Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Understanding small-scale features in DGT measurements in sediments.
AU - Sochaczewski, Łukasz
AU - Davison, William
AU - Zhang, Hao
AU - Tych, Wlodek
PY - 2009
Y1 - 2009
N2 - Measurements in sediments made using DGT (diffusive gradients in thin-films) have shown small-scale (millimetre and sub-millimetre) maxima in solute concentration (e.g trace metals and sulfide). The sediment–DGT system was simulated using a dynamic model, which incorporated a spherical microniche close to the DGT surface. DGT maxima could arise when the microniche was (1) a local source with associated elevated concentration in the pore water, and (2) when, within the microniche, the Kd for the relevant solute partitioning with exchangeable solute associated with the solid phase was much higher than for the rest of the sediment. Use of realistic values of Kd and comparison with existing data suggested that the latter mechanism was unlikely to be responsible for observed DGT maxima. Locally elevated concentrations will be reasonably accurately reproduced by DGT. Peak height measured by DGT will be between 62 and 87% of the true maxima in concentration within the sediment when DGT is not present, while peak widths will be similar. This work provides, for the first time, a means for confidently interpreting the two dimensional images of DGT-measured concentrations in sediments.
AB - Measurements in sediments made using DGT (diffusive gradients in thin-films) have shown small-scale (millimetre and sub-millimetre) maxima in solute concentration (e.g trace metals and sulfide). The sediment–DGT system was simulated using a dynamic model, which incorporated a spherical microniche close to the DGT surface. DGT maxima could arise when the microniche was (1) a local source with associated elevated concentration in the pore water, and (2) when, within the microniche, the Kd for the relevant solute partitioning with exchangeable solute associated with the solid phase was much higher than for the rest of the sediment. Use of realistic values of Kd and comparison with existing data suggested that the latter mechanism was unlikely to be responsible for observed DGT maxima. Locally elevated concentrations will be reasonably accurately reproduced by DGT. Peak height measured by DGT will be between 62 and 87% of the true maxima in concentration within the sediment when DGT is not present, while peak widths will be similar. This work provides, for the first time, a means for confidently interpreting the two dimensional images of DGT-measured concentrations in sediments.
KW - microniche
KW - sulfide
KW - trace metals
U2 - 10.1071/EN09077
DO - 10.1071/EN09077
M3 - Journal article
VL - 6
SP - 477
EP - 485
JO - Environmental Chemistry
JF - Environmental Chemistry
SN - 1448-2517
IS - 6
ER -