Name: sediment core sectioning and extraction of pore waters under anoxic conditions
Uploaded: 2016-03-07T13:00:00
Description: Watch this Scientific Journal Video about Sediment Core Sectioning and Extraction of Pore Waters under Anoxic Conditions at JoVE.com

This research was partly supported by the National Science Foundation&#39;s RAPID program (NSF-1048925, 1048919, and 1048914) to Alison Keimowitz, Ming-Kuo Lee, Benedict Okeke, and James Saunders.

1. Preparation of Equipment
<ol>
	<li>Preparation of Core Liners
	<ol>
		<li>Calculate thickness of core slice that will be obtained using Volume = &#960;r2 x thickness; the final volume must be &#60;50 cm3. With a 10 cm core diameter, 2 cm thick slices may be obtained. 
		NOTE: It is not necessary to have the volume be a full 50 ml, but porewater volumes obtained will be proportionately smaller.</li>
		<li>Using a jigsaw (or similar) slice one core liner, or a plastic tube of identi...

<ol>
	<li>Chapman, P. M., Wang, F., Germano, J. D., Batley, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pore+water+testing+and+analysis:+the+good,+the+bad,+and+the+ugly.">Pore water testing and analysis: the good, the bad, and the ugly.</a> Mar Poll Bull. 44, 359-366 (2002).</li><li>Teasdale, P. R., Batley, G. E., Apte, S. C., Webster, I. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pore+water+sampling+with+sediment+peepers.">Pore water sampling with sediment peepers.</a> TrAC. 14, 250-256 (1995).</li><li>Steinmann, P., Shotyk, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+composition,+pH,+and+redox+state+of+sulfur+and+iron+in+complete+vertical+porewater+profiles+from+two+Sphagnum+peat+bogs,+Jura+Mountains,+Switzerland.">Chemical composition, pH, and redox state of sulfur and iron in complete vertical porewater profiles from two Sphagnum peat bogs, Jura Mountains, Switzerland.</a> Geochim Cosmochim Acta. 61, 1143-1163 (1997).</li><li>Bufflap, S. E., Allen, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sediment+pore+water+collection+methods+for+trace+metal+analysis:+A+review.">Sediment pore water collection methods for trace metal analysis: A review.</a> Wat Res. 29, 165-177 (1995).</li><li>Glew, J., Smol, J., Last, W., Last, W., Smol, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+5,+Sediment+Core+Collection+and+Extrusion.">Chapter 5, Sediment Core Collection and Extrusion.</a> Developments in Paleoenvironmental Research. , 73-105 (2001).</li><li>Jahnke, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple,+reliable,+and+inexpensive+pore-water+sampler.">A simple, reliable, and inexpensive pore-water sampler.</a> L&amp;O. 33, 483-487 (1988).</li><li>Bufflap, S. E., Allen, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+pore+water+sampling+techniques+for+trace+metals.">Comparison of pore water sampling techniques for trace metals.</a> Wat Res. 29, 2051-2054 (1995).</li><li>Zheng, Y., Anderson, R. F., van Geen, A., Kuwabara, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Authigenic+molybdenum+formation+in+marine+sediments:+a+link+to+pore+water+sulfide+in+the+Santa+Barbara+Basin.">Authigenic molybdenum formation in marine sediments: a link to pore water sulfide in the Santa Barbara Basin.</a> Geochim Cosmochim Acta. 64, 4165-4178 (2000).</li><li>Keimowitz, A. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Arsenic+redistribution+between+sediments+and+water+near+a+highly+contaminated+source.">Arsenic redistribution between sediments and water near a highly contaminated source.</a> Env Sci &amp; Tech. 39, 8606-8613 (2005).</li><li>Natter, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Level+and+Degradation+of+Deepwater+Horizon+Spilled+Oil+in+Coastal+Marsh+Sediments+and+Pore-Water.">Level and Degradation of Deepwater Horizon Spilled Oil in Coastal Marsh Sediments and Pore-Water.</a> Env Sci &amp; Tech. 46, 5744-5755 (2012).</li><li>Jackson, P. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ion chromatography. , (1990).</li><li>Stookey, L. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ferrozine+-+A+New+Spectrophotometric+Reagent+For+Iron.">Ferrozine - A New Spectrophotometric Reagent For Iron.</a> Anal. Chem. 42, 779-781 (1970).</li><li>He, Y., Zheng, Y., Ramnaraine, M., Locke, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+pulse+cathodic+stripping+voltammetric+speciation+of+trace+level+inorganic+arsenic+compounds+in+natural+water+samples.">Differential pulse cathodic stripping voltammetric speciation of trace level inorganic arsenic compounds in natural water samples.</a> Anal. Chim. Acta. 511, 55-61 (2004).</li><li>Cline, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectrophotometric+Determination+of+Hydrogen+Sulfide+in+Natural+Waters.">Spectrophotometric Determination of Hydrogen Sulfide in Natural Waters.</a> L&amp;O. 14, 454-458 (1969).</li></ol>

The technique described herein is a flexible one that can be adjusted for a wide range of locations, core sizes, core section thickness, etc. There are three essential components to this system.
First, prepare a core extrusion system of the right dimensions for the core to be analyzed. Instructions here are given assuming an approximately 30&#34; core; much longer cores may require more PVC extender pieces and PVC fittings to extrude fully. Plan the extrusion system and the packing ca...

