The loss of crude oil droplets by filter feeders and the role of surfactants

Various methods of oil spill remediation exist, e.g., floating booms, controlled burning and the release of chemical surfactants. These surfactants facilitate the breakup of the slick into micron-sized droplets. Here, we studied the impact such a surfactant has on the size distribution of oil droplets in the water column and in the gut of the filter feeder Daphnia magna. We also studied the effect of surfactants on detachment conditions of chemically and mechanically dispersed oil (respectively MDO and CDO) droplets from capture fibers. Our results show that including solubilized dioctyl sulfosuccinate sodium salt in the mixing of the emulsion produces smaller droplets and a narrower size distribution in the water. In the gut, the size of ingested droplets does not change whether the oil is mixed mechanically or chemically. Also, surfactant coated droplets detach at a lower velocity than mechanically dispersed droplet because of their lower oil/water interfacial tension.

Automated summary

This study examines the effects of a surfactant on the size distribution of oil droplets in water and in the gut of Daphnia magna. It also investigates the impact of surfactants on the detachment conditions of chemically and mechanically dispersed oil droplets. The results show that the addition of solubilized dioctyl sulfosuccinate sodium salt produces smaller and more evenly distributed droplets in the water. Furthermore, surfactant-coated droplets detach at a slower velocity than mechanically dispersed droplets due to lower oil/water interfacial tension.