The temporal complexity of suspended particulate matter (SPM) transport processes in rivers limits our ability to disentangle the drivers of SPM mobilization over seasonal timescales and during storm runoff events. Therefore, in situ sensors are suited to monitor SPM dynamics and provide accurate information of fine-sediment delivery processes. High frequency monitoring of turbidity, which is used as an optical proxy for SPM concentration, refines SPM load calculations and captures short-lived changes in SPM concentration. However, the relation between turbidity and SPM concentration is highly influenced by SPM composition, size and density. As a result, a new empirical relation between turbidity and SPM concentration has to be stablished at each new site. This study deals with the use of optical in-situ sensors to characterise SPM properties at high frequency [carbon content, particle size distribution] to better understand the relationship between turbidity and SPM concentration and ultimately improve the quantification of SPM fluxes.