS production, the anode degradation presented an impact on high and low molecular weight of both carbohydrates and protein fractions of microphytobenthos suggesting that EPS play an essential role in sequestering metal contaminants to maintain the integrity of the biological membranes and the functionality of the cellular organelles. The accumulation of Al released by GACP in microphytobenthos cells could lead to physiologic problems in photosynthetic organisms.

Evidence that offshore wind farms might affect marine sediment quality and microbial communities

Offshore wind power is a typical example of clean energy production and plays a critical role in achieving carbon neutrality. Offshore wind farms can have an impact on the marine environment, especially sedimentary environments, but their influence on sediments remain largely unknown. This study, which uses the control-impact principle to define different areas, investigated the characteristics of marine sediments under the Putidao offshore wind farm in Bohai Bay, China. We used chemical and microbiological observations to evaluate sediment quality and microbial community structure. According to both the geo-accumulation index (I_geo) and contamination factor (CF) indexes, copper, chromium and zinc were the major contaminants in the offshore wind farm sediments. The pollution load index (PLI) index showed that the various sites on the wind farm were only lightly polluted compared with baseline values. Closer to the wind farm's center, the metal concentrations started to rise. The physicochemical features of the sediments could better explain changes in the microorganisms present, and screening the microbiomes showed a correlation with heavy metal levels, linking the relative abundance of microorganisms to the sediment quality index. This comprehensive study fills a knowledge gap in China and adds to our understanding of how to assess the sedimentary environments of offshore wind farms.

Effects on Growth of Juvenile Abalones Haliotis tuberculata Under Chronic Exposition to Metals Released from the Dissolution of an Aluminium-Based Galvanic Anode

In the marine environment, the galvanic anode cathodic protection system (GACP) undergoes oxidation and releases metals in the forms of ions or oxy-hydroxides into the environment. The objective of the present study was to investigate the toxicity of a cocktail of metals released from the dissolution of an aluminium-based galvanic anode (~ 95% Al, ~ 5% Zn) on the abalone Haliotis tuberculata. Juveniles were exposed for 16 weeks (i.e. 12 weeks of exposure and 4 weeks of decontamination phase) and their growth, intake rate, conversion rate and metallic concentrations were monitored. A total of 6 conditions were tested: a control, 4 concentrations based on Al and a trophic control. Results showed that the mortality reached 57% for individuals exposed to 1125 µg L^-1 of Al, and the abalone growth significantly decreased for an Al concentration greater than 495 µg L^-1. At the highest exposure concentration, intake rate measurements revealed that the appetite of abalones was affected, supported by the large increase in the conversion rate which was indicative of a poor feed efficiency. The monitoring of metallic concentrations showed that H. tuberculata strongly bioconcentrated Al relative to zinc. The diet did not appear to be the primary pathway for metal entry. Concentrations that significantly impacted abalone growth and survival during the experiment were higher than those found in natural environment, but the bioconcentration of Al into the tissues of a primary consumer such as abalone may be a potential pathway for Al to enter food webs.

Technology-critical elements in Rhine sediments - A case study on occurrence and spatial distribution

Despite their presence in almost every technical device, little is known about the occurrence, distribution, and fate of technology-critical elements (TCEs) within the environment. Due to high economic demands and short product lifespans as well as low recycling rates, many TCEs appear to become emerging contaminants. Within the scope of this work, 57 sediment samples from the German part of the Rhine river, as well as various tributaries, were collected to study the occurrence and distribution of TCEs. This specific catchment area has consistently been subjected to strong anthropogenic influences over the last century. Hierarchical cluster analysis, as well as principal component analysis were used to gain first insights into the spatial distribution and possible sources of TCEs along the Rhine. Obtained mass fractions in conjunction with corresponding geoaccumulation indices (I_geo) provide first indications of a possible enrichment along the Rhine for the TCEs of interest (Ga, Ge, Nb, In, Te, rare earth elements, and Ta). Especially the mass fractions of Zn, Ge, In, La, Sm, and Gd exhibit significant anthropogenic inputs. For stations characterized by high Ge and In mass fractions, element fingerprints imply possible atmospheric deposition stemming from e.g. combustion processes. Distinct anomalies of La and Sm most likely originate from discharges located at the city of Worms into the Upper Rhine. Statistical analysis of all analyzed 55 elemental mass fractions revealed similar behavior of TCEs compared to classical heavy metals. Diffuse as well as point sources of TCEs are likely. As a result, this study provides further insight into the role of TCEs as potential emerging contaminants in the environment.

