This study was financially supported by Experimental Technology Innovation Foundation of Institute of Geology and Geophysics, Chinese Academy of Sciences (No. 11890940), and China Ocean Mineral Resources R &#38; D Association Project (No. DY135-S2-2-07).

1. Preparing the sample, reagents, and containers
<ol>
	<li>Clean the fume hood, hotplate and the balance room bench for the chemical experiment with sprayed alcohol or ultrapure water.</li>
	<li>Prepare sub-boiled acids (2 M HCl, 8 M HCl, 7 M HNO3, and 14 M HNO3), clean beakers and any apparatus before sample processed. 
	NOTE: Sulfide samples presented in this study were collected from newly discovered hydrothermal zones in the South Atlantic. Approximately 60 mg of powdered sample was used in this process. Sample was collected into glass vials and put in the sample storage cabinet.</li>
</ol>
2. Weigh the samples
<ol>
	<li>Prepare cleaned 30 mL perfluoroalkoxy (PFA) beakers. Label twice outside the beaker (to prevent erasure).</li>
	<li>Weigh the blank beakers. 
	NOTE: The balance used is accurate to &#177;0.0001 g provided that all the vessels have had their static electricity completely removed.</li>
	<li>Read the weight and record it.</li>
	<li>Pour the sample into the beaker. Cover with a lid and weigh the samples. 
	NOTE: Sample weight depends on the 230Th content. 230Th level varies with the U concentration and age of the sample. In general, a total of 100 ng of total U is sufficient for the sample.</li>
	<li>Add some (~1 mL) ultrapure water using a bottle, rinse the inner wall and shake the beaker carefully. 
	NOTE: Add enough ultrapure water cover all the samples.</li>
</ol>
3. Dissolve and spike the sample
<ol>
	<li>Place the sample-containing beaker in the fume hood.</li>
	<li>Open the beaker lid. Add 3 mL of HNO3 (14 M) or aqua regia into the sample using a pipette.</li>
	<li>Place the beaker on the hotplate, set the hotplate temperature to 170 &#176;C and dissolve the sample completely. 
	NOTE: If there are still insoluble substances in the solution, add 12 M HCl, 22.6 M HF and 10.6 M HClO4, and use a pressurized closed tank to ensure complete dissolution of samples.</li>
	<li>Leave the solution to cool for at least 30 min. Add 0.1&#8211;0.3 g 229Th-233U-236U spike solution of known activity into the solution. 
	NOTE: Generally, the optimal ratio of 235U/233U is ~10&#8211;20:1 in the mixed solution.</li>
	<li>Place the solution onto the hotplate, set the temperature to 170 &#176;C and leave it on the hotplate until it dries. 
	NOTE: Evaporation must be done slowly when the sample approaches dryness.</li>
	<li>Dissolve the sample in 2 drops of HNO3 (0.04 mL, 14 M), and dry it on the hotplate at 170 &#176;C again.</li>
</ol>
4. Ferric hydroxide co-precipitation for U-Th
<ol>
	<li>Prepare cleaned 15 mL centrifuge tubes, label and place them in the tube stand. 
	NOTE: Add approximately 10 mg of Fe(III) (FeCl3 in 12 M HCl) into the centrifugal tube carefully if samples contain almost no Fe.</li>
	<li>Add several drops (0.1 mL) of 2 M HCl into the beaker. Shake the beaker gently and dissolve the sample completely.</li>
	<li>Transfer each sample into a centrifuge tube.</li>
	<li>Add several drops of ammonia (~0.1 mL) until the acid is neutralized; when pH is 7&#8211;8, a reddish-brown precipitate appears. U and Th isotopes are precipitated by the Fe(OH)3. 
	NOTE: The clear solution contains unwanted ions such as metal-elements, Mg2+, NO3- and NH4OH.</li>
	<li>Cap the centrifuge tubes. Centrifuge at 2,340 x g for 7 min. Discard the supernatant</li>
	<li>Add some ultrapure water to wash the precipitate. Centrifuge as above and repeat this step twice more.</li>
	<li>Dissolve the precipitate with 1.5 mL of 7 M HNO3. Transfer it into the corresponding beaker.</li>
	<li>Add 1 drop of HClO4 (to remove organic matter), and dry it on the hotplate at 170 &#176;C for about 30 min.</li>
</ol>
5. Preparation of anion exchange column
<ol>
	<li>Prepare small polytetrafluoroethylene (PTFE) columns (~2.5 mL column size) as shown in Figure 1; insert the frit into each column slowly at the bottom on the bench.</li>
	<li>Pipet cleaned anion-exchange resins into the columns. Put the columns on the holder.</li>
	<li>Fill the whole column with ultrapure water. Add 1 drop of 14 M HNO3. 
	NOTE: This step is performed in order mainly to remove the trace elements in the column.</li>
	<li>Add 2 column volumes (CV) of 7 M HNO3 to remove the trace elements. Then repeat this step.</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/59098/59098fig1.jpg" /> 
Figure 1: Ion-exchange column filling with anionic exchange resin. <a href="https://www.jove.com/files/ftp_upload/59098/59098fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
6. Purification and separation of U and Th fractions
<ol>
	<li>Dissolve the sample in 0.5 mL of 7 M HNO3. Load it onto the column carefully.</li>
	<li>Let it drip across the column into the waste beaker.</li>
	<li>Add 2 CV and 1 CV of 7 M HNO3 successively into the column. Iron and other metal-elements in the sample are removed while U and Th are retained by the resin in this step.</li>
	<li>Add 2 CV and 1 CV of 8 M HCl into the column successively to elute thorium fraction. Collect the thorium fraction using a 7 mL capacity cleaned PFA beaker. Add 1 drop of HClO4 into the beaker and dry the fraction on a hotplate at 170 &#176;C for about 30 min.</li>
	<li>Elute uranium fraction from the resin with 2 CV of 0.1 M HNO3 twice. Collect the eluate in the cleaned PFA beaker. Add 1 drop of HClO4 and dry it on the hotplate at 170 &#176;C for about 30 min.</li>
	<li>Prepare and label 2 mL capacity vials.</li>
	<li>Dissolve each sample in 1 drop HNO3 and dry it on the hotplate at 170 &#176;C for less than 5 min until 0.5 drop is left. Transfer them along with 0.2 mL of 2% HNO3 + 0.1% HF into the corresponding vials for instrument measurement.</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/59098/59098fig2.jpg" /> 
Figure 2: Uranium and thorium fractions of the submarine hydrothermal sulfides. <a href="https://www.jove.com/files/ftp_upload/59098/59098fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
7. MC-ICPMS measurement
<ol>
	<li>Measure the U and Th fractions collected through the above chemical purification process using a high-resolution MC-ICPMS instrument. 
	NOTE: U and Th isotopic ratios can be obtained by using the instrument by applying secondary electron multiplier (SEM)21 technique. The instrument parameters13 are listed in Table 1. Thorium age was calculated using the following equation: 
	<img alt="Equation 1" src="/files/ftp_upload/59098/59098eq1.jpg" /> 
	Initial ratio of 234U to 238U was measured as follows: 
	<img alt="Equation 2" src="/files/ftp_upload/59098/59098eq2.jpg" /></li>
</ol>

