Biodegradation of Poly(Styrene-<i>Alt</i>-Maleic Anhydride) in Soil and Its Toxic Effects on the Environment

In recent years, synthetic polymers have become integral to modern society, but their improper disposal has led to significant environmental challenges. Therefore, it is of great significance to investigate the environmental impact of polymer waste. Herein, we conducted comprehensive research on the biodegradability of poly(styrene-<i>alt</i>-maleic anhydride) (PSM) when exposed to soil and microbes, as well as its toxic effects on soybean seedlings and <i>Eisenia fetida</i>. The biodegradation process of PSM was thoroughly evaluated using respirometry tests, Fourier transform infrared spectroscopy, gel permeation chromatography, weight loss analysis, and bacterial reproduction tests. After 90 days of incubation in soil, the mineralization ratio of PSM reached 15%, and the weight-average molecular weight gradually decreased from 28.0 to 14.5 kg/mol in the first 14 days. Additionally, PSM experienced a 50% degradation by <i>Pseudomonas aeruginosa</i> after 30 days. In terms of phytotoxicity, PSM showed slight effects on the morphology of soybean seedlings while inducing oxidative stress in roots. The toxic effects of PSM on <i>Eisenia fetida</i> were investigated using both filter paper and soil contact methods. The filter paper contact test showed that the LC₅₀ value was above 1000.0 μg/cm² at 48 h, while the soil contact test indicated an LC₅₀ value of 93.34 g/kg at 7 days. In conclusion, PSM demonstrates excellent biodegradability and low biotoxicity, suggesting great potential for emerging environmental applications.