Characteristic regional differences in trace element pattern of 2014 German North Sea surface Wadden sediments - A judge and assessment

The European Marine Strategy Framework Directive (MSFD) requires good ecological status of the marine environment. This also includes the Wadden Sea located in the southeastern part of the North Sea and its chemical status of sediments. Based on results from campaigns conducted in the 1980s, 32 surface sediment samples were taken in 2014 to check whether the sampling strategy required for characterizing the trace element content in sediments is representative and to determine the degree of pollution and potential changes over the last decades. For this purpose the elemental mass fractions of 42 elements were assessed in the ≤20 μm grain size fraction of the surface sediments. Based on cluster analysis a clear correlation between the element distribution and the geographical location of the sampling locations of the German Wadden Sea could be found. As a result of the principal component analysis, three sub-catchments were significantly separated from each other by the characteristic element distributions in the sediments (Norderney and Weser, Elbe and offshore areas, and North Friesland). With the help of discriminant analysis, the classification was confirmed unambiguously. Small anomalies, such as potentially contaminated sites from WWII, could be identified. This proved that the sampling strategy for sediment characterization with reference to trace elements in the Wadden Sea of the German Bight is representative. The impact of regulation and changes on the overall sediment quality is most evident when looking at the environmentally critical elements such as As, Cd, Hg, and Cr. For these elements the mean mass fractions show a significant reduction over the last three decades. Current sediments feature only slightly elevated mass fractions of Ag, Cd, Ce, Cs, Nd, Pb and Se at some sampling locations.

Effects of chronic exposure of metals released from the dissolution of an aluminium galvanic anode on the Pacific oyster Crassostrea gigas

Among the anthropogenic sources releasing metallic species into the marine environment, the galvanic anode cathodic protection system (GACP) is widely used to protect submerged metallic structures from corrosion. Galvanic anodes are an alloy of metals of which the main component is aluminum or zinc. Very few studies were performed to study their potential biological effects. We investigated the chronic toxicity of an aluminum-based galvanic anode on the Pacific oyster, Crassostrea gigas. Oysters were exposed for 84 days to three concentrations of aluminum (50, 100 and 300 µg L^-1) obtained with an electrochemical experimental device simulating the dissolution of a galvanic anode. At different exposure times, we studied a battery of biomarkers of the immune system, reproductive parameters and the metabolic state of the oysters. Results demonstrated a sensitivity of oysters at the highest concentration and some biological effects were observed especially for the malondialdehyde content in the digestive gland after 84 days of exposure. In addition to these biomarkers, the bioaccumulation of the different metals composing the anode was measured in oysters' tissues. Bivalves bioaccumulated more zinc than aluminum, even if aluminium was present in greater concentrations during exposures. Moreover, exposure time did not influence the bioaccumulation of aluminum in contrast to zinc.

Occurrence and Temporal Variation of Technology-Critical Elements in North Sea Sediments-A Determination of Preliminary Reference Values

As interest in the investigation of possible sources and environmental sinks of technology-critical elements (TCEs) continues to grow, the demand for reliable background level information of these elements in environmental matrices increases. In this study, a time series of ten years of sediment samples from two different regions of the German North Sea were analyzed for their mass fractions of Ga, Ge, Nb, In, REEs, and Ta (grain size fraction < 20 µm). Possible regional differences were investigated in order to determine preliminary reference values for these regions. Throughout the investigated time period, only minor variations in the mass fractions were observed and both regions did not show significant differences. Calculated local enrichment factors ranging from 0.6 to 2.3 for all TCEs indicate no or little pollution in the investigated areas. Consequently, reference values were calculated using two different approaches (Median + 2 median absolute deviation (M2MAD) and Tukey inner fence (TIF)). Both approaches resulted in consistent threshold values for the respective regions ranging from 158 µg kg-1 for In to 114 mg kg-1 for Ce. As none of the threshold values exceed the observed natural variation of TCEs in marine and freshwater sediments, they may be considered baseline values of the German Bight for future studies.

Trophic transfer of heavy metals in the marine food web based on tissue residuals

Trophic transfer of metals has been well researched in aquatic food webs; however, most studies have examined the presence of metal residuals in the entire body of marine organisms and but not in specific tissues. In this study, we determined the concentrations of Cu, Cr, Pb, Zn, Cd, and Ni in various organs of 17 marine species, including crustaceans, gastropods, bivalves, and fishes, with different trophic levels (TLs), which were collected from the Liaodong Bay, China, in July 2019. Results showed that the liver, gill, and muscle tissues of marine species are ideal indicators for analyzing Cu, Cr, Pb, Zn, Cd, and Ni contamination in marine environments. When the entire bodies of these marine species were considered, a bio-dilution in Cu, Cr, Pb, Zn, Cd, and Ni was observed in the studied food web. In contrast, the metal tissue-specific bio-magnification in the entire studied food web showed different results. In the liver and gill tissues, negative correlations were found between the concentrations of cadmium and TLs, while copper bio-dilution was also observed in gill tissue. In the muscle tissues, Cu, Pb, and Ni showed bio-dilution and trophic magnification factors of Cu, Pb, and Ni ranged from 0.44 to 0.73. This study highlights the importance of tissue-specific considerations to obtain further accurate information on metal trophodynamics and trophic transfers in marine food webs, thereby enhancing the risk assessment of many elements in wildlife and human health.