Elevated Concentrations Of Trace Elements Research Articles

Assessment of trace and macroelement accumulation in cyprinid juveniles as bioindicators of aquatic pollution: effects of diets and habitat preferences

Juveniles of three cyprinids with various diets and habitat preferences were collected from the Szamos River (Hungary) during a period of pollution in November 2013: the herbivorous, benthic nase (Chondrostoma nasus), the benthivorous, benthic barbel (Barbus barbus), and the omnivorous, pelagic chub (Squalius cephalus). Our study aimed to assess the accumulation of these elements across species with varying diets and habitat preferences, as well as their potential role in biomonitoring efforts. The Ca, K, Mg, Na, Cd, Cr, Cu, Fe, Mn, Pb, Sr, and Zn concentration was analyzed in muscle, gills, and liver using MP-AES. The muscle and gill concentrations of Cr, Cu, Fe, and Zn increased with trophic level. At the same time, several differences were found among the trace element patterns related to habitat preferences. The trace elements, including Cd, Pb, and Zn, which exceeded threshold concentrations in the water, exhibited higher accumulations mainly in the muscle and gills of the pelagic chub. Furthermore, the elevated concentrations of trace elements in sediments (Cr, Cu, Mn) demonstrated higher accumulation in the benthic nase and barbel. Our findings show habitat preference as a key factor in juvenile bioindicator capability, advocating for the simultaneous use of pelagic and benthic juveniles to assess water and sediment pollution status.

Chemical elements in Elaeis guineensis materials and derived oil

The production of oil palm (Elaeis guineensis) in Southeast Asia is vital to the economies of Indonesia and Malaysia. Both fertilisers and pesticides used in palm production can contain elevated concentrations of Trace Elements (TEs) which may accumulate in soils and leaf tissues of plants. We hypothesised that leaves from oil palms may be deficient in essential elements, while containing elevated concentrations of non-essential TEs commonly found in agrichemicals. Samples of plant materials (leaves and fruitlets) were collected from active and former plantations in Sumatra, Indonesia, and analysed for essential and non-essential elements. Indonesian palm oil samples were sourced in New Zealand and their elemental concentrations determined. Leaf materials from both active and abandoned production sites were deficient in N, K, S and Mo, while leaf materials from abandoned sites were deficient in P. These deficiencies may have been a contributing factor to the abandonment of production at these sites. Concentrations of non-essential elements were below or comparable to average plant concentrations and no evidence of contamination was found in plant tissues. Palm oil contained low concentrations of TEs, which did not pose any toxicity risks. However, Na and Al were present in concentrations of 1198 and 159 mg kg−1 respectively, which were higher than have been previously reported. Tropical oil palm production could benefit from the determination of bioaccumulation factors for fertiliser contaminants in E. guineensis, to limit the transfer of contaminants to plants and products if increased fertiliser applications were used to correct nutrient deficiencies.

Response of L. Scoparium and K. Robusta to biosolids and dairy shed effluent application in a low fertility soil

Biosolids and Dairy Shed Effluent (DSE) can contain high concentrations of plant nutrients, making them potential resources for enhancing forest tree species growth and soil fertility. This study aimed to investigate the effects of biosolids and DSE application on the growth and nutrient uptake of Leptospermum scoparium and Kunzea robusta, while also considering the potential accumulation of contaminants. The results demonstrated that amending low-fertility soil with 2600 kg N ha-1 of biosolids and 200 kg N ha-1 of DSE positively influenced the growth of both L. scoparium and K. robusta. This improvement was evident through increased biomass production and enhanced uptake of essential elements such as calcium (Ca), potassium (K), and sulfur (S). Notably, L. scoparium exhibited superior growth when combined with DSE, while both species showed similar positive responses when combined with biosolids. However, it should be noted that the application of biosolids resulted in elevated concentrations of certain trace elements in the plants, whereas DSE did not. These trace elements included cadmium (Cd), copper (Cu), manganese (Mn), and zinc (Zn). Despite the increase, the levels of these elements did not exceed unacceptable thresholds. Considering the potential influence of biosolids on plant rhizodeposition, it is recommended that future studies investigate the interactions between plant roots and microbes, particularly in relation to plant element uptake. This line of research would further enhance our understanding of the underlying mechanisms involved. In conclusion, the findings suggest that the application of biosolids and DSE can effectively improve forest tree growth and nutrient uptake. However, careful management is necessary to mitigate the potential accumulation of trace elements. These results provide valuable insights for optimizing the use of biosolids and DSE in forestry practices, with potential economic and environmental benefits.

