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PhD in terrestral ecotoxicology: Fate of emerging contaminants in agrosystems

This offer is available in the following languages:
Français - Anglais

Date Limite Candidature : lundi 17 mai 2021

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General information

Reference : UMR5245-CAMLAR-001
Workplace : CASTANET TOLOSAN
Date of publication : Friday, March 26, 2021
Scientific Responsible name : Camille Larue
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

The goal of the project is to focus on the fate of emerging contaminants in agrosystems (or agricultural ecosystems), i.e. their mobility, their physicochemical evolution and their toxicity on different trophic levels (bacteria, primary producers i.e. crop plants and macroorganisms i.e. earthworms and/or snails) as well as the associated impacts on ecosystem services.
Agrosystems are of crucial importance for human societies as providers of food, they are also part of circular economy. Indeed, our waste (wastewater, green waste) is transformed in fertilizers (sewage sludge, compost) for agriculture. If this sector has been regulated at the legislative level for many years, in particular for metallic trace elements and some organic compounds, this legislation does not take into account the evolution of our consumption habits and the proven accumulation of so-called "emerging contaminants" in these fertilizers (1–3). Agricultural soils are therefore the final receptacles of these contaminants. Consequently, there are risks for the maintenance of ecosystem services provided by agrosystems but also risks of contaminant transfer in the food chain to humans.
Here, we will focus on two emerging contaminants. The first, titanium dioxide (TiO2) nanoparticles, has been controversed a lot lately, especially in the form of E171 in food. These nanoparticles are also found in cosmetic products (including sunscreens and toothpastes) or construction materials. Many studies have demonstrated their accumulation in sewage sludge (1) but their ecotoxicological effects are still poorly understood with studies demonstrating toxic effects and others, conversely, "positive" effects (4, 5). The second contaminant of interest is plastic, in nano and micrometric form. While society is now well aware of this pollution in the oceans, it is less well known that 80% of this pollution is of land origin (6). Agrosystems are once again particularly vulnerable through the spreading of wastewater sludge and compost, but also due to the use of plastic films (7). Very few studies today focus on the effects of nano and microplastics in agrosystems (8,9) and this field of research is still in its infancy.
The project presented here is based on research carried out in the laboratory for several years (1,10–18) and which have made it possible to considerably advance the level of our knowledge and to highlight the remaining gaps. The project is largely multidisciplinary and will call on acquired knowledge (i) in physico-chemistry and spectroscopy to characterize the materials used for exposure but also to follow their fate in environmental and biological matrices, (ii) in the biology of organisms to assess toxic effects, and (iii) in modeling to determine the primary factors influencing the transfer and toxicity of these materials.
Several lines of research can be considered (in discussion with the interests and skills of the candidate), among others: trophic transfer with quantification in each level (ICP-AES / MS) and evaluation of physicochemical modifications of contaminants (µXANES on synchrotron radiation or µFTIR / Raman depending on the contaminant), evaluation of the toxicity of contaminants according to different contamination scenarios (type of organism, type of soil, different physicochemical properties of contaminants -> screening analysis by ATR -FTIR), role of cell walls (use of model plants and mutants + molecular biology tools), modeling (construction of a database based on the literature on soil - plants - consumers transfer to determine the factors of risk; EMPA collaboration, Switzerland).

Profile and skills expected:
- Master 2 (or equivalent) in environmental sciences with knowledge in ecotoxicology and ecology
- Interest in experimental and analytical developments
- Skills in statistics (R software)
- Taste for interdisciplinary work (involving good communication skills)
- Taste for challenges (this project contains many :-))
- Good interpersonal skills (enthusiasm for research), able to work independently as well as in a team, taking initiatives
- Good command of English (research stays abroad are envisaged (Switzerland) and others are possible, possibilities of mobility grants through the University of Toulouse and the European network PLANTMETALS : https://plantmetals.eu/plantmetals-home.html)

To apply, please send:
• A resume
• A cover letter
• A copy of the transcripts of Master 1, Master 2 and / or School of Engineering
• A description of previous work (max. 3 pages)
• Letters of recommendations, if any