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Instrument</td>
			<td>Parameter</td>
			<td>Value</td>
		</tr>
		<tr>
			<td rowspan="5">MC-ICPMS</td>
			<td>RF power</td>
			<td>1325 W</td>
		</tr>
		<tr>
			<td>Cool gas</td>
			<td>16.00 L min-1</td>
		</tr>
		<tr>
			<td>Auxiliary gas</td>
			<td>1.78 L min-1</td>
		</tr>
		<tr>
			<td>Sample gas</td>
			<td>1.00 L min-1</td>
		</tr>
		<tr>
			<td>Low resolution</td>
			<td>300~400</td>
		</tr>
		<tr>
			<td rowspan="5">CETAC Aridus II</td>
			<td>Sample injection rate</td>
			<td>50~60 &#956;L min-1</td>
		</tr>
		<tr>
			<td>Ar Sweep Gas</td>
			<td>2~5 L min-1</td>
		</tr>
		<tr>
			<td>Nitrogen Gas</td>
			<td>2~10 mL min-1</td>
		</tr>
		<tr>
			<td>Spray Chamber Temperature</td>
			<td>110 &#176;C</td>
		</tr>
		<tr>
			<td>Membrane Oven Temperature</td>
			<td>160 &#176;C</td>
		</tr>
	</tbody>
</table>
Table 1: Instrument parameters for measuring U-Th isotopes by MC-ICPMS (using the instrument listed in the Table of Materials).

