How do we process seawater samples?

By Jay T. Cullen

The InFORM team is busy processing samples returned to us from our citizen scientist volunteers who collected seawater at various locations in November.  When we receive the seawater we first filter it through a 1 micron ( 1 micron = 10-6 meter) cartridge to remove larger debris and sediments that might be present.

Onset Hobo Datalogger TidbiT Temperature sensor used by InFORM and Our Radioactive Ocean.
Onset Hobo Datalogger TidbiT Temperature sensor used by InFORM and Our Radioactive Ocean.

We remove the TidbiT Temperature sensor (Onset Hobo Data Loggers) and read out the data which tells us the seawater temperature at the time of sampling. A sample for is removed to measure the salinity as well.  Knowing the temperature and salinity of the sample helps us to put understand something about the history of the seawater and how much it might influenced by river water or runoff from land.  A small amount of non-radioactive cesium is then added to the sample to help us know how well we recover radioactive cesium in the next step.

We then slowly pump (1 milliliter min-1) the sample through a 5 milliliter column of potassium-nickel-hexacyanoferrate resin beads. This resin is specifically designed to be “sticky” for cesium (stable or radioactive) and separates the cesium from other chemical elements in the sample. We use a scale to tell us how much seawater is pumped across the resin. Finally we remove a post resin sample to determine the recovery of cesium by the resin. The resin is then placed in a highly sensitive gamma radiation spectrometer where the activity of radioisotopes are measured over time.  Expect first results from November to be available in late December or early in January 2015.
The slide show below shows InFORM team members Kathryn Purdon and Sue Reynolds working in the lab to process November samples collected by Kurt in Masset on Haida Gwaii and by Katherine and the Kelly Creek Community School in Powell River BC.  For more information on the details of this sampling procedure please visit the Our Radioactive Ocean website which developed the approach for citizen scientist sampling.

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