Micro- and nano-plastics (MP (NP) s) in the environment have been widely concerned due to their large specific surface area, low surface polarity, and easy adsorption and accumulation of other pollutants. Submerged macrophytes, which are completely submerged in water, may be more sensitive to changes in pollutants in the aquatic environment than other groups of organisms.

Researchers from the Aquatic Plants and Aquatic Ecosystem Health Group of Wuhan Botanical Garden investigated the combined effects of varying types of MPs and arsenic (As (III) and As (V)) on submerged macrophytes.

The results of adsorption kinetics showed that the adsorption capacity of MP (NP) s for As (III) and As (V) increased rapidly in the first 24 h and reached the adsorption equilibrium after 36 h. The adsorption capacity at equilibrium of MP (NP) s increased with the increase of As concentration. With the increase of the pH value, the adsorption of MP (NP) s on As first increased and then decreased, and the adsorption capacity reached the peak at the pH of 6. And the adsorption process was favorable at higher temperatures. All the results indicated that the adsorption capacity of MP(NP) s for As was positive with the increase of reaction time and concentration, and the adsorption capacity was closely related to pH value and temperature. PVC (polyvinyl chloride) and PS (Polystyrene) containing complex functional groups had a larger adsorption capacity for As than PE (polyethylene), while NPs with smaller particle size showed good adsorption behavior due to their larger specific surface area.

PS- NPs significantly inhibited total chlorophyll, Fv/ Fm, soluble sugar, soluble protein, malondialdehyde, antioxidant enzyme activity and root activity of submerged macrophytes, and damaged the cellular structure of plant leaves (cell membrane, mitochondria and nucleus). In addition, the growth of submerged macrophytes was more significantly inhibited when PS- NPs and arsenic acted together, rather than reducing arsenic toxicity, further indicating that the adsorption behavior of PS- NPs and arsenic could enhance the ecological risk of pollutants.

This work provides a theoretical basis for further understanding the toxic effects and mechanism of single and combined contamination of PS- NPs and As on submerged macrophytes.

The research titled “The adsorption of arsenic on micro- and nano-plastics intensifies the toxic effect on submerged macrophytes” was published in the Environmental Pollution. It was supported by the National Natural Science Foundation of China, Wuhan Application Foundation Frontier Project and Project SAJC202102 supported by SAJOREC, CAS (Sino-Africa Joint Research Center, Chinese Academy of Sciences).

 The adsorption of arsenic on micro- and nano-plastics intensifies the toxic effect on submerged macrophytes (Image by WBG)