The growing significance of biodegradable plastics for environmental protection underscores the need to enhance their performance of degradation in natural environments. This study prepared PLA/PVA blends with varying ratios to assess the impact of PVA on their thermal properties, mechanical properties, and degradation behavior. Results indicated that as the PVA content increased from 0 to 100%, both tensile and flexural strengths initially decreased before increasing. Furthermore, the decomposition temperature of the blends decreased by 18-35 degrees C as the PVA content increased. Specifically, pure PLA exhibited a thermal degradation temperature of 332 degrees C; while, the blend with 80% PVA showed a reduced temperature of 296 degrees C. Hydrolysis tests showed that weight loss increased significantly with higher PVA content, with the 20PLA/80PVA blend losing 78.9% of its weight after 30 days, compared to only 0.13% for pure PLA. The mechanical properties of the 20PLA/80PVA blend decreased by 98.31% in tensile strength and 79.19% in hardness after 30 days of hydrolysis, demonstrating accelerated degradation. Soil degradation tests further revealed that the 20PLA/80PVA blend lost over 85% of its weight within 20 days; while, pure PLA lost less than 1%. These results suggest that altering the PLA/PVA ratio can substantially enhance degradation rates, offering valuable insights for the development of efficient biodegradable plastics.

Soil microbiomes drive many soil processes and maintain the ecological functions of terrestrial ecosystems. Microplastics (MPs, size <5 mm) are pervasive emerging contaminants worldwide. However, how MPs affect soil microbial activity has not been well elucidated. This review article first highlights the effects of MPs on overall soil microbial activities represented by three soil enzymes, i.e., catalase, dehydrogenase, and fluorescein diacetate hydrolase (FDAse), and explores the underlying mechanisms and influencing factors. Abundant evidence confirms that MPs can change soil microbial activities. However, existing results vary greatly from inhibition to promotion and non-significance, depending on polymer type, degradability, dose, size, shape, additive, and aging degree of the target MPs, soil physicochemical and biological properties, and exposure conditions, such as exposure time, temperature, and agricultural practices (e.g., planting, fertilization, soil amendment, and pesticide application). MPs can directly affect microbial activities by acting as carbon sources, releasing additives and pollutants, and shaping microbial communities via plastisphere effects. Smaller MPs (e.g., nanoplastics, 1 to <1000 nm) can also damage microbial cells through penetration. Indirectly, MPs can change soil attributes, fertility, the toxicity of co-existing pollutants, and the performance of soil fauna and plants, thus regulating soil microbiomes and their activities. In conclusion, MPs can regulate soil microbial activities and consequently pose cascading consequences for ecosystem functioning.

Biodegradable plastics (BPs) are known to decompose into micro-nano plastics (BMNPs) more readily than conventional plastics (CPs). Given the environmental risks posed by BMNPs in soil ecosystems, their impact has garnered increasing attention. However, research focusing on the toxic effects of BMNPs on soils remains relatively limited. The degradation process and duration of BMNPs in soil are influenced by numerous factors, which directly impact the toxic effects of BMNPs. This highlights the urgent need for further research. In this context, this review delineates the classification of BPs, investigates the degradation processes of BPs along with their influencing factors, summarizes the toxic effects on soil ecosystems, and explores the potential mechanisms that underlie these toxic effects. Finally, it provides an outlook on related research concerning BMNPs in soil. The results indicate that specific BMNPs release additives at a faster rate during decomposition, degradation, and aging, with certain compounds exhibiting increased bioavailability. Importantly, a substantial body of research has shown that BMNPs generally manifest more pronounced toxic effects in comparison to conventional micro-nano plastics (CMNPs). The toxic effects associated with BMNPs encompass a decline in soil quality and microbial biomass, disruption of nutrient cycling, inhibition of plant root growth, and negative impacts on invertebrate reproduction, survival, and fertilization rates. The rough and complex surfaces of BMNPs contribute to increased mechanical damage to tested organisms, enhance absorption by microorganisms, and disrupt normal physiological functions. Notably, the toxic effects of BMNPs on soil ecosystems are influenced by factors including concentration, type of BMNPs, exposure conditions, degradation products, and the nature of additives used. Therefore, it is crucial to standardize detection technologies and toxicity testing conditions for BMNPs. In conclusion, this review provides scientific evidence that supports effective prevention and management of BMNP pollution, assessment of its ecological risks, and governance of BMNPs-related products.