Analytical techniques in the GEO sediment laboratory

GEO applies a wide range of analytical techniques to determine the chemical composition of solid phase materials, be it calcareous coral structures or sediment fractions. These techniques include several non-destructive (semi-)quantitative approaches such as core scanners, as well as techniques that rely on the complete destruction of a solid phase and subsequent analysis of its composition. Our techniques and protocols are presented below.

For further information, please contact:

Wim Boer

T 022 369 386/394

@ wim.boer(at)nioz.nl

ICP-MS (Thermo Scientific Element-2)


Application		Analyzing elemental composition of sediment and corals

Equipment		Element-2 of Thermo Scientific. SF ICP-MS is a combination of inductively coupled plasma (ICP) with a mass spectrometer (MS). The SF abbreviates 'Sector Field' which warrants a high resolution. ICPMS is a popular technique due to its many advantages, such as: No matrix effects after dilution of >5000x resulting in quantitative results. Low limit of detection (ppt-ppb range). Multi element capabilities. Wide linear range (trace, minor and major elements in 1 run). High sample throughput via a fast auto sampler (200 samples/day). Ability to obtain isotopic information.
Equipment
Analysis of sediments & corals		At this moment our group uses the ICP-MS for analyzing: 9 elements (Mg, Ca, Mn, Sr, Y, Ba, La, Pb and U) in tropical corals 34 elements (Ag, Al, As, Ba, Be, Br, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Ni, P, Pb, Rb, Ru, S, Sb, Se, Sn, Sr, Ti, U, V, Y, Zn, Zr) in sediments/traps. ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios in traps and sediment.
Manager		Wim Boer T 0222 369 386/394 @ wim.boer(at)nioz.nl

Sample preparation		For every application a dissolution and dilution protocol is developed, a glassware set-up is chosen for the ICP (which spray chamber, nebulizer, pump-speed, etc) and an analytical method is developed (which elements, resolution, measurement time, etc). Discuss sample preparation with us prior to preparing your samples. Here are some general remarks for preparing you samples: The sample containers must be clean and dust free. Prepare your sample in a clean environment, and if possible in a laminar flow hood. Do not use any metals during collections or preparation of the sample. Use a ceramic mortar to grind the samples. When the samples have to be fractionated, use a nylon sieve, not a metal sieve. Amount of sample 100 mg of ground sediment. 1 mg of coral sample.
Sample dissolution and dilution		Our sample dissolution and dilution methods are for: Coral: Dissolve 1±0.3mg in 1±0.3 ml ultrapure 0.1M HNO₃ in 5ml pots_.Dissolve the coral using a Vortex mixer. Pipette a sub volume of 0.26ml into a 12ml autosampler tube. Dilute with 9.74ml of 0.1M HNO₃. Preferable, the samples are measured on the same day. Sediments: Weight 100±5mg sediment in 30ml Savillex pots. Add 6,5ml concentrated. HNO3 (ultrapure)/HF (suprapure), 10:1. Add 1ml ultrapure HCl (conc) and 1ml perchloric acid to the samples. Heat a batch of 18 samples, 3 blanks and 3 standards at 125°C in an Analab hotblock during 48 hours. Remove the matrix after heating at the lower station of the hotblock during 48 hours at the same temperature. Redissolve the sample with 20.00ml 1M HNO3. Pipette 0.4ml of subsample in a 50ml DigiPrep autosampler tube. Add 19.6ml 1M HNO3 with internal standards (scandium, indium and thallium). Measure the sample preferable within a few days. For dissolving/diluting the samples yourselves, it is important to: Use the highest quality Teflon containers (FEP, PFA). Clean the sample containers. Put them in 8M HNO₃ for at least 1 hour. Rinse them thoroughly with >17 MΩ water to remove all the acids. Dry them in a laminar flow hood. Use preferable ultrapure HNO₃ for dissolution. Other acids cause a lot of additional interferences in the mass spectra. The end concentration must be 1-6% HNO₃. Total dissolved solids must be Use only high purity reagents (ultra grade, Teflon grade quality) Use the highest purity water (>18.2 MΩ) Prepare also a monitor standard. Prepare a number of blanks. The analytical solutions must be prepared shortly before a run. The end solution can be 500 µl, but using a small volume of sample limits the number of elements that can be determined and/or the number of replicate analyses.