Researchers often wish to study the redox state and geomicrobiology of a sediment-water system. This ideally utilizes data from both sediments and pore waters, as pore waters are often sensitive monitors of the system and are a common source, though not the only source, of ecological exposure to redox-sensitive heavy metals1 such as arsenic and uranium. Pore water data may be obtained in situ using diffusion equilibrium filters, also known as &#34;peepers,&#34; installed into the sediment2. Peepers are most commonly used in settings where the field site is known prior to beginning field work and where multiple visits over an extended period of time can be made to the field site, e.g. Shotyk3. Therefore many contexts do not permit the use of peepers, such as sites only accessible for a short time or where multiple exploratory samples are obtained to determine where further investigation should occur4. Additionally peepers do not sample sediment simultaneously to water sampling.
When it is desirable to sample sediment and water together, or in field sites where peeper installation is not feasible, the most common method to obtain sediment and water is sediment coring. Obtaining an unmixed core is a crucial precursor to the procedure described in this work5. Once a core is obtained pore waters may be obtained by squeezing6 or centrifugation; both have advantages and disadvantages. Centrifugation is generally considered the most reliable method for extracting porewaters from sediment cores,7 although care must be taken to prevent oxidation of sediments or pore waters.
In this method we describe core extrusion and centrifugation to extract pore waters with minimal oxidation. The authors have used the method described herein in a variety of contexts including marine8, contaminated lake9, and wetlands10. The representative data shown demonstrates that reducing conditions can be preserved. With the exception of the centrifuge, materials used are inexpensive, and this method can be applied to a wide variety of geochemical and geomicrobiological research questions.

<table border="0" cellpadding="0" cellspacing="0" width="811">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;">&#160;Disposable glove bag(s).&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>Z106089-1EA</td>
			<td>&#160;One per two cores to be processed is usually sufficient.</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">&#160;N2 tank</td>
			<td>Praxair</td>
			<td></td>
			<td>Often gas supply companies can deliver these directly to the field laboratory.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nitrogen gas regulator</td>
			<td>VWR</td>
			<td>55850-478</td>
			<td>Or similar</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Several feet of tubing that fits the regulator</td>
			<td>VWR</td>
			<td>89403-862</td>
			<td>Or similar</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Safety equipment to secure the tank</td>
			<td>VWR</td>
			<td>60142-006</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Adjustable tubing clamp</td>
			<td>VWR</td>
			<td>62849-112</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Waterproof, good sealing electrical tape</td>
			<td>Scotch</td>
			<td>Super 33+</td>
			<td>Widely available</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#160;2-4 short bungee cords</td>
			<td></td>
			<td></td>
			<td>Widely available</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Squirt bottles of nanopure water</td>
			<td>VWR</td>
			<td>16650-082</td>
			<td>Any similar bottle is fine; pack an additional supply of nanopure water to refill these.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Large supply of paper towels and kimwipes.</td>
			<td></td>
			<td></td>
			<td>Widely available</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">50 mL centrifuge tubes</td>
			<td>VWR</td>
			<td>21008-951</td>
			<td>Acid cleaned as described in protocol.&#160; At least 2/core section needed.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Several permanent in markers.</td>
			<td></td>
			<td></td>
			<td>Widely available</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#160;Several straight razor blades and box cutters.</td>
			<td></td>
			<td></td>
			<td>Widely available</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Centrifuge</td>
			<td>Beckman-Coulter</td>
			<td>Allegra X-22</td>
			<td>Faster rotor allows greater separation.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Rotor to accommodate 50 mL tubes</td>
			<td>Beckman-Coulter</td>
			<td>SX-4250</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">]50 mL plastic syringes without black rubber tip on the barrel</td>
			<td>VWR</td>
			<td>66064-764&#160;</td>
			<td>Acid cleaned as described in protocol.&#160; At least 1/core section needed, plus 1 for overlying water.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Syringe filters compatible with aqueous solutions.</td>
			<td>VWR</td>
			<td>28143-310&#160;</td>
			<td>Either 0.45 &#956;m or 0.20 &#956;m poresizes may be used.&#160; Plan on five filters per core section processed.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plastic (disposable) spoons.</td>
			<td></td>
			<td></td>
			<td>Widely available; Acid cleaned as described in protocol.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Several boxes of disposable gloves.</td>
			<td></td>
			<td></td>
			<td>Widely available</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Large plastic beakers or other waste containers to place in the glove bag.</td>
			<td>VWR</td>
			<td>13890-148</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Laboratory balance</td>
			<td>VWR</td>
			<td>10205-008</td>
			<td>An available balance will be fine; high precision not required</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dry shipper, pre-charged with liquid nitrogen</td>
			<td>VWR</td>
			<td>82005-416</td>
			<td>Needed only if samples are being returned to the home laboratory for sensitive analyses.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Laboratory notebooks</td>
			<td></td>
			<td></td>
			<td>Water repellent can be useful</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Core liners</td>
			<td>Watermark</td>
			<td>77280</td>
			<td>Available from Forrestry Suppliers</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Core caps</td>
			<td>Ben Meadows</td>
			<td>218105</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Core slicers</td>
			<td>McMaster Carr</td>
			<td>8707K111</td>
			<td>Cut this into 9 3x3 squares</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PVC spacers</td>
			<td>McMaster Carr</td>
			<td>48925K96</td>
			<td>Cut this into short lengths</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PVC couplings</td>
			<td>McMaster Carr</td>
			<td>4880K76</td>
			<td>Approximately 12 needed</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dowel</td>
			<td></td>
			<td></td>
			<td>Widely available</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Lab stopper</td>
			<td>VWR</td>
			<td>59580-400</td>
			<td>Check to ensure the correct size to fit snugly within the core liners</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plywood for core guidance plate and top of lab jack</td>
			<td></td>
			<td></td>
			<td>Widely available</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Lab jack</td>
			<td>VWR</td>
			<td>89260-826</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Clamps</td>
			<td></td>
			<td></td>
			<td>Widely available</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Portable oxygen monitor</td>
			<td>RKI instruments</td>
			<td>OX-07</td>
			<td></td>
		</tr>
	</tbody>
</table>

