Behavior And Toxicity Of Micro/Nanoplastic Particles In The Freshwater Environment

The problem of plastic pollution has attracted the attention of the scientific community and the public.It is of great significance for ecological risk assessment to investigate the behavior and toxicological effect of micro/nanoplastic particles in aquatic environment.The effects of different aqueous conditions（p H,dissolved organic carbon,and divalent cations）on the agglomeration,stability and toxicity of different surface functionalized nanoplastic particles（NPs）were investigated;The aquatic behavior and toxicity of non-and metal-oxide-doped microplastic particles（MPs）with different surface modification were investigated.The major results in this study are shown as follows:（1）The coexistence of dissolved organic carbon and the divalent cations enhanced the extent of aggregation of the NPs in the water columns.The enhancement of NP aggregation in the presence of dissolved organic carbon and the divalent cation was caused by bridge formation.The surface modification and p H were dominant factors influencing the stability of NPs during long-term suspension when dissolved organic carbon and the divalent cations coexisted.The NPs exhibited acute toxicity and physical damage to Daphnia magna.The more complex the solution conditions,the more toxicity the amine-modified NPs and carboxyl-modified NPs.Analysis of mode of toxic action implied that the NPs mainly caused the accumulation of oxidative damage to the gut of D.magna.（2）The stability of iron-oxide-doped MPs（MPS（Fe）-NH₂and MPS（Fe）-COOH）was higher than non-doped MPs（MPS-NH₂and MPS-COOH）.The toxicity of MPS（Fe）-NH₂ to the studied organisms was greater than the MPS（Fe）-COOH and non-doped MPs.Iron-oxide-doped MPs can dissolve in the test medium.Moreover,the particles mainly contributed to the toxicity rather than their dissolved fraction.The accumulation of MPS（Fe）-NH₂in C.pyrenoidosa was higher than the MPS（Fe）-COOH at low effect concentrations.The MPS（Fe）-NH₂ was heavily adsorbed on the surface and distributed over the antennae,carapace,and apical spine of D.magna body whereas the MPS（Fe）-COOH was mainly accumulated inside the digestive tract of the daphnia.Furthermore,it was found that that the intensities of the toxic effects cannot be linked to oxidative stress induced by the particles in the algae and daphnids.