Strategies of chemolithoautotrophs adapting to high temperature and extremely acidic conditions in a shallow hydrothermal ecosystem

BackgroundActive hydrothermal vents create extreme conditions characterized by high temperatures, low pH levels, and elevated concentrations of heavy metals and other trace elements. These conditions support unique ecosystems where chemolithoautotrophs serve as primary producers. The steep temperature and pH gradients from the vent mouth to its periphery provide a wide range of microhabitats for these specialized microorganisms. However, their metabolic functions, adaptations in response to these gradients, and coping mechanisms under extreme conditions remain areas of limited knowledge. In this study, we conducted temperature gradient incubations of hydrothermal fluids from moderate (pH = 5.6) and extremely (pH = 2.2) acidic vents. Combining the DNA-stable isotope probing technique and subsequent metagenomics, we identified active chemolithoautotrophs under different temperature and pH conditions and analyzed their specific metabolic mechanisms.ResultsWe found that the carbon fixation activities of Nautiliales in vent fluids were significantly increased from 45 to 65 °C under moderately acidic condition, while their heat tolerance was reduced under extremely acidic conditions. In contrast, Campylobacterales actively fixed carbon under both moderately and extremely acidic conditions under 30 − 45 °C. Compared to Campylobacterales, Nautiliales were found to lack the Sox sulfur oxidation system and instead use NAD(H)-linked glutamate dehydrogenase to boost the reverse tricarboxylic acid (rTCA) cycle. Additionally, they exhibit a high genetic potential for high activity of cytochrome bd ubiquinol oxidase in oxygen respiration and hydrogen oxidation at high temperatures. In terms of high-temperature adaption, the rgy gene plays a critical role in Nautiliales by maintaining DNA stability at high temperature. Genes encoding proteins involved in proton export, including the membrane arm subunits of proton-pumping NADH: ubiquinone oxidoreductase, K+ accumulation, selective transport of charged molecules, permease regulation, and formation of the permeability barrier of bacterial outer membranes, play essential roles in enabling Campylobacterales to adapt to extremely acidic conditions.ConclusionsOur study provides in-depth insights into how high temperature and low pH impact the metabolic processes of energy and main elements in chemolithoautotrophs living in hydrothermal ecosystems, as well as the mechanisms they use to adapt to the extreme hydrothermal conditions.4ap83QbxwyKb6GHBwDJLyuVideo

Copper and nanocopper toxicity using integrated biomarker response in Pangasianodon hypophthalmus.

The current study focused on assessing the toxicological effects of copper (Cu) and copper nanoparticles (Cu-NPs) in acute condition on Pangasianodon hypophthalmus. The median lethal concentration (LC50 ) for Cu and Cu-NPs were determined as 8.04 and 3.85 mg L-1 , respectively. For the subsequent definitive test, varying concentrations were selected: 7.0, 7.5, 8.0, 8.5, and 9.0 mg L-1 for Cu, and 3.0, 3.3, 3.6, 3.9, and 4.2 mg L-1 for Cu-NPs. To encompass these concentration levels and assess their toxic effects, biomarkers associated with toxicological studies like oxidative stress, neurotransmission, and cellular metabolism were measured in the liver, kidney, and gill tissues. Notably, during the acute test, the activities of catalase, superoxide dismutase, glutathione-s-transferase, glutathione peroxidase, and lipid peroxide in the liver, gill, and kidney tissues were significantly increased due to exposure to Cu and Cu-NPs. Similarly, acetylcholinesterase activity in the brain was notably inhibited in the presence of Cu and Cu-NPs when compared to the control group. Cellular metabolic stress was greatly influenced by the exposure to Cu and Cu-NPs, evident from the considerable elevation of cortisol, HSP 70, and blood glucose levels in the treated groups. Furthermore, integrated biomarker response, genotoxicity, DNA damage in gill tissue, karyotyping in kidney tissue, and histopathology in gill and liver were investigated, revealing tissue damage attributed to exposure to Cu and Cu-NPs. In conclusion, this study determined that elevated concentrations of essential trace elements, namely Cu and Cu-NPs, induce toxicity and disrupt cellular metabolic activities in fish.

