Weathering of geotextiles under ultraviolet exposure: A neglected source of microfibers from coastal reclamation

Geotextiles are a group of polymeric materials widely used in coastal reclamation projects. However, long-term exposure to solar illumination deteriorates the performance of geotextiles, resulting in physicochemical changes and high risks of releasing microfibers. This study investigated the photoaging behavior of geotextiles and evaluated the capacity of geotextiles to release microfibers in coastal reclamation areas through a combination of field research and laboratory experiments. A field survey in the coastal reclamation area of Yancheng (China) confirmed that many geotextiles made from polyethylene terephthalate (PET) existed on the beach, which was accompanied by a high value of carbonyl index of 0.70-0.93. The results from laboratory experiments revealed that ultraviolet exposure activated the photooxidative process and promoted the breakdown of PET geotextiles. Data of scanning electron microscope and laser particle analyzer showed that, initially, particles with the size of less than 1 μm were generated on the surface of geotextiles, followed by fragments with sizes of 1-100 μm falling off with the passage of time. The number of particles on the surface was calculated using Image-Pro Plus software and the maximum particle density was found to be around 2.52 million particles·mm. In addition, based upon the conversion of irradiance between the simulated solar and natural solar, it was roughly estimated that the annual emissions of PET geotextile fibers in coastal reclamation areas were 0.24-0.79 million tons all over the world. It is inferred that polymer-made geotextile is a significant source of microplastic pollution in reclamation zones of coastal areas.