Page Comparison

I. Pre-Expedition

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On cruises with short transit times, perform, in port, as many of these the following as possible.:

Lab orientation/Introduction

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• • Alkalinity/pH/chloride titrations
    • Alkalinity: Prepare 20 mM and 40 mM standards if necessary 
    • Chlorinity: Prepare 2 liters of dilution solution
  • Coulometer
    • HCl solution, KOH and AgNO3 solutions if needed
  • IC 
    • all solutions except for anion eluent, which should be made shortly before analysis
    • pourable calibration standards
  • ICP
    • 2% and 3% TM nitric acid solutions, also 10% if doing analyzing hard rock
    • internal standard(s)
    • primary in-house cocktail
    • pourable in-house and IAPSO calibration standards
  • SPEC
    • Ammonium
      • Ammonium standard and (dry ammonium chloride in oven overnight) + calibration standards,
      • alkaline solution
    • Phosphate 
      • Phosphate primary standard (dry monobasic potassium phosphate in oven overnight) + calibration standards
      • Sulfuric acid solution
      • Antimony potassium tartrate solution
      • Ammonium molybdate solution

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• • • Obtain the IW sampling interval from the Curator and take the sample(s) when the core comes on deck.
    • If possible, have the geochemist assist you in determining where to take the IW sample. Never take a sample that includes a change in lithology.
    • Initially, 5 cm whole rounds are taken; as the water yield decreases, go to 10 cm whole rounds. Larger whole rounds may be taken after speaking to the SAC (Curator, EPM, and co-chiefs).
    • If possible, take the IW sample from the bottom of the same section every time. As recovery decreases you will have to take the IW sample from wherever you can.
    • A typical IW sampling plan is for 0 – 100 mbsf, take one IW per core and > 100 mbsf, take one IW every third core. Check with the Curator on the current plan.
    • Note the core, section and interval of the sample and write it on the Curator's logsheet. The interval will be entered into SampleMaster by the Curator/ALO.

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• • • Take a 5 cc headspace sample from every sediment core (non-basement), at the top of a section (try to be consistent). This sample is taken until the total depth objective is met. If doing multiple holes, you do not have to repeat the sampling if a headspace sample has already been taken at that depth but just continue after the prior hole's bottom depth.
    • For cores with IW samples, always take the headspace sample adjacent to IW, best from the top of the section immediately below the IW sample. Note the core, section and interval of the headspace sample and write it on the headspace vial. The interval will be entered into SampleMaster by the Curator/ALO.
    • Make sure nobody sprays acetone on the catwalk before sampling is completed. Acetone will contaminate the sample.
    • It is recommended to occasionally take a sample of the air on the core deck, so that any change in the headspace sample analysis can be correlated to changes in volatilized acetone.
    • Inject a standard (corresponding to concentrations seen in the recent cores) every fifty injections or so, to check on the instrument calibration.

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• • • Set the pressure to 3000 lbs and simultaneously push and hold both green (CLOSE) buttons on the hydraulic unit's base until the auto-pressure engages.
    • After the first drops flow from the hole in the squeezer's base plate, insert the syringe into the hole. Keep an eye on the syringe to make sure the pressure doesn't push out the syringe or plunger (especially for the first few cores). Keep incrementing the hydraulic unit pressure in steps of 1000 lbs until 10000 lbs; after 10000 lbs, increase in steps of 2000. Do not ever increase the pressure above 30000 lbs.
    • Select the correct core, section and sample in SampleMaster. Upload the IW sample splits (using the Excel template) into SampleMaster and distribute the labels.
    • When porewater yield is sufficient/no more water is trickling, release the hydraulic unit pressure by pressing the red OPEN button and remove the syringe from the squeezer.
    • Start sample distribution (splits).

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• • • Alkalinity/pH - If there is ample water, allocate 5 mL for shipboard analyses (alkalinity, salinity, IC, SPEC). Speak with the scientists about which analyses they would or wouldn't like performed (ie. Make a priority list). Extra water may be used for repeat analysis or stored (sent back to the repository).
    • Scientific party - split and store the remaining water into the requested aliquots as outlined by the sampling plan. Each sample's storage/preservation is up to its requestor.
    • ICP – 1 - 2 ml; must be acidified with trace metal-grade nitric acid (~ 30 10 µL).
    • Remove the plunger from the syringe, rinse with DI water and place in the HCl bath for twelve hours. Rinse the components with DI water and bake dry at a low temperature. When completely dry, reassemble syringes and store them in ziploc bags.

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Crushing, weighing and running carbonate samples require a significant portion of time. During the initial discussion of the sampling protocol the scientists will decide where they want to take the sample(s) for the carbonate/EA analyses. It can be taken from the IW squeezecake and/or at the sample table after the core is split. Either way, these samples will have to be freeze-dried (typically for twelve hours) and then crushed/homogenized using a mortar and pestle. Usually the scientists will prepare and run the analyses, and the technician will set up the system and both scientists and technicians will weigh and run the analysis.

CHNS

Again, weighing and running the samples on this instrument is time-intensive and it be best to have a good sized batch ready before running. Usually the scientists will weigh out the samples and the technician will set up the instrument and sequencessystem and both scientists and technicians will weigh and run the analysis. Replace the combustion column after approximately 100 samples.

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