Application until 05/15/21

Bibliography:
1. Pradas del Real, A.-E. et al. Searching for relevant criteria to distinguish natural vs . anthropogenic TiO 2 nanoparticles in soils. Environ. Sci. Nano (2018). doi:10.1039/x0xx00000x
2. Sun, T. Y., Bornhöft, N. A., Hungerbühler, K. & Nowack, B. Dynamic probabilistic modeling of environmental emissions of engineered nanomaterials. Environ. Sci. Technol. 50, 4701–4711 (2016).
3. Okoffo, E. D. et al. Release of plastics to australian land from biosolids end-use. Environ. Sci. Technol. 54, 15132–15141 (2020).
4. Ze, Y., Liu, C., Wang, L., Hong, M. & Hong, F. The regulation of TiO2 nanoparticles on the expression of light-harvesting complex II and photosynthesis of chloroplasts of arabidopsis thaliana. Biol. Trace Elem. Res. 143, 1131–1141 (2011).
5. Ghosh, M., Bandyopadhyay, M. & Mukherjee, A. Genotoxicity of titanium dioxide (TiO2) nanoparticles at two trophic levels: Plant and human lymphocytes. Chemosphere 81, 1253–1262 (2010).
6. Alimi, O. S., Farner Budarz, J., Hernandez, L. M. & Tufenkji, N. Microplastics and nanoplastics in aquatic environments: aggregation, deposition, and enhanced contaminant transport. Environ. Sci. 52, 1704–1724 (2018).
7. Huang, Y., Liu, Q., Jia, W., Yan, C. & Wang, J. Agricultural plastic mulching as a source of microplastics in the terrestrial environment. Environ. Pollut. 260, 114096 (2020).
8. Qi, Y. et al. Effects of plastic mulch film residues on wheat rhizosphere and soil properties. J. Hazard. Mater. 387, 121711 (2020).
9. Larue, C., Sarret, G., Castillo-Michel, H. A. & Pradas del Real, A.-E. A critical review on the impacts of nanoplastics and microplastics on aquatic and terrestrial photosynthetic organisms. Small 202005834 (2021). doi:10.1002/smll.202005834.
10. Larue, C. et al. Accumulation, translocation and impact of TiO2 nanoparticles in wheat (Triticum aestivum spp.): influence of diameter and crystal phase. Sci. Total Environ. 431, 197–208 (2012).
11. Larue, C. et al. Comparative uptake and impact of TiO2nanoparticles in wheat and rapeseed. J. Toxicol. Environ. Heal. - Part A Curr. Issues 75, 722–734 (2012).
12. Larue, C. et al. Fate of pristine TiO2 nanoparticles and aged paint-containing TiO2 nanoparticles in lettuce crop after foliar exposure. J. Hazard. Mater. 273, 17–26 (2014).
13. Larue, C. et al. Innovative combination of spectroscopic techniques to reveal nanoparticle fate in a crop plant. Spectrochim. Acta - Part B At. Spectrosc. 119, 17–24 (2016).
14. Vijayaraj, V. et al. Transfer and ecotoxicity of titanium dioxide nanoparticles in the terrestrial and aquatic ecosystems : a microcosm study. Environ. Sci. Technol. 52, 12757–12764 (2018).
15. Larue, C. et al. Influence of soil type on TiO2 nanoparticle fate in an agro-ecosystem. Sci. Total Environ. 630, 609–617 (2018).
16. Bakshi, M. et al. Assessing the impacts of sewage sludge amendment containing nano-TiO2 on tomato plants: A life cycle study. J. Hazard. Mater. 369, 191–198 (2019).
17. Liné, C., Larue, C. & Flahaut, E. Carbon nanotubes : impacts and behaviour in the terrestrial ecosystem - A review. Carbon N. Y. 123, 767–785 (2017).
18. Liné, C., Manent, F., Wolinski, A., Flahaut, E. & Larue, C. Comparative study of response of four crop species exposed to carbon nanotube contamination in soil. Chemosphere 274, 129854 (2021).

Work Context

This thesis project is part of a project funded by the ANR (National Research Agency) entitled "Integrative approach to determine the fate of nanomaterials in agrosystems" (INPAGE). It brings together French public research institutes (CNRS, INSERM, CEA) and a private company (Tronox France) and European partner (EMPA, Switzerland). The student will work in a multidisciplinary team focusing on the impacts of contaminants (metallic trace elements, carbon based nanomaterials, pesticides, etc.) in the different compartments of the environment. He/she will also be able to take part in the structuring project of the laboratory promoting citizen science concerning in particular the fate of bioplastics in soils (PlastiZen).

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