# Hyperspectral Imaging for Detecting Plastic Debris on Shoreline Sands to Support Recycling
## 1 Introduction
Indeed, each pixel in HSI images is represented by a high-dimensional vector consisting of hundreds of adjacent narrow-band spectral channels, which usually include reflectance data [25]. High spectral resolution (i.e., 5 nm or less) and sufficient spatial resolution (i.e., <100 \(\upmu\)m) are now possible with HSI technology. In the plastic waste industry, HSI is acknowledged as a potent tool for material classification, sorting, and quality control [26; 27; 28; 29; 30; 31]. Through systematic HSI-based mapping, shoreline plastic debris can be effectively assessed as a resource, facilitating several critical steps typically used in natural resource exploitation: resource evaluation, environmental impact assessment, planning and design of material collection, regulatory compliance, and logistics [32]. The insights provided by HSI enable comprehensive evaluations of debris, including polymer type, degradation level, and pollutant contamination, without requiring traditional sampling. These data support the planning of shoreline cleanup and enhance environmental impact assessment (EIA) by not only promoting plastic recovery but also benefiting local communities through shoreline remediation [33]. The organized collection of shoreline debris can be conducted systematically across pre-defined zones or in parallel to the shoreline. Following collection, plastics are sorted, washed, dried, and shredded, with different recycling methods applied depending on material condition: (i) mechanical recycling for clean, high-quality plastics, (ii) chemical recycling (e.g., depolymerization, pyrolysis) for contaminated plastics, and (iii) energy recovery for non-recyclable materials. Efficient logistics and transportation are crucial for managing collected plastics. HSI-based mapping allows for the efficient storage of materials in designated facilities to minimize contamination, optimize transport, and enhance overall process sustainability. Moreover, HSI facilitates effective health and safety management, minimizing risks related to airborne contaminants and toxic chemicals commonly found in degraded plastics [31; 34]. Baseline mapping of shoreline debris provides a valuable reference for monitoring and evaluating the outcomes of collection activities over time [33]. This approach establishes metrics for both resource exploitation and beach remediation, helping to track environmental indicators such as collection rates and pollution levels per area unit. Such systematic mapping facilitates effective engagement with local stakeholders and supports financial planning, including securing funding from investors and promoting public awareness of the benefits of recycling, waste reduction, and the responsible use of secondary resources [35]. Continuous mapping further enables the regular review and optimization of collection operations, leading to cost reductions and process improvements over time. Traditional approaches to assessing marine litter typically rely on sampling and analysis techniques that are time-consuming, labor-intensive, and often environmentally disruptive. In contrast, an HSI-based approach offers a non-invasive, scalable, and efficient alternative for identifying, classifying, and quantifying plastic debris. In this context, this study sought to analyze and characterize plastic fragments that have not yet degraded into MPs, using a proximal sensing approach based on HSI to map the composition of plastic debris. Different areas of the seashore coastline (i.e., beaches) have been thus utilized as sample areas to set up recognition/classification procedures addressed to preliminarily identify plastic fragments from sand and then classify plastics according to their composition. In more detail, three different locations along the Ponting coastline (Latina, Italy) were selected, which are: Foce Verde, Capo Portiere, and Sabaudia.