Trace Elements and Consequent Ecological Risks in Mining-Influenced Streams of Appalachia.

Appalachian (eastern USA) coal surface mines fracture geologic materials, causing release of both major ions and trace elements to water via accelerated weathering. When elevated above natural background, trace elements in streams may produce adverse effects on biota via direct exposure from water and sediment and via dietary exposure in food sources. Other studies have found elevated water concentrations of multiple trace elements in Appalachia's mining-influenced streams. Except for Se, trace-element concentrations in abiotic and biotic media of Appalachian mining-influenced streams are less well known. We analyzed environmental media of headwater streams receiving alkaline waters from Appalachian coal mines for eight trace elements (Al, As, Cd, Cu, Ni, Sr, V, and Zn) and assessed the potential consequent ecological risks. Streamwater, particulate media (sediment, biofilm, leaf detritus), and benthic macroinvertebrates (primary consumers, secondary consumers, crayfish) were sampled from six mining-influenced and three reference streams during low-flow conditions in two seasons. Dissolved Cu, Ni, and Sr were higher in mining-influenced streams than in reference streams; Ni, Sr, and Zn in fine sediments and Ni in macroinvertebrates were also elevated relative to reference-stream levels in samples from mining-influenced streams. Seasonal ratios of mining-influenced stream concentrations to maximum concentrations in reference streams also demonstrated mining-influenced increases for several elements in multiple media. In most media, concentrations of several elements including Ni were correlated positively. All water-column dissolved concentrations were below protective levels, but fine-sediment concentrations of Ni approached or exceeded threshold-effect concentrations in several streams. Further study is warranted for several elements (Cd, Ni, and Zn in biofilms, and V in macroinvertebrates) that approached or exceeded previously established dietary-risk levels. Environ Toxicol Chem 2023;42:2651-2665. © 2023 SETAC.

Distributions of trace elements within MSWI bottom and combined ash components: Implications for reuse practices

Concentrations of 25 inorganic elements were measured in both bulk ash and individual ash components from residuals at three municipal solid waste incineration (MSWI) facilities in the US (two combined ash (CA) and one bottom ash (BA)). Concentrations were assessed based on particle size and component to understand the contribution from each fraction. The results found that among facilities, the finer size fractions contained elevated concentrations of trace elements of concern (As, Pb, Sb) when compared to the coarse fraction, but concentrations varied among facilities depending on the type of ash and differences in advanced metals recovery processes. This study focused on several constituents of potential concern, As, Ba, Cu, Pb, and Sb, and found that the main components of MSWI ash (glass, ceramic, concrete, and slag) are sources of these elements in the ash streams. For many elements, concentrations were significantly higher in CA bulk and component fractions opposed to BA streams. An acid treatment procedure and scanning electron microscopy/energy-dispersive x-ray spectroscopy analysis revealed that some elements, such as As in concrete, are result of the inherent properties of the component, but other elements, such as Sb, form on the surface during or after incineration and can be removed. Some Pb and Cu concentrations were attributed to inclusions in the glass or slag introduced into the material during the incineration process. Understanding the contributions of each ash component provides critical information for developing strategies to reduce trace element concentrations in ash streams to promote reuse opportunities.

Assessment of Trace and Rare Earth Elements Pollution in Water Bodies in the Area of Rare Metal Enterprise Influence: A Case Study—Kola Subarctic

An extended study of the chemical composition of surface waters and lakes bottom sediments, which are affected to varying degrees by an enterprise that mines and processes rare metal ores in the Lovozero tundra, was carried out. Using inductively coupled plasma mass spectrometry, the content of trace elements and rare earth elements was established. Elevated concentrations of trace elements and rare earth elements were revealed in samples of water and bottom sediments of lakes receiving wastewater from the enterprise and polluted due to dusting in the tailings of the processing plant. Thus, the average content of the total REEs in the surface layers of the SR Ilma and Lovozero (at the mouth of the Sergevan River) reaches 561 and 736 mg/kg, respectively, while for the SR of Lake Krivoe this indicator was 74 mg/kg. The enrichment factor (EFi), geoaccumulation index (Igeo), potential ecological risk index factor (Eir) and potential ecological hazard index (RI) were calculated. Assessing the total pollution with trace elements and rare earth elements of bottom sediments of lakes Ilma and Lovozero at the mouth of the Sergevan River, the value of potential ecological risk reaches values corresponding to the level of moderate ecological risk pollution (RIlma = 174, RILovozero = 186). The conducted correlation analysis made it possible to establish some of the main phases containing trace elements and rare earth elements in the bottom sediments of lakes Ilma and Lovozero.

