Advances in the sample pretreatment for determination of microplastics in riverbed sediments by Raman spectroscopy

Microplastics (MPs) represent an important global environmental threat, and, among the different environmental compartments, the aquatic systems are particularly impacted by the MPs problem. River sediments act as sinks and as major pathways for MPs transportation to marine systems. Therefore, there is an increasing need for comprehensive, basin-scale monitoring of MPs in river sediments to elucidate their spatial and temporal accumulation patterns, providing data essential for risk assessment and the development of effective mitigation strategies by stakeholders. MPs extraction from complex environmental samples remains challenging as the presence of organic and inorganic matter often interferes with the analytical identification. To address this gap, we optimized a low-cost, high-throughput sample preparation protocol specifically designed for analysis of large riverine sediment sets and accurate Raman identification. The protocol was validated across a wide cross-section of sediment matrices, from the Arno River (Pisa and Florence, Italy) with different grain size distribution and organic matter concentrations. This validation, with both spiked matrices and real environmental sediments, demonstrates a workflow that is tailored to handle sediments rich in organic and inorganic matter while enabling accurate identification of MPs.