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Rhenium (Re) and uranium (U) are essential proxies in reconstructing past oceanic oxygenation evolution. However, their removal in continental shelf sediments, hotspots of early diagenesis, were previously treated as quantitatively unimportant sinks in the ocean. Here we examine the sedimentary reductive removal of Re and U and their coupling with organic carbon decomposition, utilizing the 224Ra/228Th disequilibria within the East China Sea shelf. We identified positive correlations between their removal fluxes and the rates of sediment oxygen consumption or organic carbon decomposition. These correlations enable an evaluation of global shelf reductive sinks that are comparable to (for Re) or higher than (~4-fold for U) previously established suboxic/anoxic sinks. These findings suggest potential imbalances in the modern budgets of Re and U, or perhaps a substantial underestimation of their sources. Our study thus highlights shelf sedimentary reductive removal as critical yet overlooked sinks for Re and U in the modern ocean. The sources and sinks of Re and U in the modern ocean may be imbalanced, according to sedimentary porewater analysis and assessment of reductive Re and U removal on the continental shelf [ABSTRACT FROM AUTHOR]

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Forty Tertiary coals from Mukah-Balingian and Merit-Pila coalfields of the Sarawak Basin, Malaysia were investigated using bulk and molecular geochemical techniques such as proximate analysis, gas chromatography-mass spectrometry, elemental analyser, isotope ratio mass spectrometry, and inductively coupled plasma mass spectrometry to reconstruct their paleovegetation, paleoclimate, and environments of deposition. In addition, principal component analysis (PCA) of selected geochemical parameters was carried out to determine the controlling influences on the petroleum potential of the humic coals. δ13C values and the abundance of terpenoids imply the predominant contribution of angiosperms to the paleoflora. Bimetal proxies (Sr/Ba, Sr/Cu, and C-value), and δD values are generally suggestive of a warm and humid climate during the accumulation of the paleopeats. However, n-alkane proxies (Pwax, Paq, n-C23/n-C29, etc.) and polycyclic aromatic hydrocarbons (PAHs) distribution suggest that Balingian coals accumulated under relatively drier and strongly seasonal paleoclimate in the Late Pliocene. When compared with published global average abundances, the investigated coals are mostly depleted in major oxides and trace elements, suggesting peat accumulation in freshwater-influenced environments. Nonetheless, higher (> 0.5 wt%) total sulfur content in some Mukah-Balingian coals suggests some degree of epigenetic marine influence. Furthermore, the low to moderately-high ash contents of the Sarawak Basin coals indicate the presence of ombrotrophic and rheotrophic peat deposits. PCA result of selected geochemical proxies suggests that source input, paleoflora, and marine incursions are not major controlling influences on the petroleum potential. However, climatic, and depositional conditions appear to slightly influence the petroleum potential of the studied humic coals. [ABSTRACT FROM AUTHOR]

Rhenium (Re) and uranium (U) are essential proxies in reconstructing past oceanic oxygenation evolution. However, their removal in continental shelf sediments, hotspots of early diagenesis, were previously treated as quantitatively unimportant sinks in the ocean. Here we examine the sedimentary reductive removal of Re and U and their coupling with organic carbon decomposition, utilizing the 224Ra/228Th disequilibria within the East China Sea shelf. We identified positive correlations between their removal fluxes and the rates of sediment oxygen consumption or organic carbon decomposition. These correlations enable an evaluation of global shelf reductive sinks that are comparable to (for Re) or higher than (~4-fold for U) previously established suboxic/anoxic sinks. These findings suggest potential imbalances in the modern budgets of Re and U, or perhaps a substantial underestimation of their sources. Our study thus highlights shelf sedimentary reductive removal as critical yet overlooked sinks for Re and U in the modern ocean. The sources and sinks of Re and U in the modern ocean may be imbalanced, according to sedimentary porewater analysis and assessment of reductive Re and U removal on the continental shelf [ABSTRACT FROM AUTHOR]

A systematic review and meta-analysis was performed to comprehensively evaluate the association between manganese (Mn) level and preeclampsia (PE) during pregnancy. Relevant observational studies were retrieved by searching Medline, Web of Science, Embase, and Cochrane Library from database inception to May 25, 2023. Pooling results was performed using a random-effects model incorporating heterogeneity. This meta-analysis incorporated 18 observational studies, which included 1113 women with PE and 5480 normotensive pregnant women. Pooled results showed that compared to normotensive control, women with PE had significantly lower blood Mn concentration (standardized mean difference: −0.36, 95% confidence interval: −0.50 to −0.22, p < 0.001; I2 = 67%). Subgroup analysis showed that the results were not significantly affected by study country (African, Asian, or Western), timing of blood sampling (before, at, or after the diagnosis of PE), mean blood Mn level of controls, or numbers of confounding factors adjusted (p for subgroup analysis all > 0.05), while methods for measuring blood Mn levels might affect the results (p for subgroup difference < 0.001). Finally, pooled results of three studies showed that a high level of blood Mn was related to a low risk of PE with blood Mn analyzed in continuous (risk ratio [RR]: 0.71, 95% CI: 0.59 to 0.85, p < 0.001; I2 = 0%) and categorized variables (RR: 0.50, 95% CI: 0.30 to 0.82, p = 0.006; I2 = 32%). In conclusion, a low blood level of Mn may be associated with PE in pregnant women. [ABSTRACT FROM AUTHOR]

Background and Aims: Bioremediation of soils contaminated with metal(loid)s is an attractive research area due to its sustainability and economic benefits. In the Slovak Republic, there are several abandoned mines containing high concentrations of arsenic (As) and antimony (Sb). This calls for new options for removing these hazardous metalloids from contaminated substrates. Studies on bioleaching of soils co-contaminated with both metalloids are very rare. This study aimed to test the effectiveness of bioleaching of soils heavily co-contaminated with As and Sb (up to 1463 mg.kg–1 and 5825 mg.kg–1, respectively) at a former stibnite mining site (Poproč, eastern Slovakia) through biostimulation and bioaugmentation. Methods: Bioleaching of As and Sb from four soils was induced by biostimulation of autochthonous microflora with Sabouraud medium (SAB) and SAB+glucose, and bioaugmentation of the soil with bacterial strains Cupriavidus oxalaticus and Cupriavidus metallidurans. Soil samples were subjected to determination of physico-chemical properties, microbiological parameters, and additional mineralogical analysis. Results: An inverse relationship between the total metalloid concentration and the microbial diversity was confirmed. In experiments with Cupriavidus metallidurans and Cupriavidus oxalaticus, mean bioleached As fractions were 37.6% and 41.3%, while Sb bioleaching was significantly lower, ranging between 17.0–26.2%. The mean bioleached fraction of As and Sb using SAB was 40.7% and 14.4%, respectively. The addition of glucose to SAB increased As bioleaching (50.7%) but not that of Sb. Conclusion: Collectively, the results highlighted a role of microorganisms in the mobility of metalloids in soils with their prospective applications in remediation of contaminated sites. [ABSTRACT FROM AUTHOR]

Background: Macrophytes may modify benthic biodiversity and biogeochemistry via radial oxygen loss from roots. This condition contrasts sediments anoxia, allows roots respiration, and facilitates aerobic microbial communities and processes in the rhizosphere. Simultaneously, the rhizosphere can stimulate anaerobic microorganisms and processes via exudates or by favoring the build-up of electron acceptors as nitrate. As eutrophication often results in organic enrichment in sediments and large internal nutrients recycling, an interesting research question is to investigate whether plants maintain the capacity to stimulate aerobic or anaerobic microbial communities and processes also under elevated organic pollution. Methods: A manipulative experiment was carried out under laboratory-controlled conditions. Microcosms containing bare sediments and sediments transplanted with the macrophyte Vallisneria spiralis L. were created. The effect of the plant was investigated on sediments with moderate (8%) and elevated (21%) organic matter content, after an acclimatization period of 30 days. Chemical and physical parameters, microbial community composition and the potential rates of nitrification, denitrification and nitrate ammonification were measured at two different depths (0–1 and 1–5 cm) after the acclimatization period to evaluate the role of roots. Results: Vallisneria spiralis grew and assimilated pore water nutrients at the two organic matter levels and vegetated sediments had always nutrient-depleted porewaters as compared to bare sediments. Nitrifying microbes had a lower relative abundance and diversity compared to denitrifying bacteria. However, regardless of the organic content, in vegetated sediments nitrifiers were detected in deeper horizons as compared to bare sediments, where nitrification was confined near the surface. In contrast, potential denitrification rates were not affected by the presence of roots, but probably regulated by the presence of nitrate and by root-dependent nitrification. Potential nitrate ammonification rates were always much lower (< 3%) than potential denitrification rates. Conclusions: Vallisneria spiralis affects N-related microbial diversity and biogeochemistry at moderate and elevated organic matter content, smoothing bottom water–pore water chemical gradients and stimulating nitrification and nitrogen loss via denitrification. These results suggest the possibility to deploy V. spiralis as a nature-based solution to counteract eutrophication in freshwater systems impacted by high loads of organic matter, for example, downstream of wastewater treatment plants. [ABSTRACT FROM AUTHOR]