Microbial endophytes and compost improve plant growth in two contrasting types of hard rock mining waste

The re-vegetation of mining wastes with native plants is a comparatively low-cost solution for mine reclamation. However, re-vegetation fails when extreme pH values, low organic matter, or high concentrations of phytotoxic elements inhibit plant establishment and growth. Our aim was to determine whether the combined addition of municipal waste compost and diazotrophic endophytes (i.e., microorganisms that fix atmospheric N2 and live within plants) could improve plant growth, organic matter accumulation, and phytostabilization of trace element contaminants in two types of hard rock mine waste. We grew a widespread native perennial grass, Bouteloua curtipendula, for one month in alkaline waste rock (porphyry copper mine) and tailings (Ag-Pb-Au mine, amended with dolomite) sourced from southeastern Arizona, United States. B. curtipendula tolerated elevated concentrations of multiple phytotoxic trace elements in the tailings (Mn, Pb, Zn), stabilizing them in roots without foliar translocation. Adding compost and endophyte seed coats improved plant growth, microbial biomass, and organic matter accumulation despite stark differences in the geochemical and physical characteristics of the mining wastes. The widespread grass B. curtipendula is a potential candidate for re-vegetating mine wastes when seeded with soil additives to increase pH and with microbial and organic amendments to increase plant growth.

An Assessment of Trace Element Accumulation in Palm Oil Production

African oil palm (Elaeis guineensis) is grown on 17,000,000 hectares in Southeast Asia, producing oil and the by-product, palm kernel expeller (PKE), for export. Elaeis guineensis is typically produced on weathered acidic soils, with fertilisers and fungicides used to increase production. These amendments can contain elevated concentrations of trace elements (TEs), either as the active ingredient (e.g., Cu-based fungicides) or as contaminants, including F, Zn, As, Cd, Pb and U. TEs may accumulate in soil over time, and be taken up by plants, posing a food-chain transfer risk if allowed to exceed soil guideline values. We reviewed available literature on trace elements in soil, plant material, oil and PKE to evaluate the risk of TE accumulation due to phosphate fertiliser and Cu-fungicide use. TE concentrations of Cu, Zn, and Cd were reported to be up to 69, 107 and 5.2 mg kg−1, respectively, in E. guineensis plantation soils, while Cu and As were reported to be up to 28.9 and 3.05 mg kg−1, respectively, in PKE (>50% their permissible limits). Iron, a TE, has also been reported in PKE up to 6130 mg kg−1 (>10-fold the permissible limit). TE accumulation is an emerging issue for the palm oil industry, which, if unaddressed, will negatively affect the industry’s economic and environmental sustainability. There are critical knowledge gaps concerning TEs in palm oil systems, including a general lack of research from Southeast Asian environments and information concerning key contaminants (Fe, Cu, As and Cd) in soils, plants and PKE.

Metalliferous habitats and seed microbes affect the seed morphology and reproductive strategy of Arabidopsis halleri.

Plant reproduction in metalliferous habitats is challenged by elevated concentrations of metal trace elements in soil. As part of their survival strategy, metal-tolerant plants have adjusted reproductive traits, including seed morphology, dormancy, and germination rate. These traits are particularly relevant, yet poorly understood, in metal hyperaccumulators that are promising candidates for phytoremediation. We assessed seed shape characteristics, dormancy, and germination rate in the hyperaccumulating model species Arabidopsis halleri. Seed morphological parameters were evaluated using seeds collected from two metalliferous and two non-metalliferous sites (~ 1000 seeds per location). We also addressed the potential influence of seed surface-associated microbes and endophytic fungi on germination success. Seeds from non-metallicolous populations were on average 18% bigger than those from metal-contaminated post-mining sites, which contrasts the general expectation about reproductive parts in metallicolous plants. Irrespective of their origin, surface-sterilized seeds had up to ~ 20% higher germination rates and germinated earlier than non-sterilized seeds, hinting at a negative effect of seed-associated microbial communities. Surface sterilization also facilitated the emergence of an endophytic fungus (Aspergillus niger) that is a known seed-borne pathogen. Interestingly, A. niger actually promoted germination in surface-sterilized seeds from some locations. Despite species-wide metal tolerance in A. halleri, metalliferous conditions seem to differently affect reproductive traits compared to non-metalliferous environments (e.g., smaller seeds). Yet, higher germination rates in these populations hint at the potential of A. halleri to successfully colonize post-mining habitats. This process is modulated by site-specific interactions with seed microbiota.

