For everyone who is more interested in the science we are planning, we have decided to publish our sampling protocol. Actually, this is an opportunity as well for those who do similar projects to comment and exchange ideas, all in the spirit of open science. Don’t hesitate to use my project-related contact email: firstname.lastname@example.org with suggestions or questions related to this, or leave comments / use our Facebook site for a general discussion.
Here is the protocol:
1. Collect snow samples from fresh snowfall events (if only possible). Check the time when the snow starts falling, and write it down at first opportunity. Approximate time will be useful as well.
2. Once the snow stopped falling, please take the sampling equipment: ruler/tape measure, spring scales, 250 mL stainless steel tube and a metal spatula (alternatively: 1000 mL stainless steel wedge density cutter), sampling bags and labelling markers, GPS and notepad, and walk away from your pulk/camp by at least 30 paces (from the camp preferably further), against the wind direction. This is to avoid the people and their equipment having any chemical influence on the samples.
3. Measure the thickness of the snow layer with the ruler (exposing a vertical profile in the fresh snow layer down to the boundary with the older snow and measuring the depth of it (you can dig with the metal spatula). Write down at least 3 thickness measurements (with 1 mm accuracy).
4. Wear rubber/nitrile powderfree gloves over your thin gloves (best double fleece or woollen gloves, to keep your hands warm throughout the sampling procedure). Unfortunately, thick gloves rarely allow the necessary precision of movement. Please clean the rubber gloves before each sampling by “washing” your gloved hands in the sampled snow (as if it was standing water in a bowl).
5. Insert the steel tube and spatula (or density cutter) a few times (≥3) into the sampled snow layer before the sampling (to clean the insides from any preceding samples). Measure the snow density, by taking snow samples of the exact volume of the steel tube, or if it cannot be full – measure the level to which the snow has reached. Use the spatula to keep the snow inside, transfer it into the sampling bag, and weigh with the 1 kg spring scales (or weigh e.g. 10 times the volume if too light to measure with the scales). Write down the mass measurement, and repeat it at least once, and again if the first two measurements differ by more than 10%.
6. The samples should be taken into the Teflon bags (and sealed with clips):
The clips are composed of two parts: outer half-tube and inner tube, which are to be pressed one into another, with the bag material trapped in between:
Please do not touch the inside of the bag, except with things already cleaned with the sampled snow. The inside of the sampling bags and the steel tube and spatula have been prepared prior to sampling by cleaning with: 1) deionised water, 2) poisonous methanol, and 3) dried in a clean atmosphere, preferably in nitrogen. Due to the use of methanol, please handle the equipment in rubber gloves only. Make sure you don’t eat with the outer gloves used for sampling and avoid any contact of food and the sampling kit (which is good both for you and the samples).
Further sample packing: place the Teflon bags in outer zip-lock bags, and then in supermarket cool bags to protect samples from sunlight.
7. Please keep all sampling kit (stainless steel tube/spatula/density cutter) wrapped in the provided clean bags if not in use for sampling (to protect it from contamination).
8. For each sampling location, please fill in one Teflon bag in full (5 L), putting in snow by tube-fulls and pressing it down (through the outside of the bag) as much as possible so as to compress it (e.g. with gloved hands). Ideally, I need 2 kg or more of each sample, but hopes for results start at 1 kg.
9. Once the Teflon bag is full, seal it with the attached clip, and label the bag on the outside (or on the clip). Keep in the dark (supermarket cool bags will help with this).
10. For each sampling occasion, please write down the following: GPS coordinates, sample number / label, the beginning and end time of the snowfall, type of precipitation (e.g. diamond dust, snow flakes, graupel – you can also draw the shape of snow crystals found on the ground – all extra data is very welcome here), whether wind was redistributing the snow and approximately with what speed, snow layer thickness and density.
11. Following arrival at temperatures above freezing, there are two choices: 1) strictly keep samples frozen at all times, by finding a freezer at a friendly institution; 2) melt the samples in low temperature and pour them into amber glass bottles (pre-cleaned). The amber glass bottles should be labelled with the same symbol as the appropriate sampling bag. Use two bottles per sample if necessary.
12. Add to each 1 L bottle 1 mL of the 6 N HCl and 2 mL of methanol, each with a separate syringe. Best to use a new syringe for each sample.
13. Close the bottles tight and mix by turning upside down a couple of times. You can also wrap the mouths of the bottles with a piece of parafilm for extra protection in transport. Keep at a cool temperature above freezing (≈4°C).
14. Transport in insulated boxes to the laboratory. If frozen, samples cannot be allowed to melt to avoid leaks in transport. In that case, the transfer to bottles will be only completed in the laboratory.
Sampling done! Time to celebrate 🙂