Mercury fingerprint: A comparative evaluation of lability in North Sea drill cuttings

Quantifying impacts on marine ecosystems remains pivotal in estimating risks associated with offshore industry practices. Cuttings piles, formed during drilling operations, are commonly abandoned in situ, and left to attenuate on the seabed. In the present work, the presence and lability of mercury in samples obtained from drill cuttings piles of two decommissioned North Sea oil platforms (bp Miller and bp North West Hutton) and the surrounding sediment were investigated. Maximum concentrations of total mercury were measured at 0.23 and 0.37 μg/g dry weight (dw) for bp Miller and bp North West Hutton, respectively. Background concentrations of 3.6 and 8.3 ng/g dw were measured at reference sites at 3200 metre distance. Thermofractionation and DGT-analysis of the samples to assess the effective environmental impact of the measured mercury suggests that although total mercury concentrations are increased in the proximity of the cuttings pile, the effective environmental impact may be limited.