This research was made possible in part by a grant from BP/The Gulf of Mexico Research Initiative, C-IMAGE, DEEP-C and in part by the British Petroleum/Florida Institute of Oceanography (BP/FIO)-Gulf Oil Spill Prevention, Response, and Recovery Grants Program. The authors thank Nico Zenzola for his input in development of this procedure. The authors also thank the crew of the R/V Weatherbird II for their help during the field program.
Data can be accessed at the GRIIDC website: https://data.gulfresearchinitiative.org/ (data/R1.x135.119:0004/), (data/Y1.x031.000:0003/), (data/Y1.x031.000:0006/), (R1.x135.120:0004).

1. Collect Sediment Cores
<ol>
	<li>Collect aquatic sediment core using multi-core, box core, piston core, etc.4,7,12,14. Ensure that the core section is 1 m or less.</li>
	<li>Insert polycarbonate or acrylic puck into the bottom of the core. Ensure that the puck is consistent with the inner diameter of the core tube. Insert a rubber gasket on the outermost diameter of the puck to retain the entirety of the sediment core.</li>
	<li>Upon retrieval of the core, extrude immediately or package for transport and storage (see steps 1.4 through 1.6 for storage and transport).</li>
	<li>Insert a foam or acrylic puck into the surface of the core tube and gently press down until the foam or acrylic is just above the sediment interface to maintain the integrity of the sediment-water interface during transport and storage.</li>
	<li>Place cap on top of the core tube and seal with electrical tape. Place cap on bottom of core tube and seal with electrical tape. Label the top cap with necessary project and sample identifiers.</li>
	<li>Store cores at desired temperature based on desired analysis. 
	NOTE: For example, cores used for organic chemical analysis or biological analysis can be frozen (-20 &#176;C), while short-lived radioisotope cores can be stored at ambient temperature (~20-25 &#176;C).</li>
</ol>
2. Prepare Sub-sample Vessels and Tools
<ol>
	<li>Label sub-sample vessels (e.g., jars, bags or beakers) with project name, core site and increment (e.g., PROJECT NAME_CORE SITE_0 - 2 mm), along with any other pertinent identification information (e.g., date, core type).</li>
	<li>Assemble and sterilize (methanol) necessary cutting implements (e.g., acrylic paddles, putty knives, etc.) and personal protective equipment (e.g., gloves, lab coats, etc.). 
	Note: These implements and their sterilization procedures will depend on the type of analysis to be done on each sub-sample. For example, the use of metal and acrylic implements (as opposed to plastic) is essential for organic chemical analysis, whereas acrylic and plastic implements (as opposed to metal) must be used for inorganic trace element analyses.</li>
</ol>
3. Prepare Sediment Core for Extrusion
<ol>
	<li>If the core has been stored or preserved, remove the bottom cap first. To do this cut the bottom cap off with a razor blade and allow for the top cap to maintain a vacuum, which holds the sediment in the tube while transferring to the extruder (the extrusion puck must already be inserted in the bottom of the preserved cores) (Figure 1).</li>
	<li>When extruding immediately upon collection, insert the extrusion puck into the bottom of the core. Then gently set the core tube onto the piston and fasten the core to the extruder using the clamps.</li>
	<li>Ensure that there is at least 5 cm of core tube remaining above the uppermost clamp for the sampling collar.</li>
	<li>Remove top cap.</li>
	<li>Place the sampling collar on top of the core tube. Make sure the collar is sitting flush with the uppermost extent of the core tube to avoid any sample loss.</li>
	<li>Sample (or discard if not needed) the water above the sediment at this point using a syringe or siphon.</li>
	<li>After extracting the water, begin turning the piston to align the surface-most sediment with the surface of the sampling collar.</li>
</ol>
4. Extrusion
<ol>
	<li>Turn the piston to the desired sampling resolution (typically 1-2 mm, 1 full rotation = 2 mm sub-sample)(Figure 1).</li>
</ol>
<img alt="Figure 1" src="/files/ftp_upload/54363/54363fig1.jpg" /> 
Figure 1: Photographs of Extruder. Photographs of the extruder defining the piston (1), coupling (2), threaded-rod (3), extruder base (4), clamps (5), core tube (6), sampling collar (7), and rubber band (8). <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54363/54363fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>Use the acrylic plate (cut to the inner diameter of the sampling collar) to make the initial sample cut. Subsequently move the sub-sample towards the edge of the sampling collar slowly while positioning the appropriate sampling vessel below the mouth of the sampling collar.</li>
	<li>Begin to push the sample into the sampling vessel. After the majority of the sample is in the vessel, use the smaller implements (e.g., putty knife) to move any remaining sample in the sampling collar to the sampling vessel.</li>
	<li>Use the smaller implement to clean the remaining amount of sample from the acrylic plate and any other sampling surface into the sampling vessel.</li>
	<li>Once the sample is completely transferred from the sampling collar to the vessel, clean the sampling tools with deionized water, laboratory wipes and/or other sterilizing fluid (e.g., methanol). Clean the sampling collar accordingly with laboratory wipes, deionized water and other sterilizing solution.</li>
	<li>Seal the sample vessel and prepare the next sample vessel for extrusion. Repeat steps 4.1 through 4.5 for each subsample.</li>
</ol>
5. Resetting the Extruder
<ol>
	<li>Reset the extruder manually. Use a drill and rubber band to expedite the process of resetting the piston to the bottom of the threaded-rod.</li>
	<li>Place the rubber band around the piston near the base for the most stability.</li>
	<li>Stretch the rubber band around the head of the drill and set the direction of the drill to rotate the piston downward.</li>
	<li>Rotate the piston using a low speed on the drill until it reaches the desired height above the base of the extruder. 
	Note: This height is based on the length of the core to be extruded and desired sampling height.</li>
</ol>

