Impact of Microplastics on Rice Productivity, Soil Physicochemical Properties and Greenhouse Gas Emissions in a Rice Paddy during Cultivation: A Pot Experiment

다국어 초록 (Multilingual Abstract)

Microplastics (MPs), small particle sizes (< 5 mm), are widely distributed in soil environment, recently increasing global attention. Agricultural materials including mulching film, soil conditioners, and greenhouse materials were major sources of MPs to be incorporated into agroecosysyems. MPs can influence soil physical, chemical, and biological properties, which may affect biogeochemical cycling in agricultural soils, potentially influencing greenhouse gas emissions (GHGs) and deteriorating crop productivity. However, few studies were carried out to investigate the effects of MPs on greenhouse gas emissions and productivity as well as soil quality during rice cultivation. In the pot experiment, different levels of MPs (0, 0.025%, 0.05%, 0.1% wt wt<SUP>-1</SUP> which roughly corresponded to 0.5~2 Mg ha<SUP>-1</SUP> in the field) that are mixed with the proportion of mulching film (60% wt wt<SUP>-1</SUP>), pesticide bottle (35% wt wt<SUP>-1</SUP>) as high-density polyethylene (HDPE), and other plastics (5% wt wt<SUP>-1</SUP>) including PP, PVC, PET were incorporated at the presence or absence (no cultivation, only added MPs) of rice plant with triplicate before the rice transplanting. We monitored GHG emissions (CO₂, CH₄, and N₂O), rice growth characteristics and yield, soil physical (qualitative and quantitative analyses of leachate) and chemical properties (pH, total C, N, extractables etc.) during cultivation. Our results showed MPs incorporation increased over all GHGs emissions during cultivation, showing much higher emissions in the absence of rice plant. MPs additions also suppressed rice growth and mainly reduced tiller numbers and height with increasing MPs application levels. Soil physical properties were also deteriorated by MPs additions, showing an obvious decrease in leachates at the higher levels of them. Our results indicate MPs incorporations can deteriorate overall soil quality including physical and chemical properties, which lead to significant decrease in rice productivity. Moreover, MPs can potentially increase GHGs emissions, probably due to the increased decomposition rate of MPs incorporated in rice paddy. Conclusively, our findings suggest that MPs might have a potentially hazardous impacts in rice paddy ecosystem. Therefore, the mitigation strategies of MPs should be urgently developed for a better and sustainable agricultural environment.