Use of gel probes for the determination of high resolution solute distributions in marine and estuarine pore waters

R. J.G. Mortimer, M. D. Krom, P. O.J. Hall, S. Hulth, H. Ståhl

Research output: Contribution to journalArticlepeer-review

Abstract

Pore water profiles were obtained at high resolution (millimeter scale) in marine sediments using a DET (diffusive equilibration in thin films) gel probe. A plastic probe which holds a 1-2 mm thick polyacrylamide gel covered by a 0.45 μm Millipore filter is inserted into the sediment. The gel was prehydrated in water of similar salinity to the in situ sampling conditions. Chloride and sulphate needed 24 and 48 h for complete front and back equilibration, respectively, while 6-8 h (front) and 4-6 h (back) were used for calcium and alkalinity. Ammonia-N and total CO2 were back-equilibrated for 2 h. Probes were sectioned immediately after sampling, stored for up to 1-2 days (NH4/+, ΣCO2) or for up to 1-2 weeks (Ca, alkalinity, Cl, SO4, NO3), before they were back-equilibrated into Milli-Q water or 0.7 M NaCl (calcium and alkalinity). The gel retains between 3-7% of the total sulphate. A simple procedure has been developed to correct for this incomplete recovery. Recovery tests using seawater and 50% seawater spiked to concentrations found in nearshore pore waters, showed recoveries of 101.4 ± 0.5% (chloride), 101.4 ± 0.7% (bromide), 100.3 ± 0.2% (nitrate), 96.6 ± 0.7% (sulphate), 99.7 ± 0.8% (ammonia-N), 99.1 ± 1.2% (ΣCO2), 96.9 ± 0.8% (calcium) and 96.8 ± 1.4% (alkalinity) (mean ± standard error). Pore water profiles obtained simultaneously using gel probes and conventional techniques (box core-anoxic slicing followed by centrifugation) showed excellent comparability at cm resolution though features which required higher resolution which could only be seen in the gel profiles.

Original languageEnglish
Pages (from-to)119-129
Number of pages11
JournalMarine Chemistry
Volume63
Issue number1-2
DOIs
StatePublished - Dec 1998
Externally publishedYes

Keywords

  • Estuarine
  • Gel probe
  • High resolution
  • Marine
  • Pore water

ASJC Scopus subject areas

  • Oceanography
  • General Chemistry
  • Environmental Chemistry
  • Water Science and Technology

Fingerprint

Dive into the research topics of 'Use of gel probes for the determination of high resolution solute distributions in marine and estuarine pore waters'. Together they form a unique fingerprint.

Cite this