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Task 3 - Biogeochemical cycle of metals in permafrost thaw lakes: inventory of phases, species & reactions
Task 3c - Partner in charge: Oleg Pokrovsky (GET-Toulouse, partner 3)
Isotope tracing in lake ecosystems (O. Pokrovsky; J. Viers; C. Cloquet; C. France-Lanord; post-docs; PhD students; partners engineers)
This sub-task is devoted to acquire a solid isotopic data base for all the studied thermokarst lakes. In the
different samples retrieved from the eco-geosystems a number of metals (Hg, Se, Cu, Zn, Ni, Fe) and
important life elements (C, S). Zn, Cu & Fe stable isotope analyses will also be performed in the various
size fractions separated from the water samples (100 μm - 10 μm - 1 μm - 0.22 μm - 100 kDa - 1 kDa).
We estimate that more than 250 samples will be analyzed over the 4 years of the project. Most samples
will be selected according to their chemical composition as documented in sub-task 3ab. The goal here is
to document the isotopic composition range of the different eco-geo-reservoirs of the ecosystems.
Interpretations will be in terms of "source tracing" and processes by using an elemental and multi isotope
proxi approach. On that basis, we will develop strategies to differentiate natural "geogenic" from
anthropogenic metals in the ecosystems. The isotopic compositions will be determined using state of the
art measurements in partner 2 and 3 laboratories (MC-ICP-MS for metals and gas IRMS for C and S).
Risks: the major risk here is related to the fact that we will be dealing with various sample matrices and be
obliged to adapt our chemical treatments before isotopic analyses analyzes. Very high yields are needed to
achieve accurate measurements. Our team proved their ability to deal with complex matrices.