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L., Brichet, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Actinide-series+disequilibrium+as+a+tool+to+establish+the+chronology+of+deep-sea+hydrothermal+activity.">Actinide-series disequilibrium as a tool to establish the chronology of deep-sea hydrothermal activity.</a> Geochimica et Cosmochimica Acta. 57 (6), 1221-1231 (1993).</li><li>Lalou, 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=New+age+data+for+Mid-Atlantic+Ridge+hydrothermal+sites:+TAG+and+Snakepit+chronology+revisited.">New age data for Mid-Atlantic Ridge hydrothermal sites: TAG and Snakepit chronology revisited.</a> Journal of Geophysical Research. 98, 9705-9713 (1993).</li><li>Lalou, C., Reyss, J. L., Brichet, E., Rona, P. 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L., Chen, J. H., Ku, T. -. L., Wasserburg, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precise+timing+of+the+last+interglacial+period+from+mass+spectrometric+analysis+of+230Th+in+corals.">Precise timing of the last interglacial period from mass spectrometric analysis of 230Th in corals.</a> Science. 236 (4808), 1537-1553 (1987).</li><li>Edwards, R. L., Taylor, F. W., Wasserburg, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dating+earthquakes+with+high+precision+thorium-230+ages+of+very+young+corals+[J].">Dating earthquakes with high precision thorium-230 ages of very young corals [J].</a> Earth and Planetary Science Letters. 90 (4), 371-381 (1988).</li><li>Hai, C., Jess, A., Edwards, R. L., Boyle, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=U-Th+dating+of+deep-sea+corals.">U-Th dating of deep-sea corals.</a> Geochimica et Cosmochimica Acta. 64 (14), 2401-2416 (2000).</li><li>Ishibashi, J., 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=Dating+of+Hydrothermal+Mineralization+in+Active+Hydrothermal+Fields+in+the+Southern+Mariana+Trough.">Dating of Hydrothermal Mineralization in Active Hydrothermal Fields in the Southern Mariana Trough.</a> Subseafloor Biosphere Linked to Hydrothermal Systems. , 289-300 (2015).</li><li>Jaffey, A. H., Flynn, K. F., Glendenin, L. E., Bentley, W. C., Essling, A. 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Authors have nothing to disclose.

Some critical steps must be followed to ensure success of this protocol. Ensure that all operations are carried out in clean chemistry room under fume hood with clean air circulation. Purify all regents in this process in advance and clean the apparatus before use. Dissolve the samples completely in the process of making the 7 M HNO3 solution which is then loaded onto the 7 M HNO3-conditioned resins. If there is any insoluble substance in the sample, it will be redissolved after drying. Additional i...

