Riverine emissions of microfibers from the Yangtze River into the ocean over 2 consecutive years of observation

Summary Estuaries represent critical land-sea transition zones that play vital roles in pollutant transport. As China's largest river-ocean interface, the Yangtze River Estuary (YRE) serves as a primary pathway for terrestrial microfibers entering marine environments. However, evaluating microfiber flux is challenging due to the absence of long-term continuous observations of microfibers. Here, we conducted a 2-year monthly field study in the YRE. We observe spatiotemporal heterogeneity in microfiber abundance, with an average of 1,452.60 ± 910.95 items·m−3. Hydrological conditions influence microfiber abundance: increased river discharge enhances pollutant inputs, whereas extreme river discharge leads to dilution. Notably, river discharge also affects long-term changes in microfiber length. The Yangtze River Basin annually releases approximately 241 tons of microfibers, totaling 9.21 × 1014 particles, into the ocean. Based on continuous field observations, our study enhances the estimation of the microfiber flux from rivers to the ocean, contributing to the assessment of their ecological impact on marine environments.