Although global warming increases meltwater input into the oceans, rather little is known about the distribution of high field strength elements such as the rare earths and Y (REY), Zr, Hf, Th, and U ...in arctic glacial meltwaters and glacial-fed rivers. We studied glacial meltwater and glacial-fed rivers from the Kangerlussuaq area and a glacial-fed lake and its meltwater inflow in the Isua area, both in the western part of the Greenland Ice Sheet (GRIS). Trace element concentrations were determined in 0.2μm-filtered water samples (“dissolved” fraction), in the respective filter residues (“particulate” fraction) and in ambient sediments (including cryoconite from a meltwater pond on the surface of the GRIS). We also measured “truly dissolved” REY concentrations in a 10kDa-ultrafiltered sample from glacial-fed Watson River.
Shale-normalized (“SN”) REY patterns of the particulate fraction and ambient sediments (including cryoconite) are rather similar to those of local Archean gneisses and show positive EuSN anomalies. This rules out Asian dust (which does not show positive EuSN anomalies) as a possible source of these aluminosilicate particles, but suggests that local Archean basement is eroded and currently transported by ice, water and wind to the depositional sites in front of and onto the GRIS. All 0.2μm-filtered glacial-fed rivers show very unusual REYSN patterns in comparison to tropical, temperate and boreal rivers, and are significantly enriched in light relative to heavy REY. For glacial-fed Watson River, the <10kDa-ultrafiltrate shows much lower REY concentrations than the <0.2μm-filtrate, suggesting that >99% of La and >78% of Yb in the latter are associated with nanoparticles and colloids. Although the REYSN patterns of the <0.2μm-filtrates are rather similar to those of the particulate fraction and ambient sediments, they lack any EuSN anomalies, whereas the <0.2μm-filtrates from a meltwater pond on the surface of the GRIS show positive EuSN anomalies similar to (but somewhat smaller than) the cryoconite. While the water from the meltwater pond carries nanoparticles derived from local Archean sources, the lack of EuSN anomalies in the glacial-fed rivers suggests that their nanoparticle and colloid load represents atmospheric dust that is remobilized from greater depth in the GRIS. Most of this dust probably originated from eastern Asia and shows a REY distribution similar to Post-Archean upper continental crust, i.e., lacks any EuSN anomaly. Hence, REY geochemistry suggests that the particulates and the nanoparticles/colloids in these arctic meltwaters are derived from different sources.
•Rare earths+Y, Zr, Hf, Th and U were studied in meltwaters and glacial-fed rivers.•REY distribution and ultrafiltration show these elements to be bound to nanoparticles/colloids.•Very low truly dissolved (<10kDa) concentrations of these elements in arctic rivers.•Archean basement is a source of cryoconite, river particulates and sediments.•Asian dust is a source of nanoparticles/colloids in glacial-fed rivers.
Estuarine processes may affect the flux of dissolved organic carbon (DOC), iron and other particle-reactive elements such as the rare earth elements and yttrium (REY), into the ocean via salt-induced ...coagulation and subsequent removal of river-borne (nano-)particles and colloids. We experimentally assessed the impact of the admixture of seawater on DOC, Fe and REY associated with inorganic and organic nanoparticles and colloids (NPCs) present in tropical rivers, using Rio Solimões and Rio Negro, which are particularly rich in inorganic and organic NPCs, respectively, as river water endmembers. Similar to the conservative elements Sr, Rb and U, DOC behaves conservatively in all mixing experiments, whereas strong removal of Fe and REY (and preferential removal of light over heavy REY and of Ce relative to La and Pr) is confined to experiments with inorganic NPC-rich Rio Solimões water. This removal already occurs at very low salinity and is due to the aggregation of the inorganic NPCs. However, REY removal efficiency increases gradually with increasing salinity, which is in marked contrast to DOC-poor Arctic river waters from which REY removal at lowest salinity is significantly stronger. This suggests that the DOC concentrations in the water have a profound impact on the estuarine mixing behavior of particle-reactive elements. In marked contrast to the Rio Solimões mixing experiment, Fe and the REY in experiments with Rio Negro water behave similarly to DOC and mix conservatively with seawater, indicating that the organic NPCs, most of which are humic and fulvic acids, and their associated trace elements are much less susceptible to coagulation and estuarine removal than inorganic ones. Even at higher salinities, estuarine REY removal from inorganic NPC-rich Rio Solimões water significantly exceeds REY removal from organic NPC-rich Rio Negro water. Hence, the combination of higher element concentrations in and of less estuarine removal from organic NPC-rich rivers compared to inorganic NPC-rich rivers indicates that the former are a more important source of particle-reactive elements to the oceans than previously thought. This suggests that chemical complexation with organic ligands, such as humic and fulvic acids, may have a strong impact on the riverine flux and on the marine inventory of particle-reactive elements, and hence may play an important role for the isotopic composition of such elements in seawater.
