Tracing the invisible along the surface-subsurface continuum: bisphenols and microplastic pollution in karst system waters

Bisphenols are emerging organic contaminants often released into the environment, especially in aquatic systems. Specifically, Bisphenol A (BPA) is generally used in synthetic polymers and thermal paper production, and has been found in different environments and organisms, affecting ecosystems and human life. However, bisphenol contamination in karst systems remains poorly studied, although karst groundwaters are widely exploited for drinking use. This study presents a preliminary screening of BPA, bisphenol AP (BPAP) and C (BPC) in a karst system, from surface watercourses to cave groundwaters, using the novel AptaStick system for bisphenol family. Results confirmed BPA pollution in the karst system, with highest values inside a cave. BPAP and BPC were not detected in water samples. Potential pollution sources are likely linked to diffuse anthropogenic inputs within the catchment area, combined with event-driven transport dynamics. As a potential source of BPA contamination, microplastic (MP) pollution was concurrently investigated during high-flow conditions, finding from 0 to 7.7. MPs/L. These data expand previous assessments conducted under low-flow conditions in the same karst system. Natural and regenerated microfibres (MFs) were analyzed too, finding from 0 to 136 items/L. This work wants to be a first evaluation of both bisphenol and MP pollution in karst systems, stressing the importance of monitoring pollutants in these highly vulnerable environments. Moreover, it provides a first evaluations of how pollutant distribution may vary within the different hydrological compartments of a karst system, not only between surface and groundwater environments, but also among flowing, percolation, and stagnant waters within the subterranean network. This approach contributes to a better understanding of the spatial heterogeneity and transport dynamics of emerging contaminants in karst environments, supporting the development of appropriate conservation measures for habitats and species protection, and suitable drinking water resources management.