Microplastics in landfast sea ice of Alaskan Arctic: Characteristics and potential sources

Regarding the rapid shrinkage of the Arctic cryosphere, sea ice plays a significant role in the temporal storage, transport, and release of microplastics (an emergent pollutant) among atmospheric, aquatic, and terrestrial environments. However, there are sparse studies on microplastics in the landfast sea ice and lagoon lake ice in the Alaskan Arctic region. Therefore, this study investigated characteristics and potential sources of microplastics in the landfast sea ice and lagoon lake ice in the Alaskan Arctic (Point Barrow). The results found that the average abundance of microplastics in the landfast sea ice (220.6±140.1 items/L) was comparable to that in lagoon lake ice near Point Barrow (148.9±141.8 items/L). For different layers of sea ice cores, the maximum abundance of microplastics generally occurred in the bottom layer. The overall particle sizes for the detected microplastics revealed that the abundance of microplastics decreased with increasing size for both landfast sea ice and lagoon lake ice samples. Small-sized microplastics (≤50 μm) accounted for more than 80% of the detected microplastics, with the dominant shape being fragments. The predominant polymers in sea ice were polyamide (PA), polyethylene (PE), and polyethylene terephthalate (PET). Meanwhile, PE and rubber dominated the polymers detected in lagoon lake ice. These differences between microplastics in Arctic sea ice and lagoon lake ice further indicated the discrepancies in microplastic transport pathways and deposition. Microplastics in landfast sea ice were mainly affected by seawater transported from the Pacific Ocean into the Chukchi Sea. In contrast, microplastics in lagoon lake ice were mostly influenced by the seawater of the Beaufort Sea and local vehicle emissions ( e.g. , rubber). This study further highlighted that a large abundance of microplastics was widely distributed in the sea ice of the Alaska Arctic region and may pose potential risks to the local ecosystems.