Measuring snowpack dust-loading
Many different samples from a snowpack can be returned to the lab. These are generally sampled on an ground-area or snow-volume basis, and the idea with this procedure is to filter out the dust in each sample to return a dust loading for each type of sample. Samples that can be treated this way include:
- Full or partial snow column samples taken with a coring device (like a PVC sampling tube).
- Kelly cutter samples - 1L volume samples taken along a snow depth profile.
- Surface scrapes - known-area surface snow collections.
- Thaw sample in a covered, leakproof container
- Snow samples are sometimes returned in a ziploc bag, and often these have small holes in them. Therefore they must be thawed in a leakproof container.
- There are numerous containers in the lab suitable for defrosting these bags, just be sure they are big enough not to overflow.
- It is important to cover the thawing sample with a lid to prevent evaporation (especially when water isotopes are being measured).
- Once thawed, empty all contents of the sample bag into its thawing container (make sure it is labeled with a sample ID).
- As you do this, be sure to suspend all dust in the sample bag by swishing it around
- Tare a 500ml (or larger) beaker on the balance.
- Transfer the sample from its thawing container into the tared beaker and record the weight of the sample on the datasheet.
- The sample is now ready to filter
- Record the weight of a clean, dry glass fiber filter (this can be done in advance) on the datasheet, and then place it in a clean ceramic filter funnel/sidearm flask assembly.
- Turn on the vacuum, swish the sample around to suspend the dust, and slowly pour the sample through the filter.
- The first portion of the filtrate can be saved for water isotope analysis. If this is done, the filtrate to be saved MUST be filtered into a clean, dry filter flask, then transferred to a plastic sample container. The remaining filtrate does not need to be saved.
- After all the sample has been filtered, carefully place the filter on a labeled petri and dry it in the drying oven.
- It is important that the 500ml beakers and sidearm flasks are clean and dry when they come in contact with a new sample, so rinse well and let dry between samples. Having a queue of several beakers/flasks will make things proceed faster.
- When the filter is dry (24-48hrs), weigh it and record this weight on the datasheet.