X379 Palynology processing
Table 1: Steps used on EXP379 to extract palynomorphs from sediments. Yellow marks the steps involving HF.
The palynological processing on Expedition 379 was broken down into 18 separate steps, some involve the usage of Hydrofluoric Acid (HF). These steps are marked yellow in the Table below (Table 1).
Table 2: Acid dilution calculations for washing solutions.Table 2 shows the washing steps and the resulting dilution.
HF work area on JR
A restricted work area was marked off in front of the HF hood as shown in Figure 1. Access to the spectrophotometer and titrator was restricted during active HF use. Staff could remote into the instrument host to check an ongoing analysis from the technician's workstation.
The restricted work area was organized as follows:
A) Personal Protection Equipment (PPE) storage area;
B) Working hood with centrifuge, shaker, and waste carboy inside;
C) Waste bin restricted to HF solid waste (wipes, gloves, bottles etc.)
D) HF storage under the hood, kept locked at all times;
E) HF warning sign; (Only posted when work is conducted and then taken down. Additional signs posted at the two entrances to the chem lab, as well.)
F) Caution tape to mark off the restricted area;
Figure 1: HF work area in the chemistry lab.
HF work flow during Exp 379
Each round of 8 samples took approximately 2 hours to complete.
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Figure 6. Pouring DI water into the sample bottle for a new round of centrifuge.
NOTE: See 2019 or later Shipboard Safety Policy for updated HF neutralization procedure using Acid Eater.
Figure 7 The fine-grained calcite sand (neutralizer).Waste treatment
We used the following step to prepare and manage the waste carboy.
Carboy Preparation
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- Carefully and slowly, pour HF waste into the carboy containing prepared calcite sand and water. Note Note? Does that mean you kept a log?the approximate volume of waste added.
- Note ?the level of calcite sand each time HF waste is added. When all the sand dissolves, add more sand.
- Keep track of the amount of calcite and waste added, estimate how much more calcite to add. These notes will help us refine and improve this procedure next time. Add approximately 250g at a time. This reaction will produce CO2 and heat, so be sure to leave the cap of the carboy completely unscrewed to allow the carboy to vent. Use a plastic stirrer to SLOWLY mix the solution when necessary.
- When a complete batch of HF samples have been processed and the waste has been added to the carboy, test and note ?the pH level. Monitor the pH level and the amount of sand. Gentle stirring may be needed to separate the CaF solid and unreacted calcite. If necessary, add HF Acid Eater to complete the neutralization.
- Leave at least 1/5 of the total Carboy volume empty to allow for safe storage and transport.
Waste Storage
Once we had verified that the HF and HCL were neutralized* (pH reaches around 7), the carboy lid was screwed on and the carboy transferred to the Rad Van. A large plastic tub was placed on the floor and the carboy was bagged no. we didn't.and placed inside. Warning signs were placed on the Rad Van doors and kept locked (Figure 8).
*Because we did not have fluoride test strips on board the waste was treated as hazardous. Full PPE was required to transfer the carboy from the hood to the Rad Van with the assistance of a second person to handle doors. Fluoride strips are coming to the next port call so that we can verify that all fluoride is neutralized and can be disposed of safely.
Figure 8: The carboy in the tub on the floor in the Rad Van.
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