Submarine hydrothermal sulfides have been a steady source of metals like iron, copper, zinc and lead. They are also seen as economically viable resources of silver and gold. The location and size of the deposits are a record of the history of hydrothermal venting on the seafloor. Dating of a hydrothermal sulfide can provide important information regarding the formation and alteration mechanism of the sulfide ore deposit, seafloor hydrothermal activity history, and growth rate of large sulfide deposits1,2,3. 238U-234U-230Th disequilibrium dating is an effective isotopic method of age estimation for hydrothermal sulfides4,5,6,7,8,9,10,11,12, where the purification and separation of U and Th isotopes is necessary. This text describes a protocol for U and Th isotopes separation and 230Th-U dating of sulfides sample by MC-ICPMS.
Geological materials which contain U and Th remain undisturbed for several million years, and a state of secular equilibrium between all the nuclides in the radioactive series is established. However, a combination of chemical solubility and nuclear recoil factors often create disequilibrium, in which the members of the decay series are separated from each other through processes such as deposition, transport and weathering. For example, when a sulfide deposit is formed, the state of 238U, 234U and 230Th is of disequilibrium, and the long-lived 238U can decay gradually towards short-lived 234U and 230Th subsequently. Assuming (i) the system remains closed with respect to U and Th isotopes, and (ii) initial amount of 230Th and 232Th incorporated into sulfide samples is zero, it is possible to determine the time of deposition by measuring the present-day activity ratios of 230Th/238U and 234U/238U. However, the initial amount of Th is not zero in the sample, and we assume the initial 230Th/232Th atomic ratio is 4.4 &#177; 2.2 x 10-6. The applicable dating range of this method is approximately ~10-6 x 105 years13,14. However, the large difference between the abundance of uranium and thorium makes measurement challenging. Hence, it is very important to establish a chemical procedure for U-Th dating by MC-ICPMS.
In the past 30 years, most studies focused more measurements of carbonate materials14,15,16,17 and less on sulfide deposits11,12,18,19. Alpha-particle counting methods have traditionally been used for the study of 230Th/238U disequilibrium of submarine hydrothermal sulfides1. However, analytical uncertainty of 5-17% is a limiting factor that affects the precision of age determination of sulfides1,8,9. These techniques generally suffer from the use of relatively large columns and reagent volumes and the need for multiple column passes for purification and separation U-Th from a sample. Recent developments in MC-ICPMS have greatly improved the precision of U-Th isotopic measurements (&#60;5&#8240; for ages)14 and have significantly reduced the sample size (&#60;0.2 g) required for analysis. In these works, many chemical separation procedures have been developed, and have achieved excellent chemical yields with low chemical background12,13.
Here we present a chemical-based protocol to obtain samples that are sufficiently clean for MC-ICPMS analysis. It is suitable for the dating of hydrothermal sulfide samples of age &#60;6 x 105 years14. With this technique, the separated U and Th isotopic fractions can meet measuring requirements by MC-ICPMS. The age of the hydrothermal sulfide sample can be calculated from the extent of disequilibria between 230Th and 234U and between 234U and 238U by using the described activity decay equation.

<table><tbody><tr><td>AG 1-X8 anion-exchange resin</td><td>BIO-RAD</td><td>140-1441</td><td>Separating rare elements</td></tr><tr><td>Ammonia solution</td><td>Kanto Chemical CO., INC.</td><td>1336-21-6</td><td>Reagent</td></tr><tr><td>Glass vials</td><td>BOTEX</td><td>None</td><td>Sample collection</td></tr><tr><td>Hydrochloric acid</td><td>Sinopharem chemical reagent Co. Ltd</td><td>7647-01-0</td><td>Reagent</td></tr><tr><td>Hydrofluoric acid</td><td>EMD Millipore CO.</td><td>7664-39-5</td><td>Reagent</td></tr><tr><td>Neptune Plus</td><td>Thermo Fisher Scientific CO.</td><td>None</td><td>Apparatus</td></tr><tr><td>Nitric acid</td><td>Sinopharem chemical reagent Co. Ltd</td><td>7697-37-2</td><td>Reagent</td></tr><tr><td>Perchloric acid</td><td>Kanto Chemical CO., INC.</td><td>32059-1B</td><td>Reagent</td></tr><tr><td>Ultrapure water</td><td>Merck Millipore</td><td>None</td><td>Producted by Mill-Q Advantage systerm</td></tr><tr><td>Wipe paper</td><td>Kimberley-Clark</td><td>0123-12</td><td>Wipe and clean</td></tr><tr><td>2 ml vial</td><td>Nelgene</td><td>5000-0020</td><td>Sample collection</td></tr><tr><td>229Th-233U-236U spike</td><td>None</td><td>None</td><td>Reagent</td></tr><tr><td>7 ml PFA beaker</td><td>Savillex</td><td>200-007-20</td><td>Sample treatment</td></tr><tr><td>10 ml centrifuge</td><td>Nelgene</td><td>3110-1000</td><td>Sample treatment</td></tr><tr><td>30 ml PFA beaker</td><td>Savillex</td><td>200-007-20</td><td>Sample treatment</td></tr></tbody></table>

separation of uranium and thorium for 230th-u dating of submarine hydrothermal sulfides