XRF core scanner (NIOZ-AVAATECH)


Application		Non destructive analysis of elemental composition of sediment cores

Equipment		X-ray Fluorescence (XRF) Core Scanning is developed at the department of Marine Geology of the NIOZ for analyzing the sediment composition in a fast and non-destructive way. The scanner is equipped with an Rh X-Ray source that covers the elements from Al through to Ba. We can analyze sediment cores up to 1500 cm length with a resolution down to 0.1 mm. We developed new core scanning applications based on new insights and needs that evolved from our research, such as UV-luminesces for the analyzing coral records. Both UV and visual light scans are performed with a CCD line scan camera that has an optical resolution of 70 µm.
Equipment
Analysis		Sample preparation is minimized to a cleaning of the core surface. We use a thin film (4 µm) to cover the core surface to avoid contamination of the measurement unit and desiccation of the sediment. The analyzing time depends on sample resolution and the range of elements to be analyzed.
Manager		Rineke Gieles T 0222 369 444/221 @ rieneke.gieles(at)nioz.nl

Measurement request		For a measurement request, please fill out these forms: XRF request form or contact Rineke Gieles T 0222 369 444/221 @ rieneke.gieles(at)nioz.nl

Links & Literature		XRF workshop 2010 & Workshop Report: Tjallingii and workshop participants (2011). 2010 international workshop on XRF core scanning, PAGES news, Vol 19, No 2, July 2011. pages 90-91. [ pdf ] Suggested Literature: Jansen et al., 1998. CORTEX, a shipboard XRF-scanner for element analyses in split sediment cores. Marine Geology, 151: 143-153. Richter et al., 2006. The Avaatech Core Scanner: Technical description and applications to NE Atlantic sediments. In: Rothwell, R.G. (Ed.), New ways of looking at sediment core and core data. Geological Society Special Publication, London, pp. 39-50. Röhl, U., Abrams, L.J., 2000. High-resolution, downhole, andnondestructive core measurements from Site 999 and 1001 in the Caribbean sea: Application to the Late Paleocene Thermal Maximum, Proceedings of the Ocean Drilling Program, Scientific Results, pp. 191-203. Tjallingii et al., 2007. Influence of the water content on X-ray fluorescence core scanning measurements in soft marine sediments. Geophysics, Geosystems, Geochemistry, 8(2): doi:10.1029/2006GC001393. Weltje, G.J., Tjallingii, R., 2008. Calibration of XRF core scanners for quantitative geochemical logging of sediment cores: Theory and application. Earth and Planetary Science Letters, 274(3-4): 423-438. Technical information: www.avaatech.com

Magnetic Susceptibility scanner

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Laser particle sizer (Coulter LS230 and a LS13320)


Application		Determine grain size distribution of complex particle mixtures

Equipment		We measure grain-size distributions of sediment and suspended matter via laser diffraction. We have two laser particle sizers at our disposal; a Coulter LS230 and a LS13320. They can measure particles with sizes from 0.04-2000 µm. The resolution of these instruments is relatively high in comparison with other instruments. The detection of the smallest particles in the range of 0.04-0.4 µm is performed by an additional detection technique (PIDS technology) involving multiple wave lengths of light. The amount of sample depends on the choice of the module. We have three modules (I) micro cuvet for very small (µg) amounts (II) small volume module (mg) (III) large volume module (g).

Analysis		The large volume module of our CoulterLS230 is the standard module and requires 50 mg (clay) to 3000 mg (course sand) of freeze dried bulk sediments. If less material is available we use one of the smaller modules. Our standard procedure for bulk sediments is as follows. Approximately 0.05-3 gram of freeze-dried sediment (weight is depending on grain size) is soaked in water and suspended (using either ultrasonic dispersion or boiling with NaPyP). These samples are passed through a 2 mm sieve and suspended in 1 liter water in the CoulterLS230. If necessary, the samples are diluted with water to yield a laser obscuration of 10%. The measured laser diffraction pattern is calculated into a particle-size distribution using a Mie model with a refractive index of 1.56 and adsorption coefficient of 0.2 for the solid phase. A high pump speed is used (50%), which means that, in combination with the internal sonification, there is very little chance of flocculation.

Manager		Jan-Berend Stuut/Rineke Gieles

Specific Surface Area (Micromeritics Tristar 3000)


Application		Determine the specific surface area of particles

Equipment		Our group uses a Micromeritics Tristar 3000, that can measure 3 samples at the same time. This kind of analyses requires a total degassed sample. We have a Micromeritics FlowPrep060 to degas our samples.

Manager		Wim Boer T 0222 369 386/394 @ wim.boer(at)nioz.nl

Gas Chromatography

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Alpha Spectrometry (Canberra)


Application		²¹⁰Pb analysis in sediment, traps and corals

Equipment		Our group has 12 alpha PIPS detectors (Canberra). These detectors have an active area of 600 mm² and a resolution of 23 keV. Alpha spectrometry requires dissolution of sediment and a chemical purification. Our lab performs those steps for ²¹⁰Pb analysis.

