Oral Presentation Society of Environmental Toxicology and Chemistry Australasia 2023

Deriving site-specific freshwater nickel, cobalt and chromium guidelines in the presence of naturally high background concentrations: A case study from New Caledonia (#124)

Jenny Stauber 1 , Gwil Price 1 , Peggy Gunkel-Grillon 2 , Yannick Dominique 3 , Lisa A Golding 1
  1. Environment, CSIRO, Lucas Heights, NSW, Australia
  2. University of New Caledonia, Noumea, New Caledonia
  3. Bioeko, Noumea, New Caledonia

Aim:

New Caledonia has high dissolved (<0.45 µm filtered fraction) background nickel (5-45 µg Ni/L), cobalt (1-7 µg Co/L) and chromium (6-25 µg Cr/L) concentrations in freshwaters that far exceed the Australian and New Zealand Guidelines for Fresh & Marine Water Quality and other international environmental quality standards (EQSs). We aimed to derive site-specific guideline values (SSGVs) for ecoregions in New Caledonia that provide protection against adverse effects from these three metals but also account for high background concentrations to which biota may be adapted.

Methods:

We investigated three options for deriving SSGVs:

  1. SSGVs based on a combination of global toxicity data and from bioassays generated using local freshwater microalgae and normalised to a water chemistry index condition (in the case of Ni only) for New Caledonian freshwaters.
  2. Modify the SSGVs from Option 1 to add the median values of the background dissolved Ni, Co and Cr.
  3. Use the 80th percentile of the reference site water quality monitoring data as the SSGV for each metal.

Results:

An overall index condition for New Caledonian freshwaters consisted of pH 7.8, 1 mg DOC/L, 0.26 mg Ca/L, and 8.6 mg Mg/L; however, there were insufficient quality toxicity data based on measured metal concentrations for local species to enable the use of option 1. Options 2 and 3 were able to correct for high background concentrations and gave similar results with SSGVs ranging from 18 to 35 µg Ni/L, 3 to 4 µg Co/L, and 19 to 22 µg Cr/L.

Conclusion:

This process demonstrated that it is important to have comprehensive and robust water quality monitoring data at reference sites and/or toxicity data for local species to derive SSGVs that account for naturally high background concentrations of dissolved metal.