Fate and Trophic Transfer of Rare Earth Elements in a Tropical Estuarine Food Web.

We sampled abiotic and food web components in an impacted estuarine system to assess the transfer and fate of rare earth elements (REE). REE (based on dry weight) were measured in sediments, suspended particulate matter (SPM), and organisms from different trophic levels. The highest ∑REE concentrations were measured in sediments (180 ± 4.24 mg kg-1) and SPM (163 ± 12.6 mg kg-1). Phytoplankton (45.7 ± 5.31 mg kg-1), periphyton (51.6 ± 1.81 mg kg-1), and zooplankton (68.5 ± 1.27 mg kg-1) are the major sources of exposure and transfer of REE to the food web. REE concentrations were several orders of magnitude lower in bivalves, crustaceans, and fish (6.01 ± 0.11, 1.22 ± 0.18, and 0.059 ± 0.003 mg kg-1, respectively) than in plankton. The ∑REE declined as a function of the trophic position, as determined by functional feeding groups and δ15N, indicating that REE were subject to trophic dilution. Our study suggests that the consumption of seafood is unlikely to be an important source of REE for humans. However, given the numerous sources of dietary introduction of REE, they should be monitored for a possible harmful cumulative effect. This study provides new key information on REE's baseline concentrations and trophic transfers and patterns.

Mineral and Trace Elements in Nutritious Flours: Total Contents, In Vitro Bioaccessibility and Contribution to Dietary Intake.

The consumption of fruits, vegetables, and cereals in the form of flour has been an alternative for the intake of nutrients, currently seen in a society that seeks a healthier diet. Thus, the assessment of total contents and bioaccessibility is important to better understand the actual intake of nutrients or contaminants present in foods. The objective of this study was to determine the total content and estimate the bioaccessible fraction of Cu, Fe, and Zn in nutritious flours by inductively coupled plasma optical emission spectrometry (ICP OES) after microwave acid digestion. Bioaccessibility was assessed using the in vitro method, taking into account the entire gastrointestinal tract (Unified Bioaccessibility Method (UBM)). The following concentration ranges, in µg g-1, were found: Ca (341-6275), K (2984-13,953), P (476-6110), Na (< 0.39-2995), Fe (1.4-167), Cu (< 0.01-59.6), and Zn (< 0.07-30.3). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed a tendency towards the formation of three groups. The bioaccessible fractions for Cu, Fe, and Zn were considered low, ranging from 0.96 to 40% in the gastrointestinal phase and from 4.1 to 100% in the gastric phase.

Occurrence and contents of trace metals and rare earth elements on plastic pellets.

We determined the occurrence of pellets (2-5 mm) and their composition in terms of trace metals and rare earth elements (REE) on nine sandy beaches of the coast of Bahia, northeastern Brazil. We compared the occurrence of pellets between oceanic and sheltered beaches and the effect of fluvial contribution on the occurrence of these microplastics. The number of pellets found was surprisingly low (i.e., max 45 pellets per m2 in an oceanic beach without fluvial river inputs). Thus, the studied beaches exhibited a very low pollution index. Concentrations of ∑REE in pellets varied between 0.36 and 1.74 mg kg-1 and were ~5-fold higher in white/transparent pellets than in brown pellets. The sum of trace metals (i.e., Fe, Cd, Cu, Ni, Pb, and Zn) was also highest in the white pellets (357 ± 12 mg kg-1). Plastic pellets are a potentially important vector of REE exposition to biota.

Environmental settings of seagrass meadows control rare earth element distribution and transfer from soil to plant compartments.

The role of seagrass meadows in the cycling and accumulation of rare earth elements and yttrium (REEY) is unknown. Here, we measured the concentration of REEY in the different compartments of Halodule wrightii (shoots, rhizomes, and roots) and soils in seagrass meadows near sandy beaches, mangroves, and coral reefs in the Todos os Santos Bay, Brazil. We provide data on the accumulation dynamics of REEY in seagrass compartments and demonstrate that plant compartments and soil properties determine accumulation patterns. The ∑REEY in soils were ~1.7-fold higher near coral reefs (93.0 ±â€¯5.61 mg kg-1) than near mangrove sites (53.9 ±â€¯31.5 mg kg-1) and were slightly higher than in sandy beaches (81.7 ±â€¯49.1 mg kg-1). The ∑REEY in seagrasses varied between 35.4 ±â€¯28.1 mg kg-1 near coral reefs to 59.2 ±â€¯21.3 mg kg-1 near sandy beaches, respectively. The ∑REE bioaccumulation factor (BAF) was highest in seagrass roots near sandy beaches (BAF = 0.67 ±â€¯0.48). All values of ∑REE translocation are <1, indicating inefficient translocation of REE from roots to rhizome to shoot. PAAS normalized REE was enriched in light REE (LREE) over heavy REE (HREE). The REEY accumulation in Halodule wrightii revealed a low potential of the seagrass to act as a sink for these elements. However, their bioavailability and potential uptake may change with soil properties. Our results serve as a basis for a better understanding of REE biogeochemical cycling and its fate in the marine environment. REE have experienced increased use as they are central to new technologies revealing an urgent need for further investigations of potential impacts on coastal ecosystems.

Evidence of high bioaccessibility of gadolinium-contrast agents in natural waters after human oral uptake.

