Abstract
The report summarizes the results from chemical characterisation and toxicity of low energy water accommodated fractions (LE-WAF) prepared of crude oils and their residues after in situ burning (ISB). The Alaska North Slope (ANS) crudes Alpine and North Star were used, and the chemical herders Thickslick 6535 (TS-6535) and Siltech OP-40 (OP-40) were applied to contract the oil slicks, both for the WAFs of crude oils and prior to burning. The WAFs toxicity was tested on the coldwater marine copepod Calanus finmarchicus (naupliar stage). The toxicity results indicated that the naupliar stage tested was more sensitive to WAFs of Alpine than of North Star. The WAFs of burn residue of North Star added OP-40, however, appeared clearly more toxic than all other WAFs, but it is unlikely that the toxicity is related to the addition of OP-40 since the corresponding Alpine WAF toxicity was reduced compared to the non-burned oil. We thus conclude that there must be toxic components in this burnt sample that do not occur in the other samples. Except for the North Star burnt sample with OP-40, the effect of burning is unchanged or reduced toxicity of the WAFs. The results show that there was no clear difference in chemistry or toxicity for WAF systems treated with herders compared with non-treated systems. No obvious difference between the two herders were observed and the herders did not influence the dissolution of water-soluble oil components. Based on these tests, no toxicological impacts of the use of herders as an oil spill response tool has been observed.