The age of a submarine hydrothermal sulfide is a significant index for estimating the size of hydrothermal ore deposits. Uranium and thorium isotopes in the samples can be separated for 230Th-U dating. This article presents a method to purify and separate U and Th isotopes in submarine hydrothermal sulfide samples. Following this technique, the separated U and Th fractions can meet measuring requirements by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). The age of the hydrothermal sulfide sample can be calculated by measuring the present-day activity ratios of 230Th/238U and 234U/238U. A super clean room is necessary for this experiment. Cleaned regents and supplies are used to reduce the contamination during the sample processes. Balance, hotplate, and centrifuge are also used. The sulfide sample is powdered for analysis and less than 0.2 g sample is used. Briefly, the sample is weighed, dissolved, added to 229Th-233U-236U double spike solution, Fe co-precipitated, and separated on an anion-exchange resin extraction column. Approximately 50 ng U is consumed for 230Th-U dating of sulfides sample by MC-ICPMS.

Using this procure, a submarine hydrothermal sulfide sample can be completely dissolved. Following this protocol, the Th fraction was eluted from the hydrothermal sulfide sample using 8 M HCl. Meanwhile, the U fraction of the hydrothermal sulfide sample was eluted with 0.1 M HNO3. U and Th fractions were dissolved in the 2% HNO3 (+0.1% HF) solution (see Figure 2) and stored in 2 mL capacity vials. The mixture was then analyzed by MC-ICPMS.
<p cla...

Watch this Scientific Journal Video about Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides at JoVE.com

Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides

The protocol describes a method to purify and separate the U and Th nuclide in submarine hydrothermal sulfide sample with Fe co-precipitation and extraction chromatography for 230Th-U disequilibrium dating.

Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides

The age of a submarine hydrothermal sulfide is a significant index for estimating the size of hydrothermal ore deposits. Uranium and thorium isotopes in ...

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6.4K Views.  Chinese Academy of Sciences. Dit artikel presenteert een methode om uranium en thorium isotopen te zuiveren en te scheiden in onderzeese hydrothermale sulfide monsters. Met deze techniek kunnen uranium en thorium isotoop worden gemeten door MC-ICPMS, geschikt voor het dateren van monsters met een leeftijd van minder dan 600,000 jaar en belangrijke informatie verstrekken over sulfide ertsafzettingen, hydrothermale activiteit op de zeebodem en groeipercentages van grote sulfideafzettingen. Met deze techniek wordt minder da...

Video: Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides

Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic cavitation: the nucleation, growth, and implosive collapse of microbubbles in liquids submitted to power ultrasound. The violent implosion of bubbles leads to the formation of chemically reactive species and to the emission of light, named sonoluminescence. In this manuscript, we describe the techniques allowing study of extreme intrabubble conditions and chemical reactivity of acoustic cavitation in solutions. The analysis of sonoluminescence spectra of water sparged with noble gases provides evidence for nonequilibrium plasma formation. The photons and the "hot" particles generated by cavitation bubbles enable to excite the non-volatile species in solutions increasing their chemical reactivity. For example the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions varies with uranium concentration: sonophotoluminescence dominates in diluted solutions, and collisional excitation contributes at higher uranium concentration. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble, but then diffuse into the liquid phase and react with solution precursors to form a variety of products. For instance, the sonochemical reduction of Pt(IV) in pure water provides an innovative synthetic route for monodispersed nanoparticles of metallic platinum without any templates or capping agents. Many studies reveal the advantages of ultrasound to activate the divided solids. In general, the mechanical effects of ultrasound strongly contribute in heterogeneous systems in addition to chemical effects. In particular, the sonolysis of PuO2 powder in pure water yields stable colloids of plutonium due to both effects.

