A recent Blog on the British Cave Science Centre site describes recent work on microplastics in cave waters that may be of interest:
https://www.cave-science.org.uk/post/microplastic-study-of-the-poole-s-cavern-karst-system-by-syeda-maria-zainab-second-year-phd-studen
https://www.cave-science.org.uk/post/microplastic-study-of-the-poole-s-cavern-karst-system-by-syeda-maria-zainab-second-year-phd-studen