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Denitrifying woodchip bioreactors (DBRs) are an established nitrate mitigation technology, but uncertainty remains on their viability for phosphorus (P) removal due to inconsistent source-sink behaviour in field trials. We investigated whether iron (Fe) redox cycling could be the missing link needed to explain P dynamics in these systems. A pilot-scale DBR (Aotearoa New Zealand) was monitored for the first two drainage seasons (2017-2018), with supplemental in-field measurements of reduced solutes (Fe2+, HS-/H2S) and their conjugate oxidised species (Fe3+/SO42-) made in 2021 to constrain within-reactor redox gradients. Consistent with thermodynamics, the dissolution of Fe3+(s) to Fe2+(aq) within the DBR sequentially followed O2, NO3- and MnO2(s) reduction, but occurred before SO42- reduction. Monitoring of inlet and outlet chemistry revealed tight coupling between Fe and P (inlet R2 0.94, outlet R2 0.85), but distinct dynamics between drainage seasons. In season one, outlet P exceeded inlet P (net P source), and coincided with elevated outlet Fe2+, but at â50 % lower P concentrations relative to inlet Fe:P ratios. In season 2 the reactor became a net P sink, coinciding with declining outlet Fe2+ concentrations (indicating exhaustion of Fe3+(s) hydroxides and associated P). In order to characterize P removal under varying source dynamics (i.e. inflows vs in-situ P releases), we used the inlet Fe vs P relationship to estimate P binding to colloidal Fe (hydr)oxide surfaces under oxic conditions, and the outlet Fe2+ concentration to estimate in-situ P releases associated with Fe (hydr)oxide reduction. Inferred P-removal rates were highest early in season 1 (k = 0.60 g P m3 d-1; 75-100 % removal), declining significantly thereafter (k = 0.01 ± 0.02 g P m3 d-1; ca. 3-67 % removal). These calculations suggest that microbiological P removal in DBRs can occur at comparable magnitudes to nitrate removal by denitrification, depending mainly on P availability and hydraulic retention efficiency.
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Nitratos , Fósforo , Compuestos de Manganeso , Desnitrificación , Óxidos , Reactores Biológicos , NitrógenoRESUMEN
Benzylalkyldimethylammonium chloride (BAC), a quaternary ammonium compound (QAC), is utilized in industrial and biomedical applications for antimicrobial purposes. Since the coronavirus disease (COVID-19) outbreak, various types of BAC-containing household chemicals have been produced. BACs have several adverse effects; however, their biological uptake, translocation, and excretion in animal models (essential for better understanding in vivo behavior and toxicological impact) remain unclear. In this study, we performed the first biodistribution and whole-body imaging studies of BAC in male Sprague Dawley rats, using two different administration routes. Quantitative whole-body autoradiography (QWBA) data obtained for intranasal 14C-labeled BAC ([14C]C12-BAC) exposure showed substantial uptake values for the respiratory organs (e.g. 346 ng g-1 of lung at 3 h post administration) and the radiotracer was transported to other internal organs. The amount of radiotracer in the heart, adrenal gland, and pancreas were 198, 1410, and 186 ng g-1 tissue respectively at 168 h following exposure. Autoradiograms obtained after intravenous injection also showed high accumulation and slow excretion in these organs. The cumulative excretion analysis revealed that approximately 6.4% of the administered radioactivity remained in rats after a week. The results indicated that continuous inhalation exposure to BAC leads to potential toxic effects in extrapulmonary organs and the respiratory tract. Thus, the radiolabeling method utilized may help assess various synthetic QACs in living subjects.
