propagated along the surface of this liquid stream, which increased the contact and thus the G50 in comparison to the gas discharge reactor. The turbulent and laminar jet reactors both were more efficient than the RVC HV reactor. These reactors had higher velocity liquid streams that churned the bulk liquid and caused a layer of foam to form on the surface. The foam adds complexity to the liquid surface and influences the leader propagation pattern such that the leader must follow a less direct path across the surface, which effectively increases the length of the leaders and thus the contact area. Much previous work has been done to determine how streamers propagate within gas bubbles immersed in liquid; however, the influence of bubbles adjacent to the bubble in which a streamer propagates is unknown, but may factor into why the presence of foam enhances the removal rate so dramatically [22– 24]. One possible mechanism causing the change in removal rates may involve the electric field enhancements resulting from the positive space charge produced at the head of the streamer as it propagates along the liquid film between two bubbles. This enhanced electric field may trigger small discharges over the surface of the opposite side of the film within the adjacent bubble, which would effectively increase the area exposed to plasma. Another possible mechanism involves the electrostatic interactions between neighboring leaders being dampened by the liquid films present between them, due to the films having a higher dielectric constant than the argon. This might reduce the distance between leaders and thus increase the number of leaders that emerge. Regardless of the particular mechanism, it is clear that the high surface density of the foam enhances the contact and thus accounts for the substantial increase in the G50 compared to the RVC HV reactor