<ol>
	<li>Abrahim, G. M. S., Parker, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+heavy+metal+enrichment+factors+and+the+degree+of+contamination+in+marine+sediments+from+Tamacki+Estuary,+Auchland,+New+Zealand.">Assessment of heavy metal enrichment factors and the degree of contamination in marine sediments from Tamacki Estuary, Auchland, New Zealand.</a> Env. Mon. and Assess. 136, 227-238 (2008).</li><li>Binford, M. W., Kahl, J. S., Norton, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interpretation+of+210Pb+profiles+and+verification+of+the+CRS+dating+model+in+PIRLA+project+lake+sediment+cores.">Interpretation of 210Pb profiles and verification of the CRS dating model in PIRLA project lake sediment cores.</a> J. Paleolimnology. 9, 275-296 (1993).</li><li>Brenner, M., Schelske, C. L., Keenan, L. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Historical+rates+of+sediment+and+nutrient+accumulation+in+marshes+of+the+Upper+St.+Johns+River+Basin,+Florida.">Historical rates of sediment and nutrient accumulation in marshes of the Upper St. Johns River Basin, Florida.</a> J. Paleolimnology. 26, 241-257 (2001).</li><li>Brooks, G. 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=Sediment+Pulse+in+the+NE+Gulf+of+Mexico+Following+the+2010+DWH+Blowout.">Sediment Pulse in the NE Gulf of Mexico Following the 2010 DWH Blowout.</a> PLoS ONE. 10 (7), 0132341 (2015).</li><li>Engstrom, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+lightweight+extruder+for+accurate+sectioning+of+soft-bottom+lake+sediment+cores+in+the+field.">A lightweight extruder for accurate sectioning of soft-bottom lake sediment cores in the field.</a> Limno. and Oceano. 38 (8), 1796-1802 (1993).</li><li>Gordon, E., Go&#241;i, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controls+on+the+distribution+and+accumulation+of+terrigenous+organic+matter+in+sediments+from+the+Mississippi+and+Atchafalaya+river+margin.">Controls on the distribution and accumulation of terrigenous organic matter in sediments from the Mississippi and Atchafalaya river margin.</a> Mar. Chem. 92, 331-352 (2004).</li><li>Hastings, D. W., 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=Changes+in+sediment+redox+conditions+following+the+BP+DWH+Blowout+event.">Changes in sediment redox conditions following the BP DWH Blowout event.</a> Deep-Sea Res. II. , (2014).</li><li>Jones, P. D., 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=High-resolution+palaeoclimatology+of+the+last+millennium+a+review+of+current+status+and+future+prospects.">High-resolution palaeoclimatology of the last millennium a review of current status and future prospects.</a> The Holocene. 1, 3-49 (2009).</li><li>Paris, C. B., 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=Evolution+of+the+Macondo+Well+Blowout:+Simulating+the+Effects+of+the+Circulation+and+Synthetic+Dispersants+on+the+Subsea+Oil+Transport.">Evolution of the Macondo Well Blowout: Simulating the Effects of the Circulation and Synthetic Dispersants on the Subsea Oil Transport.</a> Env. Sci. &amp; Tech. 121203084426001, (2012).</li><li>Passow, U., Ziervogel, K., Aper, V., Diercks, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Marine+snow+formation+in+the+aftermath+of+the+Deepwater+Horizon+oil+spill+in+the+Gulf+of+Mexico.">Marine snow formation in the aftermath of the Deepwater Horizon oil spill in the Gulf of Mexico.</a> Env. Res. Letters. 7, 035301 (2012).</li><li>Radovi&#263;, J. R., Silva, R. C., Snowdon, R., Larter, S. R., Oldenburg, T. B. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+screening+of+glycerol+ether+lipid+biomarkers+in+recent+marine+sediment+using+APPI-P+FTICR-MS.">Rapid screening of glycerol ether lipid biomarkers in recent marine sediment using APPI-P FTICR-MS.</a> Anal. Chem. 88 (2), 1128-1137 (2016).</li><li>Romero, I. C., 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=Hydrocarbons+in+Deep+Sea+Sediments+Following+the+2010+Deepwater+Horizon+Blowout+in+the+Northeast+Gulf+of+Mexico.">Hydrocarbons in Deep Sea Sediments Following the 2010 Deepwater Horizon Blowout in the Northeast Gulf of Mexico.</a> PLoS ONE. 10 (5), e0128371 (2015).</li><li>Santschi, P. H., Rowe, G. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Radiocarbon-derived+sedimentation+rates+in+the+Gulf+of+Mexico.">Radiocarbon-derived sedimentation rates in the Gulf of Mexico.</a> Deep-Sea Res. II. 55, 2572-2576 (2008).</li><li>Schwing, P. T., Romero, I. C., Brooks, G. R., Hastings, D. W., Larson, R. A., Hollander, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Decline+in+Deep-Sea+Benthic+Foraminifera+Following+the+Deepwater+Horizon+Event+in+the+Northeastern+Gulf+of+Mexico.">A Decline in Deep-Sea Benthic Foraminifera Following the Deepwater Horizon Event in the Northeastern Gulf of Mexico.</a> PLOSone. 10 (3), 0120565 (2015).</li><li>Valsangkar, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+device+for+finer-scale+sub-sectioning+of+aqueous+sediments.">A device for finer-scale sub-sectioning of aqueous sediments.</a> Current Science. 92 (4), 5-8 (2007).</li><li>W&#246;rmer, L., Elvert, M., Fuchser, J., Lipp, J. S., Buttigieg, P. L., Zabel, M., Hinrichs, K. -. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultra-high-resolution+paleoenvironmental+records+via+direct+laser-based+analysis+of+lipid+biomarkers+in+sediment+core+samples.">Ultra-high-resolution paleoenvironmental records via direct laser-based analysis of lipid biomarkers in sediment core samples.</a> NAS Proceedings. 111 (44), 15669-15674 (2014).</li><li>Yeager, K. M., Santschi, P. H., Rowe, G. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sediment+accumulation+and+radionuclide+inventories+(239,+240+Pu+,+210+Pb+and+234+Th+)+in+the+northern+Gulf+of+Mexico,+as+influenced+by+organic+matter+and+macrofaunal+density.">Sediment accumulation and radionuclide inventories (239, 240 Pu , 210 Pb and 234 Th ) in the northern Gulf of Mexico, as influenced by organic matter and macrofaunal density.</a> Marine Chemistry. 91, 1-14 (2004).</li><li>Ziervogel, K., 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=Microbial+activities+and+dissolved+organic+matter+dynamics+in+oil-contaminated+surface+seawater+from+the+Deepwater+Horizon+oil+spill+site.">Microbial activities and dissolved organic matter dynamics in oil-contaminated surface seawater from the Deepwater Horizon oil spill site.</a> PLoS One. 7 (4), e34816 (2012).</li></ol>

The authors have nothing to disclose.