Scandium is a critical raw material that is essential for the EU economy because of its potential application in enabling technologies such as fuel cells and lightweight materials. As there is ...currently no secure supply of Sc, several projects worldwide evaluate potential Sc sources. While elsewhere in Europe emphasis is placed upon secondary resources such as red mud, we investigated the potential of industrial garnet sand and its waste products. Since Sc readily substitutes for Mg and Fe in the crystal lattice of garnet, the garnet minerals almandine and pyrope, in particular, may show high Sc concentrations. Garnet sand, after being used as an abrasive in the cutting and sandblasting industry, is recycled several times before it is finally considered waste which eventually must be disposed of. Extraction of Sc (and rare earth elements, REE) from such garnet sand may generate added value and thereby reduce disposal cost. The studied garnet sands from different mines in Australia, India and the U.S., and industrial garnet sands commercially available in Germany from different suppliers show average Sc concentrations of 93.7 mg/kg and 90.7 mg/kg, respectively, i.e. similar to red mud. Our data also show that "fresh" and recycled garnet sands yield similar Sc concentrations. Within the framework of a minimum-waste approach, it may be feasible to utilize the industrial waste-product "garnet sand" as an unconventional source of Sc and REE, that reduces disposal cost.
•Trace element and Sm–Nd isotopic compositions of the ∼2.6Ga Krivoy Rog BIF.•Trace element systematics discriminate pure and impure BIFs.•Geochronology of the Krivoy Rog BIF constrains late Archean ...age.•REY patterns and Nd isotope compositions reveal REY sources in the BIF and seawater.•EuCN/Eu*CN (and ɛNd) of BIFs mirror magmatic history of the Early Earth.
Pure Superior-type Banded Iron Formation (BIF) samples from the Krivoy Rog Supergroup (Ukraine) are excellent archives of ambient Early Precambrian seawater. They show low concentrations of incompatible elements such as Zr, Hf, and Th, and shale-normalized Rare Earths and Yttrium (REYSN) patterns similar to those of modern seawater, i.e. heavy REYSN enriched patterns with positive LaSN, GdSN and YSN anomalies. Lack of CeSN and presence of positive EuSN anomalies indicate REY contributions to anoxic ferruginous seawater from high-temperature hydrothermal fluids.
The depositional age of the Krivoy Rog BIF is ill-defined, but a Late Archean to Paleoproterozoic age has been suggested based on U–Pb zircon ages for units stratigraphically above and below the BIF. We determined Sm–Nd isotopic compositions of pure and impure samples from the Krivoy Rog BIF, which yield an errorchron with an apparent age of 2406±350Ma (MSWD 15), that falls within this broad age range. All pure BIF samples show chondrite-normalized (subscript CN) REY patterns with strong positive EuCN anomalies that are typical for Archean but rather rare and much less pronounced in Proterozoic BIFs. Associated schists also show Archean – rather than post-Archean-style REY distributions. The REY geochemistry of both, chemical and epiclastic sediments, therefore, is more consistent with a Late Archean rather than a post-Archean depositional age of the Krivoy Rog Supergroup.
