Development of a new plant-based biotest to assess trace element phytoavailability in contamined soils : selection of target-plant species for standardisation

Concerning the threat of soil contamination, the assessment of trace element phytoavailability at an operational level still requires the identification, the development and the standardisation of a set of biological methods (i.e. biotest). The present abstract introduces the first step in the development of a new plant-based biotest, the RHIZOtest, focused on the selection of the target-plant species suggested for the standardisation of the RHIZOtest. The RHIZOtest is notably based on a complete physical separation between plant and soil compartments enabling an easy, fast and clean recovery of the roots. The RHIZOtest was deployed for ten plant species commonly used in agriculture and on three soils exhibiting a broad range of pH and a high concentration in several trace elements. The measurement of trace element phytoavailability was finally achieved as the mean flux of trace element to the plants during the exposure of the plants to the soil. Seven out of ten plant species exhibited homogenous growth of roots and shoots and consequently can be used adequately in the RHIZOtest experimental procedure. As expected, plant uptake flux of trace elements varied significantly and many-fold among the ten plant species tested. However, trace element phytoavailability also broadly varied among trace elements and soils. Finally, a procedure of ordination and scoring enabled us to select three plant species that maximised trace element phytoavailability according to a precautionary-like principle. This three plant species will be suggested for further standardisation of the RHIZOtest. This study supports the requirement of biological methods that enable to encompass the biological diversity in the assessment of trace element phytovailability whereas chemical methods are not able to take it into account. Such kind of validation procedure for a biotest is the unique opportunity for achieving operational methods based on a hard scientific background that could be standardised for the assessment of trace element phytoavailability. (Résumé d'auteur

Probing Quantum Confinement and Electronic Structure at Polar Oxide Interfaces

Polar discontinuities occurring at interfaces between two different materials constitute both a challenge and an opportunity in the study and application of a variety of devices. In order to cure the large electric field occurring in such structures, a reconfiguration of the charge landscape sets in at the interface via chemical modifications, adsorbates or charge transfer. In the latter case, one may expect a local electronic doping of one material: one sparkling example is the two-dimensional electron liquid (2DEL) appearing in SrTiO$_3$ once covered by a polar LaAlO$_3$ layer. Here we show that tuning the formal polarisation of a (La,Al)$_{1-x}$(Sr,Ti)$_x$O$_3$ (LASTO:$x$) overlayer through chemical composition modifies the quantum confinement of the 2DEL in SrTiO$_3$ and its electronic band structure. The analysis of the behaviour in magnetic field of superconducting field-effect devices reveals, in agreement with $ab\ initio$ calculations and self-consistent Poisson-Schr\"odinger modelling, that quantum confinement and energy splitting between electronic bands of different symmetries strongly depend on interface charge densities. These results not only strongly support the polar discontinuity mechanisms with a full charge transfer to explain the origin of the 2DEL at the celebrated LaAlO$_3$/SrTiO$_3$ interface, but also demonstrate an effective tool for tailoring the electronic structure at oxide interfaces.Comment: 18 pages, 4 figures, 1 ancillary file (Supporting Information

RHIZOtest: an innovative tool for phytoavailability assessment and risk management in polluted soils

