Effects Of Typical Microplastics On The Behavior And Toxicity Of Sulfonamide Antibiotics In Microalgae And Mice

In recent years,microplastics have become concerned emerging pollutants in the environmental field.Microplastics are ubiquitous in the environment and can absorb organic pollutants,causing harm to living organisms.At the same time,antibiotic pollution is also a widespread concern in the environment.Simultaneous exposure of microplastics and antibiotic to organisms is an inevitable phenomenon,but how microplastics affect the behavior and toxicity of antibiotics in organisms remains unknown.By selecting typical microplastics and sulfonamides(SAs)as the research objects,this paper analyzed microplastic-mediated enrichment,degradation and physiological response of microalgae towards antibiotics,and the effects of microplastics on the enrichment and ecotoxicity of antibiotics in mice.The details are as follows:Phaeodactylum tricornutum was selected as the test organism.The polystyrene microplastics(PS)commonly found in water,and sulfamerazine(SMR)which the most commonly detected in SAs,were taken as the research objects.While studying the composite toxic effects of PS and SMR with different particle sizes(30 ?m and 100 nm)on microalgae,and the effect of PS on microalgae degrading SMR was also studied,because microalgae has the ability to degrade SMR.Experimental results show that:(1)The composites of 30 ?m and 100 nm PS and SMR had persistent harm to the growth of microalgae.And PS exacerbated the growth-toxic effect of SMR on microalgae.The toxic effects of PS and SMR on microalgae showed that:100 nm PS and SMR > 30 ?m PS and SMR > SMR alone.The smaller the particle size of PS,the stronger the growth inhibition of microalgae when coexisting with SMR.(2)Microalgae removed less SMR by adsorption in vivo.And the biodegradation rate of SMR continued to increase with the growth of microalgae,while the photodegradation rate of SMR is stable at 20%.There were significant differences in the degradation ability of SMR by photolysis and microalgae in the presence of PS with different particle sizes.The adsorption capacity of PS for SMR in seawater was0.03 mg/g.30 ?m PS could promote the degradation of SMR by microalgae,and the total organic carbon content was increased,so it was possible that organic matter could promote SMR degradation.In addition,100 nm PS inhibited the degradation of SMR by microalgae,and the low degradation rate was related to the inhibition of the growth of microalgae.The existence of PS will enhance the toxic effect of antibiotics on organisms,change the enrichment and degradation behavior of antibiotics by microalgae,and make plankton such as microalgae face greater ecological risks.Taking polyethylene terephthalate microplastics(PET),which humans are frequently exposed to and are frequently detected in the environment,and sulfamethoxazole(SMX),which has large oral doses for medical use among SAs,as the research objects,the effects of PET on SMX enrichment in mice were investigated.Meanwhile,gut microbes and antibiotic resistance genes(ARGs)were employed to indicate ecotoxicity.The results were as follows:(1)PET significantly reduced the bioaccumulation of SMX in mice tissues(liver,lung,spleen,heart and kidney).But PET did not significantly alter the relative distributions of SMX concentrations and amounts in five organs of the mice.(2)PET or SMX alone affected the gut microbes of mice.The diversity of gut microbes and the relative abundance of multiple gut flora at the phylum and genus levels were changed when the two coexist,and these changes differed from exposure alone.These suggested a synergistic effect between PET and SMX,and PET exacerbated the effects of SMX on gut microbes.(3)PET microplastics increased the effects of SMX on antibiotic resistance genes(ARGs)profile,and we further identified that shifts in gut microbiota contributed to the changes in ARG in mice.PET resulted the relative abundances of sulfonamide resistance genes(12.48%)and multidrug genes(5.30%)being significantly increased.Experiments showed that the combination of PET and SMX might have high unknown risks to humans and the ecological environment.