Initial ɛNd values of impure BIFs and of associated schist reveal variable contributions from TTGs less radiogenic in Nd and a more radiogenic component possibly comprised of basement amphibolites or mafic volcanics of the stratigraphically underlying New Krivoy Rog Group. The purest Krivoy Rog BIF, representing local Krivoy Rog seawater, displays an ɛNd2.60Ga value of −2.3. This value is less radiogenic than impure Krivoy Rog BIFs or other near-contemporaneous Neoarchean pure chemical sediments. To preserve this specific local isotopic fingerprint in anoxic Archean seawater, the Krivoy Rog BIF must have been deposited in an isolated sea basin with limited exchange with ferruginous deep-waters of the open ocean.
A compilation of REY data for high-purity Precambrian BIFs reveals that EuCN/Eu*CN ratios of Precambrian seawater follow a general global evolution curve, that shows specific peaks which reflect times of increased high-temperature hydrothermal REY input into seawater. Following declining EuCN/EuCN ratios from the Eoarchean to the Mesoarchean, the ratios suddenly rise at 2.7Ga and reach a maximum at 2.6Ga, indicating an increased flux of high-temperature hydrothermal REY to Neoarchean seawater, which supports the hypothesis that times of widespread BIF deposition coincided with periods of intense submarine hydrothermal activity, probably triggered by major mantle plume events. This association is supported by a strong increase of the ɛNd(t) values of pure seawater archives at 2.7–2.6Ga, which reflects an increased flux of mantle Nd into seawater. These results suggest that Eu-REY systematics (and potentially ɛNd systematics) are robust tools to indentify episodes of enhanced mantle plume activity.
This minireview provides a survey of the various synthetic approaches to chiral ansa‐metallocenes of Ti, Zr, and Hf containing a carbon‐based bridge. The individual strategies to install substitution ...patterns at either the cyclopentadienyl framework or the bridging unit are highlighted with focus on the progress made towards a direct preparation of single complex stereoisomers. The review further includes the discussion of potential problems such as the formation of undesired diastereomers, the threat of racemization of enantiopure material, and synthetic challenges originating from the synthesis, purification, and isolation of the target complexes. The review has been written with the goal in mind to facilitate the design and synthesis of new chiral ansa‐metallocene derivatives for emerging research areas in asymmetric catalysis and organometallic chemistry.
The club of chiral sandwiches: Chiral carbon‐bridged ansa‐metallocenes of Ti, Zr, and Hf have made a tremendous impact on polymer synthesis, asymmetric catalysis, and organometallic chemistry. The diverse synthetic strategies to access these complexes are discussed in detail with emphasis on stereoselectivity, isolation and purification techniques.
Volcanic ashes are often referenced as examples for natural nanoparticles, yet the particle size distribution <1000nm is only rarely documented. We here report results of a geochemical study of ...glacial-fed rivers, glacial surface runoff, glacial base flow, and pure glacial meltwater from southern Iceland, that had been sampled 25days after the explosive eruptions at Eyjafjallajökull in 2010. In addition to the dissolved concentrations of rare earth elements (REE), Zr, Hf, Nb, and Th in the 450nm-filtered waters, we also studied the respective filter residues (river particulates >450nm) and volcanic ash. In spite of the low solubilities and high particle-reactivities of the elements studied, most water samples show high dissolved concentrations, such as up to 971ng/kg of Ce and 501ng/kg of Zr. Except for the pure glacial meltwater and glacial base flow, all waters display the same shale-normalized REE patterns with pronounced light and heavy REE depletion and positive Eu anomalies. While such patterns are unusual for river waters, they are similar to those of the respective river particulates and the volcanic ash, though at different concentration levels. The distribution of dissolved Zr, Hf, Nb, and Th in the waters also matches that of filter residues and ash. This strongly suggests that in all 450nm-filtered river waters, the elements studied are associated with solid ash particles smaller than 450nm. This reveals that volcanic ash-derived nanoparticles and colloids are present in these glacial-fed rivers and that such ultrafine particles control the trace element distribution in the surface runoff. Subsequent to explosive volcanic eruptions, these waters provide terrigenous input from landmasses to estuaries, that is characterized by a unique trace element signature and that subsequent to modification by estuarine processes delivers a pulse of nutrients to coastal seawater in regions not affected by plume fall-out.