Acoustic cavitation in liquids submitted to power ultrasound creates transient extreme conditions inside the collapsing bubbles, which are the origin of unusual chemical reactivity and light emission, known as sonoluminescence. In the presence of noble gases, nonequilibrium plasma is formed. The "hot" particles and the photons generated by collapsing bubbles are able to excite species in solution.

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic ...

Removal of Trace Elements by Cupric Oxide Nanoparticles from Uranium In Situ Recovery Bleed Water and Its Effect on Cell Viability

In situ recovery (ISR) is the predominant method of uranium extraction in the United States. During ISR, uranium is leached from an ore body and extracted through ion exchange. The resultant production bleed water (PBW) contains contaminants such as arsenic and other heavy metals. Samples of PBW from an active ISR uranium facility were treated with cupric oxide nanoparticles (CuO-NPs). CuO-NP treatment of PBW reduced priority contaminants, including arsenic, selenium, uranium, and vanadium. Untreated and CuO-NP treated PBW was used as the liquid component of the cell growth media and changes in viability were determined by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay in human embryonic kidney (HEK 293) and human hepatocellular carcinoma (Hep G2) cells. CuO-NP treatment was associated with improved HEK and HEP cell viability. Limitations of this method include dilution of the PBW by growth media components and during osmolality adjustment as well as necessary pH adjustment. This method is limited in its wider context due to dilution effects and changes in the pH of the PBW which is traditionally slightly acidic&#160;however; this method could have a broader use assessing CuO-NP treatment in more neutral waters.

Removal of Trace Elements by Cupric Oxide Nanoparticles from Uranium In Situ Recovery Bleed Water and Its Effect on Cell Viability

Production bleed water (PBW) was treated with cupric oxide nanoparticles (CuO-NPs) and cellular toxicity was assessed in cultured human cells. The goal of this protocol was to integrate the native environmental sample into a cell culture format assessing the changes in toxicity due to CuO-NP treatment.

In situ recovery (ISR) is the predominant method of uranium extraction in the United States. During ISR, uranium is leached from an ore body and extracted ...

Environment

Metal-silicate Partitioning at High Pressure and Temperature: Experimental Methods and a Protocol to Suppress Highly Siderophile Element Inclusions

Estimates of the primitive upper mantle (PUM) composition reveal a depletion in many of the siderophile (iron-loving) elements, thought to result from their extraction to the core during terrestrial accretion. Experiments to investigate the partitioning of these elements between metal and silicate melts suggest that the PUM composition is best matched if metal-silicate equilibrium occurred at high pressures and temperatures, in a deep magma ocean environment. The behavior of the most highly siderophile elements (HSEs) during this process however, has remained enigmatic. Silicate run-products from HSE solubility experiments are commonly contaminated by dispersed metal inclusions that hinder the measurement of element concentrations in the melt. The resulting uncertainty over the true solubility and metal-silicate partitioning of these elements has made it difficult to predict their expected depletion in PUM. Recently, several studies have employed changes to the experimental design used for high pressure and temperature solubility experiments in order to suppress the formation of metal inclusions. The addition of Au (Re, Os, Ir, Ru experiments) or elemental Si (Pt experiments) to the sample acts to alter either the geometry or rate of sample reduction respectively, in order to avoid transient metal oversaturation of the silicate melt. This contribution outlines procedures for using the piston-cylinder and multi-anvil apparatus to conduct solubility and metal-silicate partitioning experiments respectively. A protocol is also described for the synthesis of uncontaminated run-products from HSE solubility experiments in which the oxygen fugacity is similar to that during terrestrial core-formation. Time-resolved LA-ICP-MS spectra are presented as evidence for the absence of metal-inclusions in run-products from earlier studies, and also confirm that the technique may be extended to investigate Ru. Examples are also given of how these data may be applied.

