Recognizing microplastic deposits on sandy beaches by altimetric positioning, μ-Raman spectroscopy and multivariate statistical models

Understanding the extent and implications of microplastic (MP) pollution along the São Paulo State coastline in southeastern Brazil is crucial, considering the significant environmental burden imposed by industrial and port activities in this region. This research aims to understand the complex dynamics of MP deposition on sandy beaches, which poses severe environmental risks to coastal ecosystems, marine organisms, and humans. Using a comprehensive five-step methodology-geodetic surveys, sediment collection, μ-RAMAN spectrometry for polymer identification, and multivariate statistical models-we analyzed the distribution of MPs across six coastal compartments (C1 to C6). The results (128 samples from 34 profiles) revealed relatively high MP concentrations in C3 and C2, which were likely influenced by local human activities. Various shape types of MPs, such as pellets, fragments, and fibers, present distinct distribution patterns based on their physical properties and emission sources. Fragments and foam were the most prevalent, accounting for 42 % and 35 %, respectively, of the 1026 MP items identified in total. Statistical analyses revealed significant correlations between MP types and beach morphometric features, with higher elevations correlating with increased MP concentrations, particularly for pellets and foam. Beaches with intermediate slopes (0.05 < tanβ <0.12) and openings to the southern quadrant tended to accumulate more MPs. This research underscores the importance of tailored management strategies that consider the unique characteristics of each coastal region to mitigate the impacts of MP pollution. The findings contribute to the development of targeted monitoring and environmental remediation strategies, which are crucial for protecting marine life and maintaining the integrity of coastal environments.