Trace Elements Research Articles

Cathodoluminescence textures and trace elements in quartz: Constraints on Ag mineralization in adularia–sericite epithermal systems

Cathodoluminescence textures and trace elements in quartz: Constraints on Ag mineralization in adularia–sericite epithermal systems

The evaluation of trace elements and associated risk in the polar ecosystem of the Fildes Peninsula, Antarctica

The evaluation of trace elements and associated risk in the polar ecosystem of the Fildes Peninsula, Antarctica

Microscale δ34S and δ18O variations of barite as an archive for fluid mixing and microbial sulphur metabolisms in igneous rock aquifers

ABSTRACT The stable isotope compositions of sulphur (δ34S) and oxygen (δ18O) in barite are frequently used as proxies for microbial sulphate reduction (MSR) in diverse environments, such as in relation to anaerobic oxidation of methane in marine cold seeps. There, isotopically heavy barite is used as a marker for MSR from a sulphate pool that has undergone semi-closed system conditions. Closed-system MSR is also a commonly observed feature in igneous rock hosted fracture aquifers, as shown by extremely 34S-enriched pyrite. What is less well-constrained is whether δ34S in barite can be used as a proxy for MSR in such systems. Here we explore the microscale heterogeneity of δ34S and δ18O via secondary ion mass spectrometry and the trace element Sr via LA-ICP-MS maps in barite precipitated in granite-hosted boreholes during a 17-year experiment, at Äspö, Sweden. We compare it with δ18Osulfate, δ34Ssulfate, and δ34Ssulfide of the fracture fluids and with paragenetic pyrite with δ34S values reflecting closed system MSR. The δ18O values in barite (+9.4 to +16.9 ‰) represent two generations of barite, one with low values and one with high values. The latter are likely impacted by sulphur disproportionating or -oxidizing bacteria. The barite reflects a much smaller span in δ34S (+14.5 to +28.6 ‰) than the pyrite (−47.2 to +53.3 ‰). This lack of extremely high δ34Sbarite values is proposed to be due to that barite saturation only occurred in the early parts of the Rayleigh cycle. Additionally, fluid migration has affected the δ34S values to lower values, accompanied by higher Sr concentrations. Taken together, barite δ34S values cannot be regarded as a reliable independent proxy for MSR in deep sulphate-poor igneous rock hosted aquifers. However, the relation between the δ34S values of coeval barite and pyrite is regarded as a useful proxy for MSR-related fractionation during early stages of MSR.

Clostridioides difficile exploits xanthine and uric acid as nutrients by utilizing a selenium-dependent catabolic pathway.

Selenium is a trace element that plays critical roles in redox biology; it is typically incorporated into "selenoproteins" as the 21st amino acid selenocysteine. Additionally, selenium exists as a labile non-selenocysteine cofactor in a small subset of selenoproteins known as selenium-dependent molybdenum hydroxylases (SDMHs). In purinolytic clostridia, SDMHs are implicated in the degradation of hypoxanthine, xanthine, and uric acid for carbon and nitrogen. While SDMHs have been biochemically analyzed, the genes responsible for the insertion and maturation of the selenium cofactor lack characterization. In this study, we utilized the nosocomial pathogen Clostridioides difficile as a genetic model to begin characterizing this poorly understood selenium utilization pathway and its role in the catabolism of host-derived purines. We first observed that C. difficile could utilize hypoxanthine, xanthine, or uric acid to overcome a growth defect in a minimal medium devoid of glycine and threonine. However, strains lacking selenophosphate synthetase (selD mutants) still grew poorly in the presence of xanthine and uric acid, suggesting a selenium-dependent purinolytic process. Previous computational studies have identified yqeB and yqeC as potential candidates for cofactor maturation, so we subsequently deleted each gene using CRISPR-Cas9 technology. We surprisingly found that the growth of the ΔyqeB mutant in response to each purine was similar to the behavior of the selD mutants, while the ΔyqeC mutant exhibited no obvious phenotype. Our results suggest an important role for YqeB in selenium-dependent purine catabolism and also showcase C. difficile as an appropriate model organism to study the biological use of selenium.IMPORTANCEThe apparent modification of bacterial molybdenum hydroxylases with a catalytically essential selenium cofactor is the least understood mechanism of selenium incorporation. Selenium-dependent molybdenum hydroxylases play an important role in scavenging carbon and nitrogen from purines for purinolytic clostridia. Here, we used Clostridioides difficile as a genetic platform to begin dissecting the selenium cofactor trait and found genetic evidence for a selenium-dependent purinolytic pathway. The absence of selD or yqeB-a predicted genetic marker for the selenium cofactor trait-resulted in impaired growth on xanthine and uric acid, known substrates for selenium-dependent molybdenum hydroxylases. Our findings provide a genetic foundation for future research of this pathway and suggest a novel metabolic strategy for C. difficile to scavenge host-derived purines from the gut.

