Lateral sediment transport is often studied using the ²³⁰Th_xs method which relies on the essentially constant amount of dissolved uranium in sea-water. Uranium decays and forms highly particle reactive daughter isotopes (primarily ²³⁰Th and ²³¹Pa). An estimate of the horizontal component of sediment flux is made based on the well known production rate of the insoluble daughter isotope ²³⁰Th. Sediment focusing factors are estimated by comparison of measured inventories of ²³⁰Th and the expected vertical ²³⁰Th flux over a given time interval. However, little is known about the ²³⁰Th_xs distribution in different grain-size fractions of the sediment. Sediment particles with smaller grain-size or certain hydrodynamic properties are more susceptible for re-suspension and re-distribution on the sea-floor.

Separation of sediment fractions based on their hydrodynamic properties, which also determine how easily the particles can be transported by bottom currents. After separation, the individual grain-size fractions are analysed individually for their ²³⁰Th inventories. Additional isotope (²³¹Pa, ¹⁰Be) analyses are performed on selected size-fraction samples, revealing important differences in adsorption to specific particle types.