Decaying oil and gas pipelines left to fall apart in the North Sea could release large volumes of poisons such as mercury, radioactive lead and polonium-210, notorious for its part in the poisoning of Russian defector Alexander Litvinenko, scientists are warning.
Mercury, an extremely toxic element, occurs naturally in oil and gas. It sticks to the inside of pipelines and builds up over time, being released into the sea when the pipeline corrodes.
Some methylmercury, the most toxic form of the metal, is released by the pipelines although other forms can be converted into it. The international Minamata convention on mercury states that high levels in dolphins, whales and seals can lead to “reproductive failure, behavioural changes and even death”. Seabirds and large predatory fish such as tuna and swordfish are also particularly vulnerable.
Lhiam Paton, a researcher from the Institute for Analytical Chemistry at the University of Graz who has raised the alarm over the mercury pollution, told the Guardian and Watershed Investigations that “even a small increase in mercury levels in the sea will have a dramatic impact on the animals at the top of the food web”.
There are about 27,000km (16,800 miles) of gas pipelines in the North Sea, and scientists predict the amount of the metal in the sea could increase anywhere from 3% up to 160% from existing levels. In some countries, such as Australia, companies are required to remove them when the oil well stops operating. But in the North Sea companies are allowed to leave them to rot away.
Paton, whose work is published in the Journal of Hazardous Materials, said: “Pipelines left on the seabed may be holding onto considerable amounts of mercury which is waiting to be released into the local marine environment if the pipelines are left to corrode away as they are after decommissioning. There is no way to predict the impact of this right now but we do know that the bioaccumulation of mercury within the marine food web is already dramatic and an increase in oceanic mercury concentrations will only come with downsides.”
Effects on wildlife and food chains will depend on the form of mercury released from the decaying pipelines, with some forms much less likely to be taken up by marine life than others. According to Dr Darren Koppel, a research scientist from the Australian Institute of Marine Science, it is unlikely that all the mercury released from a corroded pipeline will end up in seawater. The “mercury is more likely to partition between the sediments, water, biota and atmosphere, adding to the global mercury cycle”.
“We still need to understand how clean pipelines need to be of mercury to ensure there will be no long-term impacts to the marine environment. This requires research investigating the long-term fate of mercury if left in contaminated pipelines and the conditions that will result in mercury ending up in food webs,” said Koppel.
Mercury is not the only substance worrying scientists. Dr Tom Cresswell from Australia’s Nuclear Science and Technology Organisation is also researching the impacts of naturally occurring radioactive materials, which are present in some oil and gas reservoirs under the sea floor. Natural radionuclides such as dissolved radium may be extracted with oil and gas fluids, potentially building up as scales inside subsea pipelines.
“Radium will physically decay into radioactive lead (210Pb) and polonium (210Po), which may be taken up into marine organisms and may represent a radiological risk to these organisms,” said Cresswell, who called for more research.
Hugo Tagholm, executive director of Oceana UK, described the issue as “yet another example of the extreme harm that oil and gas developments inflict on marine wildlife. Mercury is a pernicious toxin that accumulates in animals’ brains – leading to damage across the whole nervous system – and can be fatal”.
In January the North Sea Transition Authority announced that 24 new oil and gas licences have been offered to companies such as Shell, Equinor, BP, Total and Neo in the latest licensing round.
The UK is a signatory to the Minamata convention, an agreement aimed at tackling mercury pollution, named after the Japanese city of Minamata, which experienced mercury poisoning from industrial wastewater. It contaminated fish and shellfish in the bay, killing many people who ate seafood from the area and severely disabling others.
Monika Stankiewicz of the Minamata convention’s secretariat, said: “It is hard to predict what would happen, especially in the long-term, if large amounts of mercury trapped in the decommissioned pipelines were released into the environment. The rich biodiversity of the North Sea, and the millions of people who depend on it would be at increased risk.”
Ricky Thomson, Offshore Energies UK decommissioning manager, said the industry took full responsibility for meeting its obligations under national and international regulations and that all decommissioning programmes consider environmental impact before operations take place.
“Throughout the decommissioning programme, operators will apply for a series of permits and consents from the offshore environmental regulator Opred for which the operator is required to consider any potential risk to the environment and appropriate mitigation measures.
“Under current regulations, and where infrastructure may not be fully removed, the final approach to decommissioning involves a comparative assessment process which considers environmental, societal, safety, technical and economic factors to ensure the decision balances all these aspects.”
Opred is a part of the Department for Energy Security and Net Zero (DESNZ). A spokesperson for the department said: “We do not recognise the conclusions drawn from this report which ignores the routine maintenance carried out on all oil and gas pipelines. Mercury and other harmful substances are kept to a minimum during the lifetime of oil and gas pipelines, with corrosion levels monitored regularly by operators.”
“Prior to the decommissioning of oil and gas fields, the contents of a pipeline are also flushed and filled with seawater to keep contaminants to a minimum.”
Responding to DESNZ’s statement, Paton said it is “not reasonable to assume that flushing with seawater solves any issues. If the water is deposited back into the sea then it is only likely to increase the risk of contamination. If all of this water used to flush kilometres of pipeline is treated in some way to remove mercury, there must then be proof that all of the mercury has been removed from the pipeline walls. The need for transparency, collaboration and further research is clear”.
Worldwide about 1.3m km of oil and gas pipeline is currently installed.
