A method for determining in situ and in real time at least one suspended sediment property in a medium, the suspended sediment comprising a mineral and an organic fraction. The method comprises the steps of (a) measuring light absorbance with a submersible ultraviolet-visible spectrometer, the ultraviolet-visible spectrometer being configured to analyse to analyse light absorbance at wavelengths which are comprised between 220 nm and 730 nm and of (b) correlating the light absorbance to the properties of the suspended sediment, in various instances by using the Beer-Lambert's law. The method is remarkable in that the step (b) is performed by using one model calibrated for deriving the properties of the suspended sediment from the light absorbance.