The Big Microplastic Survey is a global citizen-science project where volunteers collect and sieve sediment samples using a standard protocol; a 2025 paper analysed 1,089 surveys from 39 countries. Data is analysed at the University of Portsmouth.
Honest caveat: the old bigmicroplasticsurvey.org address is dead; the live site is microplasticsurvey.org. Fewer than one in five registrants ever submit data, so only sign up if you will finish a survey.
How to start: microplasticsurvey.org/