Multidimensional risk assessment and source analysis of micro- and nanoplastics in dairy cattle farms: An Inner Mongolia case study

Microplastics and nanoplastics (MNPs) have emerged as pollutants of global concern, yet their impacts on the livestock remain underexplored. This study investigated MNP pollution in nine large-scale dairy farms in China's Inner Mongolia Autonomous Region by analyzing soil, feed, and atmospheric samples. Laser direct infrared spectroscopy was used to analyze the abundance, morphology, size, and polymer types of microplastics (MPs), showing that the soil, feed, and atmosphere samples contained an average of 1757.89, 9432.21 MPs n/kg, and 1.86 MPs/m, respectively. Fragment MPs smaller than 100 μm dominated in all samples, while chlorinated polyisoprene and polyvinyl chloride were predominant polymer types. Nanoplastics (NPs) in manure-amended soil were detected via Py-GC/MS, varying from 2.21 to 30.23 mg/kg, with polyethylene NPs ubiquitous in all samples. Backward trajectory modeling showed that atmospheric MPs originated predominantly from northwest, northeast, and southwest airflows. The Positive Matrix Factorization model identified eight potential sources for soil MNPs, eight for feed MPs, and four for atmospheric MPs. All sampling sites were assessed as low risk in terms of ecological risk, and there were no non-carcinogenic or carcinogenic risks to humans. This research provides insights into the distribution, sources, and environmental risks of MNPs in livestock farming, offering a scientific foundation for targeted mitigation strategies.