Microplastic contamination is ubiquitous in riparian soils and strongly related to elevation, precipitation and population density

Although environmental research has recently begun to focus on the ubiquity of microplastics in terrestrial systems, there is still lack of comprehensive data which describe microplastics levels in soils and the factors influencing the distribution of this contaminant. Here, we show that microplastics contamination (3877 ± 2356 p kg) is omnipresent in numerous soil samples collected along the Yangtze River. Subsoils (4005 ± 2472 p kg) showed higher levels of microplastics than topsoils (3748 ± 2301 p kg), while polyamide (32%) was the most commonly found polymer in the samples. Small microplastics particles (< 200 µm) accounted for approximately 70% of the microplastics detected in subsoils. In terms of shape, microfragments were the most common type of microplastic particle, accounting for 34% of total microplastics, followed by microfibers (30%). Furthermore, microplastics contamination was found to be positively correlated with both the population of the study area and precipitation, yet negatively correlated with the elevation of the sampling site. Our study represents the first large-scale study of microplastic contamination in riparian soils along the Yangtze River, and provides important data regarding the ecotoxicology and ecosystem effects of microplastics in terrestrial environments.