Tracking subduction-related metasomatism of the subcontinental lithospheric mantle using Ca-, O-, and H-isotopes

Mantle xenoliths provide effective records of the metasomatic processes that affect continental lithosphere evolution, such as interaction with subducted components or modification via small-degree melts. Correlations between major/trace element geochemistry with stable and radiogenic isotope compositions can help constrain the source and timing of this metasomatism. We report new δ18O, δ44/40Ca, and δD values for twelve kimberlite-hosted mantle xenoliths from the Slave Craton (NWT, Canada), which show varying degrees of metasomatism. The δ18O values of olivine (δ18Ool = +5.33 ± 0.13‰; 1σ; n = 12) overlap average mantle values. Clinopyroxene and garnet δ18O values (δ18Ocpx = +5.31 ± 0.10‰; δ18Ogrt = +5.37 ± 0.23‰; 1σ) extend below those reported in most mantle peridotites and are strongly correlated with clinopyroxene δ44/40Ca (avg. = +1.00 ± 0.10‰; 1σ) and garnet δ44/40Ca (avg. = +1.18 ± 0.19‰; 1σ) respectively, extending from typical mantle values to low δ18O and high δ44/40Ca values. In general, Δ18Ocpx-ol and Δ18Ogrt-ol (ranging from −0.19‰ to +0.19‰ and from −0.56‰ to +0.35‰, respectively) are lower than expected equilibrium values at mantle temperatures. Strong negative correlations are found between δ18Ogrt and Δ18Ogrt-ol and garnet major and trace element composition (Na2O, H2O, La/YbN). Furthermore, phlogopite-bearing kelyphitic rims have δD values (avg. = −126 ± 13‰; 1σ) lower than typical mantle values. Whole rock Sm-Nd model ages and oxygen isotope diffusion modeling suggest that metasomatism occurred during the Mesozoic, shortly before kimberlite entrainment, consistent with indications from diamond-forming fluids from the Slave craton. The combined low δ18O, δD, and high δ44/40Ca signature of the mantle peridotite xenoliths, along with the age constraints, suggest the metasomatic fluid/melt is sourced from a recycled oceanic crust component related to Mesozoic subduction in western North America.

Population connectivity of the swordtip squid Uroteuthis edulis between southern Japan and northern Taiwan using statolith trace elemental analysis

Uroteuthis edulis (Hoyle, 1885) is an Indo-Pacific squid species widely distributing in the western Pacific, and commercially important especially in Japan and Taiwan. It has been suggested that some individuals are possibly transported from the spawning ground in north Taiwan to the coasts of Japan, however, the strength of population connectivity between those areas and its influence on U. edulis population dynamics were unveiled. To understand the U. edulis population connectivity in this area, the correlations between statolith trace elements and abiotic/biotic factors were examined first, and then squid experienced environments were postulated throughout their entire life cycle. Sr/Ca ratio showed a strongly negative correlation with ambient water temperature but no correlation with individual growth rate, suggesting that Sr/Ca ratio can be used to reflect squid experienced temperatures. Most squid caught in the Sea of Japan hatched in the areas having similar water temperature with where Taiwanese squid hatched, that would be off the north Taiwan or even warmer area. Statolith trace elements successfully distinguished the catch locations but not the hatching grounds, implying that hatching grounds of Japan and Taiwan squid were largely overlapped. Thus, we suggest that there is strong population connectivity of U. edulis population between southern Japan and northern Taiwan. As there was no clear evidence for existence of local population hatched in the Sea of Japan in this study, U. edulis population might display a source-sink population dynamics, that is, population in Taiwanese waters and/or further south as the source, and the one in the Sea of Japan as a sink population. As U. edulis should be considered as a metapopulation, collaboration among countries in the northwestern Pacific is required for sustainable fishery management of this species.

