The strong increase in the consumption of rare earth elements (REE) in high-tech products and processes is accompanied by increasing amounts of REE released into the environment. Following the first ...report of Gd contamination of the hydrosphere in 1996, anthropogenic Gd originating from contrast agents has now been reported worldwide from river and estuarine waters, coastal seawater, groundwater and tap water. Recently, microcontamination with La, that is derived from a point source where catalysts for petroleum refining are produced, has been detected in the Rhine River in Germany and the Netherlands. Here we report the occurrence of yet another REE microcontamination of river water: in addition to anthropogenic Gd and La, the Rhine River now also shows significant amounts of anthropogenic Sm. The anthropogenic Sm, which enters the Rhine River north of Worms, Germany, with the same industrial wastewater that carries the anthropogenic La, can be traced through the Middle and Lower Rhine to the Netherlands. At Leverkusen, Germany, some 250km downstream from the point source at Worms, anthropogenic Sm still contributes up to 87% of the total dissolved Sm concentration of the Rhine River. Results from ultrafiltration suggest that while the anthropogenic Gd is not particle-reactive and hence exclusively present in the truly dissolved REE pool (<10kDa), the anthropogenic La and Sm are also present in the colloidal/nanoparticulate REE pool (between 10kDa and 0.2μm). Though difficult to quantify, our data suggest that the Rhine River may carry up to 5700kg of anthropogenic La, up to 584kg of anthropogenic Sm, and up to 730kg of anthropogenic Gd per year toward the North Sea. There exist no regulatory limits for dissolved REE in natural waters, but total REE and Y (∑REY) concentrations of up to 0.14mg/kg in the plume downstream of and 52.2mg/kg at the head of an effluent pipe at Rhine-km 447.3 at Worms get close to and well-above, respectively, the levels at which ecotoxicological effects have been documented. Because of the increasing use of REE and other formerly “exotic” trace elements in high-tech applications, these critical metals have now become emerging contaminants that should be monitored, and it appears that studies of their biogeochemical behavior in natural freshwaters might soon no longer be possible.
► First report of anthropogenic Sm anomaly in river water. ► Rhine River shows anthropogenic Sm, La and Gd. ► Ultrafiltration reveals anthropogenic Gd exclusively truly dissolved. ► Anthropogenic La and Sm also colloid/nanoparticle-bound. ► Rare earths have become emerging contaminants in the hydrosphere.
High-technology metals — such as the rare earth elements (REE) — have become emerging contaminants in the hydrosphere, yet little is known about their bioavailability. The Rhine River and the Weser ...River in Germany are two prime examples of rivers that are subjected to anthropogenic REE input. While both rivers carry significant loads of anthropogenic Gd, originating from contrast agents used for magnetic resonance imaging, the Rhine River also carries large amounts of anthropogenic La and lately Sm which are discharged into the river from an industrial point source.
Here, we assess the bioavailability of these anthropogenic microcontaminants in these rivers by analyzing the aragonitic shells of the freshwater bivalve Corbicula fluminea. Concentrations of purely geogenic REE in shells of comparable size cover a wide range of about one order of magnitude between different sampling sites. At a given sampling site, geogenic REE concentrations depend on shell size, i.e. mussel age.
Although both rivers show large positive Gd anomalies in their dissolved loads, no anomalous enrichment of Gd relative to the geogenic REE can be observed in any of the analyzed shells. This indicates that the speciations of geogenic and anthropogenic Gd in the river water differ from each other and that the geogenic, but not the anthropogenic Gd is incorporated into the shells. In contrast, all shells sampled at sites downstream of the industrial point source of anthropogenic La and Sm in the Rhine River show positive La and Sm anomalies, revealing that these anthropogenic REE are bioavailable. Only little is known about the effects of long-term exposure to dissolved REE and their general ecotoxicity, but considering that anthropogenic Gd and even La have already been identified in German tap water and that anthropogenic La and Sm are bioavailable, this should be monitored and investigated further.
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•Corbicula fluminea shells are bioarchives of dissolved geogenic REE in rivers.•Anthropogenic La and Sm in the Rhine River are bioavailable, hence incorporated.•Anthropogenic Gd from contrast agents is not incorporated, i.e. not bioavailable.•REE concentrations in Corbicula shells decrease with increasing size, i.e. age.
