Deciphering microplastic ecotoxicology: impacts on crops and soil ecosystem functions

Abstract

Review on microplastic toxicity in agroecosystems is scarce. Thus, we develop a conceptual model (based on literature to date) that describes various microplastic effects using a size-scale. We also classify crops depending on their observed responses, and discuss several conceptual mechanisms of soil functions. The model shows that microplastic effects on crops can be positive, toxic, lethal and no-effect. Predominantly, microfibers in a wide range of sizes can positively affect crops. However, toxic effects of microplastics with/without other pollutants are more common at different sizes. Surprisingly, biodegradable plastic effects are lethal, calling into question their environmental friendliness. No-effect on crops is also possible but less observed. Unlike other crops (e.g., wheat, maize and bean), only onion seems resistant to microplastics. Crop uptake of micro/nanoplastic demands a clear benchmark to ensure food-safety. Furthermore, mixed effects are observed on soil functions. Alternation in soil enzymes and litter decomposition can affect nutrients and organic matter biogeochemistry. Hydrophobicity can be induced by increasing evaporation. Shifts in microbial community structure and activities are inevitable.