At Macquarie Island, parts of the environment in the immediate area around the station and isthmus, particularly around the fuel farm and mechanical areas, carry the legacy of soil contamination with petroleum and hydrocarbon residues as a result of historical spills and leaks, and past poor disposal practices. Researching better methods of remediating these contaminants in the subantarctic environment, and understanding the impact on the environment, is one of the major themes of research activities here. Findings are of benefit to other oil spill scenarios in comparable delicate environments. Macquarie University PhD student Ingrid Errington is currently spending her second summer at Macca working on her research project in this field, and details her work in this week’s news.
Soil remediation works have been carried out on Macquarie Island since 2009, following a number of fuel spills. Indeed, it is one of the main long term projects running on station, with a team of scientists returning every summer to tweak the soil conditions to promote faster degradation of the remaining fuel products.
Very little is known about the actual effects of these spills on the soil biota (mostly worms, springtails and mites, but also bacteria, fungi and plants) in the subantarctic environment, and to this end my PhD topic is interested in answering the question “How much remediation is enough remediation?”.
We could spend decades working towards removing every trace of fuel contamination from the soil, but if there is a concentration at which the animals in the soil remain healthy and able to reproduce then that is a more realistic target to aim for. Furthermore, remediation works are highly resource intensive and themselves cause disturbance to the soil, so there is no gain to be had from overshooting the mark either. But how can we find out what this concentration is?
In the last five months, I have been exposing a range of common soil invertebrate species to fuel contamination. One of these techniques is an avoidance test, in which half of a container is filled will clean soil and the other half with contaminated soil. Worms are placed along the centre line and left to burrow into the soil, then a few days later I check to see whether they avoided the contaminated soil and at what concentration.
Previous work has been done using similar techniques to test the effect of fresh fuel on soil biota, but the nature and composition of the contamination changes greatly with time and exposure to the elements. The good news is that the worms seem to be far more resilient to aged diesel than we anticipated they would be based on the fresh diesel tests. More work will have to be done to verify this result, but for now it’s an unexpected but welcome finding.
This project is funded by the Australian Antarctic Division through AAS 4135, and is run in collaboration with Macquarie University and the University of New South Wales.