Assessing the ecological impacts of NORM-contaminated scale on marine infauna using sediment microcosms

Abstract

Naturally occurring radioactive materials (NORMs) can be found in decommissioned oil and gas infrastructure (e.g. pipelines), including scales. The effects of NORM contaminants from offshore infrastructure on benthic macroorganisms remain poorly understood. To test the potential ecological effects of NORM-contaminated scale, we exposed a marine amphipod, a clam and a polychaete to marine sediments spiked with low level concentrations of barium sulfate scale retrieved from a decommissioned subsea pipe. Only amphipods were included in further analysis due to treatment mortalities of the clam and polychaete. Barium (Ba) and copper (Cu) were elevated in the seawater overlying the spiked sediments, although no sediment metals exceeded guidelines. ²¹⁰Po was the only NORM detected in the overlying waters while both ²¹⁰Po and ²²⁶Ra were significantly elevated in the scale-contaminated sediments when compared with the control sediments. The whole-body burden of Ba and ²²⁶Ra were significantly higher in the scale-exposed amphipods. Using experiment- and scale-specific parameters in biota dose assessments suggested potential dose rates may elicit individual and population level effects. Future work is needed to assess the biological impacts and effects of NORM scale at elevated levels above background concentrations and the accumulation of NORM-associated contaminants by marine organisms.

Keywords: Contaminants; Natural radionuclides; Offshore decommissioning; Oil and gas; Radioecology.