Ediacaran to Early Cambrian sequences are well preserved in several synclines within the Lesser Himalaya. We have conducted multi-proxy geochemical and stable isotopic studies on carbonaceous sediments of the basal Tal Group to decipher redox conditions of the Earliest Cambrian Ocean. Organic matter is immature, predominantly aliphatic and likely derived from marine phytoplankton. The S/C(organic) ratios above 0.4; strong enrichment of redox-sensitive trace elements V, Mo, U and Cd; higher DOPT, U/Th, V/Sc, Mo/Sc and V/(V+Ni) ratios; V/Al–U/Al–Mo/Al systematics and U–Mo enrichment factors indicate anoxic to euxinic conditions of deposition. Large variations (5–7‰) in δ13C likely reflect spatial heterogeneity or vertical gradient in DIC compositions of the Early Cambrian Ocean, and possibly capture the part of Basal Cambrian negative Carbon isotope Excursion (BACE). Finely disseminated texture of pyrite framboids with sizes mostly below 10 µm suggest sulfide reduction within the water column in an open system. Isotopically heavy δ34S values (+4.5 to +22.8‰) overlap with the δ34Ssulfate of contemporary Fortunian ocean (+10 to +40‰), suggesting sulfidic conditions and small size of the sulfate reservoir. Whereas the REE+Y proxies of the same set of samples show seawater-like patterns, with strong HREE enrichment, positive Y and La anomalies and negative Ce anomaly (avg. Ce/Ce* = 0.78), indicating REE uptake by phytoplankton from an oxidized-euphotic surface zone. The combined geochemical and isotopic data suggest a strongly stratified ocean with sulfidic bottom water and oxidized surface water. Episodic shoaling of anoxic deep water onto the surface possibly caused the extinction of benthic Ediacaran fauna, and the surface oxidized zone likely provided the niche for further metazoan radiation. [ABSTRACT FROM AUTHOR]

Nonionic surfactants with ideal surface properties and lower ecotoxicities have been highly attended in metal bioleaching and pollutant bio-treatment in environmental science field. In this study, both Acidithiobacillus ferrooxidans HX3 and Tween 80 (or Triton X-100) presence in cultures, bio-production and development of schwertmannite as a potential metal scavenger were investigated. To explore their correlations, the resulting ferric oxyhydroxides under various surfactant levels (lower/optimal/higher ones for Gp I/II/III treatments) were identified by many characterization methods. Result showed that after 48 h of normally bacterial reproduction, surfactant-rich cultures with Tween 80 more than 50 mg/L (25 mg/L for Triton X-100) could only achieve down 80% of ferrous oxidation percent and 107 cells/mL of cell numbers, while those with lower surfactant level were ahead 12 h. Culture pH values decreased to about 2.4 (or 2.0) from initially 2.8. All initial ferric oxyhydroxides were only pincushion-schwertmannite spheres. When cells sequentially reproduced within 36 h–48 h, presence of surfactants (except for Triton X-100 at 75 mg/L) could induce schwertmannite-pincushion assembling on developed spherical particles with a little of diamond-jarosite. And then during bacterial stability state (48 h–72 h), the pincushion assemblages on developed schwertmannite-spheres would disappear, following occurrence of more jarosite amount. Obviously, schwertmannite stability and morphological evolvement were affected by type and level of the added surfactants. These results will give a convincing proof for understanding biomineralization principles of iron minerals in natural environments with nonionic surfactants. [ABSTRACT FROM AUTHOR]

Management of tailings at metal mine smelter sites can reduce the potential hazards associated with exposure to toxic metal(loid)s and residual organic flotation reagents. In addition, microbes in the tailings harboring multi-resistance genes (e.g., tolerance to multiple antimicrobial agents) can cause high rates of morbidity and global economic problems. The potential co-selection mechanisms of antibiotic resistance genes (ARGs) and metal(loid) resistance genes (MRGs) during tailings sulfate-reducing bacteria (SRB) treatment have been poorly investigated. Samples were collected from a nonferrous metal mine tailing site treated with an established SRB protocol and were analyzed for selected geochemical properties and high throughput sequencing of 16S rRNA gene barcoding. Based on the shotgun metagenomic analysis, the bacterial domain was dominant in nonferrous metal(loid)-rich tailings treated with SRB for 12 months. KEGGs related to ARGs and MRGs were detected. Thiobacillus and Sphingomonas were the main genera carrying the bacA and mexEF resistance operons, along with Sulfuricella which were also found as the main genera carrying MRGs. The SRB treatment may mediate the distribution of numerous resistance genes. KOs based on the metagenomic database indicated that ARGs (mexNW, merD, sul, and bla) and MRGs (czcABCR and copRS genes) were found on the same contig. The SRB strains (Desulfosporosinus and Desulfotomaculum), and the acidophilic strain Acidiphilium significantly contributed to the distribution of sul genes. The functional metabolic pathways related to siderophores metabolism were largely from anaerobic genera of Streptomyces and Microbacterium. The presence of arsenate reductase, metal efflux pump, and Fe transport genes indicated that SRB treatment plays a key role in the metal(loid)s transformation. Overall, our findings show that bio-treatment is an effective tool for managing ARGs/MRGs and metals in tailings that contain numerous metal(loid) contaminants. [ABSTRACT FROM AUTHOR]

The ~1.2 Ga Bijaigarh Shale (BS) is a significant geological formation in the Vindhyan Supergroup of Son Valley and is widely targeted for understanding Mesoproterozoic oceanic redox conditions and crustal evolution. In the present study, we have analysed the major, trace and rare earth elements compositions of the BS and attempted to infer the composition, weathering history, and tectonic setting of the Mesoproterozoic continental crust. The BS is comprised of quartz, smectite, kaolinite and illite, with occasional framboidal pyrites. High chemical index of alteration (CIA) and plagioclase index of alteration (PIA) values, and depletion of Na2O, CaO, Sr and Ba imply that the source region underwent a high degree of chemical weathering under warm and humid climatic conditions. Various immobile element ratios in the BS suggest felsic source rocks and insignificant recycling. Fractionated chondrite normalised REE patterns (La/YbN = 6.7–12.3, avg. 9.5) and negative Eu anomalies (Eu/Eu* = 0.50–0.60, avg. 0.53) also indicate felsic provenance. REE mixing modelling implies that the source area was comprised of 40% Mahakoshal Granite, 25% Bundelkhand Granite, 30% Porcellanite and 5% Chhotanagpur Granite Gneiss Complex (CGGC). The sedimentation in Kaimur basin is thought to have begun at ~1.2 Ga, accompanied with the crustal extension in the aftermath of Central Indian Tectonic Zone (CITZ) orogeny (1.6–1.5 Ga) and domal uplift of Bundelkhand craton. The positive areas were created by orogenic movements, which exposed the older crustal blocks containing granites and metamorphic rocks in the CITZ (Chhotanagpur Gneisses and Mahakoshal belt) and Bundelkhand granite complex (BGC). The Mahakoshal Group and CGGC located on the southern side, the BGC on the northern side of the basin, and the uplifted Lower Vindhyans were the likely sources of the BS. Such source areas are also indicated by the palaeoflow directions. [ABSTRACT FROM AUTHOR]

