2018-02-18
Geochemistry and Microbiology Lab Working Group
Meeting minutes
2 February 2018
Participants: Lisa Brandt, Kara Bogus, Leah Levay, Brian Levay, Don Sims, Lorri Peters, Tobias Hoefig, Trevor Williams, Carlos Zarikian, David Houpt, Brad Julson, Paul Foster, Laurel Childress
Via Zoom: Erik Moortgat, Nicolette Lawler
Updates
1. Revision to Technical Note 28 (Microbiology workshop)
· Kara and Jason met during AGU to work on the new outline
· Sections have been assigned to specific people to write
· Draft anticipated early March 2018; additional data/figures may roll in from external contributers after, but the goal is to have a document for reference before Brothers Arc
· Kara and Jason to meet 9 February to work on draft
ACTION: Meet deadline for complete draft
2. EDS trial update
· Tobias provided an update about trying out EDS systems. Three systems were trialled: two that would hook to the current onboard SEM and one that is an integrated benchtop SEM/EDS.
· Favored option would seem to be the Bruker EDS that would connect with our current SEM
ACTION: Tobias to write up results of the test, and distribute to LWG as well as to management group
3. Igpet Rockware plotting software
· Tobias gave an introduction to the software, which would make it easier to generate plots of different descriptive or chemical information
ACTION: Tobias to enquire about possible trial of the software
Discussion points
1. Exp 371 cruise evaluations
· It was excellent. Staff helped us kindly. Experimental components were provided well. Although software of weighing machine was often lagging and down, it was nice equipment. we got the nice data and could see the data profile as soon as analysis was done.
ACTION: Cahn balance software is currently being rewritten.
· The geochemistry lab is excellent except for the newly installed ICP-OES. It will help establish better geochemistry data in the future if the ICP could be well calibrated.
ACTION: None. This has been addressed on subsequent cruises (369 and 372).
· In addition, it will improve the accuracy of pore water pH if the pH scale can be adjusted to seawater scale rather than the NBS scale.
ACTION: None, at this time. This would require significant effort and has not come up before in cruise evaluations. It has been noted as a comment, but tabled for the time being (to revisit if it comes up again).
2. Exp 369 cruise evaluations
· This was my fourth IODP leg and I really was positively surprised about the new Chem lab; very much space, good instrumentation, especially the new Agilent ICP-OES. The Techs (Vinny and Eric) are absolutely superb, always helpful, interested in what we were doing, with a very good analytical background. Despite this, I do suggest to think about changing some of the analytical procedures. In particular, the alkalinity determination requires too much sample volume (3 ml). Other (photometric) methods do exist, which allow alkalinity determination with less than 0.2 ml.
ACTION: Erik to investigate options for changing the method to use less pore water and present at the July 2018 LWG meeting.
· In part the same is true for the spectrophotometric determination of ammonia and silica; here micro titer plate techniques may be helpful.
ACTION: David to investigate and report to the LWG at the next meeting.
3. Exp 372 cruise evaluations
· The new ICP works beautifully. I worked with Aaron during the transit to develop a protocol for analysis based on the methods developed by Hans Brumsack in Exp 369, but streamlining them for routine use. Worked great. It was good to have data for silica and phosphorus, as a check for spectrophotometry data. But in general, the instrument performs very well.
· Very happy with the new Hamilton autodiluter. I think it is more accurate than pipetting; it saves time; and helps prevent carpal-tunnel that is so common in techs that do a lot of repeated pipetting.
· Sulfate blank in the IC. When running samples where sulfate should be depleted, the IC data always gives a low reading, in Exp 372 it was ~0.85 mM. The same samples ran in the ICP give the expected value of zero, and both data sets agree when 0.85 is subtracted from all the readings in the IC. I have seen that problem in other legs and in other labs that use this brand of IC. Not sure how to solve it, but this should be looked at and at the very least always double check with the ICP.
ACTION: Lisa B. and Aaron to look into this on X375. It is a known issue, but as suggested, can be remedied by subtraction.
· QA/QC. I was happy to see the notebooks still being used for QA/QC and documenting the changes done to instruments etc. Once again, it was valuable in looking back at settings used when we desired to change a procedure for different concentrations, etc. It would be useful, however, to modify the software so that the files generated by the various instruments in the lab do not only list the code number for each reading, but also include sample ID (core-section-offset) and depth (mbsf). This would make checking the data quality much easier, before it is uploaded to the data base.
ACTION: Erik and Vinny quickly plot data on depth for a check before uploading, and even though it’s not necessary (as data can easily be retrieved, checked and altered if needed), Lisa and Aaron will now do the same (or at least ask the sailing geochemists their preference).
· Issue with calibrating the GC for void gas measurements.
ACTION: None at this time as we did not have enough information to discuss. Lisa will speak to Aaron on X375 about this.
4. External LWG members
· Becky Robinson and Margot Godard are rotating off after serving for a couple of years
o We thank them wholeheartedly for their input and participation!
· Suggestions for new members: Jeff Ryan, Juliane Mueller (organic geochemistry)
o Would like to solicit a pore water specialist as well
o ACTION: Send any suggestions to Kara ASAP
Technical points
1. LN2 Generator onboard is currently not working: replace or repair?
· RECOMMENDATION: Replace
2. Broken Teledyne ICP is back on shore: do we fix it to make it available for use here on shore, or should it be surplused?
· While it would be a useful piece of equipment, there were concerns about the effort, time and money required for setting up a lab to digest samples, subsequent lab and machine maintenance, and the age and type (i.e., not an ICP-MS) of the machine that seem to outweigh the benefits.
· RECOMMENDATION: Surplus
Next meeting
- End of July 2018
- Review Expeditions 374, 375, 376
- Open action items