•Icelandic glacial-fed rivers show high dissolved REE and HFSE concentrations.•Volcanic ash, filter residues and river waters show similar REE and HFSE patterns.•Volcanic ash particles <450nm control dissolved REE and HFSE concentrations.•River water composition confirms that volcanic ashes contain natural nanoparticles.
Pressurized intraperitoneal aerosol chemotherapy (PIPAC) is used in the palliative treatment of peritoneal metastasis. The combination of intraperitoneal and systemic chemotherapy seems rational, and ...the aim of this systematic review was to compare PIPAC directed monotherapy with a bidirectional treatment approach (PIPAC in combination with systemic chemotherapy). Main outcomes were survival and quality of life.
A systematic literature search in Medline, Embase, Cochrane and the "Pleura and Peritoneum" was conducted and analyzed according to PRISMA guidelines. Studies in English reporting on bidirectional treatment with PIPAC and systemic chemotherapy and published before April 2019 were included.
Twelve studies with a total of 386 patients were included. None were specifically designed to compare mono- versus bidirectional treatment, but 44% of the patients received bidirectional treatment. This was more frequent in women (non-gynecological cancers) and one-third of the bidirectional treated patients had received no prior chemotherapy. Data from the included studies provided no conclusions regarding survival or quality of life.
Bidirectional treatment with PIPAC and systemic chemotherapy is practised and feasible, and some patients are enrolled having received no prior systemic chemotherapy for their PM. The difficulty in drawing any conclusions based on this systematic review has highlighted the urgent need to improve and standardize reports on PIPAC directed therapy. We have, therefore, constructed a list of items to be considered when reporting on clinical PIPAC research.
International Prospective Register of Systematic Reviews, PROSPERO. Registration number: 90352, March 5, 2018.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Scavenging experiments were performed at pH 3.6 to 6.2 with synthetic solutions containing dissolved Fe (≈7 mg/L), Rare Earths and Yttrium (ΣREY: ≈61 μg/L) in a matrix of 0.01 M HCl, and with natural ...water from Nishiki-numa spring, Japan, with the aim to study the fractionation that results from the interaction of dissolved REY with precipitating Fe oxyhydroxide. All patterns of apparent REY distribution coefficients between Fe oxyhydroxide and solution,
appD
REY, show negative anomalies at Y, La, and Gd, and the M-type lanthanide tetrad effect. These features become more pronounced with increasing pH. At pH ≤ 4.6, positive anomalies of
appD
Ce give evidence for oxidative scavenging of Ce on the Fe oxyhydroxide. A time-series experiment at pH 3.5 suggests that a stationary exchange equilibrium for the REY(III) is reached within less than 6.5 min, whereas the Ce(IV)/Ce(III) redox-equilibrium is not attained before 120 min. Oxidation rates of Ce(III) were found to decrease significantly during the first minutes after Fe oxyhydroxide formation, indicating that the capacity for Ce(III) oxidation is drastically higher in systems in which fresh Fe oxyhydroxides precipitate than in systems in which dissolved REY interact with pre-formed Fe oxyhydroxides. This additionally complicates the use of Ce anomalies of natural precipitates as quantitative paleo-redox-proxies. Radius-independent fractionation of REY(III) is very similar in experiments using synthetic solutions and natural water, despite the additional precipitation of hydrous Al oxides from the latter. Because there is no change of solution-complexation (speciation) along the REY series, radius-independent fractionation of REY(III) is likely due to differences between the stabilities of surface-complexes of the individual members of the REY series. The results presented here are an experimental verification of a natural process that may produce the lanthanide tetrad effect in geological samples.