Bioaccumulation of trace elements affects chick body condition and gut microbiome in greater flamingos

Elevated concentrations of trace elements represent a major concern to wetland ecosystems, since river estuaries are geochemical endpoints that accumulate pollution. Although the negative impact of environmental exposure of highly toxic elements such as Pb and Hg has received substantial attention, we still lack a comprehensive understanding of the effects that these and other common trace elements have on natural populations. We used greater flamingos as a study system within three sites that represent a gradient of pollution. Controlling for environmental sediment exposure, we assessed if signatures of bioaccumulation in feathers for ten trace elements (As, Cd, Cr, Cu, Hg, Ni, Pb, Se, Sn and Zn) are associated with two known proxies of health: body condition and the gut bacterial microbiome. We found evidence of an adverse effect of Se, Hg, and Pb bioaccumulation on body condition. Furthermore, bioaccumulation of the elements As, Cu, Se, Pb and Zn influenced different aspects of the gut microbiome. Bioaccumulation of Se led to a shift in the microbiome composition, largely driven by an enrichment of Bacteroides plebeius, which is linked to the breakdown of sulphated polysaccharides of algae. Bacteroides plebeius was negatively associated with chick body condition, suggesting an adverse effect of a microalgae diet rich in Se. Pb bioaccumulation was linked with a decrease in microbial diversity (adjusted-R2 = 10.4%) and an increase in heterogeneity of the microbial community (adjusted-R2 = 10.5%), an indication of impaired gut homeostasis. As, Cu and Zn had more nuanced effects on gut microbiome heterogeneity according to breeding site and bioaccumulation concentration. Our results therefore suggest that in addition to well-studied elements, bioaccumulation of poorly studied elements also adversely affect health of natural populations.

Concentration of trace elements in forest soil affected by former timber depot

Certain parts of global forests show elevated concentrations of trace elements as a result of industry processes, places such as wood depots and plant protection products, which together degrade the forest environment. This paper examines a timber depot that used wood preservatives in World War II located in the Warcino Forest Inspectorate (Poland). It presents monitory findings on the degree to which the upper soil layer in the depot area has been contaminated by wood preservatives. Within two forest divisions, a network of soil extraction points was established, distinguished into three separate categories that demarcate the degrees of vegetation coverage and growth of the common pine. These were Area A (area with a pine stand that is several dozen years-old), Area B (areas with a pine stand that is approximately a dozen years-old) and Area C (areas without a pine stand). The Cu concentration in the surface categories was respectively 141.03/187.54/834.43 mg·kg−1. Above 600% in Cu concentration was noted in category C in comparison to category A. It was found that the content of most elements (B, Cd, Co, Cr, Fe, Mn, Mo, Ni, Pb, Zn) did not exceed the permissible values according to the Regulation of the Minister of the Environment on soil quality standards; however, in the case of Cu, the limit values established for forest and agricultural soils were exceeded, with the highest Cu contents found in the ‘C’ category. The results obtained confirm that the wood protection chemicals, such as copper sulphate, affected the long-term pollution of forest soils.

Elevated groundwater concentrations of arsenic and chromium in ultramafic environments controlled by seawater intrusion, the nitrogen cycle, and anthropogenic activities: The case of the Gerania Mountains, NE Peloponnese, Greece