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COVID-19 , Cloruros , Ratas , Masculino , Animales , Ratas Sprague-Dawley , Distribución Tisular , BioacumulaciónRESUMEN
The global shift toward green energy alternatives escalates demands for new resources, including rare earth elements (REEs), as per their implications in various green innovations. However, our understanding of their environmental cycle, especially the interactions with aquatic organisms, remains deficient, ultimately hindering environmental protection efforts. Here, we investigate the accumulation of REEs and 18 other elements in bulk and sorted plankton collected with different net mesh sizes (30, 63, 200, 333, 500 µm) in the Estuary and Gulf of St. Lawrence in the summer and winter of 2020. We observed significant correlations between the concentrations of REEs and elements of different charge numbers and ionic radii (Ba, Co, Cs, Fe, Mn, Pb, Rb and V), indicating non-selective uptake of REEs into plankton. All these elements have their highest concentrations in the fluvial corridor and upper estuary, with more significant enrichment in phytoplankton ([La] = 26.4 ± 4.8 mg kg-1) than zooplankton ([La] = 11.6 ± 8.3 mg kg-1). Their concentrations decrease to the minimum in the Gulf of St. Lawrence, especially in zooplankton ([La] = 4.8 × 10-2 ± 3.2 × 10-2 mg kg-1). We also assessed REE patterns to identify differential REE fractionation processes and anomalies. The freshwater plankton exhibits enrichment of middle REEs (MREEs) relative to the light and heavy REEs (LREEs and HREEs), potentially because of the higher binding affinity of MREEs on cellular surface transporters and metal loading effects. In estuarine and marine settings, the REE patterns in biological samples align with suspended particles, exhibiting a linear trend with LREE enrichment. This process is more noticeable in sorted macrozooplankton, which have significant Eu anomalies (Eu/Eu* up to 2), indicating differential incorporation of REEs into the chitin shells. This study highlights the significant enrichment of REEs into freshwater primary producers and the accumulation pathway similar to other inorganic elements.
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Metales de Tierras Raras , Plancton , Animales , Estuarios , Monitoreo del Ambiente , Metales de Tierras Raras/análisis , ZooplanctonRESUMEN
Exposure of the soil environment to metal nanoparticles (MNPs) has been extensive because of their indiscriminate use and the disposal of MNP products in various applications. In MNP-amended soil, various crops can absorb the nanoparticles, and accumulation of the MNPs in farm products has potential risks for bioconcentration in humans and livestock. Here, we evaluated the comparative bioaccumulation, translocation, and phytotoxicity of MNPs (ZnO and CuO NPs) and metal ions (Zn(NO3)2 and Cu(NO3)2) in four different crops, namely lettuce, radish, bok choy, and tomato. We carried out pot experiments to evaluate the phytotoxicity in the crops from the presence of MNPs and metal ions. Phytotoxicity from different treatments differed depending on the plant species, and metal types. In addition, exposure to Zn and Cu showed positive dose-dependent effects on their bioaccumulation in each crop. However, there were no significant differences in metal bioaccumulation depending on whether the crops were exposed to MNPs or metal ions. By calculating the bioconcentration factor (BCF) and translocation factor (TF), we were able to estimate the biological uptake and translocation abilities of MNPs and metal ions for each crop. It was found that lettuce and radish had greater BCFs than bok choy and tomato, while bok choy and tomato had higher TFs. Also, the uptake and translocation of Zn were better than those of Cu. However, the values for BCF and TF for each crop showed no significant differences between MNP and metal ion exposure. A micro X-ray fluorescence (µ-XRF) spectrometer analysis demonstrated that only Zn elements appeared in the primary veins and edges of all leaves and the storage root of radish. Our study aims to estimate bioaccumulation, translocation, and the implied potential risks from MNPs accumulated in different plant species.
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Nanopartículas del Metal , Nanopartículas , Contaminantes del Suelo , Humanos , Suelo , Bioacumulación , Óxidos , Contaminantes del Suelo/toxicidad , Contaminantes del Suelo/análisis , Raíces de Plantas/química , Nanopartículas del Metal/toxicidad , Metales/análisis , Iones , Productos Agrícolas , LactucaRESUMEN
Anoxic conditions within reservoirs related to thermal stratification and oxygen depletion lead to methylmercury (MeHg) production, a key process governing the uptake of mercury in aquatic food webs. Once formed within a reservoir, the timing and magnitude of the biological uptake of MeHg and the relative importance of MeHg export in water versus biological compartments remain poorly understood. We examined the relations between the reservoir stratification state, anoxia, and the concentrations and export loads of MeHg in aqueous and biological compartments at the outflow locations of two reservoirs of the Hells Canyon Complex (Snake River, Idaho-Oregon). Results show that (1) MeHg concentrations in filter-passing water, zooplankton, suspended particles, and detritus increased in response to reservoir destratification; (2) zooplankton MeHg strongly correlated with MeHg in filter-passing water during destratification; (3) reservoir anoxia appeared to be a key control on MeHg export; and (4) biological MeHg, primarily in zooplankton, accounted for only 5% of total MeHg export from the reservoirs (the remainder being aqueous compartments). These results improve our understanding of the role of biological incorporation of MeHg and the subsequent downstream release from seasonally stratified reservoirs and demonstrate that in-reservoir physical processes strongly influence MeHg incorporation at the base of the aquatic food web.