Classifying zircon: A machine-learning approach using zircon geochemistry

This study presented a novel, rapid, and accurate method for determining zircon origin via a comprehensive analysis of a dataset containing 27,818 zircon trace element sets. This method integrated back propagation neural networks with the AdaBoost algorithm. The optimal classifier characterized as a linear combination of a two-layer neural network model, comprised 100 base classifiers and 400 hidden neurons. It was rigorously trained over 1000 iterations, which resulted in an unbiased error rate of 8.31%. To facilitate practical application, the classifier was integrated into a macro-enabled Excel spreadsheet.

Two phases of granulite-facies metamorphism superimposied on retrograde eclogite: Constraints on the early Paleozoic tectonic evolution of the Qinling Orogenic Belt, central China

Existing studies provide adequate petrological evidences on ca. 500 Ma ultra-high pressure (UHP) metamorphism in the North Qinling Orogenic Belt (NQOB) in central China, but the genesis of 470–420 Ma multi-phase granulite-facies metamorphism in the NQOB and their relationship with the ca. 500 Ma UHP metamorphism remain controversial, resulting in the early Paleozoic evolution of the Qinling Orogenic Belt (QOB) highly debatable. In this study, we present mafic granulites and host felsic gneisses with a “red-eye socket” texture from the Shuanglong area, eastern NQOB, which recorded two phases of granulite-facies metamorphism superimposing on former eclogite-facies metamorphism. The former eclogite-facies metamorphism is indicated by eclogite-facies zircon trace element patterns and 496–495 Ma zircon ages, which are the same with those of the HP–UHP eclogite-facies metamorphic rocks in NQOB. The first granulite-facies metamorphism occurred at 460–448 Ma is characterized by coarse-grained minerals in matrix. Compositions and zonings of these minerals define an anticlockwise P–T path involving a prograde stage (751–763 °C), a high-temperature peak stage (9.2 kbar and 864 °C), and a near-isobaric cooling retrograde stage (8.3 kbar and 818 °C). The second granulite-facies metamorphism occurred at 422–421 Ma is represented by coronal garnet and coexisting fine-grained mineral aggregates. Coronal garnet compositional zonings suggest a clockwise P–T path consisting of a high-pressure peak stage (9.5–11.2 kbar and 748–783 °C) and a decompressing and heating retrograde stage (9.2–9.5 kbar and 789–800 °C). Combining dating results of leucosomes in these rocks and existing data, we proposed a new model for early Paleozoic tectonic evolution of the NQOB. The North Qinling Terrane (NQT), probably separated from the South China Block (SCB) during the breakup of Rodinia, drifted northwards and underwent UHP metamorphism at 500 Ma and then rapidly exhumed to crust level. Later, the Shangdan Ocean subducted northwards beneath the exhumed NQT at 470–440 Ma, resulting in the first granulite-facies metamorphism and contemporaneous migmatization and magmatism. Finally, the closure of the Shangdan Ocean led to collision between the NQT and South Qinling Terrane/SCB and the second granulite-facies metamorphism and anatexis at 422–418 Ma.

B-278 Evaluation of serum copper, zinc and selenium reference intervals using The National Health and Nutrition Examination Survey (NHANES) data

Abstract Background Serum copper, zinc and selenium, are commonly ordered for assessment of nutrient status or investigation of deficiency or overload. Review of reference intervals for these analytes is challenging as most laboratories do not have the resources to do a de novo reference interval study and many literature references are not recent. The National Health and Nutrition Examination Survey (NHANES) survey presents a unique opportunity to access a comprehensive database that includes biochemical parameters and health information in order to review reference intervals regularly, especially for more esoteric tests such as trace elements. In this study, copper, zinc and selenium reference intervals were calculated using NHANES data. Methods NHANES data for individuals 18 years of age and older was obtained from three releases between 2012-2016. Copper, selenium and zinc 95% confidence intervals were evaluated by age, sex and body mass index (BMI) partitions using quantile regression. All calculations were performed in R using the quantreg package. Results The calculated reference intervals for serum copper, zinc and selenium are shown in Table 1. Serum copper had the largest changes observed between sexes, with females having a much wider reference interval on the high end. Oral contraceptive use is known to increase serum copper levels which likely explains this trend. BMI over 30 also increased the serum copper reference interval, more clearly in women than in men. Zinc reference intervals were more aligned between women and men, with slightly higher intervals observed in men. BMI did not have much effect in either sex. For selenium, men had slightly higher reference intervals than women. Conclusions NHANES data provides a comprehensive data set for reference interval evaluation, especially for more esoteric analytes such as trace elements.

