Oil and gas decommissioning: a source for Hg bioaccumulation

Oil and gas processing has been a cornerstone of worldwide energy production for generations. However, in the coming years a significant percentage of all offshore installations will reach the end of their use and will be decommissioned. Planning such decommissioning projects requires great care and the management of many factors, including environmental impact. One environmental issue requiring consideration is how to manage decommissioned infrastructure such as pipelines currently installed along the seabed. Leaving these pipelines in-situ is a financially viable situation and comes with certain benefits like leaving ecosystems undisturbed. However, to do so first requires a risk assessment which must include the environmental impact of residual contaminants such as mercury (Hg). Hg is a contaminant in fuel sources like natural gas which is known for its toxicity and for bioaccumulating, which results in high concentrations of this toxic metal in marine life. This includes fish (i.e., tuna) which gives a route into the food chain. As such it is a priority to guarantee that should pipelines be left on the seabed that no Hg is allowed to be released into the local marine environments and no further contamination of the food web can occur. To tackle this issue this project will carry on work ongoing at the University of Graz and at the Australian Nuclear Science and Technology Organisation by using state-of-the-art spectrometric techniques to evaluate how much Hg may be present in pipelines which are currently installed in the deep sea. Furthermore, through the application of nuclear radiotracers it will be possible to investigate a scenario where Hg is released into environment and evaluate if this would result in bioaccumulation and if it is a threat to the surrounding ecosystems, or if the Hg which could be released is inert and safe. Therefore, this project aims to identify the risk associated with Hg which has accumulated along oil and gas pipelines and determine whether this Hg could enter the marine food web and contribute to Hg bioaccumulation.