Microplastics like marine litter are causing serious harm to the Earth’s soils. (Image courtesy of Flickr/CCL: Bo Eide)
DAEJEON, Nov. 17 (Korea Bizwire) – A recent study has revealed that microplastics are causing disturbances in soil ecosystems and impacting nitrogen cycling. The Korea Institute of Toxicology (KIT) disclosed on Thursday that for the first time, it has substantiated the correlation between the size and concentration of microplastics and the efficiency of nitrogen fixation in legumes such as soybeans, kidney beans, and red beans.
Rhizobacteria, which are bacteria residing in the rhizosphere of legumes, play a crucial role in facilitating plant growth by converting atmospheric nitrogen into a form usable by the plant.
To investigate the impact of microplastics on nitrogen cycling in soil, the KIT’s Center for Environmental Toxicological Effects exposed sub-micron (1-2 μm) microplastics composed of polyethylene (PE) and polypropylene (PP) to the soil where legumes were intended to grow, at an environmentally significant concentration of 50 mg/kg.
The results indicated that soybean growth remained unaffected in soils contaminated with microplastics. However, certain soil physicochemical properties, such as organic matter content and cationic capacity (the soil’s ability to retain nutrients for plants), were altered. Additionally, bacteria involved in the nitrogen cycle were activated due to the accumulation of nitrogen compounds in soil and plants.
Changes in the microbial community composition within the plant root zone (rhizosphere) were observed, with an increase in the number and gene expression of bacteria associated with nitrogen fixation and nitrification. This implies that microplastics modified both the quantity and activity of microbial communities involved in nitrogen cycling in the plant rhizosphere.
Despite the well-known negative effects of microplastics on plants, including cell damage, generation of reactive oxygen species (ROS), reduction in photosynthesis and germination, and DNA damage, this study suggests an additional impact: the alteration of nitrogen cycling by influencing the abundance and diversity of rhizosphere microorganisms in the soil-plant environment.
These findings were recently published in the Journal of Hazardous Materials, an international journal of environmental science.
Ashley Song (ashley@koreabizwire.com)
