High abundance of microplastics in groundwater in Jiaodong Peninsula, China

The occurrence of microplastics (MPs, <5 mm) in drinking water has aroused extensive concerns, whereas our understanding of their presence in groundwater, a major source of drinking water, is still limited. The present study investigated the occurrence of microplastics in groundwater sampled from five sites in Jiaodong Peninsula, China. The abundance, type, and size of MPs in the groundwater samples were determined by Laser Direct Infrared following a well-established and quality-controlled analytical route. Notably, MPs were detected in groundwater across all five sampling sites, with high abundances ranging from 87 to 6832 particles/L and an average abundance of 2103 particles/L. The variation of the abundance of MPs was correlated to the distances between sampling sites and anthropogenic activities, which suggested significant impacts of aboveground industry and agriculture on the abundance of MPs in groundwater. Polyethylene terephthalate (PET) and polyurethane (PU) were the dominant polymer types detected in all groundwater samples. The MPs with a size smaller than 100 μm were found to account for >90% of the total MPs detected in four sampling sites, which was likely associated with their migratory routes through surface water runoff and infiltration into the groundwater settings. The results of this study suggest the importance of counting small MPs when determining their abundances in groundwater or their abundances would be considerably underestimated. The present study for the first time demonstrated the occurrence of MPs in groundwater in China, which improves our understanding of the MPs distribution and raises concerns about groundwater safety in terms of MPs pollution.