Biochar modified by metal ions—particularly Mg—is typically used for the effective recovery of phosphorous. In this study, MgO-modified biochars were synthesized via the direct co-pyrolysis of MgO and raw materials such as rice straw, corn straw, Camellia oleifera shells, and branches from garden waste, which were labeled as MRS, MCS, MOT, and MGW, respectively. The resulting phosphate (PO) adsorption capacities and potential adsorption mechanisms were analyzed. The PO adsorption capacities of the biochars were significantly improved after the modification with MgO: MRS (24.71 ± 0.32 mg/g) > MGW (23.55 ± 0.46 mg/g) > MOT (15.23 ± 0.19 mg/g) > MCS (14.12 ± 0.21 mg/g). PO adsorption on the modified biochars was controlled by physical adsorption, precipitation, and surface inner-sphere complexation processes, although no electrostatic attraction was observed. Furthermore, PO adsorbed on modified biochars could be released under acidic, alkaline, and neutral conditions. The desorption efficiency of MRS was modest, indicating its suitability as a slow-release fertilizer. [ABSTRACT FROM AUTHOR]

Urban soils contaminated with heavy metals and pesticide residues are of great concern because of their adverse impact on human health. A total of 66 agricultural topsoil samples (15 cm) were collected to represent the study area and determine how anthropogenic activities adversely affect soil quality and human health. Sampling was conducted in the summer, when it was dry and hot, and in the winter, after atmospheric deposition. Seventeen potentially hazardous metals/metalloids (Ag, As, Al, B, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Mo, Pb, Se, Zn, and V) were measured in the soils. The mean concentrations of metals ranged between 0.05 and 8080 mg/kg, and their distribution was site-specific, with high pollution at the sampling sites owing to proximity to human activities. In agricultural areas, the greatest arsenic concentration was recorded at 48 mg/kg. The potential ecological risk index (PERI) and health hazard index (HI) were calculated, as well as metal contamination indices including contamination factor (Cf), geo-accumulation index (Igeo), and pollution load index (PLI). The mean PLI was calculated to be 4.89, indicating that the area is highly polluted. The potential ecological risk index showed remarkably high risks for As, Cd, and Hg, and moderate risks for Ni and Pb. The arsenic hazard index (HI) was greater than one (2.41) in children, indicating a risk of exposure through ingestion. Pesticide residue analyses were performed in areas where the metal intensity was high. Banned or restricted organochlorine pesticide (OCPs) residues, including, dieldrin, endrin ketone, endosulfan I, II, heptachlor, heptachlor epoxide, lindane (γ-HCH), PP-DDD, and methoxychlor, were detected between 0.002 and 1.45 mg/kg in the soil samples. [ABSTRACT FROM AUTHOR]

Antimony (Sb) and arsenic (As) co-contamination occurs in Sb smelting areas and is harmful to the surrounding ecological environment. The purpose of this study is to explore the spatial distribution characteristics of Sb and As in abandoned Sb smelting area and carry out risk assessments. Soil samples were collected from the smelting area profile and background points, and groundwater samples were also collected. Samples from two geological background sections were collected to understand the geological background characteristics of Sb and As. The spatial distribution was drawn via the inverse distance weighted interpolation method. The hazard assessment was carried out by the geo-accumulation index and potential ecological hazard methods. The results showed that special high geological background value of Sb and As in study area. Sb and As co-contamination is one of the characters in soil. And the contents of Sb and As decrease as depth increases, reflecting the weak migration capacity. The spatial distribution of Sb and As is affected by slag distribution and rainfall leaching. The Sb content in groundwater was higher in the wet and normal seasons than in the dry season, slag leaching may be one of the elements. The potential ecological hazards of Sb and As are high and considerable, respectively. In abandoned smelting area with high geological background values, it is necessary to focus on the pollution abatement and protection of ecological health. [ABSTRACT FROM AUTHOR]

The application of biochar from agro-industrial residues of the Amazon is a key strategy to optimize the use of phosphorus (P) in agriculture and provide the proper management of these materials. In this study, we investigated the relationship between the chemical constituents of biochars from açaí seeds (BA), Brazil nut shells (BN) and palm kernel cake (BK) with phosphorus adsorption to identify the main properties that control this process and the thermochemical stability of carbon (C). Biochars were produced under slow pyrolysis (3.33 ºC min–1) at 700 ºC and evaluated regarding their physicochemical properties, elemental composition and maximum P adsorption capacity (qm). The interrelationship between the properties of the biochars was described by multivariate techniques: factor analysis (FA), canonical correlation analysis (CCA) and hierarchical cluster analysis. The multivariate approach allowed the analysis of the properties of biochars associated with qm and provided the differentiation between the biochars derived from different agro-industrial residues. FA and CCA indicated a high association (r ≥ 0.93; p < 0.05) of qm with ash content, cation exchange capacity (CEC) and nitrogen (N) content. Therefore, small increments in these attributes can cause variation in the rate of P adsorption. The heatmap allowed the identification of greater similarities between BA and BN; and greater contrast between qm with the aromaticity indices H/C and O/C and the polarity index (O + N)/C. Our results indicate that these biochars have the potential to adsorb P, increase the thermochemical stability of C in soil and represent a sustainable alternative for waste management of eastern Amazon. [ABSTRACT FROM AUTHOR]

The growth of the world population requires greater agricultural production, which consequently increases the demand for phosphorus-based (P-based) compounds and the generation of agro-industrial residues. Biochar is an effective alternative for the recovery and reuse of P-based species, as well to mitigate the generation of environmental liabilities and provide adequate disposal for agro-industrial residues. This study investigates the phosphate adsorption capacity of biochars produced with residues of açaí seeds (BA), Brazil nut shell (BN) and palm kernel cake (BK) and the relationship with their chemical constituents. Biochars were produced at 700 ºC to evaluate the physicochemical properties, elemental composition, contact time and influence of pH on phosphate adsorption. The solid/liquid contact time varied from 1 to 24 h and the adsorption of phosphorus species on biochar was strongly pH dependent (p < 0.05) between the biochars (BN > BA > BK). The Langmuir isotherm model best described the adsorption process (R2 ≥ 0.90) and showed high efficiency in phosphate removal in aqueous solution (BA: 92.34; BN: 123.55 and BK: 79.46 mg g–1). The heterogeneity of mineral constituents was emphasized by principal component analysis and indicated that phosphate adsorption on biochars is highly and directly associated with carbon (C) content, cation exchange capacity and pH and inversely related to nitrogen (N) content, yield, point of zero charge, (O + N)/C and ash content. Therefore, these biochars constitute promising materials for phosphate adsorption and present potential to be applied to soil as a source of P in the form of biofertilizer. [ABSTRACT FROM AUTHOR]