The extruder can be modified to accommodate multiple diameters of core tube. If the core diameter is changed, then the piston, puck, and clamp diameters must be adjusted accordingly. This modification allows for broad applications in lacustrine and marine sediment collection. The sediment cores can also be extruded in the field or in the lab. A common modification to ease shipment of this extrusion system is to build it in two sections; a lower section (base and piston) can then be coupled to the upper section (clamps).
There are some limitations to this extrusion method. The first of these is that each core, or core section, must be cut to one-meter length or less. As with any extrusion method, there is also inevitably some compaction. However, compaction caused by this method is minimal. The reproducibility of multiple records extruded in this fashion is within 2-4 mm. This reproducibility is estimated on comparisons between various records (trace metal, organic geochemistry, benthic foraminifera, sedimentology) collected on the same deployment of an eight core multicore system. This extrusion method is also best suited for sediments that are primarily (&#62;50%) silt and clay sized particles. Sediment predominantly (&#62;50%) consisting of sand size particles tends to bind, causing additional compaction, due to a higher friction coefficient. The final limitation associated with this method is the amount of sediment available from each increment at millimeter-scale resolution. This method provides approximately 15-20 g of wet mass and 3-10 g of dry mass at 2 mm resolution, which may be restrictive for some analytical protocols.
The sedimentary records of the Deepwater Horizon event in the northern Gulf of Mexico demonstrate the efficacy of millimeter-scale subsampling. First of all, 234Th dating would not have been possible without millimeter-scale subsampling. This dating method can only be applied under certain circumstances, which are further discussed4. The pulse of oiled-flocculent material following the Deepwater Horizon event satisfied these conditions, depositing up to 8 mm of material at certain sites in the northern Gulf of Mexico within 6-12 months. Without mm scale sampling, the geochronology of this event would not have been resolved on the sub-annual scale (Tables 2 and 3). In addition to the 234Th records, redox-sensitive trace metals, benthic foraminiferal density, and the organic geochemistry records of this event would have been limited to one data point in the surface centimeter (Table 3). Instead, using millimeter-scale sub sampling provided a detailed and robust (5-10 data point) record of the MOSSFA event. Specifically, a 4-fold increase (n = 18) above pre-Deepwater Horizon values in total aliphatics using mm scale subsampling would have been reduced to a 2-fold increase, using cm scale subsampling (n = 6). Accordingly, a decrease in benthic foraminiferal density of 90% using mm scale subsampling would have been reduced to a decrease of 60% using cm scale subsampling. Without this high resolution sampling, discrete double peaks of Mn oxide, as well as changes in sedimentary Re concentrations associated with non steady-state redox changes would not be resolved. Overall, this extrusion system provides the ability to subsample sediment cores at the mm scale, retaining the entire volume of the sample and can be modified for broad applications in aquatic sediment sampling. Future applications of this method may include assessment of past oil spills, due to the mm scale event stratigraphy associated with subsurface oil releases. Other applications may include lacustrine records of mm scale climate variability. Millimeter scale sub-sampling has been proven effective in characterizing event stratigraphy in the context of anthropogenically influenced systems.

Sediment core samples from lacustrine, estuarine, and marine (continental shelf and slope) environments have provided records of salinity, temperature, organic and inorganic pollutants and many other environmental parameters on decadal to millennial time-scales1-3,6,8,13,17. In most cases, the standard practices are to section these cores at half-centimeter or centimeter intervals5,15. This resolution is appropriate for multi-year, decadal or higher scale resolution in most cases. The need for increased extrusion resolution has recently been demonstrated in some reports which detected variability of sedimentary biomarkers/proxies on a fine scale along the vertical profile of the sediment core11,16. In the case of recent sedimentation that occurs on time-scales of months to one year, it is then necessary to use finer resolution subsampling methods (e.g., mm scale). This is often challenging with aquatic sediments due to the unconsolidated nature of the surface sediments.
We present a sediment core extrusion method that provides mm scale sediment sub-samples. We then apply this extrusion method to the sediments of the northern Gulf of Mexico following the Deepwater Horizon (DWH) event. This application demonstrates the efficacy of millimeter-scale subsampling in characterizing sub-annual event stratigraphy related to anthropogenically influenced depositional systems.
Monthly or sub-annual scale resolution in sedimentary records is particularly advantageous when characterizing short-term event stratigraphy. Environmental assessments using sub-annual resolution are able to fully characterize anthropogenically induced sedimentation events.
Sediments in the northern Gulf of Mexico that were affected by the Deepwater Horizon oil event provide an example of event stratigraphy fully characterized using millimeter (sub-annual) scale resolution sampling. Following the Deepwater Horizon (DWH) event in 2010, continental slope sediments of the northeastern Gulf of Mexico (nGoM) came in contact with hydrocarbons through an order of magnitude increase in flocculent hydrocarbon deposition4,9,10,12,14,18. The increase in sedimentation was caused by a Marine Oil Snow Sedimentation and Flocculent Accumulation (MOSSFA) event4,9,10,12,14,18. This resulted in approximately 6-10 mm of sediment accumulation in a 6-12 month period from mid-2010 to early 20114. It was necessary to sub-sample these sediment cores at millimeter-scale to fully characterize the inputs, rates of sedimentation, and post-depositional processes.

