Impacts of Emerging Pollutants Decabromodiphenyl Ether (BDE-209) and Polylactic Acid (PLA) Exposure on Spinach...

Emerging contaminants, including brominated flame retardants and microplastics, in agricultural soils pose a serious threat to crop security and ecosystem health. This study aimed to provide an understanding of the toxicity-induced effects of decabromodiphenyl ether (BDE-209) and polylactic acid (PLA) on Spinach (Spinacia oleracea) in the soil system by examining Spinach biomass, chlorophyll content, antioxidant enzyme activity, and microbial community composition after a 42-day exposure. The pre- and post-structural, morphological, and surface chemical group analyses of PLA and BDE-209 in contact with the soil system were analyzed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The data show that the combined treatment caused the most significant growth inhibition, with a 95% reduction in shoot dry weight and a 25% reduction in chlorophyll content, suggesting continued photosynthetic damage. Antioxidant enzyme analyses revealed an impaired defence system, wherein superoxide dismutase (SOD) activity increased (BDE-5: 48.4%, and BDE-6: 44.2%), whereas catalase (CAT) and peroxidase (POD) activities decreased (0.4-2.3%) across treatments, indicating metabolic blockage and subsequent hydrogen peroxide accumulation. The soil microbial composition in response to stress showed significant structural changes, including an increase in stress-tolerant genera, such as Bacillus (30-39%), and a decrease in beneficial Oligotrophic bacterial populations (58.9-74.0%). The degradation of PLA was confirmed by FTIR and SEM, which revealed surface interaction with BDE-209 and exhibited reduced absorbance between 1200 and 1000 cm^-1, accompanied by a reduction in particle size (70-90 μm). These findings suggest that PLA may be a co-pollutant exacerbating BDE-209 toxicity by increasing oxidative stress and altering the soil microbial community.