Influencing factors for the spatial distribution and deposition history of microplastics in the sediments of Chaohu Lake, China

Microplastic (MP) pollution resulting from industrialization and urbanization is obtaining increasing attention. Focusing on the pollution status in Chaohu Lake, the spatial distribution, concentration, particle size, and polymer composition of MPs were measured. The concentration of MPs in the Chaohu Lake surface sediments (n = 26) ranged from 6.34 to 81.98 items/g, and the most abundant polymers in the samples were chlorinated polyisoprene (CPI), polyvinylchloride (PVC), and polyethyl terephthalate (PET). The spatial distribution of MPs did not correlate well with indices representing the depositional environment but corresponded well to the anthropogenic factors. Multiple risk assessment tools were employed to evaluate the surface sediments, and high-risk levels were concluded. Simultaneously, an analysis on a profile encoded CHX from Chaohu Lake was carried out. A total of 27 polymer types were identified, with PET as the dominant type, accounting for more than 85.4 % of the total. The concentration of MPs in the profile ranged from 13.51 to 6089.22 items/g, which was much higher than that in the surface sediments. The size of MPs was mainly concentrated in the range of 20-50 μm, accounting for 56.3 % in the surface sediments and 77.4 % in the profile. MPs such as chlorinated polyethylene (CPE), PET, and fluororubber (FKM) were detected at depths predating their initial industrial production or widespread application, suggesting potential downward migration. From the perspective of temporal variation, MPs in the CHX profile increased from 13.51 items/g (9 cm, 1943) to 2586.06 items/g (8 cm, 1951), which is consistent with the large-scale production of plastics in the 1950s. The current study provided a dataset for the spatio-temporal distribution of MPs and enhanced our understanding of their environmental behavior and potential hazards in Chaohu Lake sediments.