A review of the potential risks associated with mercury in subsea oil and gas pipelines in Australia

Environmental context The oil and gas industry has a significant liability in decommissioning offshore infrastructure. Following decommissioning, subsea pipelines could be left on the seabed to provide artificial reefs. Mercury is contaminant of concern which remain within pipelines. There are gaps our knowledge how mercury moves through marine environment. We review current science identify future research needs understand potential impacts from will better inform activities globally. Abstract In coming years, have infrastructure such as policies around vary depending regional laws. Australia, ‘base case’ for removal all property plugging abandonment wells line with Offshore Petroleum Greenhouse Gas Storage (OPGGS) Act 2006. Options other than complete may considered where titleholder can demonstrate that alternative activity delivers equal or environmental outcomes compared meets requirements under OPGGS regulations. Recent demonstrated situ benefits by forming reefs, increasing biodiversity, providing fishery location. An issue, been given less attention, contaminants remaining decommissioned their risks known present some pipelines, but long-term ecosystems poorly understood. synthesis information cycling environment including key drivers methylation sediments ocean waters, existing models predict methylmercury concentrations sediments, toxicological effects biota. discuss applicability water sediment quality guidelines, associated risk assessment frameworks contaminated mercury. Globally, needed comprehensive framework decommissioning. recommend areas improve understanding