From Mountains to the Coast: Microplastics in Slovenian Karst Alpine Lakes and Drinking-Water Sources—Implications for Sustainable Water-Resource Management

The study was conducted in subalpine karst and in lowland karst in Slovenia—Lake Bohinj, Lake Bled, Mt Komna, Lesce, Rižana Spring, and Malni Spring. Both lakes are karst lakes of glacio-tectonic origin, with Lake Bled being one of the largest tourist attractions in Slovenia. The lakes were sampled along different transects. We also collected two sediment samples from Lake Bohinj and one sediment sample from Lake Bled. On the other hand, we sampled two biggest karst springs in Slovenia that are used as sources of drinking water for up to 120,000 people during the peak tourist season on the Slovenian coast. In the FTIR-ATR analysis of the particles, we found mainly PA polymers in all samples, closely followed by copolymers and resins. Lake samples also contained larger amounts of PP, while the spring samples contained more rubber polymers. Of the two lakes, Lake Bohinj was the most polluted, with 0.684 MPs/m3 being the highest concentration. This is surprising because Lake Bohinj is also located in the Triglav National Park and is a less popular attraction compared to Lake Bled. Malni Spring showed a higher mean MP concentration than Rižana Spring (0.000274 ± 0.000448 vs. 0.0000498 ± 0.0000642 MPs/m3, respectively), and the negative-binomial model indicated a significant site effect (p = 0.046), but the difference could be due to the highly torrential nature of Rižana Spring. Future studies would require longer sampling campaigns under different hydrological conditions to better understand the dynamics of the MP transport in karst environments that will provide a stronger scientific basis for sustainable freshwater management, the protection of drinking-water resources, and the development of effective measures to reduce plastic pollution at the catchment scale.