Pancreatic cancer(PC) is the most aggressive type of common cancers, and in 2014, nearly 40000 patients died from the disease in the United States. Pancreatic ductal adenocarcinoma, which accounts ...for the majority of PC cases, is characterized by an intense stromal desmoplastic reaction surrounding the cancer cells. Cancer-associated fibroblasts(CAFs) are the main effector cells in the desmoplastic reaction, and pancreatic stellate cells are the most important source of CAFs. However, other important components of the PC stroma are inflammatory cells and endothelial cells. The aim of this review is to describe the complex interplay between PC cells and the cellular and noncellular components of the tumour stroma. Published data have indicated that the desmoplastic stroma protects PC cells against chemotherapy and radiation therapy and that it might promote the proliferation and migration of PC cells. However, in animal studies, experimental depletion of the desmoplastic stroma and CAFs has led to more aggressive cancers. Hence, the precise role of the tumour stroma in PC remains to be elucidated. However, it is likely that a contextdependent therapeutic modification, rather than pure depletion, of the PC stroma holds potential for the development of new treatment strategies for PC patients.
The distribution of dissolved rare earth elements (REE) in the Rhine River, Germany, shows the anthropogenic gadolinium (Gd) microcontamination that is commonly observed in rivers in densely ...populated countries with a highly evolved health care system. However, the Rhine River also carries anomalously high concentrations of lanthanum (La), which produce very large positive La anomalies in normalized REE distribution patterns. These positive La anomalies first occur north of the City of Worms and then decrease in size downstream, but are still significant approximately 400km downstream, close to the German–Dutch border. The strong La enrichment is of anthropogenic origin and can be traced back to effluent from a production plant for fluid catalytic cracking catalysts at Rhine river-km 447.4. This effluent is characterized by extremely high dissolved total REE and La concentrations of up to 52mg/kg and 49mg/kg, respectively. Such La concentrations are well-above those at which ecotoxicological effects have been observed. The Rhine River is the first case observed to date, where a river's dissolved REE inventory is affected and even dominated by anthropogenic La. Our results suggest that almost 1.5t of anthropogenic dissolved La is exported via the Rhine River into the North Sea per year. This reveals that the growing industrial use of REE (and other formerly “exotic” elements) results in their increasing release into the environment, and highlights the urgent need to determine their geogenic background concentrations in terrestrial surface waters.
► Strong anthropogenic La anomaly in Rhine River downstream of Worms, Germany. ► Point source of La related to production of fluid catalytic cracking catalysts. ► Effluent shows 49 mg/kg La, well-above levels that are ecotoxicologically effective. ► Rhine River also carries anthropogenic gadolinium (Gd) derived from contrast agents. ► In lower reaches of the river, >93% of total La and Gd are of anthropogenic origin.
Gadolinium-based contrast agents used in magnetic resonance imaging are difficult to impossible to remove in wastewater treatment plants, and may enter groundwater production wells and hence ...municipal tap water via bank filtration. As anthropogenic gadolinium (Gd) may be accompanied by other, more harmful waste water-derived (micro)pollutants such as endocrine disruptors, we investigated the potential pathway of anthropogenic Gd into popular tap water-based beverages sold in highly frequented fast food restaurants. We, therefore, determined the concentration and distribution of geogenic and anthropogenic rare earth elements (REE) in tap water and in a related tap water-based popular soft drink (Coca Cola) from two fast food franchises (McDonalds and Burger King) in six major German cities. We observed anthropogenic Gd in both tap water and corresponding soft drinks in all investigated cities, extending the database for anthropogenic Gd in tap waters and highlighting its widespread distribution. In Berlin and Düsseldorf, where tap water is (mainly) produced by river bank filtration, 85 to 99% of the total Gd is of anthropogenic origin. The surprisingly high anthropogenic fraction (91%) in tap water from Munich reveals that even the shallow groundwater tapped in two Alpine valleys is eventually exposed to anthropogenic pollution. The REE distribution in post-mix soft drinks generally follows that of the corresponding tap water, except for enrichments of ytterbium (Yb), lutetium (Lu) and cerium (Ce), which are derived from the syrup. The concentration of anthropogenic Gd is similar in the soft drinks and in the corresponding tap water, demonstrating that the highly stable Gd-based contrast agents are not removed in soda fountains but are directly transferred to the beverages. This study highlights a pathway for anthropogenic waste water-derived xenobiotics such as pharmaceuticals and endocrine disruptors into the food chain, and hence, reveals the potential for human exposure to potentially harmful anthropogenic compounds.
