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Closed-system dissolution experiment

Par tim — Dernière modification 03/04/2015 19:22

Closed-system dissolution experiment


Objectives :

  • Identifying the geochemical reactions occurring between the lithogenic matter and the seawater

  • Quantifying the processes with an emphasis on their kinetic

  • Checking if the particles reflect any modification as a result of these processes

 

Scientific and societal issues

Land to ocean transfer of solid material largely controls the chemical composition of seawater and the global cycles of the elements. Global riverine particulate flux to the oceans exceeds that of the dissolved flux by a factor of 30 to 50. Quantifying the fraction of element of lithogenic origin that is released at the particle/seawater contact and what controls this release is a major issue. Indeed, field observations and modelling demonstrate that the oceanic distribution of numerous tracers including Co, 143Nd/ 144Nd, 232Th/230Th, 56Fe/54Fe, 30Si/28Si, 87Sr/86Sr can only be interpreted by taking account of a substantial input to seawater from lithogenic material from the continental margins. This input could double the flux of macro- and micro-nutrients to the ocean. Solving this issue will impact i) our understanding of the element cycles, ii) the design of the climatic models and iii) the present knowledge of the contaminant dispersion. This is a major objective of the international program GEOTRACES.

Here we present results of closed system experiments, designed to constrain the rate and fate of the dissolution processes.

Strategy

 

Selected results

(Jones et al, EPSL 2012, GCA 2012 & Pearce et al, EPSL, 2013)

 

Perspectives

Coupling concentration and isotopic composition is particularly powerful for process quantification. Our plans are to realize new designed system experiments –the only one allowing us to determine the processes at play and their kinetics- that time as open flow and measuring more isotopes. To say the least, the missing heroes of the preliminary experiences described above are Fe and Si isotopes. We also plan to select the minerals that are dissolving the most and to study the speciation of the particle surfaces (Emergence project submitted in 2014, Toulouse Idex; RTRA STAE Project 2014)

 

Participants: Catherine Jeandel, Eric Oelkers (GET), Morgan Jones (GET) & Chris Pearce (GET)

Collaborations and funding

LEGOS, GET, IRAP (for the future)

 

Financements: CNRS-INSU/LEFE, ANR, UE




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