Geochemical fractionation of trace elements in ostreid and gastropod shells: A potential proxy for heavy metal pollution in Ghana’s coastal environment

The content of trace elements from Crassostrea tulipa (Ostreidae, Bivalvia) from four localities (Pra Estuary, Densu Estuary, Kpone Beach, and Anyanui Creek) along the coast of Ghana has been used as a bioindicator of environmental pollution. The lowest values of heavy metals correspond to the Crassostrea shells from Densu Estuary and Anyanui Creek, whereas the highest contents are recorded in the shells from Pra Estuary and Kpone Beach. Densu Estuary and Anyanui Creek are located in areas not affected by major industries, and only Densu is located in a densely urbanized setting. Crassostrea shells from Densu Estuary are only enriched in Ni. However, the Total Organic Carbon content of the sediments of the Densu Estuary indicates anthropogenic organic pollution not evidenced by the composition of Crassostrea shells. The Crassostrea shells from the Pra Estuary show enrichment in most of the analysed trace elements (Li, Be, V, Cu, Cr, Zn, Ga, Y, Sn, Pb, U, Th, ∑REE, and As) compared with other studied sites. This enrichment is related to heavy metals influx to the Pra River by the mining activities, extensive forest clearance, and loss of soil minerals. The Crassostrea shells from Kpone Beach present comparatively high content of some trace elements (Be, Ba, Cu, Zn, Nb, Pb, and REE). The metal pollutants are related to the input of the Heavy Industrial Area of Tema (located around 3.5 km west of Kpone Beach) and urban effluences from the Greater Accra Region. The high content of Ba, Cu, Zn, and Pb in Crassostrea is directly related to high phytoplankton productivity (mainly for diatoms) linked to the input of trace metals transferred into the marine food webs. In addition, some analyses of gastropod shells from Kpone Beach indicate that Cerithium and Nerita are more sensitive to accumulating Ni and As than Crassostrea. The values of trace metals from the Crassostrea shells of the Densu Estuary and Anyanui Creek are comparatively low. Considering the role of Crassostrea shells as bioindicators for heavy metals pollution, the less polluted localities are Anyanui Creek and Densu Estuary, whereas Pra Estuary and Kpone Beach are affected by anthropic activities such as mining, urban effluents, and industry.

A-115 Iron assay improvement: The need for thiourea addition in Ferene/Ferrozine reagent cartridge

Abstract Background Iron assay is often ordered along with ferritin, transferrin, and iron binding capacity in patients suspected of having iron deficiency anemia or iron overload. A ferene/Ferrozine chromogen-based iron assay is more common in College of American Pathology accredited laboratories across U.S. Recently, a product recall/field safety notice was issued by a major manufacturer for several lots of ferene based iron reagent due to unacceptable positive bias in patient iron results. However, the reason(s) underlying this positive bias was not provided. In this report, we investigated the possible causes for the recall of specific lots of iron assay reagents. Methods The performance of 2 lots of recalled iron test kits was compared against 2 good lots (Sentinel Diagnostics) on the Alinity c analyzer utilizing approved calibrator lots, quality control (QC) materials (Bio-Rad Laboratories), and excess/leftover de-identified patient samples. Spectral scan (in the visible wavelength) of good and recalled lots of reagents, R1 and R2 was performed on the Tecan microplate reader. Trace elements in R1 and R2 reagents were estimated with Quantitative Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Spiking experiments in calibrator, discarded patient samples, and reagents were undertaken to further elucidate the cause and prevention of positive bias seen with recalled reagent lots. Graphs and statistical analysis were generated using Graphpad prism 10.1. Results Iron levels in QC materials and de-identified patient samples (n=42) tested with 2 recalled lot of reagents on Alinity c analyzer showed a positive bias of 15-36% compared to unimpacted lots of reagents. Calibrator and blank absorbance of recalled lots was much higher than the unimpacted lots. Percentage change in the basal absorbance of recalled vs unimpacted R2 reagent measured from 500 to 600 nm in 25 nm increments and corrected to 700 nm ranged from 150 to 250%. No such changes were noted with both R1 reagents. Interestingly, ICP-MS heavy metal panel analysis revealed that R2 reagent of the recalled lots had unanticipated presence of Cu (∼22 υg/dL) and lead (7.5 υg/L), which was not present in R1 reagents. Increased concentrations of Cu spiking (100, 200, and 400 υγ/dL) in R2 reagent from recalled lots discernibly increased the Cal Factor values as well as patient iron results relative to unspiked reagent. Further, the presence of Cu over time deteriorated the accuracy of R2 reagent reflecting on very high rise in Cal Factor and patient iron values. Interestingly, TU addition to R2 reagent from unimpacted lot prevented the Cu-induced spurious rise in Cal Factor and iron measurements in the patient samples. Further, TU exhibited sustained preventive effect on Cu-induced iron measurement changes over time. Conclusions Based on our investigation, we conclude that copper contamination of R2 reagent is the possible cause for the positive bias in the recalled iron assay reagent lots. We recommend the addition of TU to Ferene containing R2 reagent pack as a simple and effective step to prevent Cu-induced false elevation in iron values.