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Mercurio , Compuestos de Metilmercurio , Contaminantes Químicos del Agua , Monitoreo del Ambiente , Cadena Alimentaria , Humanos , Hipoxia , Mercurio/análisis , Compuestos de Metilmercurio/metabolismo , Oxígeno , Ríos , Agua , Contaminantes Químicos del Agua/análisisRESUMEN
This study deals with the geology in areas close to a large unexploited uranium deposit and the impact of bedrock characteristics on levels of radionuclides and other elements in soil and biota. Factors influencing soil inventory and ecosystem transfer are discussed, focussing on 238U, 226Ra, and 210Pb. Field work was carried out in Salangen Valley in Northern Norway. Sampling stations for soil and biota covered different habitats - grassland, birch forest and low alpine heathland. The geological survey confirmed uranium-bearing minerals in granitic gneiss and pegmatites. There was large variation in the local occurrence of uranium, reflecting the irregular nature of the pegmatite. Activity concentrations of 238U, 226Ra, and 210Pb in surface soil were elevated at sites close to U-enhanced bedrock, compared to sites with other types of bedrock. Particularly high soil levels were found for 226Ra and 210Pb, whereas activity concentrations of 238U were more variable, depending of local soil characteristics. Levels of other natural radionuclides (40K, 232Th) merely increased with soil mineral content, and concentrations of heavy metals were generally low at all sites. External dose rate (1 m above ground surface) was closely correlated with 226Ra levels in soil. Plant levels of 238U and 226Ra varied by several orders of magnitude depending on soil level and plant species, whereas plant levels of 210Pb and 210Po were largely affected by aerial fallout. Berries generally contained lower levels of 238U and 226Ra than green plant parts. As was the case for plants, the levels of 238U in earthworms were strongly correlated with the respective concentrations in the soil. Soil-to-plant transfer was markedly higher for 226Ra than for 238U. For both radionuclides, a positive correlation was found between concentration ratios of V. myrtillus (heath) and soil organic matter content. The 238U concentration ratios for earthworms were generally two orders of magnitude higher than for plants.
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Bosques , Monitoreo de Radiación , Radiactividad , Contaminantes Radiactivos del Suelo , Animales , Biota , Ecosistema , Geología , Noruega , SueloRESUMEN
A number of marine radionuclide dispersion models (both Eulerian and Lagrangian) were applied to simulate 137Cs releases from Fukushima Daiichi nuclear power plant accident in 2011 over the Pacific at oceanic scale. Simulations extended over two years and both direct releases into the ocean and deposition of atmospheric releases on the ocean surface were considered. Dispersion models included an embedded biological uptake model (BUM). Three types of BUMs were used: equilibrium, dynamic and allometric. Model results were compared with 137Cs measurements in water (surface, intermediate and deep layers), sediment and biota (zooplankton, non-piscivorous and piscivorous fish). A reasonable agreement in model/model and model/data comparisons was obtained.
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Radioisótopos de Cesio/análisis , Accidente Nuclear de Fukushima , Modelos Químicos , Monitoreo de Radiación , Contaminantes Radiactivos del Agua/análisis , Contaminación Radiactiva del Agua/estadística & datos numéricos , Biota , Océano PacíficoRESUMEN
Understanding of the interaction of graphene with natural polysaccharides (e.g., alginate) is crucial to elucidate its environmental fate. We investigated the impact of alginate on the agglomeration and stability of 14C-labeled few-layer graphene (FLG) in varying concentrations of monovalent (NaCl) and divalent (CaCl2) electrolytes. Enhanced agglomeration occurred at high CaCl2 concentrations (≥5 mM) due to the alginate gel networks formation in the presence of Ca2+. FLG enmeshed within extended alginate gel networks was observed under transmission electron microscope and atomic force microscope. However, background Na+ competition for binding sites with Ca2+ at the alginate surfaces shielded the gelation of alginate. FLG was readily dispersed by alginate under environmentally relevant ionic strength conditions (i.e., <200 mM Na+ and <5 mM Ca2+). In comparison with the bare FLG, the slow sedimentation of the alginate-stabilized FLG (158 µg/L) caused continuous exposure of this nanomaterial to freshwater snails, which ingested 1.9 times more FLG through filter-feeding within 72 h. Moreover, surface modification of FLG by alginate significantly increased the whole-body and intestinal levels of FLG, but reduced the internalization of FLG to the intestinal epithelial cells. These findings indicate that alginate will act as a stabilizing agent controlling the transport of FLG in aqueous systems. This study also provides the first evidence that interaction of graphene with natural polysaccharides affected the uptake of FLG in the snails, which may alter the fate of FLG in aquatic environments.