To improve our understanding and guide future studies and applications, we review the biogeochemistry of the rare earth elements (REE). The REEs, which form a chemically uniform group due to their ...nearly identical physicochemical properties, include the lanthanide series elements plus scandium (Sc) and yttrium (Y). These elements, in conjunction with the neodymium isotopes, are powerful tools for understanding key oceanic, terrestrial, biological and even anthropogenic processes. Furthermore, their unique properties render them essential for various technological processes and products. Here, we delve into the characteristics of REE biogeochemistry and discuss normalization procedures and REE anomalies. We also examine the aqueous speciation of REEs, contributing to a better understanding of their behavior in aquatic settings, including the role of neodymium isotopes. We then focus on their environmental distribution, fractionation, and controlling processes in different environmental systems across the land‐ocean continuum. In addition, we analyze sinks, sources, and the mobility of REEs, providing insights into their behavior in these environments. We further investigate the sources of anthropogenic REEs and their bioavailability, bioaccumulation, and transfer along food webs. We also explore the potential effects of climate change on the cycling, mobility and bioavailability of REEs, underlining the importance of current research in this evolving field. In summary, we provide a comprehensive review of REE behavior in the environment, from their properties and roles to their distribution and anthropogenic impacts, offering valuable insights and pinpointing key knowledge gaps.
Key Points
Rare earth elements (REE) are powerful tracers of both natural and anthropogenic processes within terrestrial and ocean environments
REE are controlled by absorption, adsorption/desorption, co‐precipitation, remineralization, and particle dissolution
REE are technology‐critical metals with broad applications in the future low‐carbon global economy
•Proximity to urban regions was a key factor in the marine debris distributions.•There is a predominance of plastics among marine debris in Salvador beaches.•Public cleaning services are efficient in ...keeping low levels of contamination.•The problem of beach debris should be addressed at a regional level.•Adequate sample design and statistical tests will be always necessary in order to evaluate marine debris.
In order to test the relationship between the occurrence of marine debris and the distance from urban areas, nine beaches in the metropolitan area of Salvador, Bahia, Brazil and the adjacent northern coast were studied. Marine debris were collected, sorted in several categories and weighed. It was observed that plastics were numerically the most abundant component of the collected debris. As expected, the beaches closest to Salvador presented the largest density of debris, with the exception of the Porto da Barra beach, which has an efficient public cleaning system and does not have any vegetation, making it difficult toaccumulate solid waste. Linear regression analyses showed significant relationships between the distance from the urban center (Salvador) and the number of marine debris per m2, the total number of debris per beach (abundance), and the diversity of debris types (richness). The results showed that proximity to urban regions was a key factor in the marine debris distribution along the coast.
In order to evaluate contamination by polychlorinated biphenyls (PCBs) in a tropical bay exposed to different anthropogenic pressures, samples of bivalves: mangrove oyster (Crassotrea rhizophorae), ...mangrove mussel (Mytella guyanensis)and clams (Anomalocardia brasiliana), were collected in different parts of Todos os Santos Bay, Bahia, Brazil. In addition, samples of bivalves and fish, purchased from a seafood market in the city of Salvador were analyzed to evaluate human exposure to PCBs through ingestion. Identification and quantification of PCBs were done by GC/MS after microwave extraction and purification with sulfuric acid. In bivalves, concentrations ranged from <0.08 to 50.1 ng g −1 (dry weight), with the highest values being detected in mangrove oyster, followed by clams and mangrove mussel of the Subaé estuary and Madre de Deus/Mataripe; regions known to be impacted by anthropic activities. From the total of the 12 fish species analyzed, only 5 presented levels of PCBs above the detection limit, ranging from 0.23 to 4.55 ng g −1 and 0.51 to 26.05 ng g −1 by dry weight and lipid weight, respectively. In general, concentrations of PCBs on the bay are lower than in most regions around the world, especially those located in the Northern Hemisphere. Indexes indicated that local biota and seafood from the fish market are not adversely impacted by PCBs and do not represent a risk to human health.
