Unraveling the Roles of Temperature, Salinity, and Herder Volume on Environmental Partitioning and Efficiency of OP-40 Herder During in Situ Burning of Oil Spills

In situ burning (ISB) aided by a Siltech OP-40 chemical herding agent (OP-40) is reported as one of the most appropriate and effective oil spill response (OSR) technique for Arctic conditions. Herein, we parametrically investigate the efficiency of the OP-40 herder for ISB and the post-ISB fate of OP-40 in the environment via bench-scale laboratory ISB experiments using Alaska north slope (ANS) crude oil. Experiments were conducted at three water temperatures, two water salinities, and three herder volumes to evaluate the herding efficacy of OP-40 under different environmental and herder application scenarios. Further analyses were performed to investigate the impact of these varying experimental conditions on the ISB burn efficiency and the fate of OP-40. The results revealed that the herding efficiency of OP-40 was excellent under all environmental conditions and for all three herder volumes, and in all experiments, the herded oil was successfully ignited. OP-40 showed a higher herding efficiency for cold and low-saline water, while the burn efficiency was higher for cold water. In this environmental partitioning study and analyses, on average 34.3% and 24.1% of the applied herder was found in water and burn residues, respectively. Water temperature and salinity did not significantly impact the fate of OP-40 in water and residue. While the results from these relatively small and well-controlled laboratory-scale burn tests provide useful fundamental information and highlight sampling and other operational challenges for such studies, larger field tests will be needed to scale these results to large, unconfined, in situ burn scenarios.