CTD water sampling for δ13C of DIC in seawater

Introduction

The following protocol describes the sampling of water from the Niskin bottles of onboard CTD equipment for δ13C analyses.

Safety info

Follow the ships rules for working in exposed areas. This can involve using helmet, floating vests etc. Often it is best to close the CTD hangar before sampling.
Wear lab coat, Nitrile gloves (TouchNTuff 92-600 or equivalent), protection glasses and closed shoes when handling HgCl₂ solutions. Work on a designated area, with water absorbing bench paper with plastic coating towards the bench.

In the event of spillage of HgCl₂ containing samples on a person

Remove items that you have spilt on immediately and rinse area that has been in contact with HgCl₂ with water and soap for approximately 5 minutes. Watch to see in area becomes inflamed or irritated. If in doubt call giftkontrollen (22 59 13 00) or contact Legevakt (phone 116 117 or 113 for emergencies).
If HgCl2 containing solutions are ingested or someone get it in the eyes, call 113, wash the eyes with appropriate equipment immediately.
Samples will contain approximately 0.2 mg HgCl₂ per ml or less. HgCl₂ stock solution will be a saturated solution (7.4g/100 ml at 20 °C), often containing precipitated HgCl₂.

Spillage and waste handling

If Hg containing liquids are spilled on benches or the floor etc., wipe with paper towels, and wash properly. Paper towels etc. are put in zip bags and in yellow special waste boxes.
Waste is stored and handled on shore.
All waste and consumables that have been in contact with HgCl₂ should be packed in plastic bags and yellow special waste boxes.
Vials with Hg containing sample should be closed and packed so they will not break and be put in red hazardous waste boxes (https://www.uib.no/hms-portalen/74275/farlig-avfall) after analyses or sent back to sample owner. Remember to fill in and attach the declaration form.

Samples that are in reusable containers should be poured into a larger (e.g. 10L bucket) with approximately 100 ml (sorbent) and stirred over night. The water is then decanted out, and the sorbent is put in a closed container (e.g. plastic bottle) and put in red hazardous waste containers including a declaration form.

Equipment

Glass serum bottles (60 ml) with butyl rubber septa and crimp caps (sampling bottles)
One 30-50 cm tube silicon tube for each Niskin Bottle (tube i.d. 7mm at Kronprins Haakon)
Mercury(II)chloride (HgCl₂ in saturated solution in DI water, >7.4 g/100 mL, 20 °C)
Nitrile gloves (TouchNTuff 92-600 or equivalent)
1 ml single use syringes with needles
Water absorbing bench paper with water tight underside
Niskin bottles are part of the ships CTD equipment.

Use nitrile gloves, goggles, lab coat and closed shoes when handling the saturated HgCl₂ and the fixed samples. Set up a permanent, separate area in the ship lab for working with HgCl₂ as long as the work will go on to avoid spreading Hg spill to the rest of the lab. A fume hood dedicated to this would be suitable, but other solutions like a dedicated plastic tray or similar could work. Cover the area with water absorbing bench paper with a plastic coating below.
The bottles should be numbered before sampling, please use this number as reference.
Rinse the vial and septum with sample three (3) times. This removes any water than may have condensed inside the bottle/cap. Use the silicone tube to transfer water from the Niskin bottles to the sampling bottles.
The tube should be placed in the bottom of the sampling bottle when filling. Make sure there are no bubbles inside the tube when filling. This might require reducing the flow from the Niskin bottle.
Overfill the sample bottle with one bottle volume. Make sure no bubbles are trapped inside the sample bottle. Put the lid on so excess water runs out (squeeze sideways and down in the septas) and only a small bubble is present. DO NOT put on the crimp cap. When you have filled all sample bottles transfer them back to the laboratory to add HgCl₂ as soon as possible.
Dry all the bottles with paper towel. Paper towels go in a normal waste bag.
Using Nitrile gloves and goggles and working in the dedicated area, add 1 drop of saturated HgCl₂ using syringe w/needle to each bottle. Put the septum back on and secure it with a Crimp cap. Use bench paper and change gloves often to avoid spreading the mercury.
Dry of the bottles with paper towel in case of spillage. This paper as well as other consumables in contact with HgCl₂ goes in a labelled zip bag and is later transferred to yellow waste containers (for combustion on shore).
Put the dry bottles in the cooling room (NO FREEZING!). In case any spill dry with paper towel and put in the yellow plastic bag. All used gloves go in the problematic waste.

Updated 13/08 -19 by Pål Tore Mørkved