•Overall concentrations of PCBs on bivalves from TSB are lower than in most regions around the world•Concentrations suggest that no adverse effects should be observed in mangrove oysters and mangrove mussels•All EDI values were lower than those presenting a potential risk to human health
We determined depth profiles of total mercury (T-Hg) in six 210Pb-dated sediment cores from Todos os Santos Bay to reconstruct the history of anthropogenic Hg accumulation. We also assessed ...superficial sediments samples from five estuaries. T-Hg concentrations (5–3500 μg kg−1) presented a large spatial and temporal variability. T-Hg concentrations in Ribeira Bay increased up to 200-fold along time, whereas the fluxes of T-Hg are substantially higher (up to 10,000 fold) than present-day wet deposition for industrialized areas. Sedimentary records indicate that a chlor-alkali plant has been the main source of Hg pollution until the present, although the T-Hg records suggest that harbor, shrimp farming, and oil refinery activities, besides Hg atmospheric depositions, are important across the bay. Sediments in the Ribeira Bay act as an important Hg sink. If sediments are eroded or disturbed, they may release Hg, thus posing a serious risk to wildlife and ecosystem health.
Sedimentary cores provide data on preindustrial levels and also anthropogenic fluxes of Hg for the appraisal of the magnitude, processes and potential risks of the contamination.
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•Sediment cores provide a reliable archive of Hg contamination during the last century.•Hg levels increased up to 200-fold following the onset of a chlor-alkali plant.•Ribeira Bay acts as important sink for the legacy Hg.•Decline of the concentrations and fluxes of Hg during the last decades•Disturbance of bottom sediments may cause remobilization and reintroduction of Hg.
The evolution of the impacts of anthropogenic activities in Todos os Santos Bay was evaluated by profiles of trace metals and Pb isotopes determined in sediment cores. Fluxes of metals increased up ...to 12, 4 and 2 times for Cu, Pb, and Zn, respectively, compared to those recorded in the beginning of the 20th century. Stable Pb isotopes identified a decommissioned lead smelter and burning of fossil fuels as the main sources of Pb. Most metals showed minor to moderate enrichment factors (EF<4), but Cu and Pb were highly enriched (EF=28 and 6, respectively) at the Aratu harbor. Temporal changes in sediments were associated to different activities, namely Pb smelting, burning of fossil fuels, maritime traffic, petroleum related activities, inputs of domestic effluents, and changes in land uses. The effects of the implementation of environmental policies to improve the waters of the bay could not be identified in the evaluated cores.
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•Evolution of trace metals in dated sediment cores in a tropical industrialized bay•Pb isotopic ratios identified a smelter and fossil fuels as the main sources of Pb.•Enrichment factors indicated low to moderate contamination, except for Cu and Pb.•Cu concentrations near the Aratu harbor exceeded international sediment benchmarks.•Sedimentation rates are highly variable (0.38–2.60cmyr−1) throughout the bay.
Lipid biomarkers (sterols, alcohols and taraxerol) were quantified in 30 surface sediments from the Camamu Bay (CB), NE Brazil, with the aim of evaluating the sources and distribution of organic ...matter (OM) in a tropical, well-preserved coastal system. The total organic carbon varied in a wide range (0.8–38.3 mg g−1), reflecting distinct patterns of sediment grain size and hydrodynamics at CB. A mean C/N molar ratio of 22.2 ± 5.2 suggests an important allochthonous source of OM. This is confirmed by the distribution of the total quantified lipids (3.15 ± 2.58 μg g−1) and statistical (PCA) analysis. Taraxerol and long-chain n-alcohols indicated the major contribution of continental materials associated with the west and south catchments. The PCA also allowed for the distinction of the n-alcohols sources, suggesting that the C24 and C26 compounds are derived from mangroves and the C30 and C32, from the Atlantic rain forest vegetation. The taraxerol to total quantified lipid ratio indicated the influence of mangrove vegetation even in OM-depleted and deeper portions of the bay. Low coprostanol concentrations suggest the absent of human sewage influence and confirm previous results that suggest CB is a pristine tropical bay that could be used as a reference area.
The uptake and release of
109Cd,
51Cr,
60Co,
59Fe,
54Mn, and
65Zn were studied using end-member waters and particles from Port Jackson estuary, Australia. The kinetics of adsorption and desorption ...were studied as a function of suspended particulate matter (SPM) loading and salinity. Batch experiments showed that the position and slope of the pH edges are dependent on the metal and on the salinity of the water (except for Mn). The general effect of salinity was to move the adsorption edge to higher pH values, with the greatest change being found for Cd. Most of the metals showed relatively simple kinetics with an increase in uptake as a function of time and suspended particle concentrations. The time dependence of Cd uptake was more complex, with an initial adsorption phase being followed by strong mobilization from the suspended sediments, explained by chlorocomplexation and competition with seawater major cations. The reversibility of the sorption decreased in the order Co>Mn>Zn>Cd>Fe>Cr. The percentage of adsorbed metal released in desorption experiments was greater in seawater than freshwater for Cd, Zn, and Co. These results are important in understanding the cycling of pollutants in response to pH, salinity, and particle concentrations in estuarine environments. In addition, they give valuable insight into the important mechanisms controlling the partitioning of heavy metals in the Port Jackson estuary.
