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RESEARCH ARTICLE
Contents Vol 6(6)

Understanding small-scale features in DGT measurements in sediments

Łukasz Sochaczewski A , William Davison A B , Hao Zhang A and Wlodeck Tych A
+ Author Affiliations
- Author Affiliations

A Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK. Email: lukasz@sochaczewski.net; h.zhang@lancaster.ac.uk; w.tych@lancaster.ac.uk

B Corresponding author. Email: w.davison@lancaster.ac.uk

Environmental Chemistry 6(6) 477-485 https://doi.org/10.1071/EN09077
Submitted: 23 June 2009  Accepted: 3 November 2009   Published: 18 December 2009

Environmental context. Observations, using the technique of diffusive gradients in thin-films (DGT), of pronounced, small-scale (millimetre) maxima in concentrations of sulfide and metals in the pore water of sediments, have emphasised the importance of processes occurring in microniches. Modelling of the interactions between microniche sources and DGT devices within a sediment environment demonstrates how these sharp features arise and provides a basis for their quantitative interpretation.

Abstract. 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.

Additional keywords: microniche, sulfide, trace metals.


Acknowledgements

This work was performed within the framework of the TREAD project funded by the European Commission under contract EVK-CT-2002-00081. We thank Steve Lofts and John Hamilton-Taylor for advice on WHAM modelling.


References


[1]   H. Zhang , W. Davison , S. Miller , W. Tych , In situ high resolution measurements of fluxes of Ni, Cu, Fe and Mn and concentrations of Zn and Cd in porewaters by DGT. Geochim. Cosmochim. Acta 1995 , 59,  4181.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[2]   P. R. Teasdale , S. Hayward , W. Davison , In situ, high-resolution measurement of dissolved sulfide using diffusive gradients in thin-films with computer-imaging densitometry. Anal. Chem. 1999 , 71,  2186.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[3]   P. I. Monbet , I. A. McKelvie , P. J. Worsfold , Combined gel probes for the in situ determination of dissolved reactive phosphorus in porewaters and characterization of sediment reactivity. Environ. Sci. Technol. 2008 , 42,  5112.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |  open url image1

[4]   M. P. Harper , W. Davison , W. Tych , H. Zhang , Kinetics of metal exchange between solids and solutions in sediments and soils interpreted from DGT measured fluxes. Geochim. Cosmochim. Acta 1998 , 62,  2757.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[5]   L. Sochaczewski , W. Tych , W. Davison , H. Zhang , 2D DGT induced fluxes in sediments and soils (2D DIFS). J. Environ. Modelling 2007 , 22,  14.
        | Crossref | GoogleScholarGoogle Scholar |  open url image1

[6]   H. Ernstberger , H. Zhang , W. Davison , A. Tye , S. Young , Simultaneous in situ measurement of chromium speciation in natural systems. Anal. Bioanal. Chem. 2002 , 373,  873.
        |  CAS | | Crossref | PubMed |  open url image1

[7]   H. Ernstberger , H. Zhang , A. Tye , S. Young , W. Davison , Desorption kinetics of Cd, Zn and Ni measured in intact soils by DGT. Environ. Sci. Technol. 2005 , 39,  1591.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |  open url image1

[8]   N. J. Lehto , L. Sochaczewski , W. Davison , W. Tych , H. Zhang , Quantitative assessment of soil parameter (KD and TC) estimation using DGT measurements and the 2D DIFS model. Chemosphere 2008 , 71,  795.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |  open url image1

[9]   Davison W., Fones G., Harper M. P., Teasdale P. R., Zhang H., In situ use of dialysis, DET and DGT, in In Situ Analytical Techniques for Water and Sediments (Eds J. Buffle, G. Horvai) 2000, pp. 495–569 (Wiley: Chichester, UK).