The Devonian–Carboniferous transition marks a fundamental shift in the surface environment primarily related to changes in ocean–atmosphere oxidation states1,2, resulting from the continued proliferation of vascular land plants that stimulated the hydrological cycle and continental weathering3,4, glacioeustasy5,6, eutrophication and anoxic expansion in epicontinental seas3,4, and mass extinction events2,7,8. Here we present a comprehensive spatial and temporal compilation of geochemical data from 90 cores across the entire Bakken Shale (Williston Basin, North America). Our dataset allows for the detailed documentation of stepwise transgressions of toxic euxinic waters into the shallow oceans that drove a series of Late Devonian extinction events. Other Phanerozoic extinctions have also been related to the expansion of shallow-water euxinia, indicating that hydrogen sulfide toxicity was a key driver of Phanerozoic biodiversity.A spatial and temporal compilation of geochemical data documents a stepwise transgression of toxic euxinic waters into shallow oceans that drove a series of Late Devonian extinction events. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of the mobility of both nitrogen (N) and phosphorus (P) and the inter-relationships between P, N, and iron (Fe) in sediments is important for controlling the "internal loadings" of nutrients in lakes. In this research, diffusive gradients in thin film (DGT) assemblies with binding layers (ZrO-AT, chelex, and ZrO) were designed for PO4-P, Fe, ammonium (NH4-N), and nitrate (NO3-N) at sediment/water interface (SWI) in Western Lake Taihu (China). The biogeochemical processes of N and P related to the physicochemical properties, the dynamic P transfer, the distribution characteristics of P microniches, and the estimation of the release risks in sediments in Western Lake Taihu were simultaneously revealed by the passive sampling technique-DGT with the high spatial resolutions (millimeter and sub-millimeter). Based on DGT concentration (CDGT) related to physicochemical properties in sediments, (1) P biogeochemical reactions included P release from Fe-bound P during Fe reduction, algae biomass decomposition, and phosphatase enzyme activity increased by NH4-N; (2) denitrification and dissimilatory nitrate reduction to ammonium (DNRA) led to exchangeable ammonium (NH4ex) enrichment and NH4-N release; anammox depleted NH4-N transfer; organic matter (OM) mineralization favored NH4-N release; and (3) aerobic nitrification led to NO3-N remobilization; denitrification and DNRA reduced NO3-N release. Redox status, OM, Fe, aluminum, or calcium influenced mobilization of nutrients. The numerical model of DGT-induced fluxes in sediments was used for dynamic P transfers with resupply types ("slow" ~ "fast") controlled by labile P pool, resupply constant, response time, and Dspt rate. The formation of P microniches in two dimensions was revealed. Sediment P release risk index (0.49 ~ 36.85 [lg (nmol cm−3 d−1)]) with "light" ~ "high" risks and diffusive fluxes across SWI (µg m−2 d−1) of 15.0 ~ 639 (PO4-P), − 1403 ~ 5010 (NH4-N), and − 1395 ~ 149 (NO3-N) were derived and lake management strategies were provided. The DGT technique provides the characterization of the mobilization of nutrients and evidence for biogeochemical processes at the fine spatial scales for control of internal loadings in sediments. [ABSTRACT FROM AUTHOR]

In this work, a new resin gel incorporated with layered double hydroxide nanoparticles modified with diethylenetriaminepentaacetic acid is developed for application in diffusive gradients in thin-film devices (abbreviated as LDHs DGT) to monitor eight anions and cations (such as Fe, Mn, Co, Ni, Cu, Cd, Pb, and As) in natural waters and soils. The accumulated anions and cations were quantitatively recovered by one-step elution using 0.5 mol·L−1 HNO3 with an optimized elution time of 30 min. The performance of the LDHs DGT was independent of solution pH (5–8) and ionic strengths (5–100 mmol·L−1). The capacities of the LDHs DGT for Mn(II), Fe(II), Co(II), Ni(II), Cu(II), As(V), Cd(II), and Pb(II) individually are determined to be 202.9, 363.6, 246.9, 88.8, 99.5, 75.3, 159.8, and 671.7 μg·cm−2. During the field deployments in a nature river, LDHs DGT measured concentrations of cations and anions were almost like those measured by the traditional sampling method (except Fe(II), Cd(II), and Co(II)). In addition, bioavailable Cd measured by LDHs DGT correlated well with Cd in rice grains (R2 = 0.55), indicating that LDHs DGT is a reliable tool for assessing the risk of Cd. [ABSTRACT FROM AUTHOR]

The persistent bioavailability of toxic metal(oids) (TM) is undeniably the leading source of serious environmental problems. Through the transfer of these contaminants into food networks, sediments and the aquatic environmental pollution by TM serve as key routes for potential risks to soil and human health. The formation of iron oxyhydroxide plaque (IP) on the root surface of hydrophytes, particularly rice, has been linked to the impact of various abiotic and biotic factors. Radial oxygen loss has been identified as a key driver for the oxidation of rhizosphere ferrous iron (Fe2+) and its subsequent precipitation as low-to-high crystalline and/or amorphous Fe minerals on root surfaces as IP. Considering that each plant species has its unique capability of creating an oxidised rhizosphere under anaerobic conditions, the abundance of rhizosphere Fe2+, functional groups from organic matter decomposition and variations in binding capacities of Fe oxides, thus, impacting the mobility and interaction of several contaminants as well as toxic/non-toxic metals on the specific surface areas of the IP. More insight from wet extraction and advanced synchrotron-based analytical techniques has provided further evidence on how IP formation could significantly affect the fate of plant physiology and biomass production, particularly in contaminated settings. Collectively, this information sets the stage for the possible implementation of IP and related analytical protocols as a strategic framework for the management of rice and other hydrophytes, particularly in contaminated sceneries. Other confounding variables involved in IP formation, as well as operational issues related to some advanced analytical processes, should be considered. [ABSTRACT FROM AUTHOR]

Purpose: The objectives of this study were to (1) analyze heavy metals (Cr, As, Cu, Zn, Cd, and Pb) in the rhizosphere soil and roots, leaves, stems, and grains of maize and wheat crops using different methods; (2) evaluate the advantages of diffusive gradients in thin films technology (DGT) for predicting the bioavailability of heavy metals; and (3) compare the characteristics of DGT with other methods. Materials and Methods: In this study, we collected maize and wheat samples and their rhizosphere soil over a pollution gradient in Kaifeng City, China. Six heavy metal (Cr, As, Cu, Zn, Cd, and Pb) levels in rhizosphere soil were determined using DGT, EDTA, soil solution, and total amount methods, respectively. The heavy metal content in the roots, leaves, stems, and grains of maize and wheat was also analyzed. The relationships between six heavy metal soils concentrations detected by different methods, and their contents in the different parts of wheat and maize, were analyzed using statistical methods. The characteristics and application scope of the different methods were evaluated. Results and Discussion: The accumulation of heavy metals in maize and wheat was generally higher in the roots than in the above-ground parts (i.e., stems, leaves, and grains). For the soil solution method, only soil As levels showed a significantly positive correlation with its content in different parts of wheat and corn. For the EDTA method and the soil total amount method, only As, Zn, and Pb levels were significantly correlated with their contents in different parts of wheat and corn. Six heavy metal concentrations detected by DGT were all significantly positively correlated with their contents in the different parts of wheat and maize. Furthermore, DGT was less affected by the soil pH than EDTA. Conclusions: DGT was more accurate in simultaneously predicting plant-available Cr, As, Cu, Zn, Cd, and Pb. However, other methods, like EDTA, soil solution, and total amount methods, can also be considered when predicting the bioavailability of a single heavy metal (e.g., As or Zn) in rhizosphere soil. [ABSTRACT FROM AUTHOR]

Mesozoic oceanic anoxic events are recognized as widespread deposits of marine organic-rich mudrocks temporally associated with mass extinctions and large igneous province emplacement. The Toarcian Oceanic Anoxic Event is one example during which expanded ocean anoxia is hypothesized in response to environmental perturbations associated with emplacement of the Karoo–Ferrar igneous province. However, the global extent of total seafloor anoxia and the relative extent of euxinic (anoxic and sulfide-rich) and non-euxinic anoxic conditions during the Toarcian Oceanic Anoxic Event are poorly constrained. Here we present estimates of the global total anoxic and euxinic seafloor areas before and during the Toarcian Oceanic Anoxic Event based on rhenium and molybdenum enrichments, respectively, in organic-rich mudrocks of the Fernie Formation (British Columbia, Canada). We find that mass balance models depict an expansion of up to ~7% total seafloor anoxia, which was dominated by euxinia, at the onset of the Toarcian Oceanic Anoxic Event, followed by a contraction before the end of the event. The global ocean redox trends revealed by the rhenium data mirrors the collapse and recovery patterns of global ammonite and foraminiferal biodiversity. Geochemical modeling shows that just a several percent expansion of O2-free areas with toxic sulfide build-up likely contributed to biodiversity loss or reorganization during the Toarcian mass extinction 183 million years ago. [ABSTRACT FROM AUTHOR]