sediment core sectioning and extraction of pore waters under anoxic conditions

We demonstrate a method for sectioning sediment cores and extracting pore waters while maintaining oxygen-free conditions. A simple, inexpensive system is built and can be transported to a temporary work space close to field sampling site(s) to facilitate rapid analysis. Cores are extruded into a portable glove bag, where they are sectioned and each 1-3 cm thick section (depending on core diameter) is sealed into 50 ml centrifuge tubes. Pore waters are separated with centrifugation outside of the glove bag and then returned to the glove bag for separation from the sediment. These extracted pore water samples can be analyzed immediately. Immediate analyses of redox sensitive species, such as sulfide, iron speciation, and arsenic speciation indicate that oxidation of pore waters is minimal; some samples show approximately 100% of the reduced species, e.g. 100% Fe(II) with no detectable Fe(III). Both sediment and pore water samples can be preserved to maintain chemical species for further analysis upon return to the laboratory.

The type of results obtained depends on analyses performed and on the geochemical setting from which the core was obtained. Dissolved oxygen may be measured in the extracted porewaters, but in many settings this will be zero below the first few cm of the core. Analyses that usually provide more meaningful information include iron speciation (Fe II/Fe III)12, arsenic speciation (As III/As V)13, and sulfide14. Presence of reduced species such as sulfide indi...

Watch this Scientific Journal Video about Sediment Core Sectioning and Extraction of Pore Waters under Anoxic Conditions at JoVE.com

Sediment Core Sectioning and Extraction of Pore Waters under Anoxic Conditions

A protocol for sectioning sediment cores and extracting pore waters under anoxic conditions in order to permit analysis of redox sensitive species in both solids and fluids is presented.

We demonstrate a method for sectioning sediment cores and extracting pore waters while maintaining oxygen-free conditions. A simple, inexpensive system is ...