[10]   S. Tankere-Muller , H. Zhang , W. Davison , N. Finke , O. Larsen , H. Stahl , R. N. Glud , Fine scale remobilisation of Fe, Mn, Co, Ni, Cu and Cd in contaminated marine sediment. Mar. Chem. 2007 , 106,  192.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[11]   H. Zhang , W. Davison , R. Mortimer , M. Krom , P. Hayes , I. Davies , Localized remobilization of metals in a marine sediment. Sci. Total Environ. 2002 , 296,  175.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |  open url image1

[12]   G. R. Fones , W. Davison , O. Holby , B. B. Jorgensen , B. Thamdrup , High-resolution metal gradients measured by in situ DGT/DET deployment in Black Sea sediments using an autonomous benthic lander. Limnol. Oceanogr. 2001 , 46,  982.
        |  CAS |  open url image1

[13]   G. R. Fones , W. Davison , J. Hamilton-Taylor , The fine-scale remobilization of metals in the surface sediment of the North-East Atlantic. Cont. Shelf Res. 2004 , 24,  1485.
        | Crossref | GoogleScholarGoogle Scholar |  open url image1

[14]   W. Davison , G. R. Fones , G. W. Grime , Dissolved metals in surface sediment and a microbial mat at 100 μm resolution. Nature 1997 , 387,  885.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[15]   C. DeVries , F. Wang , In situ two-dimensional high-resolution profiling of sulfide in sediment interstitial waters. Environ. Sci. Technol. 2003 , 37,  792.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |  open url image1

[16]   M. Motelica-Heino , C. Naylor , H. Zhang , W. Davison , Simultaneous release of metals and sulfide in lacustrine sediment. Environ. Sci. Technol. 2003 , 37,  4374.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |  open url image1

[17]   A. Widerlund , W. Davison , Size and density distribution of sulfideproducing microniches in lake sediments. Environ. Sci. Technol. 2007 , 41,  8044.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |  open url image1

[18]   M. P. Harper , W. Davison , W. Tych , One-dimensional views of three-dimensional sediments. Environ. Sci. Technol. 1999 , 33,  2611.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[19]   M. P. Harper , W. Davison , W. Tych , Estimation of pore water concentrations from DGT profiles: a modelling approach. Aquat. Geochem. 1999 , 5,  337.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[20]   M. P. Harper , W. Davison , W. Tych , DIFS – a modelling and simulation tool for DGT induced trace metal remobilisation in sediments and soils. Environ. Model. Softw. 2000 , 15,  55.
        | Crossref | GoogleScholarGoogle Scholar |  open url image1

[21]   H. W. Jannasch , B. B. Honeyman , L. S. Balistrieri , J. W. Murray , Kinetics of trace-element uptake by marine particles. Geochim. Cosmochim. Acta 1988 , 52,  567.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[22]   E. Tipping , WHAM – A chemical equilibrium model and computer code for waters, sediments, and soils incorporating a discrete site/electrostatic model of ion-binding by humic substances. Comput. Geosci. 1994 , 20,  973.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[23]   Tipping E., Cation Binding by Humic Substances 2002 (Cambridge University Press: Cambridge, UK).

[24]   L. Sigg , F. Black , J. Buffle , J. Cao , R. F. M. J. Cleven , W. Davison , J. Galceran , P. Gunkel , et al. Comparison of analytical techniques for dynamic trace metal speciation in natural freshwaters. Environ. Sci. Technol. 2006 , 40,  1934.
        | Crossref | GoogleScholarGoogle Scholar | CAS | PubMed |  open url image1

[25]   R. N. Glud , N. B. Ramsing , J. K. Gundersen , I. Klimant , Planar optrodes, a new tool for fine scale measurements of two dimensional O2 distribution in benthic communities. Mar. Ecol. Prog. Ser. 1996 , 140,  217.
        | Crossref | GoogleScholarGoogle Scholar |  open url image1

[26]   T. J. Shaw , J. M. Gieskes , R. A. Jahnke , Early diagenesis in differing depositional environments: The response of transition metals in pore water. Geochim. Cosmochim. Acta 1990 , 54,  1233.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1

[27]   M. Leermakers , Y. Gao , C. Gabelle , S. Lojen , B. Ouddane , M. Wartel , W. Baeyens , Determination of high resolution pore water profiles of trace metals in sediments of the Rupel River (Belgium) using DET (diffusive equilibration in thin films) and DGT (diffusive gradients in thin films) techniques. Water Air Soil Pollut. 2005 , 166,  265.
        | Crossref | GoogleScholarGoogle Scholar | CAS |  open url image1