Toxicological Effects Of Nano-sized BiOBr To Pseudokirchneriella Subcapitata

Nano-sized BiOBr?n-BiOBr?is a highly active photocatalyst with diverse applications.Because of its response to visible light,discharged n-BiOBr can pose potential risk to water ecosystems.At present,the research and development proportion of n-BiOBr materials is in an increasing trend,but relatively little attention has been paid to the biological toxicity of n-BiOBr.Inthis paper,freshwatergreen algae?Pseudokirchneriella subcapitata?was selected as a model organism and the effects of n-BiOBr on growth,photosynthesis pigments,protein content,superoxide dismutase?SOD?,catalase?CAT?,and malondialdehyde?MDA?to the algae were investigated.The results were present as follows:?1?It was confirmed by X-ray diffraction pattern that the sample prepared in this experiment is a nano-BiOBr with high purity,and its particle size is 30 nm,the thickness is5 nm,and it is easy to form agglomerates.In addition,the n-BiOBr did not cause significant changes in the pH and conductivity of the P.subcapitata medium,that is,it did not affect the growth environment of P.subcapitata.?2?The n-BiOBr can strongly inhibit growth of P.subcapitata.Moreover,the higher the concentration of n-BiOBr,the more toxic effect it had on lunula amniocera,and 50%effective concentration(EC₅₀)is 7.047 mg·L^-11 during 72 h exposure period.According to the standard of toxicity assessment of OECD and EU,the toxicity of n-BiOBr to P.subcapitata can be defined as Rank 2 of acute toxicity.?3?The aggregation between n-BiOBr and P.subcapitata greatly affected the toxicity,and led cells'deformation/wilt.After 72 h treatment,the total content of chlorophyll a and b and their ratio?a/b?were both decreased with the increase of n-BiOBr concentrations.In the low concentration treatment group,the protein synthesis in the algal cells was increased compared to the control group,but the total protein content in the algal decreased at higher concentration.?4?The plot of activities of SOD and CAT,as well as the content of MDA against concentration of n-BiOBr showed a“Bell-shaped curve”,i.e.,increasing at first and then decreasing.Theexposureofn-BiOBrproducedoxidativedamageto P.subcapitata.Furthermore,it was further determined that the amount of ion Bi³⁺dissolved in the n-BiOBr suspension was not much,and the experimental study on the toxicity of ion Bi³⁺found that the release of ion Bi³⁺was not the major factor causing the toxicity of n-BiOBr to P.subcapitata.In all,this research on the toxic effect of n-BiOBr to P.subcapitata,it was found that n-BiOBr had a certain growth inhibition effect on P.subcapitata,and it was discovered that it had an effect on photosynthetic pigments and protein synthesis in P.subcapitata cells.Meanwhile,find that the production of intracellular ROS,which in turn produces oxidative stress,inhibits the growth and development of P.subcapitata and affects the normal life activities of the body.These results are valuable for the risk assessment of nano-sized BiOBr in aquatic environment.