Establishment of a separation and quantification method for microplastics in agricultural soil and clarification of the actual contamination status

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K21348
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 41:Agricultural economics and rural sociology, agricultural engineering, and related fields
• Research Institution: Niigata University
• Principal Investigator: Harada Naoki 新潟大学, 自然科学系, 教授 (50452066)
• Project Period (FY): 2020-07-30 – 2023-03-31
• Keywords: マイクロプラスチック / 土壌 / 油分離 / 劣化 / 被覆肥料外殻 / 海岸漂着物

Outline of Final Research Achievements

Plastics are used extensively in modern agriculture, and some of them may remain on farmland and degrade, causing microplastic (MP) contamination. However, there is no established separation method, and the actual situation is not clear. The discharge of coated fertilizer capsules from rice fields into the ocean is also a major problem. In this research, we investigated the oil separation as a simple and economical method to extract MPs from agricultural soils to understand the environmental dynamics and degradation process of MPs. The temporal changes in the appearance and chemical structure of coated fertilizer capsules under waterlogged soil conditions were investigated in field and laboratory experiments, and a survey of the amount of drifted coated fertilizer capsules was conducted on the coast of Niigata City to get a better understanding of the extent of fertilizer capsule outflow into the ocean.

Free Research Field

土壌学

Academic Significance and Societal Importance of the Research Achievements

海洋では1970年代からプラスチックごみによる生態系破壊や景観毀損などが問題となっているが，陸上にはその4-23倍ものプラスチックごみが投棄・埋設されていると言われている。農地もマルチフィルム等のプラスチック資材が多用されており，例外ではない。さらに近年は，5 mm以下のマイクロプラスチック（MP）への関心も高まっている。こうした中，本研究の成果は農耕地土壌からのMPs分離法の確立に資する他，被覆肥料外殻の土壌中での劣化過程や海洋流出の一旦を明らかにしたものである。