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•Anthropogenic Gadolinium in municipal tap water in six major cities in Germany•Study proves entrainment of polluted surface water into shallow groundwater aquifers.•Anthropogenic gadolinium directly transferred into in tap water-based soft drinks.•First evidence that anthropogenic Gd used as contrast agent enters human food chain.•Reveals potential human exposure to possibly harmful waste-water derived compounds
It is widely assumed that atmospheric oxygen concentrations remained persistently low (less than 10(-5) times present levels) for about the first 2 billion years of Earth's history. The first ...long-term oxygenation of the atmosphere is thought to have taken place around 2.3 billion years ago, during the Great Oxidation Event. Geochemical indications of transient atmospheric oxygenation, however, date back to 2.6-2.7 billion years ago. Here we examine the distribution of chromium isotopes and redox-sensitive metals in the approximately 3-billion-year-old Nsuze palaeosol and in the near-contemporaneous Ijzermyn iron formation from the Pongola Supergroup, South Africa. We find extensive mobilization of redox-sensitive elements through oxidative weathering. Furthermore, using our data we compute a best minimum estimate for atmospheric oxygen concentrations at that time of 3 × 10(-4) times present levels. Overall, our findings suggest that there were appreciable levels of atmospheric oxygen about 3 billion years ago, more than 600 million years before the Great Oxidation Event and some 300-400 million years earlier than previous indications for Earth surface oxygenation.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Only few datasets on scandium (Sc) and rare earths and yttrium (REY) in rivers are available and the behaviour of Sc in the hydrosphere is poorly understood. We determined Sc and REY concentrations ...in the dissolved fraction of twelve boreal rivers in Sweden, which show low conductivity, circumneutral pH and elevated dissolved organic carbon (DOC). Scandium concentrations vary between 189 and 1170 pmol/l and are at the high end of the range reported for rivers worldwide. Unusually high Sc concentrations in the Dalsälven and Västerdalälven could be tracked to the Vanån, a tributary to the headwaters of the latter. Increasing Sc with increasing DOC and Yb concentrations suggest that organic ligands play a major role in the distribution of Sc. The REY
patterns are similar for all rivers (except the Västerdalälven) and are slightly light REY-depleted with negative Ce and Eu anomalies, and positive Y anomalies. These patterns appear to be a general feature of freshwater draining the Fennoscandian Shield into the Baltic Sea for at least the past 28 years. Our results clearly demonstrate that Sc and REY are fractionated in river waters relative to their crustal source and that they should not be discussed jointly as "REE".
The distribution of the rare earths and yttrium (REY) in co-existing hydrous Mn oxides and Fe oxides that form marine hydrogenetic ferromanganese crusts is used to better describe the partitioning ...and fractionation of the REY between these (hydr)oxides and seawater in the natural marine system. Four fractions (easily exchangeable, Mn-oxide-bound, Fe-oxide-bound, and insoluble-residue-bound REY) were separated by an adjusted sequential leaching procedure from two ferromanganese crusts from the Central Pacific. The distribution of the REY differs significantly between these leaching fractions and gives evidence for decoupling of La, Ce, Gd, Y, and Lu from their respective neighbours in the REY series during partitioning between hydrous Fe oxides, Mn oxides and seawater. Both the Mn oxides and the Fe oxides display pronounced positive Ce anomalies of almost similar size. This suggests that in the natural marine system oxidative scavenging of Ce from seawater is not restricted to Mn oxides but also occurs on hydrous Fe oxides. The distribution of Ce between the Mn oxides and the hydrous Fe oxides follows that of the trivalent REY and contrasts sharply with that of tetravalent Zr, Hf and Th. This suggests that preferential Ce removal from seawater does not result from the oxidation of dissolved Ce(III) within the marine water column, but that Ce(III) is oxidized after its sorption at the metal (hydr)oxide surface. Patterns of apparent hydrous Fe oxide/Mn oxide distribution coefficients show a sigmoidal shape and display negative anomalies for La, Gd, Y, and Lu (and the M-type lanthanide tetrad effect), indicating preferential scavenging of these elements by the Mn oxides as compared to the Fe oxides. The pronounced differences between the REY distribution in the Mn oxides and that in the Fe oxides cannot solely be explained by the REY speciation in seawater, but require additional and mineral-specific REY fractionation during surface-complexation.