Resulting from 25 years of research at Inra and Cirad in France, RHIZOtest is a plant-based test that was standardized at ISO to assess the phytoavailability of trace elements in polluted soils. Initially, mainly developed on moderately contaminated soils, the objective is now to apply the RHIZOtest as a tool to assess the phytoavailability in heavily Polluted Sites and Soils. The RHIZOtest concretely measures the transfer of soil contaminants (mainly trace elements) to the plant, i.e. the phytoavailability. It takes into account the interactions between several contaminants, i.e. the mixture effect. By mimicking soil-plant interactions specific to each type of soil and plant species, the RHIZOtest reproduces natural processes to assess the actual risk. Finally, the RHIZOtest allows to reproduce, in few weeks in a laboratory, widely generalizable studies hardly achievable in the field for reasonable implementation time and cost. Today operational for transfer analysis of trace elements in the agricultural context, the RHIZOtest deployed by the spin off MetRHIZLab, offers new perspectives for the risk assessment and management of polluted sites and soils, such as: (i) assessing risk of transfer according to use, (ii) proving the effectiveness of remediation techniques, (iii) optimizing a site, (iv) attending revegetation or (v) characterizing the state of contaminated soil to be recycled. In order to test these new perspectives for the risk assessment and management of polluted sites and soils, a preliminary study was conducted on three soils from polluted sites. Soil 1 and 2 were collected in an ancient mine in southern France. Soil 1 and 2 are exhibiting high concentrations in Zn, Pb and Cd. Soil 3 is highly contaminated with As, Cd, Cr, Cu, Ni, Zn and even more Pb by atmospheric fallouts from a battery recycling plant. The three reference plant species, cabbage, fescue and tomato, were cultivated on these soils according to the ISO 16198 standard. Firstly, no difference of plant biomass was observed between the three soils. This shows that the RHIZOtest was able to assess phytoavailability of trace elements without any phytotoxic artefact. Secondly, the three plant species highlighted the same phytoavailability for each soil and each trace element. Thus, the RHIZOtest showed its capacity to give a robust measure of the phytoavailability of trace elements in heavily contaminated soils. Based on this preliminary study, a R&D program is underway to confirm these results with soils exhibiting contrasted physical-chemical properties and contaminations. Soils will be selected among different types of polluted sites such as ancient mines and industrial wasteland managed with various techniques (washing, phytomanagement or bioremediation), to create a decision support method based on RHIZOtest. Dedicated to design offices, laboratories and experts, the RHIZOtest is an innovative decision support tool that should enable soon to assess risks and to optimize the management of polluted sites and soils

Summer Academy:for social media trainers in local regional governments and business

One of the work packages which Hanzehogeschool emphatically has a role, is Research and Training. In the Summer Academy teachers are trained by translating their knowledge back to their own schools. The Summer Academy is given on 27-30 May 2013, as part of "Opening Up". This project aims to find better service to citizens and businesses through the use of social media and open data. The opening-up project started in October 2011 and lasts three years. Hanze University Groningen is an important partner in the project

Root-induced alterations of copper speciation in solution in the rhizosphere of crop species

As a prerequisite to establish trace metal phytoavailability, it is essential to determine trace metal speciation in the solution of the rhizosphere, where substantial alterations of physicalchemical properties (e.g. pH, Eh, organic matters) are induced by root activities. Investigations in the past decades were mainly dedicated to studying illustrative cases of how each individual rhizosphere process is able to influence trace metal speciation in solution. On a more integrative perspective, the present study aimed at investigating (i) the diversity of chemical modifications occurring in the solution of the rhizosphere of crop species cultivated on soils exhibiting a very wide range of physical-chemical properties and (ii) their consequent impact on copper (Cu) speciation in solution. Three plant species from three distinct botanical families, i.e. one graminaceous species, red fescue (Festuca rubra), two dicotyledonous species, tomato (Lycopersicon esculentum) and cabbage (Brassica oleracea), and 55 soils exhibiting a wide variety of physico-chemical properties (e.g. pH 4.4-8.2, 1-126 g Corg kg-1 , 6-1077 mg Cutotal kg-1 ) were selected for this study. Plants were grown using the RHIZOtest experimental design. This biotest consists in growing plants for two weeks in hydroponics, then for 8 days in contact with soil. Soils harvested from planted and unplanted devices are considered to be representative of rhizosphere and bulk soil, respectively. The solution of each rhizosphere and bulk soil was extracted with an unbuffered salt solution, and pH, concentrations of major ions and trace elements, dissolved organic matter (DOM), as well as the free Cu2+ activity were measured. The reactivity of DOM towards Cu was also estimated by modeling of Cu speciation, using the Humic Ion-Binding Model VII. Root activities induced variation in pH and in DOM concentration and its reactivity, thereby inducing substantial alterations of Cu speciation in solution. Fescue induced an overall alkalization of the rhizosphere that tended to be stronger as the bulk soil was more acidic. Conversely, tomato and cabbage induced an acidification or alkalisation of the rhizosphere depending on soil type. Surprisingly, the concentration of DOM tended to decrease in the rhizosphere, especially for soils initially exhibiting the highest DOM concentrations. This result could be explained by an increase in microbial activity in the rhizosphere leading to a higher rate of DOM mineralization. The reactivity of DOM varied in a complex pattern the rhizosphere , either increasing or decreasing compared to the bulk soil depending on soil properties and plant species. As a result of the drastic alteration of chemical properties in the solution of the rhizosphere and of Cu uptake by roots, the free Cu2+ activity was changed by up to three orders of magnitude in the rhizosphere compared to the bulk soil. Free Cu2+ activity tended to decrease in the rhizosphere for soil exhibiting the highest free Cu2+ activities in the bulk soil. Conversely, free Cu2+ activity increased up to 1 to 2 orders of magnitude in the rhizosphere for soil exhibiting the lowest free Cu2+ activities. In such soils, the decrease in DOM reactivity could explain the increase in free Cu2+ activity in the rhizosphere. Our results show a consistent picture of how root activities can substantially alter trace metal speciation in the rhizosphere in a wide range of soils and plant species. Among the rhizosphere properties relevant for trace metal biogeochemistry and phytoavailability, the characterization of DOM reactivity should deserve further attention. (Texte intégral

