Microplastic characteristics in rain/snow sampled from two northern Chinese cities

Atmospheric precipitation is recognized as a significant source of environmental microplastics, especially in inland waters and remote areas. However, due to the limited availability of existing data, further information on microplastics in precipitation is essential. Therefore, this study aims to elucidate the contamination of microplastics in both snowfall and rainfall while identifying potential factors that may influence their presence during atmospheric deposition. Samples of snowfall and rainfall were collected from two representative cities in Northern China across winter and summer seasons. Subsequently, microplastics were identified and quantified automatically using laser-assisted direct infrared imaging techniques. The findings indicate that microplastic concentrations are higher in snowfall (City A: 182.30 ± 190.25 items/L; City B: 301.74 ± 325.81 items/L) compared to rainfall (City A: 58.90 ± 51.00 items/L; City B: 39.20 ± 30.31 items/L), revealing significant variations in the polymer composition of microplastics. Moreover, a greater diversity of polymers was identified in snowfall relative to rainfall, despite some commonalities among polymers; fragments measuring between 20 μm to 100 μm comprised the majority of detected microplastic particles across both types of precipitation. Crucially, the frequency of precipitation events (rainfall versus snowfall) appears to affect the concentration of atmospheric microplastics, resulting in notably higher levels within snowfalls. These findings offer valuable insights into wet deposition processes by underscoring the atmospheric origins contributing to environmental microplastic pollution.