Expedition 379 Palynology Processing

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.

1. Prior to starting any process, the following is checked:

   • Level of HF waste in the carboy is not past the ¾ full mark. We leave a ¼ of the volume for the final addition of the HF Acid Eater.

   • Before using the HF, the waste carboy level is checked. _With the neutralization method used on this expedition, we needed to leave ¼ of the volume for the final addition of the HF Acid Eater._

   • A spray bottle of HF Acid Eater is ready in the hood for any possible HF spills.

   • Only one bottle of HF is in use.

   • HF warning signs have been posted.

   • LOs or ALO on duty have been notified.

   • Confirm that a least one additional lab personnel (not involved with HF processing) will remain in the lab until the HF work has been completed.

1. 5-15 g of each sample are ground and treated with HCl acid in the paleontology lab in 220 ml polypropylene bottles.

1. 5 ml of HF is added to each sample (Figure 4) and then 2-3 minutes are allowed for the reaction to finish before the next addition. This process repeated two more times for a total 15-ml of HF. once the last 15ml addition had reacted, an additional 75-ml of HF is added for a final 100-ml.

1. Before placing the sample in the shaker, we made sure that there were no signs of visible reaction. The bottle was loaded into the shaker and processed for one hour (Figure 2).

Figure 2. Pouring HF into the samples bottle in the HF hood and loading samples on the shaker machines

Figure 3: Centrifuge samples inside the HF hood.After shaking, 200ml of DI water was added before placing into the centrifuge. 4 bottles at a time were centrifuged at 2200 rpm for 5 minutes (Figure 3).

1. The fluids (HF) were decanted into a small beaker and then transfer it to the waste carboy (Figures 4 and 5).

 Figure 4. Pouring HF waste from sample bottle into polypropylene beaker.  Figure 5. Dump the HF waste into the carboy

1. Additional DI water was added to bottle, slightly swirl, and decanted. This process was repeated three times diluting any remaining HF to a concentration around 0.01% (Figure 6).

 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

1. Take an empty 20 L Carboy and add Calcite fine sand to an approximate ½ of an inch thick layer (Figure 9). Note how much calcite is used;

2. In the same Carboy, add 2L-3L of waterWe used the acid eater in the second carboy. ;

3. Agitate the Carboy to create a slurry;

4. Place the Carboy in hood;

Carboy Management

1. 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.

2. Note ?the level of calcite sand each time HF waste is added. When all the sand dissolves, add more sand.

3. 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.

4. 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.

5. 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.