We present a procedure to determine the metal-silicate partitioning of siderophile elements, emphasizing techniques that suppress the formation of metal inclusions in experiments for the noble metals. The results of these experiments are used to demonstrate the effect of core-formation on the highly siderophile element composition of the mantle.

Estimates of the primitive upper mantle (PUM) composition reveal a depletion in many of the siderophile (iron-loving) elements, thought to result from ...

Speciation and Bioavailability Measurements of Environmental Plutonium Using Diffusion in Thin Films

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can potentially contribute to the exposure of biota and humans. The diffusive gradients in thin films technique is introduced here for in-situ measurements of Pu bioavailability and speciation. A diffusion cell constructed for laboratory experiments with Pu and the newly developed protocol make it possible to simulate the environmental behavior of Pu in model solutions of various chemical compositions. Adjustment of the oxidation states to Pu(IV) and Pu(V) described in this protocol is essential in order to investigate the complex redox chemistry of plutonium in the environment. The calibration of this technique and the results obtained in the laboratory experiments enable to develop a specific DGT device for in-situ Pu measurements in freshwaters. Accelerator-based mass-spectrometry measurements of Pu accumulated by DGTs in a karst spring allowed determining the bioavailability of Pu in a mineral freshwater environment. Application of this protocol for Pu measurements using DGT devices has a large potential to improve our understanding of the speciation and the biological transfer of Pu in aquatic ecosystems.

The technique of diffusive gradients in thin films (DGT) is proposed for speciation studies of plutonium. This protocol describes diffusion experiments probing the behavior of Pu(IV) and Pu(V) in presence of organic matter. DGTs deployed in a karstic spring allow assessment of the bioavailability of Pu.

The biological uptake of plutonium (Pu) in aquatic ecosystems is of particular concern since it is an alpha-particle emitter with long half-life which can ...

Engineering

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.

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, ...

Atom Probe Tomography Analysis of Exsolved Mineral Phases

Element diffusion rates and temperature/pressure control a range of fundamental volcanic and metamorphic processes. Such processes are often recorded in lamellae exsolved from host mineral phases. Thus, the analysis of the orientation, size, morphology, composition and spacing of exsolution lamellae is an area of active research in the geosciences. The conventional study of these lamellae has been conducted by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and more recently with focused ion beam (FIB)-based nanotomography, yet with limited chemical information. Here, we explore the use of atom probe tomography (APT) for the nanoscale analysis of ilmenite exsolution lamellae in igneous titanomagnetite from ash deposits erupted from the active Soufri&#232;re Hills Volcano (Montserrat, British West Indies). APT allows the precise calculation of interlamellar spacings (14&#8211;29 &#177; 2 nm) and reveals smooth diffusion profiles with no sharp phase boundaries during the exchange of Fe and Ti/O between the exsolved lamellae and the host crystal. Our results suggest that this novel approach permits nanoscale measurements of lamellae composition and interlamellar spacing that may provide a means to estimate the lava dome temperatures necessary to model extrusion rates and lava dome failure, both of which play a key role in volcanic hazard mitigation efforts.

Analysis of the morphology, composition, and spacing of exsolution lamellae can provide essential information to understand geological processes related to volcanism and metamorphism. We present a novel application of APT for the characterization of such lamellae and compare this approach to the conventional use of electron microscopy and FIB-based nanotomography.

Element diffusion rates and temperature/pressure control a range of fundamental volcanic and metamorphic processes. Such processes are often recorded in ...

Automated 90Sr Separation and Preconcentration in a Lab-on-Valve System at Ppq Level

A quick, automated and portable system for the separation and determination of radiostrontium in aqueous samples, using Sr-resin and multi sequential flow injection analysis, has been developed. The concentrations of radioactive strontium were determined by flow scintillation counting, allowing for on-line and also on-site determination. The proposed system can determine radioactive strontium at industrial relevant levels without further modification using overall analysis time of less than 10 min per aqueous sample. The limit of the detection is 320 fg&#183;g-1 (1.7 Bq/g).