<table><tbody><tr><td>Extruder</td><td>Custom Fabrication</td><td></td><td>Aluminum base and clamps, steel threaded rod&amp;nbsp;</td></tr><tr><td>Piston</td><td>Custom Fabrication</td><td></td><td>PVC tubing with acrylic cap</td></tr><tr><td>Polycarbonate Core Tube</td><td>SABIC Poymershapes</td><td>68374192</td><td></td></tr><tr><td>Acrylic puck/Rubber Gasket</td><td>Custom Fabrication</td><td></td><td></td></tr><tr><td>Acrylic sampling collar</td><td>Custom Fabrication</td><td></td><td></td></tr><tr><td>Acrylic plate</td><td>Custom Fabrication</td><td></td><td>One edge bevelled at 45 degree angle</td></tr><tr><td>Putty knife</td><td>Fisher Scientific</td><td>&lt;a href=&quot;https://www.fishersci.com/shop/products/ampco-safety-putty-knives-4/19166432&quot;&gt;19-166-432&lt;/a&gt;</td><td></td></tr><tr><td>Steel/Acrylic Plates</td><td>Custom Fabrication</td><td></td><td></td></tr><tr><td>Electrical tape</td><td>McMaster Carr</td><td>76455A28</td><td></td></tr><tr><td>Siphon or Syringe</td><td>Fisher Scientific</td><td>14-176-227, 14-823-2A</td><td></td></tr><tr><td>Razor blade</td><td>Fisher Scientific</td><td>12-640</td><td></td></tr><tr><td>Drill</td><td>Ryobi</td><td>P-882</td><td></td></tr><tr><td>Thick rubber band</td><td>Staples</td><td>831636</td><td>2 - 3 cm in width, larger diameter than piston</td></tr><tr><td>Personal protection equipment</td><td>Fisher Scientific</td><td>Gloves-19-058-801C,&lt;br/&gt; lab coat- 17-100-850,&lt;br/&gt; Goggles-19-181-501</td><td>&lt;i&gt;e.g.&lt;/i&gt;, gloves, lab coat, goggles</td></tr><tr><td>Sample labels</td><td>Fisher Scientific</td><td>&lt;a href=&quot;https://www.fishersci.com/shop/products/fisherbrand-patient-id-labels-addressograph-2/15920&quot;&gt;15920&lt;/a&gt;</td><td></td></tr><tr><td>Sample vessels</td><td>Fisher Scientific</td><td>Whirlpak- 01-812-3,&lt;br/&gt; &amp;nbsp;Jar- 02-911-791</td><td>&lt;i&gt;e.g.&lt;/i&gt;, whirlpak bags, jars, &lt;em&gt;etc.&lt;/em&gt;</td></tr><tr><td>Laboratory wipes</td><td>Fisher Scientific</td><td>06-666-11</td><td>&lt;i&gt;e.g.&lt;/i&gt;, kim wipes</td></tr><tr><td>Methanol</td><td>Fisher Scientific</td><td>BP1105-1</td><td></td></tr><tr><td>Deionized water</td><td></td><td></td><td></td></tr></tbody></table>

sediment core extrusion method at millimeter resolution using a calibrated, threaded-rod

Aquatic sediment core subsampling is commonly performed at cm or half-cm resolution. Depending on the sedimentation rate and depositional environment, this resolution provides records at the annual to decadal scale, at best. An extrusion method, using a calibrated, threaded-rod is presented here, which allows for millimeter-scale subsampling of aquatic sediment cores of varying diameters. Millimeter scale subsampling allows for sub-annual to monthly analysis of the sedimentary record, an order of magnitude higher than typical sampling schemes. The extruder consists of a 2 m aluminum frame and base, two core tube clamps, a threaded-rod, and a 1 m piston. The sediment core is placed above the piston and clamped to the frame. An acrylic sampling collar is affixed to the upper 5 cm of the core tube and provides a platform from which to extract sub-samples. The piston is rotated around the threaded-rod at calibrated intervals and gently pushes the sediment out the top of the core tube. The sediment is then isolated into the sampling collar and placed into an appropriate sampling vessel (e.g., jar or bag). This method also preserves the unconsolidated samples (i.e., high pore water content) at the surface, providing a consistent sampling volume. This mm scale extrusion method was applied to cores collected in the northern Gulf of Mexico following the Deepwater Horizon submarine oil release. Evidence suggests that it is necessary to sample at the mm scale to fully characterize events that occur on the monthly time-scale for continental slope sediments.