This study aimed to investigate the role of seawater intrusion, nitrogen (N)-cycle, and anthropogenic activities on the elevated groundwater concentrations of oxyanion-forming trace elements in an ultramafic environment and to study the factors controlling the hydrogeochemical characteristics of groundwater in a broader, ultramafic-dominated area of the Gerania Mountains in NE Peloponnese, Greece. Sixty-eight groundwater samples from the a) Schinos area, b) Loutraki area, and c) springs in the Gerania Mountains were analysed for an extensive set of physical and chemical parameters. Elevated concentrations of As, up to 15 μg/L, along the coastline in the Schinos area, and abnormally high concentrations of Cr6+, up to 460 μg/L, in the central part of the Schinos area, were recorded. The strong spatial correlation of Cr6+, NO3-, and P in the central part of the Schinos area, indicated that the release and subsequent oxidation of geogenic Cr in groundwater can be triggered by N and P anthropogenic inputs, such as a) septic tank effluents or N-bearing fertilisers that lead to nitrification and subsequent soil acidification and drive Cr3+ oxidation by the NO2−/NO3− redox couple and b) P-bearing fertilisers that cause the desorption of anionic Cr6+ with simultaneous PO43- adsorption and contribute additional Cr and other trace elements to the soils. Unlike Cr, geogenic As follows a different pattern of groundwater release mechanism, which is driven by seawater intrusion and initial stages of denitrification along a flowpath near the Schinos coastline, as pointed out by the strong positive correlation coefficient between As and Cl− (0.78). The increased salinity controls the mobilisation of As and other oxyanion-forming trace elements, such as B, Se, and V, resulting in their elevated groundwater concentrations through a) their desorption from the surface of Fe/Mn-oxyhydroxides under alkaline pH conditions, b) the reductive dissolution of Fe/Mn-oxyhydroxides under local hypoxic conditions, and c) an increase in the ionic strength of groundwater favouring the dissolution of Fe/Mn-oxyhydroxides.

A Reconstitution Approach for Whole Rock Major and Trace Element Compositions of Granulites from the Kapuskasing Structural Zone

Current estimates for the composition of the lower continental crust show significant variation for the concentrations of the highly incompatible elements, including large uncertainties for the heat-producing elements. This has consequences for models of the formation of lower crust. For example, is lower continental crust inherently poor in incompatible elements or has it become so after extraction of partial melts caused by thermal incubation? Answering these questions will require better agreement between estimates for the chemistry of the lower crust. One issue is that granulite samples may have been altered during ascent. Xenoliths often experience contamination from the entraining alkaline magma, potentially resulting in elevated concentrations of incompatible trace elements when analysed by conventional bulk rock techniques. To avoid this, we assessed an in situ approach for reconstructing whole rock compositions with granulites from the Kapuskasing Structural Zone, Superior Province, Canada. As terrain samples, they have not been affected by host magma contamination, and as subrecent glacial exposures, they show minimal modern weathering. We used scanning electron microscope electron dispersive spectroscopy (SEM-EDS) phase mapping to establish the modal mineralogy. Major and trace element concentrations of mineral phases were determined by electron microprobe and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), respectively. These concentrations were combined with the modal mineralogies to obtain reconstructed whole rock compositions, which were compared to conventional bulk rock analyses. The reconstructed data show good reproducibility relative to the conventional analyses for samples with massive textures. However, the conventional bulk rock chemistry systematically yields higher K concentrations, which are hosted in altered feldspars. Thus, even in terrain samples, minor alteration can lead to elevated incompatible element estimates that may not represent genuine lower continental crust.

Exposure of earthworm (Eisenia fetida) to bauxite residue: Implications for future rehabilitation programmes.

Bauxite residue is typically alkaline, has high sodium content and elevated concentrations of trace elements. Effective rehabilitation strategies are needed to mitigate potential environmental risks from its disposal and storage. Increasingly, the importance of viable soil faunal populations as well as establishment of vegetation covers is recognized as key components of successful rehabilitation. Inoculation with earthworms is a strategy for accelerating mine site rehabilitation, but little is known on the effects of bauxite residue properties on earthworm survival and viability. In the current study, earthworms (Eisenia fetida) were exposed for 28days to a series of bauxite residue/soil treatments (0, 10, 25, 35, 50, 75 and 100% residue) to evaluate possible toxic effects on earthworms, investigate the bioavailability of relevant elements (e.g. As, Cr, V), and assess the risk of element transfer. Results showed that soil containing ≥25% residue (pH≥9.8; ESP≥18.5%; extractable Na≥1122mg/kg) significantly impacted survival (mortality ≥28%) and reproduction (cocoon production inhibition ≥76%) of the exposed earthworms. Alkalinity, sodicity and bioavailable Na were identified as major factors causing toxicity and some earthworms were observed to adopt compensative response (i.e. swollen body) to cope with osmotic stress. Conversely, soil containing 10% residue (pH=9.1; ESP=9.2%; extractable Na=472mg/kg) did not elicit significant toxicity at the organism level, but biomarker analysis (i.e. superoxide dismutase and catalase) in earthworm coelomocytes showed an oxidative stress. Furthermore, earthworms exposed to soil containing ≥10% residue took up and accumulated elevated concentrations of Al, As, Cr and V in comparison to the control earthworms. We concluded that earthworm inoculation could be used in future rehabilitation programmes once the key parameters responsible for toxicity are lowered below specific target values (i.e. pH=9.1, ESP=18.5%, extractable Na=1122mg/kg for Eisenia fetida). Nonetheless, trace element uptake in earthworms should be regularly monitored and the risk to the food chain further investigated.

