Funded by ACARP, we seek to trial a new in-situ method for determining heavy metal and arsenic concentrations which will be cheaper than conventional methods and more representative of in-stream concentrations over the monitoring period. The method, called Diffusive Gradient Technique (DGT), measures heavy metal and arsenic concentrations by uptake onto a resin.

Purpose: The project aims to trial a new real-time in situ sampling method of DGT for determining labile heavy metal and arsenic concentrations in river water receiving mine water releases. The outcomes of this project will provide more accurate information on water quality and a lower water monitoring cost than conventional sampling methods.

Significance and Innovation: The premise of the DGT approach is to integrate the concentration of labile metals and metalloids in the water throughout the deployment period (hours/days to weeks). The instantaneous grab sample is representative of a time-integrated sample only when the variability in water quality is low on the timescales of sampling. If however, an aquatic system hosts some degree of variability (such as is often the case where mine-water is discharged into a natural water course), then grab samples are not comparable to the time-integrated assay yielded by DGT. One DGT unit could potentially replace numerous water samples and will provide a far more representative view of in-stream concentrations over the monitoring period.

Other advantages of the DGT technique for water monitoring are

  1. The labile metals and metalloids accumulated on the DGT gel is known to mimic biological uptake of these constituents thereby providing a more robust indication of toxicity to aquatic organisms.
  2. Under low metal/loid concentrations which may be below the detection limits of the ICP-MS, DGT has the benefit of concentrating the elements of interest to levels which can be determined using ICP-MS.
  3. The in-situ DGT capture of heavy metals and metalloids will reduce the possibility of contamination of water samples during collection that can easily occur in low concentration waters.