Investigating The Effects Of Microplastics On The Toxicological Properties Of Freshwater Organisms

Microplastics(diameter less than 5mm)pollution has become a hot environmental issue of global concern,of which polystyrene is one of the main components of microplastics pollution.At present,the research on microplastic pollution is mainly concentrated in the marine field,but the biological toxicology research in the freshwater field is still very scarce.Therefore,the toxicological effects of polystyrene on Candida and Daphnia,which are widely present in the freshwater field,have been studied in this paper.For the convenience of tracing,fluorescent polystyrene is selected.At present,fluorescent polystyrene on the market is expensive and there is a problem of leakage of fluorescent dyes.Therefore,the preparation method of fluorescent polystyrene is optimized in this paper.The results are as follows:(1)The experimental results of the preparation of fluorescent polystyrene show that the optimal conditions were:CS₂ 35m L,immersion time 9h,Al Cl₃ 1.161g,AC1.17g,water bath temperature 50?,water bath time 5h.The acetylated polystyrene reacted under this condition has good fluorescence intensity and coverage effect,large fluorescence intensity,strong acid and alkali resistance,low temperature resistance,light resistance and low toxicity,and does not generate fluorescence leakage.(2)The results of Candida exposure experiments show that when the same concentration of polystyrene particles were added,the 150-200?m particles had the greatest effect on the density,biomass weight,and chlorophyll of Candida.When the same particle size was added,the higher the concentration was,the greater the effect was.When Candida was dosed with 0.12g of 150-200?m particle size,it had a half-lethal rate.When 0.20g of 150-200?m particle size was added,almost all the algae died.(3)Daphnia exposure experiments show that Daphnia can only ingest polystyrene particles with a particle size of less than 40?m and a very small amount of 40-100?m,and polystyrene particles will be discharged with the metabolism of Daphnia.A small number of larger-sized polystyrene particles remain in the intestine.Daphnia has a persistent toxic effect,resulting in the death of Daphnia magna and a decrease in spawning rate.This article studies the toxicity of polystyrene particles to freshwater organisms represented by Candida and Daphnia,and provides scientific basis for the monitoring,management,control of microplastics pollution and the development of related technologies and measures.