As the last barrier preventing river pollutants from entering the ocean, mangroves have strong absorption and purification abilities, and strong tolerance. We collected mangrove surface water and sediment samples from the Xixi Estuary of Xiamen city. The results showed that the abundance of microplastics in seawater ranged from 620 to 13,100 n/m³, the abundance of microplastics in sediment ranged from 143 to 488 n/kg, the distribution of microplastics was uneven, and the abundance of microplastics in the Xixi Estuary mangrove was significantly higher than that in the non-mangrove area. The sediment column sample results also showed that microplastics were detected in each layer of the sediments, indicating that microplastics were trapped in each layer of mangrove sediments. Therefore, we believe that mangrove forests have an ecological interception effect on microplastics. After entering mangroves, microplastics are affected by tidal reciprocating current scouring, river runoff, sunlight, wind erosion and other factors and gradually break into increasingly smaller particles through physical, chemical and biological effects. Microplastics accumulate in the sediments and experience sedimentation, suspension and reprecipitation processes together with the surface sediments. Mangroves should be widely planted in estuaries to reduce microplastic entry into the ocean.

作为阻止河流污染物进入海洋的最后一道屏障，红树林具有很强的吸收净化能力和较强的耐受性。我们从厦门市西溪河口采集了红树林地表水和沉积物样品。结果表明，海水中微塑料的丰度范围为620~13,100 n/m ³，沉积物中微塑料的丰度为143~488 n/kg，微塑料分布不均，西溪河口红树林微塑料丰度明显高于非红树林区。沉积物柱样品结果还显示，在每层沉积物中都检测到微塑料，表明微塑料被困在红树林沉积物的每一层中。因此，我们认为红树林对微塑料具有生态拦截作用。进入红树林后，微塑料受到潮汐往复冲刷、河流径流、阳光、风蚀等因素的影响，通过物理、化学和生物作用逐渐分解成越来越小的颗粒。微塑料在沉积物中积累，并与表层沉积物一起经历沉降、悬浮和再沉淀过程。应在河口广泛种植红树林，以减少微塑料进入海洋。