Adjacent magnetite and chert bands and reference standards
FeR-3 and
FeR-4 from the Neoarchean Temagami iron-formation (IF) show shale-normalized rare earth and yttrium (REY) patterns with low Nd/Yb ...ratios and positive Eu, Gd and Y anomalies, indicating that they formed as marine chemical sediments. In contrast to previous claims, none of the samples shows any Ce anomaly, indicating the absence of oxidative Ce-REY decoupling and arguing against oxic conditions in the wider vicinity of the Neoarchean “Temagami seabasin”. The distribution of Zr, Hf and Ta yields Zr/Hf and Hf/Ta ratios that differ from those of chondrites, average upper continental crust and local shales, suggesting that the Temagami IF is the only case observed so far in which a significant fraction of these elements is non-detrital but sourced from seawater. If Neoarchean seawater was characterized by Zr/Hf and Hf/Ta ratios similar to those of modern seawater these ratios point towards preferential scavenging of Hf over Zr and Ta, as is typical of the modern ocean. Similar to the 2.9
Ga old Mozaan IF in the Pongola Supergroup, South Africa, the Temagami IF shows low Th/U ratios that differ from those of the respective local shales and from that of average upper continental crust. Decoupling of U and Th results from U
4+ oxidation in the Earth's surface system and fractionated Th/U ratios in these marine chemical sediments are, therefore, at odds with the lack of Ce anomalies. This suggests a different redox-sensitivity of the two paleo-redox-proxies Th–U and Ce-REY and demonstrates that the Temagami IF and the Mozaan IF warrant further study of other paleo-redox-proxies.
Rare earth elements and yttrium (REY) are often used as proxies for (paleo)environmental conditions and for the reconstruction of element sources and transport pathways. Many geological systems are ...well described with respect to the behavior of REY but deep-sea sediments with their manifold processes impacting the sediment during early diagenesis leave some questions about the origin and development of the shale-normalized REY (REYSN) patterns unanswered. Here we report REY data for sediment solid phase and pore water from the upper 10 m of deep-sea sediments from the Clarion Clipperton Zone (CCZ) in the central equatorial Pacific. The solid-phase REY profiles show highest concentrations at depth below 5–8 m. The REYSN patterns show an enrichment in middle REY (MREY) (LaSN/GdSN between 0.35 and 0.60; GdSN/YbSN between 1.19 and 1.47) and either no or negative CeSN and YSN anomalies (i.e. chondritic to sub-chondritic Y/Ho ratios between 24.7 and 28.7). Based on correlation analyses of bulk sediment element concentrations and sequential extractions, we suggest that a Ca phosphate phase controls the distribution and the patterns of REY in these silty clay pelagic sediments rich in siliceous ooze. The MREY enrichment develops at the sediment-water interface and intensifies systematically with depth. The negative CeSN anomaly intensifies with depth possibly because Ce is mostly bound to Mn- and Fe-(oxyhydr)oxides. Therefore, Ce concentrations remain relatively constant throughout the sediment core, while its trivalent REY neighbors are mostly hosted by the Ca phosphate phase that continuously incorporates REY from ambient pore waters. The non-redox-sensitive trivalent REY concentrations increase with depth, producing or enhancing a negative CeSN anomaly through coupled substitution of REY3+ and Na+ for Ca2+. The solid-phase REYSN pattern is therefore determined by the pore-water REYSN pattern and not suitable for paleoceanographic interpretation. The similarity of the pore-water and solid-phase REYSN patterns suggests, however, that only minor fractionation occurs during REY incorporation into the Ca phosphate crystal structure.
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