First report of metals and metalloids on bone and claw tissues of Humboldt penguins (Spheniscus humboldti)

Samples of bones (humerus) and claws of adult Humboldt penguins (Spheniscus humboldti) were opportunistically obtained from twenty-seven carcasses at two important nesting sites in northern Chile: Chañaral Island (CHI) and Pan de Azúcar Island (PAI). The concentrations of trace elements (Cu, Zn, Pb, Ni, Fe, Se, As, Br, Mn and Cr) were determined by X-ray fluorescence. The highest levels (mean ± standard deviation, micrograms/g dry weight) of Cu (26.57 ± 4.08), Zn (163.9 ± 42.7), Pb (1.86 ± 1.53), Ni (0.31 ± 0.03), Se (7.70 ± 4.87) and Cr (0.25 ± 0.24) were detected in bones, whereas the highest levels of Fe (3,162 ± 1,579), As (6.75 ± 4.21), Br (0.12 ± 0.06) and Mn (76.7 ± 47.9) were found in claws. In bones, Se and Ni levels were higher (P < 0.05) in CHI than in PAI. In claws, the contents of Pb, Fe, and Mn were higher at CHI than those at PAI, whereas only As exhibited higher contents at PAI than those found at CHI. The trace element content in the claws and bones found herein may be the result of either acute or chronic exposure to penguins, respectively. These findings may serve as a baseline for further studies to design adequate and opportune plans to protect this vulnerable species.

A-184 Evidence-based Test Utilization: Test Ordering Patterns in Functional Medicine and Community Clinics, and Implications for Laboratory Stewardship

Abstract Background Functional Medicine Physicians (FMPs) use a holistic approach to identify and address “the root cause of a disease”. These physicians routinely order laboratory tests that are not supported by clinical suspicion and practice guidelines (i.e., Centers for Disease Control and Prevention Laboratory Medicine Best Practices, and local diagnostic algorithms) and are unnecessarily duplicative, with inappropriate testing patterns. Ordering unnecessary tests does not improve diagnosis; indeed, 5% of disease-free patients falsely test positive for a given diagnostic test. Test overutilization increases the rate of false positives, leading to unnecessary medical follow-ups, compromised patient care, and financial constraints on the healthcare system. The objective of this study is to: 1) Compare test ordering patterns between FMPs and General Practitioners (GPs) to identify disparities and opportunities for laboratory stewardship improvements. 2) Analyze the potential factors impacting test utilization in areas served by FMPs, 3) investigate the proper approach to improve test utilization. Methods Using our laboratory’s information system, we conducted a retrospective study spanning from January 2022 to December 2022 to assess testing patterns by 15 FMPs in Southern Alberta, comparing them to those of randomly selected community GPs within the same geographical region. A query was executed to retrieve data on the top 50 chemistry tests ordered by functional medicine clinics and community clinics. These tests were further categorized into six groups: general chemistry, endocrinology, immunology, trace elements, toxic metals, and vitamins. Data analysis included determining the geographical locations of functional medicine clinics and assessing the socioeconomic status of their patient populations. Additionally, the percentage of abnormal test results were calculated for both functional medicine clinic and community clinics. Furthermore, the average cost of tests per patient, per physician, and per clinic was computed to evaluate the financial implications of testing practices. Results Our preliminary results showed significant variability in test ordering practices among FMPs, with potential implications for patient care and healthcare costs. Most tests ordered by FMPs were normal (94%), suggesting a need for further scrutiny regarding the necessity and appropriateness of these tests. A notable trend observed was the disproportionate preference of FMPs for expensive tests, including hormones, vitamins, and toxic metals. Our analysis reveals that the cost per reportable test from FMPs was four times higher compared to the tests ordered by GPs. Furthermore, on average, functional medicine clinics in urban areas ordered around 60% more tests annually compared to their rural counterparts. Conclusions Our preliminary findings clearly show a need to monitor the testing behavior more carefully by the functional medicine clinics. The data from this study will be shared with the physicians practicing functional medicine in Alberta. Strategies to improve the test utilization and patient care include educating the functional medicine doctors and provincial healthcare authorities about the appropriate test utilization and the impact of inappropriate use of lab on patient care. In addition, using algorithms for test ordering will be used if the pattern of inappropriate testing continues.

