Occurrence and Sources of Microplastics in groundwater divided by well depth and Hydrogeology in South Korea

Groundwater plays a critical role as a vital and renewable water resource for drinking, domestic, and agricultural purposes. Unfortunately, it is under threat from various emerging contaminants, including antibiotic resistance genes, per- and poly-fluoroalkyl substances (PFAS), and micro- and nano-plastics (MNPs). MNPs act as agents, transporting trace heavy metals, hydrophobic pollutants, and toxic chemicals into groundwater from terrestrial and aquatic environments through physical, chemical, and biological processes. The transported MNPs have an impact on human health and ecological species. The objectives of this study were to: (1) assess the abundance of microplastics based on hydrogeology and well depth; (2) characterize the properties of aquifer; (3) identify possible sources of microplastics. The study aims to establish a baseline for the area, contribute to databases on microplastic pollution, and may lead to new solutions for this type of pollution. Data were collected from 17 wells of the National Groundwater Monitoring Network in South Korea. Sixteen water quality parameters, as well as the abundance and properties of microplastics, were analyzed based on depth and hydrology groups. As a result, the average number of microplastics (MPs) detected in 17 groundwater wells, each with a volume of 1.5 liters, was 4.8 particles per liter. In the groundwater samples, a total of six polymer types were identified, including PP, PE, PVC, PS, PA, and PU, with PP and PE being the predominant polymer types. There is a trend where the concentration of MPs tends to be higher in groundwater wells with shallower depths. The main source of MP contamination in groundwater is expected to be the transport through groundwater flow from adjacent industrial and agricultural areas with higher energy levels.