Study Of Toxicity On Zebrafish Embryos And Mechanism Of Ozonation Of Naproxen

Pharmaceuticals and personal care products (PPCPS) can be persistent in the environment, result in endangering the ecological environment because of their inherently biological activity. As a typical PPCP, naproxen is one of the world’s major anti-inflammatory and analgesic medications of non-prescription drugs. It’s concentration in the aquatic environment has reached to a ng/L level. Because the non-biodegradablity of naproxen, traditional sewage treatments showed low efficiency on its degradation and the detection rate of effluent is even high in sewage treatment plants. A long-term exposure to naproxen with a low-concentration showed a population growth inhibition to Ceriodaphnia dubia., and had negative effects on metabolism of fish liver cell.One objective of this study is to evaluate the acute and developmental toxicity of naproxen on zebrafish embryos. The research results showed that embryo mortality was80%when embryos were exposed to naproxen with a concentration of60μmol/L at96hpf, and the96LC50was27.37μmol/L. The exposure experiments of zebrafish embryos to naproxen caused malformations including pericardial edema (PE), yolk sac edema (YSE), crooked body (CB). The occurrence rate of PE was100%when embryos were exposed to high-level of naproxen, the rate of hatching was decreased significantly. The expression levels of CYP1A and CYP2J26genes in zebrafish embryos were significantly increased and the expression levels of UGT1A1gene was significantly reduced because of the effect of naproxen.The acute joint toxicity of naproxen and heavy metal Cu2+to zebrafish embryos had been studied after single toxicity experiments. The results indicated that96LC50of Cu2+was10.97μmol/L. In the combined toxicity tests, naproxen and Cu2+were mixed based on toxic unit ratio of4:1,2:1,1:1,1:2,1:4, and the combined toxicity was evaluated by AI method. The results of all ratios of combined toxicity tests indicated that the toxic effect on zebrafish embryonic lethality of naproxen and Cu2+were antagonism. The complexation occurred when naproxen and Cu2+were mixed and the complex was formed by the mononuclear copper molecule bind the carboxyl oxygen of two naproxen molecules through the complexation mechanism analysis.We further studied the mechanism of the ozonation of naproxen, examined the influence of ozone dosage, pH, initial concentration and humic acid on degradation of naproxen, discussed the degradation kinetics and determined the intermediate products. The results showed that ozone can remove naproxen rapidly and completely. When the flow of ozone was5,10,20mL/min under neutral pH condition, the degradation of naproxen were basically completed in32,14,8min respectively. The degradation rate would be promoted by increasing the flow of zone or be restrained by increasing pH and initial concentration. The degradation of naproxen by ozone could be inhibited by humic acid and the inhibition were proportion to the concentrations of humic acid. The kinetics of degradation followed zero-order kinetics when pH is between4～8and followed pseudo-first order kinetics when pH was10. Intermediate products were analyzed by GC/MS system, several intermediate products which were formed by ozonation of branched chain on naphthalene ring had been identified.