Temporal and spatial variation of microplastics in Baotou section of Yellow River, China

Freshwater rivers play the key role in providing drinking water sources and building the bridge of oceans and lands. Hence, environmental pollutants can be transferred into drinking water through a water treatment process and transported land-based microplastics into the ocean. Microplastics are considered a new pollutant that is becoming a threat to freshwater ecosystems. The present study investigated the temporal and spatial variation of microplastics abundance and their characteristics of occurrence in surface water, sediment and soil samples of Baotou section of Yellow River in China in March 2021 and September 2021. According to the LDIR analysis, the average abundances of microplastics in wet season (surface water 2510.83 ± 2971.27n/L, sediment 6166.67 ± 2914.56n/kg) were higher than that in dry season（surface water 432.5 ± 240.54n/L, sediment 3766.67 ± 1625.63n/kg), particularly being significant difference in the dry and wet seasons of surface water. The predominant polymer types in surface water (PBS and PET during the dry season, PP during the wet season) demonstrated that the temporal variation of microplastics abundance in surface water could be attributed to the combined effect of the regional precipitation, fishing activities and improper disposal of plastic waste. And the results of spatial abundances of microplastics showed that the microplastics abundance of soil and sediment was higher than that in river water and microplastics abundance in the river of the south side was the higher than other water sampling sites, revealing the differences of microplastics burden at the different sampling sites. Moreover, it is worth noting that a large amount of PAM was detected in sediments and soil, but not in water, and the biodegradable plastics PBS and PLA were also detected in the Yellow River. It was a very useful information for evaluating environmental impacts and ecological effects of degradable plastics compared to the traditional plastics after the implementation of a new environmental policy in the future. Thus, this study provided insights into the temporal-spatial characteristics of microplastics in an urban river and raised environmental management awareness of the long-term threat to drinking water safety by microplastics.