Study On The Joint Effects Of Microplastics And Tetracycline On Microcystis Aeruginosa

The pollution of microplastics in the water bodies of natural environment has attracted global attention.Currently,reports and studies on the pollution of water bodies by microplastics emerge in an endless stream.However,there are few studies on the effects of microplastics on microalgae,a primary producer in fresh water.Microplastics are widely found in freshwater environment.As a new persistent pollutant in water environment,microplastics will inevitably affect the environmental behavior of microalgae.Phytoplankton microalgae,one of the most common prokaryotes and primary producers in aquatic ecosystems,play an indispensable role in the whole aquatic ecosystem.However,the influence mechanism of microplastics on microalgae is still not clear,and it is necessary to explore the influence mechanism and toxicological mechanism of microplastics on microalgae.It is of great significance to clarify the environmental behavior changes of microalgae under the influence of microplastics for water quality evaluation.In recent years,the abuse of antibiotics has become a global environmental problem.Due to the potential harm,toxic effect and persistence of antibiotics,the harm to the ecological environment and human health has attracted widespread attention.However,in the natural freshwater water environment,microplastics are often not independent of the ecosystem,but will interact with other water pollutants,resulting in compound pollution to the water environment and increasing the complexity of water pollution.At present,many studies have reported that harmful pollutants are easy to be adsorbed by microplastics and thus have compound effects on the growth of microalgae.Therefore,it is necessary to conduct further studies on the toxic effects on the growth of microalgae under the single and joint stresses of microplastics and antibiotics.In this study,two kinds of microplastics with the highest detected concentration and most widely used in water were selected: Polypropylene(PP)and Polyvinyl chlorid(PVC),Tetracycline(TC)were selected as the typical antibiotics,and microcystis aeruginosa from cyanobacteria was used as the test organism.The toxic effects of microplastics and tetracycline on Microcystis aeruginosa were investigated,including the single and combined toxic effects of microplastics and tetracycline on Microcystis aeruginosa.Through the growth stress response of Microcystis aeruginosa under different stresses,the toxicity mechanism of microplastics and tetracycline on Microcystis aeruginosa was explored,and at the same time,the potential risks of microplastics and antibiotics in aquatic plants of fresh water environment were provided with a scientific basis for evaluation.In addition,considering the adsorption behavior of microplastics to pollutants in water in the environment,the adsorption behavior of microplastics to tetracycline and the influence of adsorption behavior on algae toxicity test were systematically studied.The main contents and conclusions of this study are as follows:(1)It was found that high concentration of microplastics had a certain inhibitory effect on the growth of Microcystis aeruginosa.On the contrary,there was no significant change in the growth of algae at low concentration,and the inhibitory effect of PVC on algae was stronger than that of PP.It was found that the total organic carbon content in algal fluid was affected by the accumulation of algal biomass,and the consumption rate of total nitrogen and total phosphorus by algal cells increased with the increase of algal density.(2)The compound system of microplastics and TC showed antagonistic effect on the toxicity of Microcystis aeruginosa.The inhibition effect of the composite system of microplastics and TC on the growth of algae was lower than that of TC alone.Moreover,the toxicity of the composite system of PVC and TC decreased more than that of PP and TC,and the composite toxicity of PVC and TC to algae was lower than that of PP and TC.The adsorption capacity of PVC and PP on TC is an important reason for the decrease of its toxicity.(3)The adsorption isotherm data of PVC and PP on TC conforms to the Freundlich isotherm model.The adsorption behavior of tetracycline on PVC and PP is mainly affected by electrostatic action,and is not affected by the change of ionic strength.