The current status of microplastic pollution and ecological safety risks in the Karst World Natural Heritage Sites in Southwest China

Karst is one of the main landform types in the world, and Karst in southwest China is known worldwide for its largest continuous distribution area, the most complete types of development, and the most fragile ecological environment. It is also located in the upstream of the Yangtze River and Pearl River basins, serving as an important national ecological security barrier. Meanwhile, the area boasts beautiful landscapes and is dotted with world natural heritage sites. The booming tourism industry and other human activities have generated a large amount of microplastic pollution, posing a potentially significant threat to ecosystems and human health. To systematically study the current status of microplastic pollution and ecological safety risks in Karst World Natural Heritage Sites in southwest China, multi-scale environmental matrices such as water bodies, sediments, and organisms in heritage sites including Jiuzhaigou and Huanglong in Sichuan, Wulong in Chongqing, Libo in Guizhou, and Lijiang River in Guangxi were collected to investigate the pollution status, including the abundance, types, sources, spatial distribution, and compositional characteristics of microplastics. Furthermore, using spectroscopic analysis techniques and molecular biology methods, the loading and transmission of microplastics carrying heavy metals, pathogenic microorganisms, and antibiotic resistance genes were elucidated to assess their ecological safety risks. Then, by integrating environmental factors such as lake organic matter, nutrients, and hydrodynamic conditions, and conducting a detailed survey of local tourist numbers and socio-economic parameters, the driving factors of spatial and temporal changes in microplastic pollution in different regions were explored. Finally, a comprehensive assessment of the potential risks and influencing factors of microplastics was conducted, and targeted management countermeasures and forward-looking suggestions were proposed.