UAV-Based Above-Water Spectroradiometry for Detecting Sunscreen UV Filters in Coastal Waters

Sunscreen-derived ultraviolet (UV) filters are emerging pollutants of increasing concern in coastal ecosystems. This study presents the development, optimization, and field validation of Mar_Spectra, a compact spectroradiometric system mounted on an unmanned aerial vehicle (UAV) designed to detect sunscreen UV filters in surface waters. The system integrates an Ocean Optics microspectrometer with a Raspberry Pi microprocessor, a GPS receiver, an altimeter, and an RGB camera for synchronized image acquisition. Spectral measurements were processed to derive remote sensing reflectance (Rrs) using a Zenith Lite reference panel. Controlled calibration experiments confirmed the system’s sensitivity in the 300–380 nm range and allowed the definition of a convenient index iS exhibiting a strong linear relationship with total UV-filter concentration (R2 = 0.964). Environmental tests indicated that wind, turbidity, and algal presence reduced detection capacity, while stable solar conditions improved spectral consistency. Despite its sensitivity to environmental variability, the Mar_Spectra device demonstrated consistent and reproducible performance under real field conditions, providing a cost-effective and scalable approach for near-real-time monitoring of UV filters and enhancing spatially resolved coastal pollution surveillance