Contributions of artifactual materials to the toxicity of anthropogenic soils and street dusts in a highly urbanized terrain

A study was undertaken to test the hypothesis that the presence of fly ash and other artifactual materials (AMs) significantly increases the toxicity of urban soil and street dust. AMs were distinguished as artifacts (artificial particles > 2 mm in size), and particulate artifacts (≤2 mm in size); street dust was the <63 μm fraction of street sediments. Reference artifacts, street dusts, and topsoils representing different land use types in Detroit, Michigan were analyzed for miscellaneous radionuclides, trace elements, magnetic susceptibility (MS), and acetic acid-extractable (leachable) Pb. Background levels were established using native glacial sediments. Street sediments were found to have a roadside provenance, hence street dusts inherited their contamination primarily from local soils. All soils and dusts had radionuclide concentrations similar to background levels, and radiological hazard indices within the safe range. Artifacts, fly ash-impacted soils and street dusts contained elevated concentrations of toxic trace elements, which varied with land use type, but none produced a significant amount of leachable Pb. It is inferred that toxic elements in AMs are not bioavailable because they are occluded within highly insoluble materials. Hence, these results do not support our hypothesis. Rather, AMs contribute to artificially-elevated total concentrations leading to an overestimation of toxicity. MS increased with increasing total concentration, hence proximal sensing can be used to map contamination level, but the weak correlation between total and leachable Pb suggests that such maps do not necessarily indicate the associated biohazard. Home site soils with total Pb concentrations >500 mg kg−1 were sporadically toxic. Thus, these results argue against street dust as the local cause of seasonally elevated blood-Pb levels in children. Lead-bearing home site soil tracked directly indoors to form house dust is an alternative exposure pathway.

New insights into environmental controls on the occurrence and abundance of Group I alkenones and their paleoclimate applications: Evidence from volcanic lakes of northeastern China

The distinctive long-chain alkenones (LCAs) produced by Group I Isochrysidales from freshwater and oligohaline lakes have great potential for quantitative paleotemperature reconstructions. The widespread application of sedimentary Group I LCAs, however, is hampered by an incomplete understanding of the environmental controls on the occurrence of Group I LCAs in freshwater lakes. The correspondence between Group I LCA concentrations and pH (6.2–8.5) in northern Alaskan freshwater lakes (Longo et al., 2016) suggests that Group I Isochrysidales may preferentially thrive in freshwater lakes with high pH. Here, we systematically study LCA distributions, haptophyte-specific 18S rDNA sequences, and concentrations of major ions and trace elements in 18 freshwater volcanic lakes in northeastern China with an extended pH range from 7.17 to 9.99. We find that 11 of the 18 lakes examined contain Group I LCAs and the corresponding DNA sequences of their producers. Our DNA results indicate that the dominant alkenone producer in all 11 lakes is closely related to the Group I Greenland OTU 5 genotype, with the exception of two anthropogenically impacted lakes where small numbers of Group II sequences are found. Statistical analyses indicate that the highest concentrations of Group I LCAs are found in oligotrophic freshwater lakes with pH ranging from ∼7.3 to 8.8. We find that elevated concentrations of certain trace elements may lead to the disappearance of Group I LCAs despite lake water falling within the optimal pH range. Together with previously published Group I LCA data from the temperature calibration in Northern Hemisphere freshwater lakes (Longo et al., 2018), we find, for the first time, that Group I R3b (R3b = C37:3b/(C38:3bEt + C37:3b)) values are most sensitive to winter temperature changes when mean winter temperature is higher than ∼−20°C. Our results suggest that the freshwater volcanic lakes in northeastern China are highly valuable targets for paleotemperature reconstructions using Group I LCAs.

