In one of the first investigations into the potential effects of plastic pollution on plants, an international research team has shown that nanoplastics can accumulate in plant tissues.
The researchers noted that as concern grows about micro- and nanoplastics in the oceans and in seafood, they are increasingly studied in marine environments. However, “little is known about the behavior of nanoplastics in terrestrial environments, especially agricultural soils.”
Study lead author Baoshan Xing is an environmental scientist at the University of Massachusetts Amherst Stockbridge School of Agriculture. Xing collaborated with researchers at Shandong University in China, who conducted the experiments.
The experts said that prior to this study, there was no direct evidence that nanoplastics are internalized by terrestrial plants.
“Our findings provide direct evidence that nanoplastics can accumulate in plants, depending on their surface charge. Plant accumulation of nanoplastics can have both direct ecological effects and implications for agricultural sustainability and food safety,” the researchers said.
According to Xing, widespread global use and persistence in the environment result in an “enormous” amount of plastic waste. “Our experiments have given us evidence of nanoplastics uptake and accumulation in plants in the laboratory at the tissue and molecular level using microscopic, molecular and genetic approaches. We have demonstrated this from root to shoot.”
Xing explained that nanoplastic particles can be as small as a protein or a virus. In the natural environment, these particles are very different from the pristine polystyrene nanoplastics often used in the lab.
The processes of weathering and degradation change the physical and chemical properties of plastic and the particles become electrically charged. “This is why we synthesized polystyrene nanoplastics with either positive or negative surface charges for use in our experiments,” said Xing.
The team grew Arabidopsis plants in soil mixed with differently charged, fluorescently labeled nanoplastics. After seven weeks, exposure to nanoplastics had adversely affected plant biomass and height compared to control plants.
“Nanoplastics reduced the total biomass of model plants,” said Xing. “They were smaller and the roots were much shorter. If you reduce the biomass, it’s not good for the plant, yield is down and the nutritional value of crops may be compromised.”
“We found that the positively charged particles were not taken up so much, but they are more harmful to the plant. We don’t know exactly why, but it’s likely that the positively charged nanoplastics interact more with water, nutrients and roots, and triggered different sets of gene expressions. That needs to be explored further in crop plants in the environment. Until then, we don’t know how it may affect crop yield and food crop safety.”
The study is published in the journal Nature Nanotechnology.