Stress of polyethylene and polylactic acid microplastics on pakchoi（Brassica rapa subsp. chinensis） and soil bacteria: Biochar mitigation

Abstract

It remains essential to investigate the differences in phytotoxic effects between conventional and biodegradable microplastics (MPs). Furthermore, the mechanisms by which biochar mitigates the toxic effects of MPs on crops and soil remain poorly understood. The results of this research indicated that, compared to control treatment (CK), the application of 2% polyethylene (PE) alone led to a significant reduction in the fresh weight of pakchoi by 36.8% (P<0.05). In examining the activities of antioxidant, as well as the concentrations of MDA and GSH in pakchoi, the 2% PE treatment exhibited the highest levels. In contrast, the treatment that received a mixed application of biochar and MPs did not surpass the levels observed in the microplastic-only application. The combination of 0.2% polylactic acid (PLA) with biochar resulted in a substantial increase in Chao1 index, with improvements of 46.4% to CK. The findings also suggested that biochar can significantly impact bacterial diversity in soil with MPs, thereby altering the functions and metabolic pathways. Consequently, this modification partly influences the growth characteristics of pakchoi. Notably, PE demonstrated a higher level of toxicity to both plants and soil microorganisms than PLA at same applied quantity. These findings open avenues for innovative sustainable agricultural practices.