PhD fellow on Isotope and Geochemical characterization of Atmospheric Inputs to Tropical Environments

Applications are welcome for a three-year PhD position at the GEOPS laboratory at the University of Paris-Saclay, FRANCE. The PhD project is part of a larger research topic, "Evaluating the Impact of atmospheric Deposits on biogeochemical cycles at the scale of the AMazonian basin".

PhD project description

In a context of rapid perturbations initiated by climate change, the presentation of the Amazonian rainforest as an essential carbon sink on Earth is challenged in its Southeastern part due to severe deforestation and ecosystem stress promoted by the intensification of dry. In South America and particularly within the Amazon Basin, the role of atmospheric dust inputs in the active contribution to the biogeochemical cycles of elements (e.g., phosphorus, potassium, or iron) is assumed to explain the persistence of the Amazonian rainforest despite its growth on highly weathered terrains. Dust aerosols act as a source of bio-essential nutrients like phosphorus, potassium, or iron; thus, they directly impact their respective biogeochemical cycles. Most of this dust is blown from the Saharan-Sahelian region through the easterly winds that prevail during the boreal winter when the Intertropical Convergence Zone is at its southern position. The detection and characterization of dust events have been considerably refined through satellite observations, and the discrimination of North African dust emission sources has been significantly improved over the past decade using a combination of mineralogical and chemical/isotopic proxies. As these different sources are lithologically (paleolakes vs. alluvial deposits) and chemically variable (Si-rich vs. Si-Al-rich), their identification and characterization is a prerequisite for correctly extrapolating dust-derived elementary to the Amazon Basin on a multi-annual scale.

The PhD project focuses on the determination of dominant North African dust sources reaching the Amazon Basin through dust filter sampling performed on two observatories; the ATMO coastal site at Cayenne, French Guiana, and the Amazon Tall Tower Observatory (ATTO), a 300-m tower located in an isolated place 150 km northeast of Manaus, Brazil. Source apportionment and elemental flux estimates will be performed by combining geochemical and radiogenic isotope (Sr-Nd-Pb) measurements on collected dust, supported by on-site analysis (PM10 concentrations), mineralogical observations, satellite imagery (CALIPSO) and air-mass back trajectories (HYSPLIT). Before this work, a methodological improvement will be needed to characterize the importance of seasalt, anthropogenic and natural end-members in collected aerosols. Long-term sampling campaigns are planned within the frame of a collaboration involving local (ATMO Guyane, FRANCE and the University of São Paulo, BRAZIL) and international partners (Max Planck Institute for Chemistry, Mainz, GERMANY and the University of Miami, USA) for the period 2024-2025 and the successive dust seasons (2024-2026) in the two observatories ATMO and ATTO. Simultaneous sampling will help estimate the decrease in dust flux with continentalization and its potential impact on the chemical and isotope signature of transmitted dust. This PhD scholarship is part of a larger project (EVIDAM ) that will assess the impact of all atmospheric deposits (wet, dry, dust, biomass burning) at the scale of the Amazon basin.

Additional information can be found here: https://filesender.renater.fr/?s=download&token=5e9442a7-f5f6-433a-b171-01e814ff9248

Applications will require the following:

• A Master degree in geochemistry, biogeochemistry, environmental chemistry and/or atmospheric sciences within the last five years
• Experience in fieldwork
• Good analytical chemistry skills
• Excellent written and spoken English skills
• The ability to work in an interdisciplinary team with scientists, engineers, and technicians from international laboratories (MPIC, Mainz, GERMANY, UNI. Miami, USA, Uni. São Paulo, BRAZIL)
• Creativity, curiosity, independent thinking
• A first experience in isotope geochemistry is an advantage.

The position is for 36 months. We offer salary and social benefits according to French public sector regulations. Employment is conditional upon your successful enrolment as a PhD student at the SMEMAG doctoral school, Université Paris-Saclay. This requires submitting an application and its acceptance for the specific project formulated by the applicant.

Our group and international collaborations

The PhD research will be carried out in the Alterations team of the GEOPS laboratory of the Université Paris-Saclay (http://geops.geol.u-psud.fr). The selected candidate will be integrated into a team of Professors, Assistant professors, technical staff, PhDs, and MScs students. The research work of the ALTS team focuses on weathering processes in continental environments, including the atmospheric reservoir. Research activities focus on understanding the carbon cycle in the continental environment, particularly at the scale of large rivers, and the weathering and erosion processes controlling the elementary fluxes. Studies also focus on anthropogenic, environmental, and climatic forcings in the evolution of (bio-)geochemical cycles within sensitive continental ecosystems.

The PhD project will be performed closely with researchers from the Max Planck Institute for Chemistry, Mainz, GERMANY, the University of Miami, USA, and the University of São Paulo, BRAZIL. Scientific exchanges (2-6 months) are planned with the MPIC during the PhD project.

Closing date for applications is April 25, 2023. Starting period will be October 1, 2023.

Principal supervisor: Professor Cécile Quantin and Assistant Professor Damien Guinoiseau, GEOPS Laboratory, UMR 8148, Université Paris-Saclay, E-mail: damien.guinoiseau@universite-paris-saclay.fr & cecile.quantin@universite-paris-saclay.fr

In your application, please include:

1. Motivation letter of application (max. one page) to the project
2. Curriculum vitae including information about your education, experience, language skills, and other skills relevant to the position
3. Original diplomas for Master of Science and transcript of records in the original language, including an authorized English translation if issued in another language than English, or French.
4. Publication list (if possible)
5. 1-3 References and any available Reference letters

Final application should be performed on the ADUM website where all the needed documents are listed (https://adum.fr/as/ed/voirproposition.pl?site=PSaclay&matricule_prop=46525), but a preliminary contact by mail with the PhD supervisors is possible.

Questions

For specific information about the PhD fellowship, please contact the supervisors.