We present experimental results on the sorption behavior of rare earth elements and yttrium (REY) on precipitating manganese (hydr)oxide in the presence of the biogenic siderophore desferrioxamine B ...(DFOB). In marked contrast to inorganic systems, where preferential adsorption of HREY and depletion of LREY is commonly observed in manganese (hydr)oxide precipitates, sorption of REY in presence of the DFOB siderophore leads to HREY-depleted and LREY-enriched patterns in the precipitates. Moreover, our data indicate that surface oxidation of Ce(III) to Ce(IV) during sorption onto manganese (hydr)oxides and the resulting development of a positive Ce anomaly, which are commonly observed in inorganic experiments, are prevented in the presence of DFOB. Instead, Ce(III) is oxidized to Ce(IV) but associated with the dissolved desferrioxamine B which forms complexes with Ce(IV), that are at least twenty orders of magnitude more stable than those with Ce(III) and REY(III). The overall result is the formation of a positive Ce anomaly in the solution and a negative Ce anomaly in the Mn (hydr)oxides. The distribution of the strictly trivalent REY and Eu(III) between the manganese (hydr)oxide phase and the remaining ambient solution mimics the distribution of published stability constants for complexes of REY(III) with DFOB, i.e. the heavy REY form more stable complexes with the ligand and hence are better shielded from sorption than the LREY. Surface complexation modeling corroborates our experimental results. Negative Ce anomalies in Mn precipitates have been described from biogenic Mn oxides. Our results provide experimental evidence for the development of negative Ce anomalies in abiogenic Mn (hydr)oxide precipitates and show that the presence of the widespread siderophore desferrioxamine B during mineral precipitation results in HREY-depleted Mn (hydr)oxides with negative Ce anomalies.
Polyvalent trace elements such as the high field strength elements (HFSE) are commonly considered rather immobile during low-temperature water–rock interaction. Hence, they have become diagnostic ...tools that are widely applied in geochemical studies. We present results of batch leaching experiments focused on the mobilization of certain HFSE (Y, Zr, Hf, Th, U and rare earth elements) from mafic, intermediate and felsic igneous rocks in the presence and absence, respectively, of the siderophore desferrioxamine B (DFOB). Our data show that DFOB strongly enhances the mobility of these trace elements during low-temperature water–rock interaction.
The presence of DFOB produces two distinct features in the Rare Earths and Yttrium (REY) patterns of leaching solutions, regardless of the mineralogical and chemical composition or the texture of the rock type studied. Bulk rock-normalized REY patterns of leaching solutions with DFOB show (i) a very distinct positive Ce anomaly and (ii) depletion of La and other light REY relative to the middle REY, with a concave downward pattern between La and Sm. These features are not observed in experiments with hydrochloric acid, acetic acid or deionized water. In DFOB-bearing leaching solutions Ce and U are decoupled from and selectively enriched relative to light REY and Th, respectively, due to oxidation to Ce(IV) and U(VI). Oxidation of Ce3+ and U4+ is promoted by the significantly higher stability of the Ce(IV) and U(VI) DFOB complexes as compared to the Ce(III) and U(IV) DFOB complexes. This is similar to the relationship between the Ce(IV)- and Ce(III)-pentacarbonate complexes that cause positive Ce anomalies in alkaline lakes. However, while formation of Ce(IV) carbonate complexes is confined to alkaline environments, Ce(IV) DFOB complexes may produce positive Ce anomalies even in mildly acidic and near-neutral natural waters. Siderophore-promoted dissolution processes also significantly enhance mobility of other ‘immobile’ HFSE and may not only cause or modify Ce anomalies and Th–U fractionation, but also mobilization of and fractionation between Zr, Hf, Th and redox-insensitive REY during weathering, pedogenesis, diagenesis and incongruent dissolution of particles in seawater and freshwater.
Siderophores may significantly affect the use of HFSE as geochemical tools. Concave downward light REY patterns may be used as a biosignature for water–rock interaction in the presence of siderophores. Enhanced and preferential mobilization of U relative to Th in the presence of siderophores may produce Th–U signals comparable to those indicative of weathering under oxidized conditions, which might constrain the use of U concentrations and Th/U ratios as a paleoredox-proxy. The enhanced mobilization of Zr and especially Hf from igneous rocks in the presence of DFOB might have implications for the use of the latter as a tracer for the impact of continental weathering on seawater chemistry. Because siderophore complexes affect the particle-reactivity of Hf and Zr, they may prevent effective removal of terrigenous Hf and Zr during aggregation/coagulation of riverine particles in estuaries. Siderophore-promoted solubilization and stabilization might hence be an additional way to transport continental Hf and Zr to the oceans. Furthermore, siderophore-enhanced mobilization may also have implications for the remediation techniques employed to immobilize HFSE such as U, Th and REY, at nuclear waste and reprocessing sites and at REY ore processing plants, where soils are commonly contaminated with these (sometimes radioactive) heavy metals.
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