How clean is clean enough?

Two rows of Antarctic mosses grown in normal soil or soil contaminated with fuel.
Antarctic mosses (a) Schistidium antarctici, (b) Bryum pseudotriquetrum, (c) Ceratodon purpureus, and the Antarctic terrestrial alga (d) Prasiola crispa following 28 days of exposure in control soils (no fuel) (top row) and in soils spiked with Special Antarctic Blend fuel (61 800 mg/kg soil) (bottom row). (Photo: Anna Nydahl)
Springtails on Antarctic soil.

How clean should contaminated soil be to protect its ecological function and value? That is the question Australian Antarctic Division ecotoxicologist Dr Catherine King and her team will answer as they develop remediation targets for contaminated sites in Antarctica.

The team is currently working with the Casey station remediation team (see main story) to develop targets based on ecotoxicity testing for a range of native Antarctic organisms.

The team has used similar methods on Macquarie Island to establish interim remediation targets for fuel contaminants in the subantarctic.

The Antarctic targets will eventually inform clean-up manuals that can also be used by other Antarctic nations dealing with their own contamination and remediation issues.

‘We’re aiming to identify fuel concentrations that, on average, would protect say 80% of the biological function of a disturbed site, such as occurs around a station, or 95% for a pristine site,’ Dr King said.

‘So the targets will depend on the land use and the values of the land. But even if you get back to 80%, that’s still a well-functioning ecosystem.’

Remediation in Antarctica, however, poses more of a challenge than the subantarctic.

‘Antarctic soils have the same diverse microbial communities that you’d expect worldwide, but they have few microinvertebrates, no macroinvertebrates and they have very few plants – only mosses, lichens and algae,’ Dr King said.

‘So we just don’t have the biological diversity and the organisms that you would typically use for ecotoxicology experiments, like flowering plants or grasses for seed germination tests, or macroinvertebrates for survival and reproductive tests.’

Instead, the team will focus more on developing toxicity tests with Antarctic mosses and terrestrial algae, and with two Antarctic microinvertebrates – nematode worms and springtails. They will also study the soil microbial communities and their functioning using bacterial genes to identify changes in species richness and diversity.

The results from the ecotoxicology work will be used to develop robust remediation targets to inform the Casey remediation team when they can return the biopile soil to the station for reuse. The work will also provide ‘trigger values’ that will allow Australia and other countries to prioritise sites for clean up in the future.

‘The trigger values will allow us to determine the risks posed by a site, so that, on an international scale, if we have say 50 sites to clean up across Antarctica, we can make an informed decision about how to prioritise them,’ Dr King said.

Wendy Pyper