Marine Environmental Risk Assessment Of Camptothecin And Study On Its Release In Antifouling Systems

Marine biofouling causes serious damage to human marine economic activities,and adversely affects the environment due to the increase in the greenhouse gas emissions of ships and the invasion of species.Many studies have shown that organotin,cuprous oxide,and some organic antifouling assistants have a relatively high toxic effect on marine organisms,are not easily degraded or degraded slowly,and endanger the marine ecological environment.They have been banned or restricted in succession.Therefore,there is an urgent need for environmental friendly marine antifoulants.One of the important sources of friendly marine antifouling agents is natural antifouling products.Although a variety of natural antifouling products have been discovered so far,there are few reports on their environmental risk assessment.In addition,when the natural antifouling product is further applied to an antifouling paint,there are many phenomena that the release rate is too fast,resulting in a large amount of waste of the antifouling agent.This study is based on the above two issues and targets the natural antifouling product camptothecin which has been granted a patent,evaluating its toxicities on aquatic organisms and the degradation rate.Moreover,this toxicity assessment of degradation products samples were carried on.In addition,the evaluation of the release rate and the study of sustained-release technology were conducted to evaluate environmental risk of camptothecin as an antifoulant used as environmental friendly marine antifouling coatings.The main results were listed as followed.1.In the assessment of the toxicity on the four trophic levels of aquatic organisms,camptothecin was found to have growth inhibition effects on Phaeodactylum tricornutum(72 h EC50-51.16 ?M)and Isochrysis galbana(96 h ECs50 6.48 ?M).,having acute toxicity to Daphnia magna(48 h LC50-12.77 pM),Moina mongolica(48 h LC50-6.83 ?M)and Ruditapes philippinarum(24 h LC50-2×10-7 ?M),affecting Oryzias melastigma(21 d LC50-9×10-5?M)survival of embryos,but when in the range of 0.29%-287 pM,did not affect the heart rate of surviving embryos,and had no obvious teratogenic effects on embryos;observing the EROD fluorescence-inducing activity of seawater barley embryos and exploring the toxicity mechanism of camptothecin,it was found that there was no induction effect,indicating that camptothecin does not produce toxic effects on Oryzias melastigma by the CYP1A gene expression pathway.Compared the toxicity of camptothecin,algae and Cladocera has relatively high L/EC50 and low toxicity,meanwhile,more sensitive on fish and bivalve embryos2.The degradation of camptothecin in seawater was evaluated,and degradation kinetics and degradation products were analyzed under the three conditions of light degradation,biodegradation,hydrolysis(temperature degradation,pH degradation),and camptothecin was obtained under different conditions.The half-lives were:sunlight degradation(0.34 d),20000 lux(0.39 d),10000 lux(0.45 d),5000 lux(0.86 d),1000 lux(0.98 d),biodegradation(23.3 d),25?(21.7 d),35?(31.6 d),4?(32 d),pH7(25.8 d),pH4(51 d).The results show that light is the essential factor affecting the degradation of camptothecin,the natural light half-life is only 0.34 days,Degradation products of camptothecin was determined by LC-MS and showed that there were mainly 5 degradation products of camptothecin.In addition,Artemia saline was used as a bioassay to detect the toxicity of camptothecin degradation products.The results showed that camptothecin degradation significantly reduced its toxicity.3.Through the determination of the release rate of camptothecin in different formulations,the content of camptothecin in the coating was found to be the most critical factor in its release rate,and the release rate increased with the increase of camptothecin content,and it stabilized with time.In the laboratory,the average release rate of camptothecin in the range of 1%to 20%was 0.18-2.9 ?g cm-2 d-1.In addition,ZnO and rosin in coating formulations can also affect the release of camptothecin.Comparing the release rate determination results of the laboratory and the seaboard pegs,it was found that the release rate of camptothecin from paints in the natural sea area was higher than that in the laboratory,which was about 1 to 2 times higher.The effects of different ratios of mesoporous silica,graphene oxide and montmorillonite on the sustained release of camptothecin were compared in the coating.It was found that when the proportion of montmorillonite and camptothecin was 37.5%and 75%respectively,the sustained-release effect of camptothecin was significant,and no other two materials were found to have slow-release effects on camptothecin.In summary,camptothecin is easily degraded under natural conditions,does not accumulate in the environment,and does not produce a higher cumulative toxicity to the environment and organisms after degradation,indicating that camptothecin is a potential environment.Friendly marine antifouling agent.