Three rounds of water sampling were performed at the Berge Helene FPSO at the Chinguetti field in Mauritania using passive samplers attached to the FPSO to determine the levels of contamination that could potentially accumulate in organisms. Two rounds were carried out prior to the commencement of oil production (pre-PFW) and one following the start of produced formation water discharge (post-PFW). Although water was sampled at 3-m and 10-m depths, bioaccumulation data were possible to report only for 3-m depth due to the repeatable loss of samplers deployed at 10-m depth. The reason for these losses remains un-known. Retrieved passive samplers from each round were analysed for total bioaccumulative (petroleum) hydrocarbons, 9 phenols, benzene, toluene, ethylbenzene, xylene and 16 EPA polycyclic aromatic hydrocarbons. The accumulated amounts of chemicals during the two pre-PFW samplings were very similar and both of them can be considered to be representative for the pre-PFW phase. Surprisingly, the accumulated amount of chemicals during the post-PFW sampling round (i.e. after and during regular PFW discharges) was lower than in the pre-PFW sampling round. The most probable explanation is that drilling activities have stronger impact than the regular PFW discharges, but the possibility that the results were influenced by a variation in meteorological and hydrological conditions, such as ,e.g., direction and strength of the currents, could not be fully rejected. The biomimetic nature of the Empore® disk extraction was used to estimate total body residues of chemicals in biota. These values were compared with critical body residues for three toxicological effects to evaluate baseline toxicity of the environment under the FPSO. Results showed that the total body residue levels in the aquatic environment under the FPSO are below the no-effect level for sub-lethal fish toxicity. However, in all measurements the levels exceed safe level for effects on ecosystem (HC5): in pre-PFW sampling significantly, while in post-PFW only slightly. As these levels were observed directly at the source of possible contamination, the effects on the environment are likely to be substantially lower at increased distance from the FPSO.
|Place of Publication||IJmuiden|
|Number of pages||19|
|Publication status||Published - 2007|
|Name||Report / Wageningen IMARES|
- aquatic organisms
- water quality
- marine environment