Occurrence patterns and ecological implications of microplastic contamination in citrus orchard soils on Karst Sloping Terrains, South China

Microplastics have emerged as pervasive pollutants in soil ecosystems, posing threats to fragile karst environments. However, their occurrence characteristics and ecological consequences remain poorly understood. In the present study, we investigated the pollution characteristics, ecological risks, and relationships among soil environment indicators and microplastics in citrus-cultivated soils in the Lijiang karst sloping terrains, South China. The average concentration of soil microplastics was 3160 ± 342 items/kg, and the particle abundance and pollution load index increased with cultivation years and declined with slope position. Moreover, we detected significant correlations among the abundance, shape, and composition of microplastics and key soil parameters. Notably, microplastics were observed to have significant effects on the structure, network relationships, and functionalities of soil microbial communities. Positive relationships were identified between the soil microplastic abundance and the energy-sourcing function of bacteria and the symbiotic mode of nutrition in fungi. Shape differences of microplastics were significantly positively correlated with saprophytic nutrition in fungi. Our findings provide valuable insights into the ecological risks posed by microplastics and highlight the urgent necessity of implementing sustainable strategies for plastic waste management to mitigate adverse impacts on ecologically sensitive regions, including agricultural soils in the karst sloping terrains of South China.