Bioaccumulation Effect Of Polycyclic Aromatic Hydrocarbons In Zebrafish

Polycyclic aromatic hydrocarbons(PAHs)are a kind of typical persistent organic pollutants.PAHs are easily absorbed and enriched by fish in aquatic ecosystems due to its highly lipophilic,which poses a greater potential threat to human health.As an international model organism,zebrafish has not much research on the toxicity mechanism of polycyclic aromatic hydrocarbons.Most use zebrafish for acute toxicity tests or zebrafish embryos for monitoring toxic substances,and there are few studies on the accumulation and metabolism of polycyclic aromatic hydrocarbons in living organisms.In this study,the zebrafish(Barchydanio rerio var)was used as the test organism,and six polycyclic aromatic hydrocarbons of naphthalene,2-methylnaphthalene,fluoranthene,phenanthrene,pyrene and acenaphthene were studied as target compounds.Different from the previous method used a solvent,a constant concentration of exposed platform was constructed by free diffusion of polycyclic aromatic hydrocarbons in this study.The zebrafish was subjected to a 32-day exposure phase and a 32-day removal phase,then we measured the content of polycyclic aromatic hydrocarbons in fish at different time points.We calculated the bioconcentration kinetic parameters of polycyclic aromatic hydrocarbons in zebrafish through a hydrophobic model.In addition,we investigated the effect of metabolism on bioaccumulation by measuring the concentration of polycyclic aromatic hydrocarbons and their metabolites in the feces.The effects of feeding on the bioaccumulation process were studied by feeding comparisons.This study shows that:(1)The exposed platform was constructed by free diffusion method.The concentration of polycyclic aromatic hydrocarbons in the aqueous phase was close to the respective solubility,and the concentration range was 156.546-187.61 mg/L.(2)In the 32-day exposure phase and the 32-day removal phase,six kind of polycyclic aromatic hydrocarbons in the zebrafish were detected and the polycyclic aromatic hydrocarbon concentration was consistent.The concentration of polycyclic aromatic hydrocarbons in zebrafish increased rapidly in the first 4 days before the exposure phase.From 4th to 32nd day,the concentration increased slowly and turned to a steady state.Then,the concentration gradually decreased after entering the elimination stage.(3)According to the bioaccumulation kinetics model,bioconcentration facters of six polycyclic aromatic hydrocarbons were calculated,and the absorption rate k1 was higher than the elimination rate k2,the bioconcentration factor increased with the increase of Logkow(octanol-water partition coefficient),and the six polycyclic aromatic hydrocarbons did not have obvious enrichment in zebrafish.(4)The concentration of polycyclic aromatic hydrocarbons in the zebrafish manure varied with the concentration of polycyclic aromatic hydrocarbons in the body,the concentration of the body increased and the feces also increased.Only metabolites of naphthalene,phenanthrene and anthracene were detected in the feces,and the concentration changes of metabolites were less correlated with the concentration of corresponding polycyclic aromatic hydrocarbons in the fish.It was indicated that zebrafish can excrete polycyclic aromatic hydrocarbons through feces,and at least three polycyclic aromatic hydrocarbons such as naphthalene,phenanthrene and anthracene are metabolized to form metabolites.This study not only studied the bioaccumulation and metabolism characteristics of polycyclic aromatic hydrocarbons,but also provided basic data on the bioaccumulation and toxicological mechanisms of the pollutants.