Potentially toxic elements (PTEs) re-release from sediment is an essential process in the sediment-water interface (SWI), especially for the influent river estuary as an important accumulation site. In this study, the diffusive gradient in thin films (DGT), high-resolution dialysis (HR-peeper) technique, and BCR sequential extraction were employed to evaluate the release risk of PTEs (As, Cu, Pb, Zn, Cd) in the New Zhuzhao River Estuary of Nansi Lake. Results showed that Cd existed primarily in the non-residual fraction (accounting for 59.87%), and the residual fractions of As, Cu, Pb, and Zn accounted for a greater proportion (12.65 to 33.07%). The mobility of Cd was the highest with a risk assessment code of 33.53% reaching the medium risk category. The resupply capacity calculated by CDGT/CDis showed that As was the largest, with an average value of 0.43, indicating the strongest release capacity of As from the sediment to pore water. Furthermore, the diffusive fluxes using DGT and HR-peeper showed that As possesses a much higher potential to release upward overlying water than other elements. [ABSTRACT FROM AUTHOR]

Purpose: Development of new binding gels for rapid and simultaneous quantification of bioavailability concentrations of various heavy metals in soils by diffusive gradients in thin film technique. Methods: Four binding gels including zinc-aluminum hydrogel (ZnAl-LDH), ethylenediaminetetraacetic acid intercalated zinc-aluminum hydrogel (ZnAl-EDTA-LDHs), polyglutamic acid (PGA), and polyglutamic acid–sodium alginate resin (SA-PGA) were prepared and used for the simultaneous measurement of Cr, Ni, Cu, Cd, and Pb. Results: The adsorption process reached equilibrium in 2 h, which could be considered a pseudo-second-order reaction. Three mol L−1 nitric acid was the best eluent with elution efficiency over 91% for the five heavy metals. Then, SA-PGA gel was assembled into DGT device (SA-PGA-DGT). Its performance was virtually unaffected by pH (5–9), ionic strength (1–50 mM), and soil properties with adsorption capacities 5.02 μg cm−2, 11.38 μg cm−2, 8.16 μg cm−2, 17.11 μg cm−2, and 89.43 μg cm−2 for Cr, Ni, Cu, Cd, and Pb, respectively. A good linear correlation was observed between the concentrations of Cr, Ni, Cu, Cd, and Pb determined by SA-PGA-DGT in soil samples from Tanggu District in China and the exchangeable contents of the five metals determined by the Tessier method, with R values of 0.64, 0.63, 0.59, 0.72, and 0.64 (p < 0.01). Conclusion: SA-PGA gel exhibited the best adsorption properties among the four gels. SA-PGA-DGT can be used as a reliable tool for rapid and simultaneous quantification of bioavailability concentrations of multiple heavy metals. [ABSTRACT FROM AUTHOR]

The realization of accurate and continuous detecting of dissolved ammonia was of great essential in developing smart aquaculture. The appealing properties of electrochemical sensors for ammonia provided a great technical potential in wrestling with these challenges. In this study, self-supported NiC2O4/PANI nanocomposite was successfully fabricated on nickel foam via a two-step in-situ method and employed as a sensitive electrochemical dissolved ammonia sensor. The 3D structure PANI provided fast electronic channel between NiC2O4 nanoparticles and largely reduce the internal resistance. With the help of the specific reaction of nickel oxalate with ammonia, the proposed self-supported NiC2O4/PANI electrode showed remarkable sensitivity of 41 mA µM−1 cm−2 and low detection limit of 0.83 µM. Moreover, the anti-interference ability, reusability reproducibility and stability of this sensor was investigated and exhibited decent performance. The obtained results indicated that the NiC2O4/PANI electrode was of great potential in detection of dissolved ammonia and exhibited a broad applicability for practical application. [ABSTRACT FROM AUTHOR]

The impact of water and bottom sediment pollution of a river subjected to a strong industrial anthropogenic pressure of metal(loid) (including arsenic and its species) accumulation in riverbank plants such as Solidago virgaurea L., Phragmites L. and Urtica dioica L. was investigated. The high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) technique was used to study organic and inorganic arsenic species in selected plants and their response to heavy metal and arsenic contamination. The modified BCR extraction results showed that arsenic was mainly bound to the mobile reducible and organic-sulfide fractions in the Kłodnica River bottom sediments. Research has shown that the bottom sediments of the Kłodnica River are contaminated with metals, including Pb, Zn, Ni, As, and among arsenic species, the As(V) form dominated quantitatively, with its highest concentration being 49.3 mg kg−1 and the organic species occurred extremely rarely. The highest concentration of arsenic, among the tested plants, occurred in Phragmites communis L. The evaluation of the bottom sediment pollution was performed using Sb/As factor, geoaccumulation index (Igeo), enrichment factor (EF) and pollution load index (PLI). The ability of the plant to assimilate metals from the substrate was studied by calculation of the bioaccumulation factor (BAF). Values of the Igeo change in a wide range from class 1 (uncontaminated to moderately polluted for Cu and Zn) at the first sampling point, to 5 (highly to extremely polluted for Ba and Fe) at the K4 sampling point. The Igeo results show an increase in the contamination with elements toward the runoff of the Kłodnica River. [ABSTRACT FROM AUTHOR]

Water column hypoxia, low partial pressure of oxygen (pO2), and hydrogen sulfide (H2S) intrusion, a phytotoxin, are factors linked to global seagrass decline. While many lab experiments have examined these relationships, field studies are needed to elucidate complex drivers of internal pO2 in situ. Herein, we examined plant pO2 and H2S dynamics using microsensors in a dominant tropical seagrass Thalassia testudinum in Florida Bay, a subtropical estuary with recurrent seagrass die-off events. Based on 12 field deployments (48–72 h) across seasons, we show that T. testudinum has a high capacity for daytime leaf oxidation (42–53 kPa) that sustains oxic conditions in its tissues and supersaturates the water column with O2 (> 21 kPa). Although internal daytime O2 is rapidly consumed near sunset, daytime seagrass O2 production leads to supersaturation in the water column beyond sunset. This is an important feedback mechanism as high water column pO2 at night buffers against internal leaf hypoxia via diffusion. Even with high daytime irradiance, however, shoot meristems went anoxic/hypoxic (0.6 kPa) at night, indicating high plant and ecosystem O2 consumption. Hydrogen sulfide was only detected in the meristem when water column pO2 was close to anoxia (< 1 kPa) coincident with maximum water column temperatures (33 °C), an occurrence likely to increase with global warming. Our results support the hypothesis that meristem H2S intrusion in Florida Bay, and likely globally, is primarily driven by insufficient internal plant oxidation by the water column at night, even when high irradiance sustains supersaturation of tissue O2 during the day. [ABSTRACT FROM AUTHOR]

The Ediacaran biota were soft-bodied organisms, many with enigmatic phylogenetic placement and ecology, living in marine environments between 574 and 539 million years ago. Some studies hypothesize a metazoan affinity and aerobic metabolism for these taxa, whereas others propose a fundamentally separate taxonomic grouping and a reliance on chemoautotrophy. To distinguish between these hypotheses and test the redox-sensitivity of Ediacaran organisms, here we present a high-resolution local and global redox dataset from carbonates that contain in situ Ediacaran fossils from Siberia. Cerium anomalies are consistently >1, indicating that local environments, where a diverse Ediacaran assemblage is preserved in situ as nodules and carbonaceous compressions, were pervasively anoxic. Additionally, δ238U values match other terminal Ediacaran sections, indicating widespread marine euxinia. These data suggest that some Ediacaran biotas were tolerant of at least intermittent anoxia, and thus had the capacity for a facultatively anaerobic lifestyle. Alternatively, these soft-bodied Ediacara organisms may have colonized the seafloor during brief oxygenation events not recorded by redox proxy data. Broad temporal correlations between carbon, sulfur, and uranium isotopes further highlight the dynamic redox landscape of Ediacaran-Cambrian evolutionary events.Geochemical data from sedimentary rocks in Siberia indicate that members of the soft-bodied Ediacara biota (the earliest macroscopic life on Earth) were tolerant of low-oxygen conditions, suggesting they had the capacity for anaerobic metabolisms. [ABSTRACT FROM AUTHOR]

