Record of microplastic deposition revealed by ornithogenic soil and sediment profiles from Ross Island, Antarctica.

Microplastics (MPs) are a global concern as an emerging pollutant, and the investigation on MPs in Antarctic aids in informing their global pollution assessments. Therefore, there are urgent scientific concerns regarding the environmental behavior, origins, influencing factors, and potential hazards of MPs in Antarctica. This study presents the characteristics of MPs from one ornithogenic sediment profile (coded CC) and two ornithogenic soil profiles (coded MR1 and MR2) from ice-free areas on Ross Island, Antarctica. We explored the potential sources of MPs and the main influencing factors for deposition based on their distribution with depth in the profiles. Through laser-infrared imaging spectroscopy (LDIR), a total of 30 polymer types were identified in all samples, with polyethylene terephthalate (PET) and polyvinyl chloride (PVC) as the dominant types, accounting for more than 70% of the total. The abundance of MPs in the CC sediment profile ranged from 2.83 to 394.18 items/g, while in MR1 and MR2 soil profiles, the abundance ranged from 2.25 to 1690.11 and 8.24 to 168.27 items/g, respectively. The size of MPs was mainly concentrated in the range of 20-50 μm, and possible downward movement of certain polymer types was revealed. From the perspective of temporal variation, we suggest that MPs were heavily influenced by local human activities including scientific research, fishing, and tourism, balanced by protective regulations, while no solid evidence was obtained to support strong influence from biological transport through penguins. This research enhances our understanding on the environmental behavior of MPs in the terrestrial systems of remote polar regions.