Spatiotemporal variations of microplastics and influencing factor analysis in coastal seawater of Qingdao, China

Microplastic pollution in coastal zones has attracted widespread attention, as coastal zones act as significant reservoirs of microplastics. Yet impacts of human and environmental factors on microplastic distribution in specific coastal areas remain elusive. This study combined stereomicroscope and micro-FT-IR technical to investigate the abundance and composition characteristics of microplastics in the coastal seawater of Qingdao in 2024 and analyze the potential factors affecting the spatiotemporal distribution of seawater microplastics. Results showed that the average microplastic abundance in coastal seawater was 293.0 ± 125.4 items/m³ in June and 412.0 ± 152.4 items/m³ in August. An east-to-west increasing trend in the microplastic abundance was observed, with the Zhanqiao Pier (ZQ) exhibiting the highest values. The microplastics found in the coastal seawater were mainly fibers in shape, black and blue in color, 1000-2000 microm in size, and rayon and PET in polymer types. Principal Component Analysis (PCA) showed large spatial heterogeneity in microplastic characteristics between study sites, particularly in August. The results demonstrated that tourism activities, population density, ocean currents, and rainfall were the major factors affecting the spatiotemporal distribution of seawater microplastics. These findings underscore the need for effective management strategies to mitigate the impact of human activities on microplastic pollution in coastal environments.