Changes in the metabolic profile within the intestine of lenok (Brachymystax lenok) when challenged to acute and lethal heat stress (HS) are studied using no-target HPLC–MS/MS metabonomic analysis. A total of 51 differentially expressed metabolites (VIP > 1, P < 0.05) were identified in response to HS, and 34 occurred in the positive ion mode and 17 in negative ion mode, respectively. After heat stress, changes in metabolites related to glycolysis (i.e., alpha-D-glucose, stachyose, and L-lactate) were identified. The metabolites (acetyl carnitine, palmitoylcarnitine, carnitine, and erucic acid) related to fatty acid β-oxidation accumulated significantly, and many amino acids (L-tryptophan, D-proline, L-leucine, L-phenylalanine, L-aspartate, L-tyrosine, L-methionine, L-histidine, and L-glutamine) were significantly decreased in HS-treated lenok. The mitochondrial β-oxidation pathway might be inhibited, while severe heat stress might activate the anaerobic glycolysis and catabolism of amino acid for energy expenditure. Oxidative damage in HS-treated lenok was indicated by the decreased glycerophospholipid metabolites (i.e., glycerophosphocholine, 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine, 1-palmitoyl-sn-glycero-3-phosphocholine, 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine, and 1, 2-dioleoyl-sn-glycero-3-phosphatidylcholine) and the increased oxylipin production (12-HETE and 9R, 10S-EpOME). The minor oxidative pathways (omega-oxidation and peroxisomal beta-oxidation) were likely to be induced in HS-treated lenok. [ABSTRACT FROM AUTHOR]

Seagrass meadows are hotspots of biodiversity with considerable economic and ecological value. The health of seagrass ecosystems is influenced in part by the makeup and stability of their microbiome, but microbiome composition can be sensitive to environmental change such as nutrient availability, elevated temperatures, and reduced pH. The objective of the present study was to characterize the bacterial community of the leaves, bulk samples of roots and rhizomes, and proximal sediment of the seagrass species Cymodocea nodosa along the natural pH gradient of Levante Bay, Vulcano Island, Italy. The bacterial community was determined by characterizing the 16S rRNA amplicon sequencing and analyzing the operational taxonomic unit classification of bacterial DNA within samples. Statistical analyses were used to explore how life-long exposure to different pH/pCO2 conditions may be associated with significant differences in microbial communities, dominant bacterial classes, and microbial diversity within each plant section and sediment. The microbiome of C. nodosa significantly differed among all sample types and site-specific differences were detected within sediment and root/rhizome microbial communities, but not the leaves. These results show that C. nodosa leaves have a consistent microbial community even across a pH range of 8.15 to 6.05. The ability for C. nodosa to regulate and maintain microbial structure may indicate a semblance of resilience within these vital ecosystems under projected changes in environmental conditions such as ocean acidification. [ABSTRACT FROM AUTHOR]

Chemical pollutants present a substantial threat to the survival of the green turtle (Chelonia mydas). In this study, the concentrations of 12 trace elements (TEs) in seawater, sediments, and green turtle forage and eggshells from the Xisha Islands in the South China Sea, along with their patterns of transfer and accumulation, were identified. The results revealed that the median TE concentrations in seawater and sediments were lower than the first-grade limit values of the national standard in China, indicating a low ecological risk. The concentrations (μg·g−1) of TEs in forage ranged from 0.05–0.69, 3.43–14.4, 157–2391, 27.9–124, 2.05–9.39, 0.30–9.78, 2.01–80.50, 0.18–5.76, 0.06–0.98, 2.00–18.4, 0.02–0.24, and 0.01–0.09 for Cr, Mn, Sr, Fe, Ni, Cu, Zn, Se, Cd, As, Pb, and Hg, respectively. Seawater, sediments, turtle forage, and eggshells exhibited different TE profiles, which were driven by Hg, Sr, Cr, and Pb in seawater and sediments; Fe and Ni in sediments; Cd and As in forage; and Zn, Se, and Cu in eggshells. The contents of Cu, Zn, and Se increased slightly with trophic level, indicating that they were transferred through dietary pathways. Although Cd and As appeared to bioaccumulate in green turtle forage, it was not transferred to their eggshells, which may be related to the excretion and metabolism process in the mother's body. Thus, eggshells may be a poor bioindicator for the exposure of female green turtles to these toxic elements. [ABSTRACT FROM AUTHOR]

The Arabian Sea encompasses oxygen minimum zone with denitrifying conditions. For the present study, sediments were collected across three transects off Goa transect (GT), Mangalore transect (MT) and Kochi transect (KT) in contact with water column dissolved oxygen (DO) range of 1.4–118.0 µM. Sediments were investigated for texture, clay mineralogy, total organic carbon (Corg), total nitrogen, CaCO3, δ15N, δ13C, metal content to infer their distribution with changing DO and their use as possible palaeo-proxies. The Corg (0.9–8.6%) is largely marine and δ15N from GT and MT preserves signatures of higher water column denitrification. Al normalised ratios of Cu, Ni, Zn, V and Mo are GT > MT > KT. Nickel could be a productivity proxy for DO <80 µM; Cr, U could be a redox proxy for DO <20 µM; Co and Mn could be a better proxy for DO <80 µM; U/Mo vs. DO could separate sediments with DO less than and >80 µM. We observed that eastern Arabian Sea dataset does not always fall within the defined proxies of the other anoxic basins. The metal concentrations in modern day sediments from the eastern Arabian Sea may be used as a proxy to infer the ancient sediment redox conditions. Highlights: Organic carbon distribution in anoxic sediments. Provenance of sediments. Nitrogen isotopes and geochemistry as palaeo-proxy for anoxic basins. [ABSTRACT FROM AUTHOR]

Progressive industrialization in recent decades has contributed to the increase of metal levels in the environment, which has a dangerous impact on human health, primarily pregnant women. In this study, we aimed to compare levels of various elements in maternal and umbilical cord (UC) plasma samples collected from 125 healthy pregnant women, conduct correlation analysis among paired plasma samples, and compare our data with other populations worldwide. The study design included the following elements: essential (Mn, Co, Cu, Zn, Se, Mo), non-essential (Be, Al, Ni, As, Rb, Sr, Cd, Sb, Pb, U), rare earth (La, Pr, Ce, Nd, Sm, Eu, Gd, Dy, Ho, Er), and noble metals (Ru, Rh, Re, Pt). Levels of 30 elements were higher in maternal plasma than in UC plasma samples. However, no disparities at the statistically significant level were found for Be, Zn, Rb, Cd, Ce, and Ho. Correlation analysis among paired plasma samples revealed only positive/synergistic correlations of different strengths between most elements. Compared to other countries across the globe, our participants had considerably lower plasma levels of Zn and higher levels of Co, Ni, and As. This study provides not only a new and deeper comprehension, but also the first insight into the levels, correlation, distribution, and potential transplacental transfer of 30 elements. [ABSTRACT FROM AUTHOR]

The large-scale use of antimony by humans has caused antimony pollution in the ecological environment, which is harmful to microorganisms, animals, plants, and humans, and Sb(III) is the most toxic. Therefore, removing Sb(III) in water has the dual significance of protecting the ecological environment and reducing health risks. In this paper, MnFe2O4@SiO2@MIL-101(Cr)-NH2 (MSM) was synthesised and used to adsorb Sb(III) in water. Use X-ray diffraction, Fourier transform infrared spectroscopy, environmental scanning electron microscopy, X-ray energy spectrum analysis (EDS), X-ray photoelectron spectroscopy, specific surface area analysis (BET), thermogravimetric analysis, magnetic hysteresis loop (VSM) and other means to characterise MSM. The BET specific surface area and total pore volume of MSM are 599.47 m2/g and 0.41 cm3/g, respectively. The saturation magnetisation of MSM is 8.93 emu/g. When the dosage is 150 mg/L, the pH is 3, the temperature is 298.15 K, and the adsorption time is 120 min, the adsorption capacity of MSM for Sb(III) reaches 30.26 mg/L. The increase in pH and temperature will both decrease the adsorption of Sb(III) by MSM. The adsorption of Sb(III) by MSM relies on chemical adsorption and intra-particle diffusion. Its adsorption behavior conforms to be a single-layer adsorption, and the maximum theoretical adsorption capacity is 86.35 mg/g. Through response surface optimization, it is estimated that the deviation between the maximum Sb(III) adsorption capacity and the measured value is about 2.4%. This study shows the great potential of MSM to remove antimony in practical applications. [ABSTRACT FROM AUTHOR]