Early outcomes of gastrostomy feeding in paediatric allogenic bone marrow transplantation: A retrospective cohort study

Background: Nutrition support is an essential component of care for a child undergoing bone marrow transplantation (BMT). Enteral nutrition (EN) is becoming increasingly recognised as having advantages over parenteral nutrition (PN) and recommended as first-line nutrition support. EN has traditionally been provided via nasogastric tube (NGT). Gastrostomies avoid certain complications associated with NGTs and could provide a preferential alternative. Aims: To compare nutritional and post-transplantation outcomes during admission, the primary outcome being PN use, between children who had a gastrostomy placed prophylactically prior to BMT versus those who had not. Methods: Electronic medical records of children transplanted between January 2014 and May 2018 within a single-centre were retrospectively reviewed. Outcomes between the gastrostomy group (n = 54) and non-gastrostomy group (n = 91) were compared. Results: Multivariate regression analyses showed children in the gastrostomy group were less likely to require PN (odds ratio (OR) 0.4; 95% confidence interval (CI) 0.2–0.9; P = 0.049), initiated PN later if required (hazard ratio 0.6; 95% CI 0.4–0.8; P = 0.005), more often received EN as first-line nutrition support (P < 0.001) and more frequently required EN post-discharge (OR 2.4; 95% CI 1.1–5.4; P = 0.029). No differences were found between groups on length of admission, day 100 overall survival, incidence of graft-versus-host-disease, positive blood cultures and changes in weight or albumin during admission. Conclusions: Providing EN via gastrostomy is feasible in this population and may be more acceptable to older children than NGTs. Weighing up the potential benefits against the potential risks of prophylactic gastrostomy placement in these high-risk children is a challenging decision. Further research investigating safety, longer-term outcomes and family perceptions of gastrostomy feeding is required

Layered LiNi0.5Co0.5O2 cathode materials grown by soft-chemistry via various solution methods

[Abstract] The lithiated nickel–cobalt oxide LiNi0.5Co0.5O2 used as cathode material was grown at low-temperature using different aqueous solution methods. The wet chemistry involved the mixture of metal salts (acetates or nitrates) with various carboxylic acid-based aqueous solutions. Physicochemical and electrochemical properties of LiNi0.5Co0.5O2 products calcined at 400–600°C were extensively investigated. The four methods used involved complexing agents such as either citric, oxalic, aminoacetic (glycine), or succinic acid in aqueous medium which functioned as a fuel, decomposed the metal complexes at low temperature, and yielded the free impurity LiNi0.5Co0.5O2 compounds. Thermal (TG–DTA) analyses and XRD data show that powders grown with a layered structure ( space group) have been obtained at temperatures below 400°C by the acidification reaction of the aqueous solutions. The local structure of synthesized products was characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical properties of the synthesized products were evaluated in rechargeable Li cells using a non-aqueous organic electrolyte (1 M LiClO4 in propylene carbonate, PC). The LiNi0.5Co0.5O2 positive electrodes fired at 600°C exhibited good cycling behavior