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 language | English |
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Pages (from-to) | 119-129 |
Number of pages | 11 |
Journal | Marine Chemistry |
Volume | 63 |
Issue number | 1-2 |
DOIs | |
State | Published - Dec 1998 |
Externally published | Yes |
Keywords
- Estuarine
- Gel probe
- High resolution
- Marine
- Pore water
ASJC Scopus subject areas
- Oceanography
- General Chemistry
- Environmental Chemistry
- Water Science and Technology