DGT (diffusive gradients in thin films) technique has been developed for measuring nitrogen in freshwaters and applied to assess the bioavailability of phosphorus in soils/sediments. These two elements are the main nutrients causing algae bloom, but DGT has never been used in the field water conditions with algae bloom. In our study, a pair of DGT devices were used in comparison with grab sampling to characterize the performance of this technique to measure labile NO3-N, NH4-N, and PO4-P concentrations in algae-cultivated Taihu Lake water. The results showed that DGT measurement was highly affected by algae bloom and the environmental conditions using the current assemblies, especially for NH4-N measurement. For in situ measurement of nutrients in the real environment, an improvement to the DGT technique is required. The comprehensive assessment of the level of eutrophication needs to consider a variety of environmental factors rather than just the concentration of nutrients. [ABSTRACT FROM AUTHOR]

Many contaminants have been released into the environment in recent times, requiring the need to investigate these compounds presence, impact, and destination in different environmental compartments. The use of ex situ techniques is quite common; however, in this type of analysis, the distribution and characteristics of the chemical species present can be altered. A choice to avoid such problems is to use passive sampling based on diffusive gradients in thin-films (DGT), an in situ technique developed to measure labile concentrations, species, and distribution of various solutes in soil, sediment, and water. One of the focuses applied to these materials is finding, testing, and validating new binding layers to increase the range of target analytes for these devices. Among the materials that can be tested, the nanomaterials, compared with conventional binding agents, have excellent adsorptive capabilities due to their properties, such as high specific surface area. In this context, in this review, we will present the recent developments in samplers that have their configurations modified using nanomaterials as binding agents for application in aqueous systems. [ABSTRACT FROM AUTHOR]

In recent years, as the abuse of antibiotics, hormones, and herbicides has worsened in aquaculture industry, it is important to monitor the concentrations of those trace contaminants in aquaculture water more effortlessly. The aim of this study was to develop a reliable sampling method for chemical monitoring in aquaculture ponds based on the technique of diffusive gradients in thin films (DGT). A binding material (XDA-1 resin) with high adsorption capacity for antibiotics, hormones, and herbicides was selected. In laboratory, the diffusion coefficients of 11 antibiotics, 3 hormones, and 3 herbicides of the XDA-1-DGT devices were tested and ranged from 1.0×10−6 to 8.7×10−5 cm2/s. During the in situ application of XDA-1-DGT devices in different aquaculture ponds, concentrations of 11 antibiotics, 3 hormones, and 3 herbicides in aquaculture water (CSOLN) via grab sampling were also analyzed and found ranging from 0.03 to 6.3 ng/L, lower than the results based on DGT (CDGT) (1.2–1.3×102 ng/L). The values of CDGT/CSOLN were larger than one unit, suggesting that the rates of resupply of target chemicals (antibiotics, hormones, and herbicides) by the desorption and diffusion of pond water were higher than the rates of uptake by XDA-1-DGT, and pond water was proved a sufficient reservoir of antibiotics for DGT application. The value of Log (CDGT/CSOLN) of 1.1 derived from the application in the aquaculture ponds of 14 regions in Eastern China can be a reference value for future chemical monitoring based on DGT technique. And the accuracy of this value was found hardly affected by the physical and chemical properties of chemicals with pKa ranging from −1 to 12, Log Kow ranging from 0 to 4.5, and Log solubility ranging from 0.0 to 4.0. [ABSTRACT FROM AUTHOR]

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The world-class McArthur River Zn-Pb-Ag deposit is the type example of stratiform sediment-hosted deposits found in the Proterozoic basins of northern Australia. However, the McArthur River deposit is enigmatic in that, aside from a few sub-economic deposits within the same camp, other deposits of this type have not been discovered regionally. Understanding the key components of McArthur River-type mineral systems and the regional distribution of these components is crucial to further discovery. The recent discovery of the similar but pyrite-dominated system at Rosie ~ 90 km north of the McArthur River Mine sheds new light on the formation of this deposit class and provides a counterpoint to compare and contrast with the high base metal endowment at McArthur River. Stratiform pyrite mineralization at Rosie is finely laminated and is affected by erosional sedimentary processes superficially indicating it formed during sedimentation to early diagenesis and at or near the sediment–water interface. The conventional ore horizon in the McArthur River camp is the HYC Pyritic Shale Member in the lower Barney Creek Formation (~ 1640 Ma) within sub-basin architecture. Rosie is contained within a similar sub-basin architecture, but it occurs in the upper Barney Creek Formation. The absence of mineralization in the lower Barney Creek Formation at Rosie is attributed in part to prohibitive tectono-sedimentary conditions during early sub-basin development. The HYC Pyritic Shale Member equivalent is relatively thin beneath the Rosie mineralization and is only weakly enriched in hydrothermal elements. Its deposition was abruptly superseded by infill of the sub-basin by a thick barren sequence of fine turbidites. The fine turbidites were a rapid phase of accommodation space fill that diluted brines entering the sediment pile and effectively precluded hydrothermal sulfide mineralization as well as low temperature alkali metasomatism. Permissible tectono-sedimentary conditions did not return until late in sub-basin development, and by this time, sub-basin geometry had broadened and shallowed, and the hydrothermal fluid had evolved. Rosie mineralization is subsequently poorly focused and base metal deficient. The observation that sedimentation rate may play a role in mineralization is a significant addition to the field of basin-hosted mineral systems. [ABSTRACT FROM AUTHOR]

Supply of phosphorus (P) as an agricultural input depends on a limited mineral rock phosphate reserve, but inefficient use means this resource is not being used sustainably. Moreover, losses of P from historically accumulated soil reserves can cause substantial environmental harm. Development of sustainable P management will require optimization of P use efficiency, with this needing a better understanding of the distribution and chemical behaviour of P in soils, including both P applied as a fertilizer and native P. In this review, we discuss in-situ methods for microscopic mapping of P distribution, speciation and plant-available P fractions in soils, including scanning electron microscopy-based energy-dispersive X-ray spectroscopy, nanoscale secondary ion mass spectroscopy, X-ray fluorescence microscopy (and associated X-ray absorption spectroscopy), Raman and infrared spectroscopies, diffusive gradients in thin films coupled with laser ablation inductively coupled plasma mass spectrometry or colorimetry, and autoradiography. These methods can complement the traditional (bulk) methods for P analysis as well as deliver valuable information in their own right or in conjunction as part of an imaging cascade. We compare the merits and limitations of these techniques, which can serve to play a key role in answering questions about P behaviour in soil, from the microscopic to macroscopic scale, and provide some examples of how they may support researchers in their particular research. [ABSTRACT FROM AUTHOR]

Arsenic (As) is commonly sequestered at the sediment–water interface (SWI) in mining-impacted lakes through adsorption and/or co-precipitation with authigenic iron (Fe)-(oxy)hydroxides or sulfides. The results of this study demonstrate that the accumulation of organic matter (OM) in near-surface sediments also influences the mobility and fate of As in sub-Arctic lakes. Sediment gravity cores, sediment grab samples, and porewaters were collected from three lakes downstream of the former Tundra gold mine, Northwest Territories, Canada. Analysis of sediment using combined micro-X-ray fluorescence/diffraction, K-edge X-ray Absorption Near-Edge Structure (XANES), and organic petrography shows that As is associated with both aquatic (benthic and planktonic alginate) and terrestrially derived OM (e.g., cutinite, funginite). Most As is hosted by fine-grained Fe-(oxy)hydroxides or sulfide minerals (e.g., goethite, orpiment, lepidocrocite, and mackinawite); however, grain-scale synchrotron-based analysis shows that As is also associated with amorphous OM. Mixed As oxidation states in porewater (median = 62% As (V), 18% As (III); n = 20) and sediment (median = 80% As (-I) and (III), 20% As (V); n = 9) indicate the presence of variable redox conditions in the near-surface sediment and suggest that post-depositional remobilization of As has occurred. Detailed characterization of As-bearing OM at and below the SWI suggests that OM plays an important role in stabilizing redox-sensitive authigenic minerals and associated As. Based on these findings, it is expected that increased concentrations of labile OM will drive post-depositional surface enrichment of As in mining-impacted lakes and may increase or decrease As flux from sediments to overlying surface waters. [ABSTRACT FROM AUTHOR]

