SS2.02 Biogeochemical Process at the Sediment-Water Interfaces
Date: Tuesday, June 11, 2002
Time: 11:30:00 AM
Location: Carson B
 
MOTELICA-HEINOM, Lancaster University, Lancaster, United Kingdom, m.motelica-heino@lancaster.ac.uk
Naylor, C, , Lancaster University, Lancaster, United Kingdom, c.naylor1@lancaster.ac.uk
Davison, W, , Lancaster University, LANCASTER, United Kingdom, w.davison@lancaster.ac.uk
 
METAL RELEASE FROM AMORPHOUS IRON SULFIDE IN SEDIMENTS REVEALED BY DGT
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Metal mobility in sediments is controlled by chemical interactions - redox reactions, (de)sorption and solubility- that take place at the interface between solid phases and solution. These reactions occur locally at the cluster of mineral or organic particles involved and are probably affected by microorganisms: small-scale remobilisation (microniches) appears to be superimposed on the relatively macro features of systematic vertical changes associated with redox zones. Therefore any measurements to unravel the mechanisms responsible for the microniche distribution of metals, particularly the role of Fe, Mn, S(-II) phases and microorganisms, must be made not only at a similar fine spatial scale, but also at exactly the same location as the metal measurements. A single DGT (diffusive gradient in thin-films) probe that could measure metals and sulfide simultaneously at 100 microns resolution in 2D was developed and deployed in both freshwater and marine sediments. It showed simultaneous mobilisation of metals and sulfide on a mm scale from the same phase. Results suggest that the amorphous FeS may more readily release metals than the more normal binding sites of sediments (e.g. iron oxides).