TITLE:
Separation and Measurement of Microplastics in Paddy Soil
AUTHORS:
Yumei Kang, Yuma Hirota, Kou Tsukayama, Kou Ikejima, Katsutoshi Sakurai
KEYWORDS:
Microplastics, Gravity Separation, Soil, Paddy Field
JOURNAL NAME:
Journal of Environmental Protection,
Vol.15 No.12,
December
25,
2024
ABSTRACT: Accumulation of microplastics (MPs) in soil is a worldwide concern, but a standardized analysis method for soil MPs has not been established yet. In this study, we compared deionized water, zinc chloride and sodium iodide solution with specific gravities of 1.0, 1.4 and 1.5, respectively, for the separation of MPs in paddy soil that had a history of coated fertilizer application. Organic matter in the paddy soils was digested with Fenton’s reagent (30% peroxide and 0.05 M iron sulfate) before density separation. Separation efficiency of MPs in soil was significantly high for sodium iodide, followed by zinc chloride, then water. The abundance of MPs in the soil ranged 100 - 5800 pieces/kg. The particle sizes of MPs in the soil were found to be extremely small, ranging from 1 - 111 μm. Since paddy fields are waterlogged during plantation and are drained about two weeks before harvest, large MPs might be flushed out by water. It can be concluded that MPs in paddy soil may have large range of plastic materials with different gravity and small particle size.