A Trachytic Monogenetic Volcano in the Changbaishan Volcanic Field, Xitudingzi Volcano: Petrogenesis, Magma Plumbing System and Implications for Non-basaltic Monogenetic Volcanism

Abstract The Changbaishan volcanic field is the largest Quaternary volcanic field in China and includes the most dangerous polygenetic volcano, Tianchi volcano. In addition to the Tianchi volcano, the Changbaishan volcanic field contains two other polygenetic volcanoes (Wangtian’e volcano and Namphothe volcano) and at least 150 monogenetic volcanoes. The compositions of these monogenetic volcanoes range from basalt to rhyolite. Basaltic monogenetic volcanoes are the most abundant and spread throughout the volcanic field, whereas intermediate to evolved monogenetic volcanoes are found only within the Touxi subfield. We know very little about these non-basaltic monogenetic volcanoes, especially the magmatic petrogenesis, volcanological origins and structure of the magma plumbing system beneath them. Therefore, in this study, the Xitudingzi volcano within the Touxi subfield is used as an example to study the petrogenesis of silicic magma and explore the structure of the magma system by combining new 40Ar/39Ar dating, whole-rock geochemistry, Sr-Nd isotopes, and mineral chemistry. The 40Ar/39Ar chronology results showed that the Xitudingzi volcano erupted at 1.17 Ma; this volcano is younger than the other monogenetic volcanoes in the Touxi subfield. The geochemical results indicated that the eruption products of the Xitudingzi volcano are trachytic and formed from the assimilation fractional crystallization (AFC) process of an alkaline basaltic parental magma. The results from the Rhyolite-MELTS and thermobarometry indicated that the magma plumbing system of the Xitudingzi volcano contained two magma chambers at depths of 8 km and 19 km, respectively. The trachytic magma of Xitudingzi was produced by the AFC process from the alkaline basaltic magmas in the deep magma chamber and then transported to the shallow magma chamber. Furthermore, differences in the trace element concentrations between the different units of the Xitudingzi volcano indicated that the shallow pre-eruptive magma chamber was compositionally zoned. Based on the results from our study, the upper crustal magma plumbing system of the Xitutingzi volcano existed independently of the magma plumbing system of the cone-construction stage of the Tianchi volcano, even though the two volcanoes had similar ages of activity as well as the same chemical composition of eruptive products. Based on these results and other existing studies, a relatively thick crust and the developed faults are likely the key factors for the formation of intermediate to evolved monogenetic volcanos in the Touxi volcanic field.

Stable isotopes analysis combined with X-ray absorption spectroscopy reveal the fate of organic waste-borne copper and zinc in amended soils

Copper (Cu) and zinc (Zn), two potentially toxic trace elements, are commonly abundant in organic wastes (OWs) recycled in soils as fertilizer. Yet current knowledge on the long-term behavior and fate of Cu and Zn in soil following OW spreading is scant. We addressed this issue by studying the fate of OW-borne Cu and Zn in amended soils from four different long-term field experiments. By combining the stable isotope analysis and X-ray absorption spectroscopy, we identified changes in Cu and Zn concentrations, speciation and isotopic compositions in the amended soils only when OW had been applied at high rates over long periods. Under these conditions, we highlighted that: (i) all OW-derived Cu and Zn had accumulated in the topsoil layer regardless of the soil and OW type; (ii) the amended soil isotopic signatures were the result of the mixing of OW-borne and natural Cu and Zn; and (iii) Cu and Zn exhibited distinct speciation patterns in amended soils. Indeed, the unprecedented persistence of OW-borne crystallized Cu(I)-sulfide in the amended soils contrasted with the complete transformation of pig slurry-borne nanosized Zn-sulfide or household compost-derived amorphous Zn phosphate and Zn complexed by organic matter.