Cores from site DSH08 were collected in December 2010 (29&#176; 7.25&#39; N, 87&#176; 51.93&#39; W, 1,143 m depth) using an Ocean Instruments MC-800 multicorer. These cores were extruded at 2 mm for the surficial 15 cm (or more) using the protocol above. The pre-DWH (before 2010) and post-DWH (2010) intervals of the core were determined using a paired short-lived radioisotope (234Th and 210Pb) geochronology4. Several other analyses were performed to constrain the sedimentary inputs, deposition rates, and post-depositional processes at this site following the Deepwater Horizon event. In addition to short-lived radioisotope analysis, total aliphatic concentration12, redox sensitive metals (manganese, rhenium)7, and total benthic foraminiferal density14 were quantified. A comparison of each of these parameters at the mm scale and cm scale was performed (Tables 2 and 3, Figure 2). Centimeter scale data was composed of integrated, mean mm scale data.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Top Depth (mm)</td>
			<td>Excess 
			&#160;Pb-210 
			(dpm/g)</td>
			<td>Excess 
			Th-234 
			(dpm/g)&#160;</td>
			<td>Th-234 and Pb-210 Merged Age model 
			(year)</td>
			<td>Total 
			Foraminiferal 
			Density 
			(indiv./cm3)</td>
			<td>[Re] 
			&#160;(ng/g)</td>
			<td>[Mn] 
			&#160;(mg/g)</td>
			<td>Total Aliphatics 
			(ng/g)&#160;</td>
		</tr>
		<tr>
			<td>0</td>
			<td>71.81</td>
			<td>6.19</td>
			<td>2010.9</td>
			<td>1</td>
			<td></td>
			<td></td>
			<td>336922.6</td>
		</tr>
		<tr>
			<td>2</td>
			<td>71.81</td>
			<td>5.14</td>
			<td>2010.9</td>
			<td>3</td>
			<td>0.69</td>
			<td>10.2</td>
			<td>53701.4</td>
		</tr>
		<tr>
			<td>4</td>
			<td>69.91</td>
			<td>2.72</td>
			<td>2010.8</td>
			<td>2</td>
			<td>0.53</td>
			<td>15.9</td>
			<td>77081.2</td>
		</tr>
		<tr>
			<td>6</td>
			<td>70.32</td>
			<td>1.57</td>
			<td>2010.8</td>
			<td>6</td>
			<td>0.57</td>
			<td>12.1</td>
			<td>48057.4</td>
		</tr>
		<tr>
			<td>8</td>
			<td>69.67</td>
			<td>1.15</td>
			<td>2010.7</td>
			<td>10</td>
			<td>0.61</td>
			<td>11.3</td>
			<td>42888.0</td>
		</tr>
		<tr>
			<td>10</td>
			<td>61.39</td>
			<td>0.29</td>
			<td>2009.6</td>
			<td>10</td>
			<td>0.73</td>
			<td>8.30</td>
			<td>50786.4</td>
		</tr>
		<tr>
			<td>12</td>
			<td>56.50</td>
			<td>0.64</td>
			<td>2008.5</td>
			<td>12</td>
			<td>0.75</td>
			<td>7.1</td>
			<td>51582.9</td>
		</tr>
		<tr>
			<td>14</td>
			<td>63.31</td>
			<td>0.00</td>
			<td>2007.5</td>
			<td>11</td>
			<td></td>
			<td></td>
			<td>52126.8</td>
		</tr>
		<tr>
			<td>16</td>
			<td>51.55</td>
			<td>0.00</td>
			<td>2006.5</td>
			<td>11</td>
			<td>0.79</td>
			<td>6.9</td>
			<td>59046.6</td>
		</tr>
		<tr>
			<td>18</td>
			<td>51.69</td>
			<td>0.00</td>
			<td>2005.6</td>
			<td>10</td>
			<td>0.77</td>
			<td>7.1</td>
			<td>48384.8</td>
		</tr>
		<tr>
			<td>26</td>
			<td>44.26</td>
			<td></td>
			<td>2000.7</td>
			<td>9</td>
			<td></td>
			<td></td>
			<td>31774.7</td>
		</tr>
		<tr>
			<td>32</td>
			<td>38.25</td>
			<td></td>
			<td>1997.2</td>
			<td>9</td>
			<td>0.83</td>
			<td>8.3</td>
			<td>37128.4</td>
		</tr>
		<tr>
			<td>34</td>
			<td>41.57</td>
			<td></td>
			<td>1996.0</td>
			<td>12</td>
			<td></td>
			<td></td>
			<td>25849.4</td>
		</tr>
		<tr>
			<td>38</td>
			<td>39.11</td>
			<td></td>
			<td>1993.1</td>
			<td></td>
			<td></td>
			<td></td>
			<td>29901.6</td>
		</tr>
		<tr>
			<td>42</td>
			<td>35.18</td>
			<td></td>
			<td>1990.1</td>
			<td>10</td>
			<td>0.89</td>
			<td>8.0</td>
			<td>25730.4</td>
		</tr>
		<tr>
			<td>46</td>
			<td>38.80</td>
			<td></td>
			<td>1987.0</td>
			<td>12</td>
			<td></td>
			<td></td>
			<td>23159.6</td>
		</tr>
		<tr>
			<td>48</td>
			<td>32.58</td>
			<td></td>
			<td>1985.3</td>
			<td></td>
			<td></td>
			<td></td>
			<td>21387.0</td>
		</tr>
		<tr>
			<td>50</td>
			<td>26.71</td>
			<td></td>
			<td>1983.3</td>
			<td>9</td>
			<td>0.94</td>
			<td>5.3</td>
			<td>15331.0</td>
		</tr>
		<tr>
			<td>70</td>
			<td>17.32</td>
			<td></td>
			<td>1965.8</td>
			<td>11</td>
			<td>1.33</td>
			<td>2.2</td>
			<td></td>
		</tr>
		<tr>
			<td>90</td>
			<td>10.32</td>
			<td></td>
			<td>1945.9</td>
			<td></td>
			<td>2.04</td>
			<td>1.3</td>
			<td></td>
		</tr>
		<tr>
			<td>110</td>
			<td>5.36</td>
			<td></td>
			<td>1923.3</td>
			<td></td>
			<td>2.12</td>
			<td>1.2</td>
			<td></td>
		</tr>
		<tr>
			<td>130</td>
			<td>2.21</td>
			<td></td>
			<td>1899.1</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>140</td>
			<td>1.71</td>
			<td></td>
			<td>1888.5</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>
Table 1: Millimeter-scale Resolution Data from Core Site DSH08. Short-lived radioisotope activities, geochronology, benthic foraminiferal density, solid-phase redox sensitive metal concentrations (Mn, Re), and total aliphatic concentration records for core site DSH08 collected in December 2010, subsampled at two millimeter increments4,7,12,14.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Top Depth (mm)</td>
			<td>Excess 
			&#160;Pb-210 
			(dpm/g)</td>
			<td>Excess 
			&#160;Th-234 
			(dpm/g)&#160;</td>
			<td>Th-234 and Pb-210 Merged Age model 
			(year)</td>
			<td>Total 
			&#160;Foraminiferal 
			Density 
			(indiv./cm3)</td>
			<td>[Re] 
			&#160;(ng/g)</td>
			<td>[Mn] 
			&#160;(mg/g)</td>
			<td>Total Aliphatics 
			(ng/g)&#160;</td>
		</tr>
		<tr>
			<td>0</td>
			<td>70.70</td>
			<td>N/A</td>
			<td>2010</td>
			<td>4</td>
			<td>0.60</td>
			<td>12.4</td>
			<td>111730.1</td>
		</tr>
		<tr>
			<td>1</td>
			<td>56.89</td>
			<td></td>
			<td>2006.2</td>
			<td>11</td>
			<td>0.76</td>
			<td>7.3</td>
			<td>52385.5</td>
		</tr>
		<tr>
			<td>2</td>
			<td>44.26</td>
			<td></td>
			<td>2000.5</td>
			<td>9</td>
			<td>0.00</td>
			<td></td>
			<td>31774.7</td>
		</tr>
		<tr>
			<td>3</td>
			<td>39.65</td>
			<td></td>
			<td>1995.5</td>
			<td>12</td>
			<td>0.83</td>
			<td>8.3</td>
			<td>30959.8</td>
		</tr>
		<tr>
			<td>4</td>
			<td>35.52</td>
			<td></td>
			<td>1989.7</td>
			<td>11</td>
			<td>0.89</td>
			<td>8.0</td>
			<td>22273.3</td>
		</tr>
		<tr>
			<td>5</td>
			<td>26.71</td>
			<td></td>
			<td>1981.9</td>
			<td>9</td>
			<td>0.94</td>
			<td>5.3</td>
			<td>15331.0</td>
		</tr>
		<tr>
			<td>6</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>7</td>
			<td>17.32</td>
			<td></td>
			<td>1967.1</td>
			<td>11</td>
			<td>1.33</td>
			<td>2.2</td>
			<td></td>
		</tr>
		<tr>
			<td>8</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>9</td>
			<td>10.32</td>
			<td></td>
			<td>1945.2</td>
			<td></td>
			<td>2.04</td>
			<td>1.3</td>
			<td></td>
		</tr>
		<tr>
			<td>10</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>11</td>
			<td>5.36</td>
			<td></td>
			<td>1917.6</td>
			<td></td>
			<td>2.12</td>
			<td>1.2</td>
			<td></td>
		</tr>
		<tr>
			<td>12</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>13</td>
			<td>2.21</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>14</td>
			<td>1.71</td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>
Table 2: Centimeter-scale Resolution Data from Core Site DSH08. Short-lived radioisotope activities, geochronology, benthic foraminiferal density, solid-phase redox sensitive metal concentrations (Mn, Re), and total aliphatic concentration records for core site DSH08 collected in December 2010, integrated at one centimeter increments4,7,12,14.
<img alt="Figure 2" src="/files/ftp_upload/54363/54363fig2.jpg" /> 
Figure 2: Graphical Representation of Millimeter and Centimeter-scale Resolution Data. Short-lived radioisotope activities, age model, benthic foraminiferal density, solid-phase redox sensitive metal concentrations (Mn, Re), and total aliphatic concentration records for core site DSH08 collected in December 2010, subsampled at two millimeter increments (blue diamonds) and one-centimeter increments (red squares)4,7,11,13. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/54363/54363fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Millimeter-scale subsampling (and sedimentary conditions, see4) allowed for 234Th to be used as a chronometer on the sub-annual scale (n = 7). At the cm scale, this data would not be viable for producing a geochronology because the surface centimeter would be reduced to one measurement (n = 1). Total aliphatic concentrations increased from 36,322.3 ng/g dw (pre-DWH) to 336,922.6 ng/g dw (post-DWH) according to the mm scale records, whereas the post-DWH increase according to the centimeter-scale integrated mean was 111,730.1 ng/g dw. Total benthic foraminiferal density decreased from pre-DWH (mean = 11 indiv./cm3) to post-DWH (mean = 1 indiv./cm3) at the mm scale (n = 17) and from pre-DWH (mean = 10 indiv./cm3) to post-DWH (mean = 4 indiv./cm3) at the cm scale (n = 7). The subtle increase in rhenium in the surficial 2 mm, which is indicative of reducing conditions, would also not be resolved at centimeter resolution.