The overall goal of this procedure is to section sediment cores and extract pore waters from these sediment cores while maintaining the original oxidation state. This method can allow researchers in geochemical fields to examine metal speciation in pore waters and sediments from redox-sensitive areas such as lakes and wetlands. The main advantages of this technique are that it's flexible and adaptable, field portable, inexpensive, and does not disrupt sediment layers.Demonstrating the procedure will be Rahul Sinha, an undergraduate from my laboratory. Begin preparing the field laboratory by setting up the glove bag. First, clamp the core guidance plate to a work surface.Position the hole for the core liner extending in front of the counter to ensure it is open. Next, secure the nitrogen tank using a bench clamp. Then, place the glove bag over the plate and run tubing between the bag and the gas regulator.Extend about eight inches of tubing into the bag. Now, seal the tubing connection at the bag with electrical tape and inside the bag slide a clamp onto the tube but leave the clamp open. Next, cut an X into the bottom of the bag over the hole in the plate then load the bag with the listed items.Double check the lists, because forgetting an item is very inconvenient. The next task is to set up the core. First, put a lab jack on the floor under the work surface.The lab jack should have a piece of plywood on it with a hole in the center to stabilize the core. Then, with the core in an upright position, push it through the core guidance plate and through the X in the glove bag. About four to six inches of core should extend above the plate.Now, while one person supports the core, tape the core to the bag around the X with electrical tape. Then, set up the core extruder. First insert the handle into a six-inch long, two-inch diameter PVC spacer followed by a three-inch long coupling and then another space and another coupling and so forth until the handle is completely covered.Now, place the core extruder below the core and support it with the jack. The jack should be cranked as low as possible. Next, with a box cutter carefully cut around the bottom of the core cap.Leave a ring of core cap around the core liner and leave a circular piece of cap against the core materials. Now, one person must reach into the glove bag to secure the core while the other raises the jack. Gradually move the core extruder into the core liner raising the sediment upwards.It may be necessary to wiggle the extruder a little. Continue raising the core until the sediment and overlying water reaches to the top of the core liner. The last task is to seal the bag.First, double check that everything is in there. Then, open all the objects in the bag that contain trapped air. Now, ideally with another person's help, purge the glove three times.First, with the bag as deflated as possible, seal the main opening with a few bungee cords. Then, with an assistant regulating the nitrogen flow at 50 psi, direct the gas around the bag, especially into crevices where air could be trapped. When the bag is highly inflated, turn off the regulator or close the clamp to shut off the gas.Then, open the main opening and push out as much gas from the bag as possible. Repeat the process of filling the bag with nitrogen, including all crevices, and emptying the bag two more times. Once this is completed, the glove bag should contain very low levels of oxygen.Finish with a comfortable amount of gas in the glove bag. This procedure is best performed while working in pairs. For this procedure, put a pair of disposable gloves over the built-in gloves in the bag.Change these gloves whenever they are dirty or torn. First, remove all the standing water from the top of the core using a syringe. Then, filter this water through a 0.45-micron syringe filter.Next, place a core sectioning ring over the top of the core liner. Then, raise the core until the sediment meets the top of the ring. Inside the bag, secure the core liner so when the core moves the liner does not.It may be necessary for the operator working inside the glove bag to push down slightly on the core liner so that the core material is at the top of the ring. Next, push a core slicer between the top of the liner and the ring so that the sediment section is above the slicer. This is the first section of core.With plastic spoons, move the section to a 50-milliliter conical tube and cap it tightly. Wash the tools and repeat the process until the whole core is sectioned and placed into tubes. During the core sectioning process the lab jack may become fully extended.If this occurs, hold the core in place, lower the jack, and position the PVC pieces to extend the core extruder. Then secure the jack back in place. During this process, the bag may get too deflated or inflated.Make adjustments by briefly opening the nitrogen gas valve or by briefly opening the main bag opening to release gas. Once the core is sectioned and all the sediment is in centrifuge tubes, these tubes can be removed from the glove bag and the glove bag closed. Then, prepare the collected tubes for centrifugation as explained in the text protocol.Then, spin them down at 1, 100 g or faster for 20 minutes. After the centrifugation, return the tubes to the oxygen-free environment and introduce some empty tubes for the sample collection. The bag should then be purged again two to three times as before.Now, open a centrifuged tube and remove the porewater using a syringe with tubing on the end. Then, using a 0.45-micron syringe filter, filter the water into a collection tube. The text protocol explains how to further process the samples.Using the described protocol, a core was taken from a wetland near New Orleans nine months after the Deep Water Horizons Bill. This wetland was heavily oiled. Using a Hach DR 2700 portable spectraphotometer, the data showed extremely high sulfide concentrations.Iron concentrations were low and iron in the three plus oxidation state was not detected. So after watching this video you should have a good understanding of how to purge the glove bag of oxygen, extrude the core inside the glove bag to allow sectioning, and separate the porewaters from the sediments. Once mastered, this technique can be done in one to three hours per core, depending on the core length.While attempting this procedure, it's important to remember to purge the glove bag thoroughly and adjust the core height slowly. Following this procedure methods like iron speciation by ferrousing, arsenic speciation by voltammetry or column separation, and mythylmercury separation can be performed in order to answer questions about the redox state of the system. Don't forget that working with compressed gasses can be extremely hazardous and securing the tank is essential while performing this procedure.Some sediment samples may be contaminated with hazardous materials and appropriate cautions should be taken.

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