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Deploying passive samplers at Little Forest, Australia

A monitoring update from our associated partner ANSTO

The Australian Nuclear Science and Technology Organisation (ANSTO) has been making significant strides in environmental monitoring. With this monitoring exercise, we will validate the passive samplers for the measurement of groundwater pollutants in a different climate.  

At Little Forest, a site on the fringes of Sydney in New South Wales (Australia) with a complex history, ANSTO has deployed ceramic passive samplers (CPS) and diffuse gradients in thin films (DGT) within the monitoring network that was already available. Four major potential land uses of this site include: low-level nuclear waste, urban landfill, disposal of liquid industrial chemical waste and night soils.

Figure 1 – Ready to deploy in the well at Little Forest

Before the deployment of the CPS, some effective groundwork was undertaken. Wells at the site were purged and sampled, employing a combination of techniques to ensure accurate and comprehensive data collection. This included the use of 12V impeller and peristaltic pumps, adapted based on groundwater levels, and the monitoring of physio-chemical parameters to guide sampling efforts.

Subsequently, the sampling could commence (Figure 1). Our aim was to collect samples for major ions, minor elements and water stable isotopes, through high-capacity filtering units. Additionally, unfiltered samples were collected to accompany passive samplers. They were preserved for further analysis back at our labs, adhering to the protocols to maintain sample integrity. Samples for anions, cations, minors and water stable isotopes are now in the lab for analysis.

Simultaneously with the deployment of the CPS, the deployment of diffuse gradients in thin films (DGT) took place. Based on a model from IDAEA-CSIC, partner on the Bèsos case study, ANSTO set up the monitoring equipment at the site: we built a special double-layered cage using the materials we had. Inside this cage, we put our DGT devices, which are used to test water quality, at the bottom. We added quartz pebbles inside plastic bags to keep everything weighed down. Right above the DGTs, in the top part of the cage, we placed the CPS, making sure they were spaced out a bit from each other (Figure 2).

Figure 2 – Samplers ready for deployment. In the lower position DGTs with weights (quartz pebbles in plastic bags). In the upper position CPS with strong fishing line to place samplers in the monitoring well.

This set-up made it easy to quickly grab the DGT when needed, just by cutting one tie. This means we can get the DGTs without having to disturb the CPS too much, minimising redeployment time for the CPS. We’re planning to head back to the site in a few days to collect the DGT.

Figure 3. Careful with the spiders. A red-back spider supervising the deployment of the passive samplers.

And of course, being in Australia, we ran into some extra challenges we had to work around (Figure 3)!

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