Watch this Scientific Journal Video about Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod at JoVE.com

Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod

An extrusion method using a calibrated threaded-rod is presented, which allows for mm scale subsampling of aquatic sediment cores. Millimeter-scale sampling is necessary to fully characterize recent event stratigraphy in sediment records.

Aquatic sediment core subsampling is commonly performed at cm or half-cm resolution. Depending on the sedimentation rate and depositional environment, ...

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11.2K Views.  University of South Florida. An extrusion method using a calibrated threaded-rod is presented, which allows for mm scale subsampling of aquatic sediment cores. Millimeter-scale sampling is necessary to fully characterize recent event stratigraphy in sediment records.

Video: Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod

Laboratory-determined Phosphorus Flux from Lake Sediments as a Measure of Internal Phosphorus Loading

Eutrophication is a water quality issue in lakes worldwide, and there is a critical need to identify and control nutrient sources. Internal phosphorus (P) loading from lake sediments can account for a substantial portion of the total P load in eutrophic, and some mesotrophic, lakes. Laboratory determination of P release rates from sediment cores is one approach for determining the role of internal P loading and guiding management decisions. Two principal alternatives to experimental determination of sediment P release exist for estimating internal load: in situ measurements of changes in hypolimnetic P over time and P mass balance. The experimental approach using laboratory-based sediment incubations to quantify internal P load is a direct method, making it a valuable tool for lake management and restoration.
Laboratory incubations of sediment cores can help determine the relative importance of internal vs. external P loads, as well as be used to answer a variety of lake management and research questions. We illustrate the use of sediment core incubations to assess the effectiveness of an aluminum sulfate (alum) treatment for reducing sediment P release. Other research questions that can be investigated using this approach include the effects of sediment resuspension and bioturbation on P release.
The approach also has limitations. Assumptions must be made with respect to: extrapolating results from sediment cores to the entire lake; deciding over what time periods to measure nutrient release; and addressing possible core tube artifacts. A comprehensive dissolved oxygen monitoring strategy to assess temporal and spatial redox status in the lake provides greater confidence in annual P loads estimated from sediment core incubations.

Lake eutrophication is a water quality issue worldwide, making the need to identify and control nutrient sources critical. Laboratory determination of phosphorus release rates from sediment cores is a valuable approach for determining the role of internal phosphorus loading and guiding management decisions.

Eutrophication is a water quality issue in lakes worldwide, and there is a critical need to identify and control nutrient sources. Internal phosphorus (P) ...

Environment

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.

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 Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations

The measurement of sediment-water exchange of gases and solutes in aquatic sediments provides data valuable for understanding the role of sediments in nutrient and gas cycles. After cores with intact sediment-water interfaces are collected, they are submerged in incubation tanks and kept under aerobic conditions at in situ temperatures. To initiate a time course of overlying water chemistry, cores are sealed without bubbles using a top cap with a suspended stirrer. Time courses of 4-7 sample points are used to determine the rate of sediment water exchange. Artificial illumination simulates day-time conditions for shallow photosynthetic sediments, and in conjunction with dark incubations can provide net exchanges on a daily basis. The net measurement of N2 is made possible by sampling a time course of dissolved gas concentrations, with high precision mass spectrometric analysis of N2:Ar ratios providing a means to measure N2 concentrations. We have successfully applied this approach to lakes, reservoirs, estuaries, wetlands and storm water ponds, and with care, this approach provides valuable information on biogeochemical balances in aquatic ecosystems.

The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations

Here, we present small core incubations for the measurement of sediment-water gas and solute exchange. These will provide reliable measurements of sediment-water exchange that assess the role of sediment in influencing biological and biogeochemical processes in aquatic ecosystems.

The measurement of sediment-water exchange of gases and solutes in aquatic sediments provides data valuable for understanding the role of sediments in ...

Soil Lysimeter Excavation for Coupled Hydrological, Geochemical, and Microbiological Investigations

Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled Earth-system processes. Such knowledge is imperative in improving predictions of hydro-biogeochemical cycles, especially under climate change scenarios. We present an experimental method, designed to capture sub-surface heterogeneity of an initially homogeneous soil system. This method is based on destructive sampling of a soil lysimeter designed to simulate a small-scale hillslope. A weighing lysimeter of one cubic meter capacity was divided into sections (voxels) and was excavated layer-by-layer, with sub samples being collected from each voxel. The excavation procedure was aimed at detecting the incipient heterogeneity of the system by focusing on the spatial assessment of hydrological, geochemical, and microbiological properties of the soil. Representative results of a few physicochemical variables tested show the development of heterogeneity. Additional work to test interactions between hydrological, geochemical, and microbiological signatures is planned to interpret the observed patterns. Our study also demonstrates the possibility of carrying out similar excavations in order to observe and quantify different aspects of soil-development under varying environmental conditions and scale.

