Plumes are of relevance to nature and real consequence to industry. Whilst the Morton, Taylor Turner (1956) plume model is able to estimate the mean physical flux parameters, the process of entrainment is only parametrised in a time-averaged sense. Indeed, a deep understanding of turbulent entrainment is not widespread. We perform simultaneous PIV and plume-edge detection on a saline plume in water. We identify that significant mass is transported in regions of relatively high-momentum fluid between the large scale edges. This suggests that the large scale processes, whereby ambient fluid is engulfed into the plume, contribute significantly to the entrainment. This is in contrast to recent studies which have identified small scale nibbling as the dominant process. It may therefore be illuminating to consider entrainment as a series of distinct but interlinked processes occurring at multiple scales with each imparting a characterisation of plume fluid to the

Keywords: Experimental techniques, Applied fluid dynamics, Turbulence