Automated 90Sr Separation and Preconcentration in a Lab-on-Valve System at Ppq Level

Here, we present the portable autoRAD platform for quick radiometric separation and determination of 90Sr, an important fission product highly pertinent to nuclear waste.

A quick, automated and portable system for the separation and determination of radiostrontium in aqueous samples, using Sr-resin and multi sequential flow ...

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 ...

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

A methodology is described to generate an isotopically pure 229Th ion beam in the 2+ and 3+ charge states. This ion beam enables one to investigate the low-lying isomeric first excited state of 229Th at an excitation energy of about 7.8(5) eV and a radiative lifetime of up to 104 seconds. The presented method allowed for a first direct identification of the decay of the thorium isomer, laying the foundations to study its decay properties as prerequisite for an optical control of this nuclear transition. High energy 229Th ions are produced in the &#945;&#160;decay of a radioactive 233U source. The ions are thermalized in a buffer-gas stopping cell, extracted and subsequently an ion beam is formed. This ion beam is mass purified by a quadrupole-mass separator to generate a pure ion beam. In order to detect the isomeric decay, the ions are collected on the surface of a micro-channel plate detector, where electrons, as emitted in the internal conversion decay of the isomeric state, are observed.

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

We present a protocol for the generation of an isotopically purified low-energy 229Th ion beam from a 233U source. This ion beam is used for the direct detection of the 229mTh ground-state decay via the internal-conversion decay channel. We also measure the internal conversion lifetime of 229mTh as well.

A methodology is described to generate an isotopically pure 229Th ion beam in the 2+ and 3+ charge states. This ion beam enables one to investigate the ...

U2O5 Film Preparation via UO2 Deposition by Direct Current Sputtering and Successive Oxidation and Reduction with Atomic Oxygen and Atomic Hydrogen

We describe a method to produce U2O5 films in situ using the Labstation, a modular machine developed at JRC Karlsruhe. The Labstation, an essential part of the Properties of Actinides under Extreme Conditions laboratory (PAMEC), allows the preparation of films and studies of sample surfaces using surface analytical techniques such as X-ray and ultra-violet photoemission spectroscopy (XPS and UPS, respectively). All studies are made in situ, and the films, transferred under ultra-high vacuum from their preparation to an analyses chamber, are never in contact with the atmosphere. Initially, a film of UO2 is prepared by direct current (DC) sputter deposition on a gold (Au) foil then oxidized by atomic oxygen to produce a UO3 film. This latter is then reduced with atomic hydrogen to U2O5. Analyses are performed after each step involving oxidation and reduction, using high-resolution photoelectron spectroscopy to examine the oxidation state of uranium. Indeed, the oxidation and reduction times and corresponding temperature of the substrate during this process have severe effects on the resulting oxidation state of the uranium. Stopping the reduction of UO3 to U2O5 with single U(V) is quite challenging; first, uranium-oxygen systems exist in numerous intermediate phases. Second, differentiation of the oxidation states of uranium is mainly based on satellite peaks, whose intensity peaks are weak. Also, experimenters should be aware that X-ray spectroscopy (XPS) is a technique with an atomic sensitivity of 1% to 5%. Thus, it is important to obtain a complete picture of the uranium oxidation state with the entire spectra obtained on U4f, O1s, and the valence band (VB). Programs used in the Labstation include a linear transfer program developed by an outside company (see Table of Materials) as well as data acquisition and sputter source programs, both developed in-house.

U2O5 Film Preparation via UO2 Deposition by Direct Current Sputtering and Successive Oxidation and Reduction with Atomic Oxygen and Atomic Hydrogen

This protocol presents the preparation of U2O5 thin films obtained in situ under ultra-high vacuum. The process involves oxidation and reduction of UO2 films with atomic oxygen and atomic hydrogen, respectively.

We describe a method to produce U2O5 films in situ using the Labstation, a modular machine developed at JRC Karlsruhe. The Labstation, an essential part ...

Separation of Uranium and Thorium for ²³⁰Th-U Dating of Submarine Hydrothermal Sulfides

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