This study presents an excavation method for investigating subsurface hydrological, geochemical, and microbiological heterogeneity of a soil lysimeter. The lysimeter simulates an artificial hillslope which was initially under homogeneous condition and had been subjected to approximately 5,000 mm of water over eight cycles of irrigation in an 18-month period.

Studying co-evolution of hydrological and biogeochemical processes in the subsurface of natural landscapes can enhance the understanding of coupled ...

Resurrection of Dormant Daphnia magna: Protocol and Applications

Long-term studies enable the identification of eco-evolutionary processes that occur over extended time periods. In addition, they provide key empirical data that may be used in predictive modelling to forecast evolutionary responses of natural ecosystems to future environmental changes. However, excluding a few exceptional cases, long-term studies are scarce because of logistic difficulties associated with accessing temporal samples. Temporal dynamics are frequently studied in the laboratory or in controlled mesocosm experiments with exceptional studies that reconstruct the evolution of natural populations in the wild.
Here, a standard operating procedure (SOP) is provided to revive or resurrect dormant Daphnia magna, a widespread zooplankton keystone species in aquatic ecosystems, to dramatically advance the state-of-the-art longitudinal data collection in natural systems. The field of Resurrection Ecology was defined in 1999 by Kerfoot and co-workers, even though the first attempts at hatching diapausing zooplankton eggs date back to the late 1980s. Since Kerfoot&#39;s seminal paper, the methodology of resurrecting zooplankton species has been increasingly frequently applied, though propagated among laboratories only via direct knowledge transfer. Here, an SOP is described that provides a step-by-step protocol on the practice of resurrecting dormant Daphnia magna eggs.
Two key studies are provided in which the fitness response of resurrected Daphnia magna populations to warming is measured, capitalizing on the ability to study historical and modern populations in the same settings. Finally, the application of next generation sequencing technologies to revived or still dormant stages is discussed. These technologies provide unprecedented power in dissecting the processes and mechanisms of evolution if applied to populations that have experienced changes in selection pressure over time.

Resurrection of Dormant Daphnia magna: Protocol and Applications

Long-term studies are essential to understanding the process of evolution and the mechanisms of adaptation. Generally, these studies require commitments beyond the life-time of researchers. Here, a powerful method is described that dramatically advances state-of-the-art data collection to generate longitudinal data in natural systems.

Long-term studies enable the identification of eco-evolutionary processes that occur over extended time periods. In addition, they provide key empirical ...

Stress Distribution During Cold Compression of Rocks and Mineral Aggregates Using Synchrotron-based X-Ray Diffraction

We report detailed procedures for performing compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus (D-DIA) coupled with synchrotron X-radiation. A cube-shaped sample assembly is prepared and compressed, at room temperature, by a set of four X-ray transparent sintered diamond anvils and two tungsten carbide anvils, in the lateral and the vertical planes, respectively. All six anvils are housed within a 250-ton hydraulic press and driven inward simultaneously by two wedged guide blocks. A horizontal energy dispersive X-ray beam is projected through and diffracted by the sample assembly. The beam is commonly in the mode of either white or monochromatic X-ray. In the case of white X-ray, the diffracted X-rays are detected by a solid-state detector array that collects the resulting energy dispersive diffraction pattern. In the case of monochromatic X-ray, the diffracted pattern is recorded using a two-dimensional (2-D) detector, such as an imaging plate or a charge-coupled device (CCD) detector. The 2-D diffraction patterns are analyzed to derive lattice spacings. The elastic strains of the sample are derived from the atomic lattice spacing within grains. The stress is then calculated using the predetermined elastic modulus and the elastic strain. Furthermore, the stress distribution in two-dimensions allow for understanding how stress is distributed in different orientations. In addition, a scintillator in the X-ray path yields a visible light image of the sample environment, which allows for the precise measurement of sample length changes during the experiment, yielding a direct measurement of volume strain on the sample. This type of experiment can quantify the stress distribution within geomaterials, which can ultimately shed light on the mechanism responsible for compaction. Such knowledge has the potential to significantly improve our understanding of key processes in rock mechanics, geotechnical engineering, mineral physics, and material science applications where compactive processes are important.

We report detailed procedures for compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus coupled with synchrotron X-radiation. Such experiments allow quantification of the stress distribution within samples, that ultimately sheds light on compaction processes in geomaterials.

We report detailed procedures for performing compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus (D-DIA) ...

Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors

Denitrification is the primary biogeochemical process removing reactive nitrogen from the biosphere. The quantitative evaluation of this process has become particularly relevant for assessing the anthropogenic-altered global nitrogen cycle and the emission of greenhouse gases (i.e., N2O). Several methods are available for measuring denitrification, but none of them are completely satisfactory. Problems with existing methods include their insufficient sensitivity, and the need to modify the substrate levels or alter the physical configuration of the process using disturbed samples.This work describes a method for estimating sediment denitrification rates that combines coring, acetylene inhibition, and microsensor measurements of the accumulated N2O. The main advantages of this method are a low disturbance of the sediment structure and the collection of a continuous record of N2O accumulation; these enable estimates of reliable denitrification rates with minimum values up to 0.4-1 &#181;mol N2O m-2 h-1. The ability to manipulate key factors is an additional advantage for obtaining experimental insights. The protocol describes procedures for collecting the cores, calibrating the sensors, performing the acetylene inhibition, measuring the N2O accumulation, and calculating the denitrification rate. The method is appropriate for estimating denitrification rates in any aquatic system with retrievable sediment cores. If the N2O concentration is above the detection limit of the sensor, the acetylene inhibition step can be omitted to estimate the N2O emission instead of denitrification. We show how to estimate both actual and potential denitrification rates by increasing nitrate availability as well as the temperature dependence of the process. We illustrate the procedure using mountain lake sediments and discuss the advantages and weaknesses of the technique compared to other methods. This method can be modified for particular purposes; for instance, it can be combined with 15N tracers to assess nitrification and denitrification or field in situ measurements of denitrification rates.

Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors

This method estimates sediment denitrification rates in sediment cores using the acetylene inhibition technique and microsensor measurements of the accumulated N2O. The protocol describes procedures for collecting the cores, calibrating the sensors, performing the acetylene inhibition, measuring the N2O accumulation, and calculating the denitrification rate.

Denitrification is the primary biogeochemical process removing reactive nitrogen from the biosphere. The quantitative evaluation of this process has ...

Isolation of Quartz Grains for Optically Stimulated Luminescence (OSL) Dating of Quaternary Sediments for Paleoenvironmental Research

Optically stimulated luminescence (OSL) dating quantifies the time since mineral grains were deposited and shielded from additional light or heat exposure, which effectively resets the luminescence clock. The systematics of OSL dating is based on the dosimetric properties of common minerals, like quartz and feldspar. The acquired luminescence with exposure to natural ionizing radiation after burial provides a depositional age for many Quaternary sedimentary systems, spanning the past 0.5 Ma. This contribution details the procedures for separating pure quartz grains of a known range of particle sizes to facilitate luminescence analysis with small or single grain aliquots. Specifically, protocols are given for the needed data and interpretations for effective OSL dating of terrestrial sediment cores or sample tubes from exposures. These cores, 5-20 m long in 1.2 m sections, are split lengthwise and crown-cut leaving 80% of core volume undisturbed, which facilitates sampling of light-protected sediment for OSL dating deep within the core. Sediment samples are then subjected to a series of physical separations to obtain a certain grain-size interval (e.g., 150-250 &#181;m). Magnetic minerals are removed in wet and dry states using magnets. A series of chemical digestions starts with soaking in H2O2 to remove organic matter, followed by HCl exposure to remove carbonate minerals, followed by density separation. Subsequently, grains are soaked in HF for 80 min and after in HCl to render solely quartz grains. The mineralogic purity (&#62;99%) of the quartz extract is quantified with grain petrographic assessment and Raman spectroscopy. Repeating this quartz isolation procedure may be necessary with sediment that contains &#60;15% quartz grains. Excitation of the purified quartz grains by LED-derived blue and IR light allows calculations of the fast and IR depletion ratios, which are metrics to assess the dominance of luminescence emissions from quartz.

Isolation of Quartz Grains for Optically Stimulated Luminescence OSL Dating of Quaternary Sediments for Paleoenvironmental Research

This protocol is for the isolation of quartz grains by size for luminescence dating of sediments. Outlined are physical cleansing and chemical digestions by soaking sequentially in H2O2, HCl, HF, and HCl again to isolate quartz grains. The quartz purity is quantified with microscopic assessment, Raman spectroscopy, and IR depletion ratio.

Optically stimulated luminescence (OSL) dating quantifies the time since mineral grains were deposited and shielded from additional light or heat ...

Advanced Workflow for Taking High-Quality Increment Cores - New Techniques and Devices

In dendroecological research, precise dating of each single growth ring is a basic requirement for all studies, focusing on ring-width variations only, chemical or isotope analyses, or wood anatomical studies. Independent of the sampling strategy for a certain study (e.g., climatology, geomorphology), the way samples are taken is crucial for their successful preparation and analyses.
Until recently, it was sufficient to use a (more or less) sharp increment corer to obtain core samples that could be sanded for further analyses. Since wood anatomical characteristics can be applied to long time series, the need to obtain high-quality increment cores has taken on a new meaning. Essentially, the corer needs to be sharp(ened) when used. When coring a tree by hand, there are some problems in handling the corer, resulting in the hidden occurrence of micro cracks along the entire core: When starting to drill by hand, the drill bit is strongly pressed against the bark and the outermost ring until the thread has fully entered the trunk. At the same time, the drill bit is moved up and down as well as sideward. Then, the corer is drilled all the way into the trunk; however, it is necessary to stop after each turn, change the grip, and turn again. All these movements, as well as the start/stop-coring, puts mechanical stress on the core. The resulting micro cracks make it impossible to create continuous micro sections, as they fall apart along all these cracks.
We present a protocol to overcome these obstacles by applying a new technique using a cordless drill to minimize these problems when coring a tree, as well as its effect on the preparation of long micro sections. This protocol includes the preparation of long micro sections, as well as a procedure to sharpen corers in the field.

Here, we present a protocol on how to avoid micro cracks in increment cores by applying a cordless drill with a torque multiplier to minimize problems when coring trees, as well as its effect on preparing long micro sections. This protocol also includes a procedure to sharpen corers in the field.

In dendroecological research, precise dating of each single growth ring is a basic requirement for all studies, focusing on ring-width variations only, ...

Protocol for Field to Lab Tree Ring Digitization in Dendroecological Studies

A New Workflow for Sampling and Digitizing Increment Cores

Here we present a new workflow from taking increment cores in the field, storing and transporting them to the lab, to digitizing their tree rings for further analyses for subsequent dendroecological analyses. The procedure involves the use of new sample carriers for increment cores. These new G&#228;rtner Schneider Core (GSC) holders are designed using three-dimensional (3D) modeling software and finally printed with a 3D printer. Using these mounts from the beginning in the field, the cores can directly be cut with a core microtome, and their surface can then be digitized without further rearrangement using a new high-resolution image-capturing system. They are thus available for direct analysis. This system allows digitizing tree rings from cores and disks, and also taking images from long micro sections (up to 40 cm) using transmitted light. This feature is of special interest for dendroecological and geomorphic applications to identify the onset of any disturbance in micro sections cut with a core-microtome.

Author Spotlight: Innovative Device Development for Advancing Dendroecology and Wood Anatomy Research

We present a protocol to use 3D-printed mounts to fix increment cores in the field without the necessity of unpacking and gluing them on wooden mounts. The new GSC holder allows placing the cores in a core microtome to cut their surface and directly transfer them to digital image capturing.

Here we present a new workflow from taking increment cores in the field, storing and transporting them to the lab, to digitizing their tree rings for ...

Sediment Core Extrusion Method at Millimeter Resolution Using a Calibrated, Threaded-rod

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Isolation of Quartz Grains for Optically Stimulated Luminescence (OSL) Dating of Quaternary Sediments for Paleoenvironmental Research

Advanced Workflow for Taking High-Quality Increment Cores - New Techniques and Devices

A New Workflow for Sampling and Digitizing Increment Cores