Non-invasive imaging of hydrocarbon contamination in permafrost soils at Marble Point, McMurdo Sound region, Antarctica
Summary: Hydrocarbon spills can cause extensive environmental damage and can last a long time in dry permafrost environments like that in Antarctica. Intrusive sampling and attempts at remediation can cause more harm to a site already damaged, particularly in the harsh yet fragile Antarctic environment. Additionally, even carefully planned intrusive sampling programmes can miss the target, in this case the location and extent of contamination. With negligible physical disturbance, non-invasive, non-destructive geophysical methods determined the extent of hydrocarbon contamination in the permafrost soil at Marble Point, in the McMurdo Sound region. Limited sampling was done for calibration, with minimal and highly restricted disturbance. The contamination is 35 to 40 years old; however the electromagnetic response was electrically resistive, the same as relatively young contamination in temperate soils, whereas older temperate spills tend to be electrically conductive. Radar profiles were acquired across the eastern half of the site, crossing two contaminated locations. The radar reflections were enhanced, again as observed for young contamination in temperate soils. Correlation between the radar and electromagnetic responses was excellent. The cold polar climate slows chemical and physical changes to contaminants, so that they respond as if young and relatively fresh. Geophysical imaging provided a viable non-invasive means to map the extent of hydrocarbon contamination in Antarctic permafrost soils with little or no site disturbance.