As the global population is projected to increase by two billion people by 2050, so will the demand for phosphorus (P), an essential nutrient for all living organisms and a major driver of eutrophication. To sustainably meet these challenges, we apply the conceptual framework of transition management (TM) to demonstrate how the trajectory of the current linear P use system could be strategically shifted toward a more circular P system. We present US case studies to examine P transitions management in intensive agriculture, wastewater disposal, and food waste management. Our goal is twofold. By first understanding past transitions in P management in the USA, we can build upon these insights for future management. This can then be applied to other global regions such as developing countries to bypass stages of transition as they intensify agriculture, incorporate sewers into cities, and expand waste management, to avoid becoming entrenched in unsustainable P management. We suggest how spaces for experimentation and collaboration can be created, how and which actor networks can be mobilized, and what action strategies and policies can be recommended to accelerate their transition to P sustainability. Our case studies show that while substantial improvements have been made, the transition toward a circular economy of P is far from complete. Our findings point to the value of utilizing TM for future progress in the US Development of TM frameworks for managing P in other regions of the world may enable them to achieve sustainable P development faster and more effectively than the USA. [ABSTRACT FROM AUTHOR]

Aims: The biogeochemical cycles of elements from soils to plants are mainly governed by their rhizosphere processes. Understanding these processes is challenging and remains largely unresolved due to the complex interrelationships among different elements and due to a lack of appropriate techniques for simultaneous spatiotemporal monitoring. Methods: This study employed an updated In-situ Porewater Iterative (IPI) sampler to collect porewater across the rice rhizosphere at a spatial resolution of 1.7 mm and a time interval of 3–10 days. An IPI sampler array (0–22 mm measurement distance every 1.7 mm) was adopted to capture the in situ spatiotemporal dynamics of ten elements (Fe, Mn, As, P, S, Cr, Co, Zn, Sb and Cd) in the paddy rhizosphere to examine their covarying changes in time and space dimensions, with an emphasis on As and Cd. Results: The findings revealed that the solute-phase concentration of most elements, other than Sb and Cd, increased to a peak after 30 days of paddy soil flooding and then decreased. Additionally, Sb and Cd continuously decreased during flooding. Fe (−52%), Mn (−17%), P (−43%), Co (−11%), and As species (−74%) were substantially immobilized within a 10 mm zone around the roots, while Zn (28%) and Cd (41%) increased. Almost all arsenite-oxidizing genes were significantly promoted in the rhizosphere. Conclusions: Our study showed most sampled elements covaried with Fe both in time and space in the rhizosphere, but the elements are temporally and spatially determined by multiple biogeochemical processes in soils as well as exudates from plant roots. [ABSTRACT FROM AUTHOR]

The determination of the concentration of an environmental pollutant is not sufficient to assess the related health risk because this pollutant may not be bioavailable. Therefore, methods to determine pollutant bioavailability are more relevant to assess toxicity than measuring the total concentration. For instance, the diffusive gradient in thin films (DGT) is an in situ dynamic technique used to measure the concentration of labile compounds in the environment. Here we review the latest developments achieved in speciation and bioavailability of metals and metalloids using this technique. We detail the technique, common binding agents and diffusive gels. We give laboratory procedures to prepare the gels, and we explain calculations using the DGT-induced fluxes in soils (DIFS) modeling. DIFS models can predict the resupply capacities from soils to porewater, and the uptake of trace elements by plants. Procedures for in situ field deployments, including issues of biofilm growth, are also discussed. [ABSTRACT FROM AUTHOR]

Introduction: Poor gestational outcomes due to placental insufficiency can have lifelong consequences for mother and child. Objective: There is a need for better methods of diagnosis, and elemental metabolomics may provide a means to determine the risk of gestational disorders. Methods: This study used blood plasma samples collected at 36 weeks' gestation from women who later developed preeclampsia (n = 38), or small-for-gestational age babies (n = 91), along with matched controls (n = 193). Multi-element analysis was conducted by inductively coupled plasma mass spectrometer (ICP-MS), allowing simultaneous measurement of 28 elements. Results: Women who later developed PE, exhibited significantly increased concentrations of K, Rb and Ba. For SGA pregnancies, there was a significant increase in Cu and a decrease in As concentrations. Despite significant differences in single elements, the elemental profile of groups indicated no clustering of control, PE, or SGA samples. Positive predicative values correctly identified approximately 60% of SGA and 70% of PE samples. Conclusion: This is the first-time elemental metabolomics has been used to predict SGA and PE at 36 weeks. Though significant changes were identified, routine clinical use may be limited but may contribute to a multi marker test. Future analysis should include other biomarkers, metabolic data or clinical measurements made throughout gestation. [ABSTRACT FROM AUTHOR]

The trace element of As and Sb have resulted in serious threats to ecological sustainability and human health in the Xijiang River basin, China. The geoaccumulation index (Igeo) results showed the sediment of Xijiang River was heavily contaminated by Sb as well as moderately contaminated by As. The effect of inorganic anions on the released As and Sb from the sediment increases in the following sequence: Cl− < SO42− < CO32− < PO43−. The presence of PO43− and CO32− had the greater effect over As mobility from the sediment compared to Sb. The effect of Ca(II), Al(III), and Mg(II) on the released amount of Sb from the sediment is negligible. Meanwhile, in the case of As, Ca(II) and Mg(II) had small impacts, but the released amount of As increased slightly with an increase of Al(III) concentration. The stability of As and Sb in the sediment was found to be the best at pH 5. The effect of organic compounds (≤ 0.05 mol/L) on the dissolved As percentages from the sediment increased in the following sequence: ethylenediaminetetraacetate (EDTA) < oxalate < citrate, and the effect on Sb release was oxalate < EDTA < citrate at concentrations (≤ 0.025 mol/L). This study provides the basic theoretical basis to manage the mobilization of co-contamination of sediments with As and Sb under the influence of external perturbations. [ABSTRACT FROM AUTHOR]

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Purpose: Biochar is a promising alternative for the remediation of areas contaminated by mining waste. However, depending on the pyrolysis temperature, the biochar may not be equally effective for immobilizing cationic and anionic contaminants. Our objectives in this study were to evaluate (i) the effect of biochar on arsenic (As) and lead (Pb) availabilities in sediments of a contaminated area and (ii) the effect of the biochar pyrolysis temperatures on the enzymatic activity of the microorganisms. Material and methods: The contaminated sediment was sampled in an area that served as a lead ore refining plant for 10 years in Brazil. The biochar was produced from sugarcane straw (Saccharum officinarum) and pyrolyzed at 350 (BC350), 550 (BC550), and 750 °C (BC750). We performed an incubation experiment to investigate the effects of pyrolysis temperature on the dynamics of As and Pb in the sediment. The availabilities of As and Pb were measured by the diffusive gradients in the thin film, and the quality of organic carbon in the sediment was investigated by laser-induced fluorescence spectroscopy and UV–vis spectroscopy in solution. In addition, the effect of the application of the biochar on the microbial community was evaluated through the activities of the enzymes β-glucosidase, acid, and alkaline phosphatase. Results and discussion: The application of biochar changed the chemical composition of the carbon structures and altered the availability of As and Pb. Increases in As availability after application of biochar is directly linked to the chemical composition of the dissolved organic carbon present in BC350, with the activity of phosphatase and phosphorus release (BC550 and BC750) and, finally, with pH (B550 and BC750). The availability of Pb was reduced after the application of the B550 and B750, which suggests that pyrolyzed biochars at high temperatures may help to reduce the environmental risk associated with Pb contamination. The application of biochar reduced the activity of the enzymes β-glucosity and acid phosphatase, while the alkaline phosphatase activity increased and was dependent on the pyrolysis temperature. Conclusions: The increase in As availability after the application of the biochar is related to the chemical composition of dissolved organic carbon and the increase in phosphatase activity. The availability of Pb has been reduced due to the increase in pH, which suggests that pyrolyzed biochars at high temperatures may help to reduce the environmental risk associated with Pb contamination. [ABSTRACT FROM AUTHOR]