Enhancing short-chain fatty acids production from waste activated sludge anaerobic fermentation with addition of red mud: Performance and mechanisms

Red mud (RM) as hazardous waste produced from aluminum refining industry has threatened the environment and human health. In this study, RM was added into the fermenter to promote short chain fatty acids (SCFAs) production from waste activated sludge (WAS) anaerobic fermentation. Results showed that the addition of RM could effectively improve the SCFAs production, especially, acetic acid. In particular, the production of total SCFAs and acetic acid in 20 g/L RM added fermenter were 1108.1 mg COD/L and 415.5 mg COD/L, which were 116.0% and 1308.0% higher than that in control fermenter. Batch experiment revealed that RM could enhance the hydrolysis and acidification process. Further study indicated that the activity of enzyme related to hydrolysis-acidification, abundance of fermentative bacteria for SCFAs production and functional metabolism genome were all improved with the addition of RM. The potential mechanism maybe that the RM promoted the hydrolysis-acidification process with the contained varies Fe(Ⅲ) oxides as electron acceptor, and the produced Fe2+ could serve as necessary trace elements to synthesize enzyme and then stimulate the expression of enzyme genes.

From mother to egg: Variability in maternal transfer of trace elements and steroid hormones in common eider (Somateria mollissima)

The Baltic Sea is among the most polluted seas worldwide with elevated concentrations of trace elements (TEs). TEs can induce negative effects on organisms and may be transferred to eggs causing endocrine-disrupting effects on embryos. The Baltic Sea population of common eider (Somateria mollissima) has declined over the last thirty years, but the potential contribution of TEs to this decline is understudied. The aim of this study was to assess maternal transfer of TEs during the incubation period. Associations between TEs and steroid hormone concentrations in eggs (androstenedione, testosterone, pregnenolone and progesterone) were also investigated. Ten nests from Bengtskär (Finland) were monitored, for which hens at the beginning and end of the egg-laying were blood-sampled and their clutches were collected. Red blood cells from females (n = 10) and homogenized eggs (n = 44) were analyzed for 10 TEs (As, Ca, Cd, Cu, Hg, Mg, Ni, Pb, Se and Zn). Maternal and egg concentrations were correlated for Cu, Hg and Se (R2 = 0.51, R2 = 0.51, R2 = 0.52, respectively and all p-values ≤0.01). Three eggs had the highest Pb concentrations (1.43–2.24 μg g−1 ww) ever reported for this species. Although maternal and egg Pb concentrations were not significantly correlated, those eggs were laid by the same female, also having the highest Pb concentration (3.4 μg g−1 ww). Most blood TE concentrations in females were below known toxicity limits, except for Pb where 20 % of 10 females (including one outlier) had concentrations above the toxicity limit reported for subclinical poisoning in Anatini (> 0.2 μg g−1 ww). Steroid hormones in eggs were interrelated, but not correlated to TEs. Overall, the results call for more urgent research into the origin and consequences of high Pb concentrations and continued monitoring of the common eider populations in the Baltic Sea.

Influence of habitat utilization strategies on trace element signatures in egg contents of green turtles nesting on Xisha Islands, South China Sea

Habitat utilization significantly influences the accumulation of chemical pollutants, including trace elements (TEs), in the tissues of large marine organisms. Previous research has demonstrated that sea turtles nesting in the same location may employ distinct foraging strategies. This study investigated the influence of habitat use strategies on the concentrations of 16 TEs in the eggs of green turtles (Chelonia mydas) nesting on the Xisha Islands. The analysis incorporated stable carbon (δ13C) and nitrogen (δ15N) isotopes, as well as characteristic elements. Additionally, inter-relationships between TEs were examined. The nesting female green turtles were categorized into two foraging groups based on isotopic signatures, namely oceanic (δ13C values: −21.5 to −17.0 ‰; δ15N values: 7.10 to 12.5 ‰) and neritic (δ13C values: −14.4 to −9.95 ‰ and δ15N values: 5.10 to 10.0 ‰). Different TE patterns were observed in the egg contents of these two groups. The neritic group exhibited elevated levels of V and Cu, which positively corrected with δ13C values. Conversely, the oceanic group displayed higher levels of Zn, Cd, Se, Sn, As and Hg, which positively associated with δ15N values. This distribution pattern is attributed to variations in background TE concentrations in the respective foraging habitats. Additionally, prey items and trophic levels of green turtles may contribute to the observed inter-group differences in TE concentrations (e.g. Zn, As, Se, Sn) found in their eggs, warranting further research. This study provides valuable information about habitat utilization patterns and TE distribution in green turtles nesting on the Xisha Islands. The findings enhance our understanding of TE accumulation mechanisms in turtle tissues and eggs, which is significant for the conservation of this endangered species, the green sea turtle.