Release of Nutrients and Trace Elements from Wood-, Agricultural Residue- and Manure-Based Biochars

Biochar has been used in many applications as a remediation material, but less attention has been paid to the potential release of various soluble components that may alter the effectiveness of the remediation process. Here, we report the release of nutrients, trace elements, anions and cations from 36 types of biochars. A batch-style experiment was performed by mixing biochar and water at a mass ratio of 1:75. Elevated concentrations of these components were observed in the majority of the solutions mixed with the biochars. No significant differences were observed between low-temperature (low-T, 300 °C) and high-temperature (high-T, 600 °C) biochars in terms of NO3−, Cl−, Na+, Ca2+, Fe, Cu, PO4-P, NH3-N, and K+ concentrations (P < 0.05). Agricultural residue biochars released significantly less Cl−, Na+, Mn, Ca2+, and K+ than manure-based biochars. The observation of nutrients and metal ions in solution was supported by the results of scanning electron microscope/energy-dispersive X-ray (SEM/EDX) analysis. The release of elevated concentrations of anions, cations, trace elements, and nutrients may affect receiving water bodies after the application of biochar.

Genesis of the giant Shizhuyuan W–Sn–Mo–Bi–Pb–Zn polymetallic deposit, South China: Constraints from zircon geochronology and geochemistry in skarns

The giant Shizhuyuan W–Sn–Mo–Bi–Pb–Zn polymetallic skarn-type deposit, which lies in the world-famous Nanling W–Sn metallogenic belt, has a close affinity with the Qianlishan granite complex. Previous studies focused on the Qianlishan granitoids rather than relevant skarns, where the evolutionary processes of skarn-forming fluids, mineralized fluids and sources of metals are debated. This study carried out systematic EPMA and LA-ICPMS zircon U–Pb dating, major- and trace-element and Lu–Hf isotopic analyses for three types of skarns: ore-free, greisen stockwork and sulfide-bearing skarns at Shizhuyuan. The whole skarn zircons were classified into six age clusters (125–187 Ma, ∼235 Ma, 345–509 Ma, 677–772 Ma 811–921 Ma and >1000 Ma) and three genetic types (detrital, magmatic and hydrothermally-altered). Among them, the majority of the skarn zircons are of detrital origin (345 to 2225 Ma, peaking at ∼410 Ma, ∼710 Ma and ∼905 Ma) and showing a wide range of Th/U ratios (0.05–7.09). They share similar characteristics of zircons hosted by Devonian strata in South China, suggesting the inheritance from wall-rock. The magmatic zircons in skarns can be further subdivided into two clusters: Triassic (∼235 Ma) and Jurassic (∼150 Ma), which are derived from the corresponding granite. Ore-free skarn contains only detrital zircons that have experienced the weakest alteration, indicating the minor participation of granitic fluid. The greisen stockwork skarn consists of both detrital zircons and Jurassic magmatic–hydrothermal zircons, implying that granitic and stratigraphic materials may both contribute greatly to the W–Sn polymetallic mineralization. Sulfide-bearing skarn includes abundant detrital zircon, a few of Triassic zircons but no Jurassic zircons, indicating that the latest sulfide mineralization was dominated by sediments rather than granitic rocks. The two mineralized skarn zircons display elevated concentrations of most trace elements (e.g., U, REE, Ti, Y, P, Nb and Ta) coupled with decreased Si and Zr, which reflects strong fluid-rock reaction. The lowest ratios of Ce/Ce* (1.22–89.78, mean = 24.13) in greisen stockwork skarn zircons reveal the most reducing environment for the main W–Sn mineralizing event. Jurassic zircons are homogeneous in 176Hf/177Hf (0.282352–0.282454) and εHf (t) (−11.58 to −7.27), in well accord with local granitic rocks. Triassic zircons have variable εHf (t) (−9.5 to −1.6) values, suggesting more mantle input of precursor pluton before the Jurassic main mineralization event. Based on the zircon geochronology in skarns, we speculate that concealed Triassic magmatism exists in the deep Shizhuyuan area. Consequently, a three-stage ore-forming model was established for the giant Shizhuyuan deposit. This study further illustrates that zircon can be used as an important indicator for ore genesis in complex metallogenic systems.