The following is triple oxygen isotope data analyzed in August 2024 on Reactor 30 (at end of R30). The main goal of this analytical session was to test for memory effects potentially caused by direct injection of hypersaline (~80g/L) sample water from Mono Lake.

Testing: Salt crystal formation in the injection port during water vaporization in the fluorination step would trap fluid inclusions that could release into subsequent samples and cause isotopic mixing between injected waters.

Overall Result: No memory effect is observed after hypersaline water injections.

Notes on run procedure

  • USGS standards (48, 46) were used as a reference frame representing high and low isotope endmembers

  • USGS47 was used as a monitoring standard between samples

  • One Mono Basin freshwater creek water (MB_23_08_250) was run in comparison to one Mono Lake hypersaline, pH=10 water sample (MB_23_08_259)

  • After injecting saline water into the Autoline, the syringe was triple rinsed using DI water following the same uptake and expulsion method used to clean syringe before each water injection.

  • Primes were done at start of the analytical day (1x prime) and between waters with large isotopic differences (1x prime if >5 permil different; 2x prime if 10 permil different; 3x >2 0permil).

  • SMOWs and SLAPs are being run actively at the end of the session to close out Reactor 30, but were not run at the beginning of this session in order to maximize usage of the R30 (not sure when it was going to die).

A few caveats:

  • This run was started when R30 was ~75% spent (based on previous reactor total injections/reactions), which means that slight shifts in standard values (e.g., USGS48) from the beginning to end of the run is due to the reactor coming to its reactive limit

  • Mass spec considerations: Before this run session, there was a NUB power outage that caused hard shut downs of the triple MS and Autoline, which included the source being vented to atmosphere. The source had to been turn off and restarted (07/31/2024) to get sensitivity back up to pre-outage levels. Source also threw a “source out of regulation” error at 5383 (08/12/2024) and then USGS48s directly after resetting the trips are offset of previous USGS48s by ~2 permil in dp18O.

1 Data

Sample.ID Water.Type dp17O.avg dp17O.sd dp18O.avg dp18O.sd D17O.permeg.avg D17O.permeg.sd N_D17O Yield.avg Yield.sd
MB_23_08_250 Fresh -8.51 0.23 -16.20 0.44 39.60 4.22 5 358.55 20.16
MB_23_08_259 Saline -3.03 0.20 -5.72 0.38 -8.86 3.72 7 353.89 18.39
USGS46 USGS46 -15.81 0.06 -30.01 0.13 37.25 3.40 4 356.21 12.10
USGS47 USGS47 -10.10 0.13 -19.20 0.25 41.71 6.70 7 369.14 26.13
USGS48 USGS48 -1.30 0.36 -2.53 0.68 39.33 5.79 6 367.35 16.65

2 Isotopes

2.1 vs time

  • Plotted isotopic compositions through analytical session to assess for significant drift in values between water types and values “smearing” after saline injection.
    • USGS standards as well as the fresh and saline water samples do not show mixing between isotopically distinct values by run order
    • The Mono Basin freshwater sample does have slight drift towards larger values (e.g., dp18O vs ipl.num), but this may be result of vial being opened and used multiple times causing sample water to exchange with atmosphere

2.2 by water type

3 Yield

  • Yield was monitored throughout run and waters with yield lower than 300 mbar were excluded.
  • Mean yields are overlap within one standard deviaiton for all water types. I speculated that the saline water sample would produce lower yields, but did not consistently find this to be true.
    Sample.ID Water.Type Yield.avg Yield.sd
    MB_23_08_250 Fresh 358.55 20.16
    MB_23_08_259 Saline 353.89 18.39
    USGS46 USGS46 356.21 12.10
    USGS47 USGS47 369.14 26.13
    USGS48 USGS48 367.35 16.65

4 D17O vs d18O

  • Saline water has D17O >35 permeg more negative than Mono freshwater and USGS standards and populations are clustered and distinct. There is no apparent memory effect in D17O between fresh and saline waters

5 d17O vs d18O

  • In this plot, the saline samples appear to fall on 0.528 equilibrium line, but if you zoom close in they fall off the line. The axes are really extended due to the large isotopic range between USGS 48 and 46.

6 Error

6.1 vs time

  • Plots used to assess if saline waters have consistently higher errors on d18O, d17O, and D17O.
    • No obvious trend in errors between water types through time or run order.
    • USGS46 has more variant error than the other USGS standards and higher. The bottle of USGS4^ used is almost down to half so I think its more variable bc of potenital atm exchange

6.2 by water type