Study On The Toxicity Effect Of Polystyrene Microplastics On Perfluorooctanoic Acid In Zebrafish

Perfluorooctanoic acid(PFOA),as a existing persistent organic pollutant widely present in the aquatic environment,has been found to have toxic effects on the growth,development and reproduction of aquatic organisms.Microplastics(MPs),as an emerging pollutant,have been found to affect organisms at many levels,such as individual,tissue,and cell.It has been proved that the toxic effects of the coexistence of microplastics and other organic pollutants on aquatic organisms are different.For these reasons,it is of practical significance to study the toxicity of PFOA to zebrafish in the presence or absence of microplastics.This study took tha aquatic model organism zebrafish as the research subject.The toxicity effects of PFOA on zebrafish in the presence or absence of 0.2,2,and 20μm polystyrene microplastics(0.2 PS,2 PS and 20 PS),were studied by 96 hour exposure experiment.Acute toxicity test showed that 96-hour median lethal concentration(LC50)of PFOA was 72.643 mg/L.The toxicity of the three microplastics was 2 PS>0.2 PS>20 PS from large to small,and their 96-hour LC50 was 193.939,297.006,and 969.117 mg/L,respectively.The 96-hour LC50 of PFOA in the presence or absence of microplastics was PFOA+20 PS,PFOA+2 PS,PFOA,and PFOA+0.2 PS in order.The enrichment results of PFOA in zebrafish under different exposure conditions showed that bioconcentration factor(BCF)was around 4.2-7.8 mL/g when PFOA existed alone,and BCF was around 2.5-6.8 mL/g when PFOA coexisted with PS.The histopathological observation of the gill,intestine,and muscle of zebrafish under different exposure conditions showed that the gill of zebrafish in each treatment group was not significantly affected,while the intestinal and muscle tissues were significantly damaged with the increase of PFOA exposure concentration.The intestinal damage was the most severe when 80 mg/L PFOA coexisted with 40 mg/L 20 PS.Muscle damage was most severe when 80 mg/L PFOA coexisted with 40 mg/L 2 PS.Transcriptome sequencing results showed that PFOA significantly affected the transchemical synaptic transmission pathways in the nervous system by affecting the neurotransmitter release cycle,acetylcholine neurotransmitter release cycle and glutamate neurotransmitter release cycle.PFOA+0.2 PS significantly affected the internal rectory K+pathway in potassium channels of the nervous system,and the significant up-regulation of genes gng8 and gnb3a indicated that the transmembrane transport of K+was significantly affected.PFOA+2 PS and PFOA+20 PS significantly affected a variety of amino acid metabolic pathways,as well as glycine,serine and threonine metabolic pathways,including activation of serine and conversion between glycine and serine.All three kinds of microplastics caused significant effects on myocardial contraction pathways,affecting ATP transport and myofilament contraction and relaxation.2 PS and 20 PS also significantly effected on Ca2+ transport across cell membranes and H+ transport across mitochondria.In this study,the toxic effects and mechanism of PFOA on zebrafish in the presence or absence of PS were explored.The results showed that the addition of microplastics could change the acute toxicity of PFOA to living organisms and its accumulation in living organisms,the damage to the tissue and the mechanism of the effect.These results are helpful to understand the toxicity of PFAS and microplastics to aquatic organisms,and provide the research ideas and basis for the study of the biotoxicity of microplastics coexisting with other pollutants.