Laboratories from 14 countries (with different levels of expertise in radionuclide measurements and 210Pb dating) participated in an interlaboratory comparison exercise (ILC) related to the ...application of 210Pb sediment dating technique within the framework of the IAEA Coordinated Research Project.
The laboratories were provided with samples from a composite sediment core and were required to provide massic activities of several radionuclides and an age versus depth model from the obtained results, using the most suitable 210Pb dating model. Massic concentrations of Zn and Cu were also determined to be used for chronology validation.
The ILC results indicated good analytical performances while the dating results didn't demonstrate the same degree of competence in part due to the different experience in dating of the participant laboratories. The ILC exercise enabled evaluation of the difficulties faced by laboratories implementing 210Pb dating methods and identified some limitations in providing reliable chronologies.
•Interlaboratory comparison exercise (ILC) finds difficulties of the Pb-210 method.•ILC results indicate good analytical performance of the participants.•ILC dating results did not show the same degree of confidence.
References areas are sites that have undergone little or no anthropogenic impact and therefore represent the natural state of an environment. The objective of this study was to test if the Camamu Bay ...(CB), Bahia, can be used as a reference area for tropical coastal environments. Trace and major elements, polycyclic aromatic hydrocarbons (PAH), and the structure of the benthic macrofauna were determined. To compare the studied sites and identify the possible occurrence of anomalous concentrations, trace elements were normalized by Al and linear regressions were also performed. For all trace elements (except Cu), regressions showed a significant correlation (p<0.05) and few outliers (<3% of cases), showing that the concentrations found represent natural values for this bay. In the case of Cu, the highest concentrations were found near small municipalities, which may be associated with domestic sewage. About 60% of the organic compounds occurred at levels below the limit of quantification (<0.26ngg−1). The sum of PAHs was low for all stations, ranging from 1.17 to 313ngg−1. The benthic assemblages also indicated that the CB is a healthy, well-preserved ecosystem that deserves conservation efforts. The integrated use of geochemical and biotic data supported the use of CB as a reference area.
Capsule: Organic and inorganic contaminants together with macrobenthic assemblages indicated that Camamu Bay is a pristine, tropical reference area.
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•Organic and inorganic contaminants indicate that Camamu bay is a pristine environment.•Benthic assemblages show that Camamu is a healthy and diverse tropical bay.•The use of multiple lines of evidence is essential in the characterization of reference areas.•Camamu Bay promotes multiple ecological services and must be preserved.
Concentrations of dissolved metals (Cd, Cu, Ni, Mn and Zn) were determined for summer and winter, under low-flow conditions in Port Jackson, a microtidal, well-mixed estuary in south-east Australia. ...Mean concentrations of Cd (0.04
±
0.02 μg/l), Ni (0.86
±
0.40 μg/l), Mn (20.0
±
25 μg/l) and Zn (6.47
±
2.0 μg/l) were below water quality guidelines. Concentrations of Cu (1.68
±
0.37 μg/l), however, slightly exceeded recommended values. Dissolved Ni and Mn behaved mostly conservatively, whereas Cd, Cu and Zn showed mid-estuarine maxima. Peaks in Cd, Cu and Zn concentrations were located in the upper estuary, independent of the salinity and suspended particulate matter loading, and were consistent with anthropogenic inputs of metals in the estuary. Concentrations of dissolved Cu were highest in summer, whereas concentrations of Cd, Ni and Mn were significantly lower in summer than winter (
P⩽0.05). The increase in temperature and biological activity during summer explained the seasonal variation. The sequence of log
K
d values (20–30 salinity) was Mn>Zn>Cu>Ni. These results give unique information concerning the contemporaneous distribution of dissolved trace metals in the Port Jackson estuary and they provide a data set against which the long-term contamination may be assessed.
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