LOT / ABM Meeting

Malmö, May 9-10, 2012

Proposed analytical work for next ABM parcel

Urs Mäder, Paul Wersin, Andreas JenniRock-Water InteractionInstitute of Geological Sciences, University of Bern

Proposed work for new ABM parcel

Trace minerals• Focus on soluble salts (sulphates, carbonates)

• Clay context: WC, Xi (minimize sample mass)

Dissolved organic acids• Performed qualitative measurements with IC.• New separation columns: attempt to quantify LMWOA

in aqueous extracts (possibly in combination with core infiltration experiments).

Iron-bentonite interaction

• Analysis of interaction zone (SEM, XRD, XRF, XAS…)

• Collaboration with other labs (ABM and others)

Trace mineral components

• Trace mineral components control pore water composition and exchanger composition (Ca-sulfate, cristobalite/amorphous silica, calcite, dolomite, pyrite, solid organic material).

• Some trace components react rapidly relative to experimental timescales or even times for analytical procedures.

• LOT experience shows that re-distribution of trace minerals may be efficient and relatively rapid (Ca-sulfate).

The distribution and re-distribution of trace mineral components should therefore also be investigated in conjunction with mass transfer processes observed in the ABM experiment.

MX-80 core infiltration experiment (LOT core); Metrosep ASUPP1_250

Standards on upper horizontal axis; bentonite samples #10-#15

Decreasing oa concentration from #10 to #15;

Dissolve organic acids in MX-80 pore water

Cl

F

system

O1

O2

O3

Why look at Fe-bentonite interaction?

Fe(0) + 2H2O Fe2+ + H2 + 2OH-

Prec. of corrosion products Fe-clay interactions

Fe3O4, GR, FeCO3, FeS… >Fe(II)-clay, Fe-smectite, berthierine….

Mont. dissolution

A lot has already been done ...

> Destabilisation of structure by Fe(III) reduction (Lantenois et al. 2005)

> Transformation to berthierine / chlorite at higher T (Cathelineau et al..)

> Dissolution via corrosion induced pH increase (Kumpulainen et al. 2010)

> Reaction of hydrogen with Fe(III) in clay (Didier et al. 2012)

but process details are still not understood.

What about long-term?

> Experimental artefacts from O2 ingress

> Transient effects may mask slow, long-term processes

> Long-term simulations based on simplistic models

Birgersson & Wersin 2011

Fe-bentonite in ABM (1)

> Possibility to study longer term processes at realistic «accelerated» conditions

> Valuabe experience gained from prev. field studies should allow adequate sampling/storage and analysis

> Study interaction «skin» zone: SEM, -XRD, -XRF, XAS...

Fe-bentonite in ABM (2)

> Different clay materials: interlayer cation, Fe content, accessories

> Supported by modelling

> Possibility to design new test with iron – avoid galvanic bridging to study corrosion (ABM-2)

> Last bu not least: ABM team qualified to do the job