Glyphosate application may influence the transfer of trace elements from soils to both soil solutions and plants

Trace elements dynamics in the soil-plant system depends on multiple parameters, including chelating organic compounds from natural or synthetic organic matters. In this study, we evaluated the influence of one of the most common pesticides—glyphosate—on the mobility of trace elements considering contrasted soils (uncontaminated, anthropogenically contaminated, and naturally-enriched) in a greenhouse experiment. Four modalities have been tested: one control without any application, two with different glyphosate doses (1 and 3 times the authorised field dose), and one with compost addition to evaluate its potential ability to mitigate the impact of glyphosate on trace element mobility. Both, trace element and glyphosate concentrations were measured in the soil solutions and trace element contents were determined in plants at the end of the experiment. The results showed that, although glyphosate concentrations rapidly decreased in soil solutions, glyphosate application still influenced the transfer of trace elements to both soil solution (up to 12-times higher) and plant (up to 5.2-times higher). This influence was highly dependent on both the specific elements and the type of soils considered. For instance, in uncontaminated soils, glyphosate especially increased the mobilization of Mn, Co, Zn, Mo, and Pb to soil solution. This effect diminished of 2.5 times on average with increasing soil contamination. A similar trend was observed for the transfer of trace elements from soil to plant (i.e., on average 2.2-times lower in the most contaminated compared to the uncontaminated soil). However, in the naturally-enriched soil, opposing trends were noted between soil solutions and plants. The impact of compost addition on the transfer of trace elements to plants remains unclear: compost enhanced the transfer of trace elements to soil solution in uncontaminated and naturally-enriched soils likely due to trace element input through the compost, but decreased the transfer in anthropogenically-contaminated soils likely due to adsorption processes. Therefore, glyphosate could potentially increase the exposure of trace elements through food consumption and their transfer to the ecosystem, particularly in uncontaminated and weakly contaminated soils. In highly contaminated soils, compost could mitigate the glyphosate-induced enhancement of trace element mobility to soil solutions.

Experimental constraints on the role of temperature and pyrogenic mineral assemblage in wildfire-induced major and trace element mobilisation

Wildfires impact a large and increasing proportion of the Earth’s surface. With documented soil surface temperatures of up to ∼850 °C, wildfires may fundamentally alter the mineralogy and geochemistry of soils and regolith, more conventionally thought to be dominated by low temperature weathering processes. Here we use an experimental approach to test the effect of temperature on the formation of pyrogenic minerals, and on the distribution and mobility of major, trace and rare earth elements following post-fire chemical weathering. We focus on ferruginous nodules, common Fe-oxide cemented components of soils, which transform from non-magnetic to maghemite-bearing, magnetic nodules under wildfire conditions. These transformations provide a valuable record of fire impacts and facilitate the study of thermal processes and element mobility. Our results show heating produces a typical pyrogenic mineral assemblage of hematite, maghemite, metakaolin and transition alumina. At 900 °C the high temperature Fe2O3 polymorph luogufengite forms, which has never been reported in natural fire-affected substrates and therefore places an upper boundary on palaeowildfire temperatures at the soil-fire interface. Chemical leaching, employed to simulate the impacts of post-fire weathering, demonstrates that formation and subsequent breakdown of these pyrogenic minerals results in increased mobility of several elements including Li, Si, Sc, Cr, Co, Cu, Zn, Rb, Cs, La, Pb and U. Further, we propose that incongruent dissolution of pyrogenic metakaolin may be responsible for the formation of fusic material, an aluminous cement commonly found in soils. We conclude by discussing the significance of these results for the release of potentially toxic metals following a fire, identify trace elements that have the greatest potential to be used as palaeowildfire geochemical proxies (decreased alkali metal concentrations, decreased U/Th ratios, and decreased La compared to other rare earth elements), and the potential impact of wildfire on global geochemical cycles.