Environmental statement - Flyndre and Cawdor - Maersk Oil

Flyndre and Cawdor Environmental Statement
Section 3 Environmental Baseline
Total Poly Aromatic Hydrocarbons (PAH) concentrations ranged from 0.026 µg g ‐1 at section 1 (near
the Flyndre and Clyde drill locations) to a high of 0.497 µg g ‐1 (near the Clyde platform), with an
average of 0.089 µg g ‐1 . The total PAH concentrations were comparable to previous data from the
region (Gardline Environmental 2007, 2009).
PAHs were detected with predominantly higher molecular weight species, these are likely to have
originated from pyrogenic inputs (associated with combustion of hydrocarbons), the only exception
was a sample from section 1 (near Flyndre and Cawdor drill location) which appeared to have mixed
inputs of petrogenic and pyrogenic PAHs.
Results of the metals analyses (with the exception of Arsenic and Copper) appear generally
comparable to or lower than previous data from the region, with all concentrations within
background levels (OSPAR, 2005). The majority of metals were recorded in higher concentrations at
sections 2 and 3, which might be expected given the higher proportion of fines and hydrocarbons at
those stations, and the proximity to the Janice FPU and Clyde platform. Barite is an essential
constituent of drilling muds hence Ba occurs in high concentrations in sediments surrounding any
drilling activity. Concentrations of Barium (extracted using hydrofluoric acid) ranged from 160 µg g ‐
1 to 426 µg g ‐1 , with a mean concentration of 235 µg g ‐1 (+/‐ 74 standard deviation); Barium
concentrations determined using an alternative method (alkali fusion) ranged form 141 µg ‐1 to
339 µg g ‐1 , with a mean concentration of 194 µg g ‐1 (+/‐ 60 standard deviation). To put the Barium
concentrations into a wider context, UKOOA (2001) recorded mean total Ba concentrations
(measured by sodium fusion) more than 5 km from the installations in the central North Sea, typically
in the region of 178 µg g ‐1 , with 95% of stations having concentrations