Analysis		After measuring the grain size, we decide if ²¹⁰Pb analyses are performed on bulk or fractionated samples. We are able to measure ²¹⁰Pb directly with gamma-spectrometry, but we prefer the more sensitive method of measuring it indirectly via its granddaughter ²¹⁰Po with a half-life of 138.4 days. The advantage of alpha spectrometry is that our equipment can measure up to 12 samples in 1 or 2 days. The analysis is normally performed 3-9 month after date of sampling to obtain total equilibrium between ²¹⁰Pb and ²¹⁰Po. For analysis, 100 - 500 mg of freeze-dried and ground sediment is spiked with ²⁰⁹Po and totally digested with 9 ml concentrated HNO₃ and 3 ml concentrated HF in a microwave oven for 3 h. Subsequently, 2 ml 3.5% HClO₄ is added and thereafter the acids are removed by evaporation. The resulting precipitate is re-dissolved in 5 ml concentrated HCl for 30 minutes and thereafter 40 ml 0.5M HCl (with 12 g/l boric acid), 4 ml NH₄OH and 5 ml of 40 g/litre ascorbic acid (in 0.5M HCl) are added. Spontaneous deposition of Po-isotopes onto silver occurs at 80°C. This is done for 4 hours and the silver plates remain in solution overnight at room temperature to increase the deposition efficiency. The counting error (1s) is normally 3-7%.

Manager		Wim Boer T 0222 369 386/394 @ wim.boer(at)nioz.nl

Gamma Spectrometry (Canberra)


Application		Analyzing²³⁴Th, ²²⁶Ra and ¹³⁷Cs in sediment and traps.

Equipment		Our group has three Canberra gamma detectors, (I) a low energy, (II) a coaxial and (III) a well type detector. The low energy detector has a 1000 mm² active area, a diameter of 35.7 mm and a thickness of 20 mm. The detection range is from 10 to 1000 keV. The resolution for ⁵⁷Co is 0.57 keV. The absolute efficiency is for a silicate matrix and a tube for 63 keV: 36 – 42% and for 609 keV: 4.3-4.6% (the range is for weights from 1.3.-1.7 gram). The coaxial detector has a diameter of 53 mm. The detection range is from 50-1200 keV and the resolution is 0.80 keV for ⁵⁷Co. The absolute efficiency is for a silicate matrix and a Petri-dish of 5.5 cm diameter for 63 keV: 3.1 – 3.8% and for 609 keV: 2.3-2.6% (the range is for weights from 5-25 gram). The well type detector has a nominal volume of 140 cm³, a relative efficiency of 25%. The resolution for ⁵⁷Co is 1.2 keV. The absolute efficiency is for a silicate matrix and a Petri-dish of 5.5 cm diameter for 63 keV: 9.2 – 11% and for 609 keV: 0.66-0.80% (the range is for weights from 5-25 gram).

Analysis		For gamma spectrometry analyses a large quantity of sediment is preferred. This results in a shorter counting time. We prefer 5-20 gram of freeze dried sediment. For the well type detector 1 gram is sufficient. ²²⁶Ra To calculate mass accumulation rates or mixing rates from a²¹⁰Pb profile, the supported ²¹⁰Pb has to be subtracted from the total ²¹⁰Pb. The supported ²¹⁰Pb can be determined by analyzing the²²⁶Ra activity with gamma spectrometry. This is done as follows. ²²⁶Ra is analyzed indirectly by counting the ²¹⁴Pb lines (295 and 352 keV) and the ²¹⁴Bi line (609 keV). ²²⁶Ra decays to ²²²Rn. This is a gas, therefore the containers has to be sealed. The sample can be counted after at least 1 month. The detector is calibrated with an external standard of a uranium ore mixed with a silicate matrix. ²³⁴Th Box core or multi-core samples are normally used for ²³⁴Th analysis, to assess mixing rates. The ²³⁴Th activity is measured either by counting the 92 keV gamma emission with a high-resolution coaxial germanium detector, or by counting the 63keV and 92 keV gamma emissions with a low energy detector. Samples from a single core are all measured with the same detector. Calibration is done by means of the external standard method. This standard is a uranium-ore diluted with a silica powder. Uranium is in secular equilibrium with all its daughters in this standard. Samples with excess thorium were re-analyzed after at least three months. Excess ²³⁴Th activity is decay corrected for the time elapsed between sample collectionand counting. The self-absorption correction factor can be measured according to the method of Cutshall (1983). ¹³⁷Cs This isotope can be used to validate ²¹⁰Pb mass accumulation rates. The ¹³⁷Cs activity can be measured with all three gamma detectors, but the coaxial detector is preferred. The 661 keV line is used and normally counted for 1-2 days. The detector is calibrated with a QCY48 standard, which is a mixture of different isotopes including ¹³⁷Cs.

Manager		Wim Boer T 0222 369 386/394 @ wim.boer(at)nioz.nl

In situ techniques and methods

GEO truly is a seagoing research department, involved in many national and international ocean research projects. For in situ observations, both short and long-term up to a year, we have developed 'intelligent' bottom landers and camera systems in close collaboration with NIOZ MTec. Please find below a compilation of our seagoing equipment.

BOttom BOundary Lander (BOBO)

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Hopper camera

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Sediment traps

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