Performance evaluation and environmental partitioning of OP-40 chemical herder during herder mediated in situ burning of crude oil at varying environmental conditions

Abstract

In situ burning (ISB) aided by chemical herders is one of the most suited and effective oil spill response (OSR) techniques for Arctic conditions. OP-40 has been reported as the most efficient and suitable herding agent among the two US EPA-approved herders; however, the fate of OP-40 in the environment after an effective ISB is not fully understood. Previous studies reported partial accumulation of OP-40 in water and confirmed the absence of OP-40 in the air after a burn. The only other possible place of OP-40 accumulation is burned oil residues; however, there was no standard method in previous peer-reviewed literature to quantify OP-40 in burned residues. Therefore, the first part of this study developed a novel OP-40 quantification method to quantify OP-40 in burned residues. The method used column chromatography followed by Gas Chromatography-Mass Spectrometry (GC/MS) analysis to quantify OP-40 in the residues. The method quantified more than 90% of the applied OP-40 from the burned residues. In the later part of the study, the efficiency of OP-40 herder at in situ burning and its fate in the environment after burning were parametrically investigated in bench-scale laboratory experiments with Alaska North Slope (ANS) crude oil. Experiments were conducted in three different water temperatures and two different water salinities to check OP-40's efficacy at the different environmental conditions and how those changes affect its fate in the environment. This study also investigated the effect of different herder volumes on the efficacy of OP-40 and the fate of OP-40 in the environment. The herding efficiency of OP-40 was excellent at all environmental conditions and for all three herder volumes. OP-40 showed higher herding efficiency in cold and low saline water, while burn efficiency was higher in cold water. This study recorded a maximum of 99.5% burn efficiency, with a minimum of 8.1%. On the other hand, the environmental partitioning study recovered a maximum of 99.7% of the applied OP-40 from the collected samples. An average of 34.4% and 24.1% of herder was found in water and residues, respectively. A higher percentage of applied OP-40 was found in burned residues at cold temperature and saline water.