Considering the large occurrence of anthropogenic Gd concentrations in natural waters, its continuous usage increase in technology developments and products and the lack of data on potential Gd human exposure due to ingestion of contaminated waters, it is urgently needed to understand how gadolinium contrast agents (Gd-CAs) reacts in the human digestive system. Here, we aimed to identify through in vitro bioaccessibility tests whether Gd-CAs can be potentially assimilated by humans after oral uptake and if there is a significant difference between contrast agents. We also roughly estimated the potential bioaccessibility of anthropogenic Gd for tap waters worldwide. Gd-CAs are highly bioaccessible (77 to 112%). The macrocyclic complexes pose the highest potential risk, because there are more stable than linear complexes in the gastrointestinal tract and, as such, tend to remain in solution and thus might bring Gd at the intestinal barrier making it potentially bioavailable. The estimated range of potential intake of Gd varied from 13 to 4839 µg in a lifespan of 70 years. The high bioaccessibility of anthropogenic Gd in tap waters calls for appropriate actions to develop better practices to treat wastewater contaminated by Gd-CAs in order to safeguard population and ecosystem health.

Neonatal pyridoxine administration long lastingly accelerates cortical spreading depression in male rats, without affecting anxiety-like behavior.

Objectives: Pyridoxine plays a key role in the development of the human nervous system. Several reports suggest that administration of high doses of pyridoxine can be helpful in improving disturbances such as anxiety and pyridoxine-dependent epilepsy, although it has also been associated with a proconvulsive action. In this study, we investigated in developing rats the effects of repeated administration of various doses of pyridoxine on anxiety-like behavior and the brain excitability-related phenomenon known as cortical spreading depression (CSD).Methods: From postnatal day (P) 7 to P27, Wistar rat pups received per gavage pyridoxine hydrochloride (1 mg/kg/day, or 5 mg/kg/day, or 10 mg/kg/day). On P60-70, the animals were tested in the elevated plus maze (EPM) to evaluate anxiety-like behavior. On P71-80, we recorded the CSD (4-hour recording session).Results: Compared with naïve (gavage-free) and saline-treated controls, pyridoxine-treated groups displayed a significant (p < 0.001) increase in CSD propagation velocity and amplitude of the CSD negative direct-current (DC)-shift, and a decrease in the CSD DC-shift duration. These effects were long-lasting and dose-dependent. In the EPM, no significant pyridoxine-associated effect was observed.Discussion: Our data demonstrate a novel action of pyridoxine on an electrical activity-related phenomenon (CSD) in the developing brain, confirming the hypothesis that the chronic treatment with pyridoxine early in life modulates CSD. Data on CSD propagation suggest that pyridoxine at a high dose might act as a prooxidant agent in the developing brain, a hypothesis that deserves further testing.

Evaluation of the Mineral Content in Forage Palm (Opuntia ficus-indica Mill and Nopalea cochenillifera) Using Chemometric Tools.

An acid digestion procedure of the forage palm (Opuntia ficus-indica Mill and Nopalea cochenilifera) employing a closed digestor block applied full 24 factorial design was optimized. The optimal conditions were HNO3 5.0 mol L-1, 2.0 mL of H2O2 30% m m-1, 120 min of digestion, and heating temperature of 180 °C. The certified reference materials of apple leaves (NIST 1515) and tomato leaves (Agro C1003a) were used to evaluate the accuracy of the analytical method. The concentrations of the macroelements were (in % m m-1) Ca (1.32-3.71), K (0.88-5.29), Mg (0.70-1.78), and P (0.03-0.32). For the microelements, the concentrations (in µg g-1) obtained were As (< 1.39), Cd (< 0.10), Cu (< 0.17-5.6), Fe (8.0-50.2), Na (< 1.85), Sr (41-348), and Zn (17.3-159). Essential elements such as Ca, Mg, and Zn made good contributions to daily intake, being an alternative to meet the nutritional needs of these macroelements and microelements in humans. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to evaluate the results, obtaining trends between the samples in relation to their mineral composition.

Flow-through dynamic microextraction system for automatic in vitro assessment of chyme bioaccessibility in food commodities.

An automatic flow-through dynamic extraction method is proposed for the first time for in vitro exploration, with high temporal resolution, of the transit of the chyme from the gastric to the duodenal compartment using the Versantvoort's fed-state physiologically relevant extraction test. The flow manifold was coupled on-line to an inductively coupled plasma optical emission spectrometer (ICP OES) for real-time elucidation of the bioaccessible elemental fraction of micronutrients (viz., Cu, Fe and Mn) in food commodities across the gastrointestinal tract. The simulated intestinal and bile biofluid (added to the gastric phase) was successively pumped at 1.0 mL min-1 through a large-bore column (maintained at 37.0 ±â€¯2.0 °C) initially loaded with a weighed amount of linseed (250 mg) using a PVDF filter membrane (5.0 µm pore size) for retaining of the solid sample and in-line filtration of the extracts. The lack of bias (trueness) of the on-line gastrointestinal extraction method coupled to ICP OES was confirmed using mass balance validation following microwave assisted digestion of the residual (non-bioaccessible) elemental fraction. Mass balance validation yielded absolute recoveries spanning from 79 to 121% for the overall analytes and samples. On-line dynamic extraction was critically appraised against batch counterparts for both gastric and gastrointestinal compartments. Due to the lack of consensus in the literature regarding the agitation method for batch oral bioaccessibility testing, several extraction approaches (viz., magnetic stirring, end-over-end rotation and orbital shaking) were evaluated. Improved gastric extractability of Fe along with bioaccessible data comparable to the dynamic counterpart based on the continuous displacement of the extraction equilibrium was obtained with batchwise magnetic stirring, which is deemed most appropriate for ascertaining worst-case/maximum bioaccessibility scenarios.