Evidencing the role of plants vs soils in the understanding of 137Cs phyto availability using a coupled experimental and modelling approach

International audience137Cs is a radionuclide with a half-life of 30 years that is commonly found in soils after nuclear fallout due to nuclear incidents or atmospheric nuclear weapon testing. Due to their properties of accumulation and retention, soils are key compartments for the transfer of contaminants such as 137Cs in the trophic chain. Ingestion of contaminated agricultural products being one of the main component of human exposure, it is essential to be able to predict the fate of 137Cs throughout the soil-plant continuum.The contaminant mobility into the soil, its transfer to the plant and its final distribution between all components are generally described by simple models (equilibrium-based, linear distributions). These models are operational but are not able to account for the variability of soils and plants encountered.Bioavailability is function of both soil physico-chemical characteristics, that impact the environmental availability, and plant physiology which determines the uptake rate and accumulation. The aim of this work is to highlight the preponderant factors controlling the 137Cs bioavailability in the soil-solution-plant continuum by using a model that account for both soil and plant characteristics. The proposed mechanistic model is based on thermodynamic reactions describing the interactions of Cs with the different soil reactive components, coupled with a physiological model of root absorption.Series of experiments were conducted to produce a contrasted data set of 137Cs soil to plant transfer. For those experiments, 2 different plants with contrasted Cs uptake capacities (Millet, Mustard) and 3 different soils with varying texture and mineralogy have been studied. Three weeks exposure studies were conducted with the RHIZOtest® which is a normative device to assess the bioavailability of contaminants in soil. They were completed with batch experiments aiming at characterizing the environmental availability of Cs in soils. A large range of 137Cs soil to plant transfer rates was measured for the different soil/pant combinations. For example a contrasted bioavailability of 137Cs was observed, with the same plant accumulating 10% to 40% of total Cs’s stock depending on the soils. We also observed that during the time of the experiment the plant had absorbed most of the estimated environmental available Cs.Modelling those experiments allowed us to highlight the main soil and plant properties that have a great impact on the contaminant mobility. For example, plant physiological factors were the main driver of bioavailability in condition where environmental availability was not limited (e.g. sandy soils), whereas their roles were reduced in soils with high 137Cs sorption capacity. Such a model may help to reduce uncertainties in the prediction of 137Cs transfer to plants in environmental risk assessment, with a great potential to cover a large range of soils and plants

PHYTOREMEDIATION APPLIQUEE AU TRAITEMENT DE SOLS CONTAMINES PAR DES HYDROCARBURES AROMATIQUES POLYCYCLIQUES

NANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF

Pipette Pasteur extraction : a fast, convenient, exhaustive and environmentally friendly method for the extraction of solid samples

International audienceA simple and fast (~ 5 min.) method has been set up to extract small soil samples (~ 300 mg) by elution of a small volume of methylene chloride (2000 μl) on a modified Pasteur pipette. Pasteur pipette extraction thus allows to minimize sample losses by evaporation, degradation, contamination, and experimental handling. Moreover, shake and ultrasonic extractions were found to give lower extract yields, amounting respectively to 1.8 and 1.9 mg/g dry weight, than pipette Pasteur extraction (3 mg/g). This method may be applied to extract the soluble organic matter of any kind of solid sample such as sedimentary rocks, coals, aerosols, food, and biological substances, prior molecular analyses such as gas chromatography coupled to mass spectrometry

Fossil fuel biomarkers in plant waxes as pollution parameters

International audienceHopane and sterane derivatives typical of highly mature sedimentary organic matter, e.g. petroleum, have been identified in several plant species growing near Nancy, France. Analyses of plant waxes by gas chromatography-mass spectrometry over a restricted mass interval (m/z 185-195) allows definition of pollution parameters based on the relative concentration of fossil hopanes versus modern plant n alkanes. Indeed, such parameters are higher for Pinus nigra growing along a high traffic highway than for Pinus nigra growing in a less polluted suburb area. Molecular pollution parameters based on fossil molecules are thus promising tools for measuring the extent of fossil fuel input into plant and food

Comprehensive framework for overcoming scientific challenges related to assessing radioactive ultra-fine (nano/micro) particles transfer at the atmosphere-leaf interface

International audienceFood products are prone into contamination after a nuclear emission of radionuclides. While the mechanisms of emission and deposition of ultrafine radioactive particles are well documented, the transfer of these species from the atmosphere into plants is poorly assessed. This is evident in the lack of quantification of particles distributed within plants, especially regarding particles physical-chemical criteria to plant of different properties. Such knowledge gaps raise the concern about the representativeness of risk assessment tools designed for the transfer evaluation of ionic/soluble species to be qualified for simulating insoluble species exposure and proposes a possible underestimation. This highlights the possible need for special particle codes development to be implemented in models for future emissions. In addition, the later tools utilize transfer factors aggregating relevant sub-processes, suggesting another weak point in their overall reliability. As researchers specialized in the nuclear safety and protection, we intend in this perspective, to develop a compressive analysis of the interaction of ultrafine particles with plants of different specificities at different level processes starting from particles retention and gradual translocation to sink organs. This analysis is leveraged in providing insights for possible improvements in the current modeling tools for better real-life scenarios representation

Phytotoxicity of ancient gaswork soils. Effect of polycyclic aromatic hydrocarbons (PAHs) on plant germination

International audienceThe phytotoxicity of various contaminated soils was assessed by plant inventories on ancient industrial fields and by phytotoxicity tests. Industrial fields are well colonised by numerous weedy plants. Phytotoxicity was tested with pure PAHs, ancient industrial soils, soil leaches, liquid tar and tar volatile compounds. Both field studies and toxicity tests show that contaminated samples can be classified into two categories: first, a recently excavated soil/liquid tar that was foul-smelling and phytotoxic and second, an ‘aged', surface soil that was weathered and non-phytotoxic. Plant germination and growth are strongly inhibited by the presence of volatile, water-soluble low molecular-weight hydrocarbons (<3 rings) such as benzene, toluene, xylene (BTX), styrene, indene, naphthalene and other possibly toxic substances. On the other hand, high molecular weight PAH (3–5 rings) did not show any phytotoxicity under the conditions studied. These findings suggest that once low molecular weight aromatic hydrocarbons are removed, e.g. by volatilization, biodegradation, weathering, tillage and fertilising, plants should be able to grow