Carnosic acid alleviates polystyrene microplastic-induced soil degradation and enhances maize growth

The increasing contamination of soils with microplastics (MPs), particularly polystyrene (PS), poses a threat to agricultural productivity by disrupting soil properties and impairing plant growth. Carnosic acid (CA), an organic acid with antioxidant properties, has been proposed as a potential solution to counteract these negative effects. This study investigates the impact of PS contamination and CA amendments on maize (Zea mays L.) growth and soil health. Soil samples were treated with varying concentrations of PS (0.0%, 1.0%, 5.0%, and 10.0%) and CA (0.0%, 1.0%, 2.0%, and 3.0%) and incubated for 45 days. Plant growth was evaluated through biomass, chlorophyll index, and leaf area. Results showed that PS contamination significantly reduced maize growth, with the highest PS concentration (10.0%) leading to reduction in root dry weight from 2.86 to 2.09 g, chlorophyll content from 32 to 14, and plant height from 73.67 to 52 cm. CA amendments enhanced maize growth, with the highest CA concentration (3.0%) increasing root dry weight from 2.86 to 3.29 g, chlorophyll index from 32 to 36.8, and leaf area from 309 to 355.35 cm2. This study suggests that CA can effectively alleviate the detrimental effects of PS contamination on plant growth, offering a potential strategy for enhancing agricultural sustainability in contaminated soils.