Occurrence and distribution of microplastics in groundwater of a heavy agricultural area of Korea

In this study, we investigated the occurrence and distribution of microplastics (MPs) in groundwater of a heavy agricultural basin of Korea. The area of the basin is 57.5 km2, 10.5 km long and 6.7 km wide. It is bowl shaped and the elevations of the basin range from 400 m to 1,242 m but most agricultural activities occur at elevations of 400-600 m. Farmers are growing a variety of vegetables (cabbage, carrot, potatoes, sweet potatoes, corn), fruits (mainly apples), and ginsengs. They usually use plastic mulching for their growing. We can easily find abandoned used plastic mulches all over the basin. There are over 300 groundwater wells, mainly used for agriculture. Depths of the wells range from 10 to 200 m with a mean of 30 m. Thus there is a possibility of groundwater contamination with MPs. For the investigation, we collected 14 MP samples from 12 groundwater wells, 1 treated wastewater effluent, and 1 stream water. To avoid any contamination of MPs from sampling equipments, we cleaned them twice both in the laboratory and in the field site prior to using. All the related equipments are made of stainless steel, not plastics. The connection pipe is made of silicon. A totally 500 L water was flowed into two steel filters step by step whose mesh sizes are 100 and 20 m. Here we report on the investigation results. This research was supported by Korea Environment Industry & Technology Institute (KEITI) through Measurement and Risk assessment Program for Management of Microplastics Program, funded by Korea Ministry of Environment (MOE) (2020003110010).