Faculty of Bioresources and Environmental Sciences, Ishikawa Prefectural University, 1-308 Suematsu, Nonoichi, Ishikawa, 921-8836, Japan.
Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, 1-308 Suematsu, Nonoichi, Ishikawa, 921-8836, Japan.
Chemosphere. 2021 Sep;279:130574. doi: 10.1016/j.chemosphere.2021.130574. Epub 2021 Apr 15.
Polymer-based microcapsules derived from coated fertilizers are not recovered after use. Therefore, they are a source of microplastics to the agricultural lands and coastal areas of Japan. In this study, we investigated the input-output balance of microcapsules in three paddy fields and the timing of microcapsule discharge from the fields with the aim of developing effective techniques to reduce microcapsule discharge. Microcapsules were discharged from the paddy fields primarily during puddling, when the weir plate was overflowed, and when surface drainage was implemented. About 50% of the total discharge during the irrigation period occurred during puddling, which is a process for leveling paddy fields. Therefore, contamination of the surrounding environment by microcapsules from paddy fields can be effectively reduced by preventing the release of microplastics from paddy fields during puddling. We also showed that the total microcapsule discharge cannot be controlled solely by irrigation water management, such as by adjusting the height of the weir plate. We found that about 0.067-0.076% of the total number of microcapsules accumulated in the soil of the paddy fields was discharged during the irrigation season in 2020. Furthermore, 70% of the microcapsules discharged from one field in 2020 had resided in the soil for at least two years. The use as fertilizer coatings of biodegradable polymers that would degrade completely in the soil within a few years could therefore substantially reduce the amount of microplastics released into the ocean from agricultural fields, and their development is thus urgently needed.
由包膜肥料衍生的聚合物微胶囊在使用后不会被回收。因此，它们成为日本农田和沿海地区微塑料的来源。在这项研究中，我们调查了三个稻田中微胶囊的投入产出平衡以及微胶囊从稻田中排放的时间，旨在开发有效的技术来减少微胶囊的排放。微胶囊主要在稻田的淹水期、堰板溢出时和表面排水时从稻田中排出。在灌溉期，约 50%的总排放量发生在淹水期，这是一个平整稻田的过程。因此，通过防止淹水期间农田中微塑料的释放，可以有效减少农田周围环境受到微胶囊的污染。我们还表明，仅通过灌溉水管理（例如调整堰板的高度）无法控制微胶囊的总排放量。我们发现，2020 年灌溉季节，约有 0.067-0.076%的累积在稻田土壤中的微胶囊总数被排放。此外，2020 年从一个田块排放的微胶囊中，有 70%至少在土壤中停留了两年。因此，将可在几年内在土壤中完全降解的生物降解聚合物用作肥料包膜，可以大大减少从农田释放到海洋中的微塑料数量，因此迫切需要开发这种聚合物。
