Study On The Ecotoxicity, Mechanism And Influencing Factors Of Layered Double Hydroxide Nanomaterial

It is crucial to explore the environmental behavior and toxicological consequences of layered double hydroxides(LDHs)-based nanomaterials to address the potential environmental concerns that could be caused by their release into the environment.In this work,we investigated the toxic effects and main influencing factors of two typical LDHs(Mg-Al-LDH and Zn-Al-LDH)on two freshwater microalgae(Scenedesmus obliquus and Chlorella pyrenoidosa),and explored the impacts of the presence of dissolved organic matter(DOM)and dealkaline lignin(DL)on the toxic effects and mechanisms of action of LDHs,as well as evaluated and predicted the effects of LDHs and graphene nanoplates(GNP)in combination with the organic pollutant 3,4 dichloroaniline(DCA)in binary mixtures on the ecotoxicity of freshwater microalgae,respectively.The main findings are as follows:(1)The Zn-Al-LDH exhibited a stronger growth inhibition toxicity to S.obliquus than the Mg-Al-LDH.This toxicity difference was connected to the stability of particle dispersion in water and the metallic composition of LDHs.The contribution of the dissolved metal ions to the overall toxicity of the LDHs was lower than that of their particulate forms.Moreover,the joint toxic action of different dissolved metal ions in each LDH belonged to additive effects.The Mg-Al-LDH induced a stronger oxidative stress effect in algal cells than the Zn-Al-LDH,and mitochondrion was the main site of LDH-induced production of reactive oxygen species.Both LDHs caused severe damage to the algal cell surface.At environmentally relevant concentrations,the LDHs exhibited joint toxic actions with two co-occurring contaminants(oxytetracycline and nano-titanium dioxide)on S.obliquus in an additive manner mainly.(2)The presence of DOM or DL altered the aquatic toxicity and oxidative stress responses induced by the LDHs with various metallic contents(Mg-Al-LDH and Zn-Al-LDH)at relatively low exposure concentrations to C.pyrenoidosa.Exposure to DOM or DL in combination with LDHs produced antagonistic effects on the growth inhibition of algae.The combined effects of DOM and LDHs on the oxidative stress response of algae at various concentration combinations were synergism mainly.DOM showed a stronger effect than DL in modifying the oxidative stress response of LDHs.Furthermore,the zeta potential and hydrodynamic diameters of the suspended LDH particles might be associated with the DOM or DL effects on the induced oxidative stress response by the LDHs in C.pyrenoidosa.(3)In the presence of LDHs or GNP,there is a linear relationship between the different levels(10,50,and 90%)of effect concentrations obtained for the DCA and a Freundlich adsorption coefficient(K_F)calculated by isotherm models and adsorption energy(E_a)obtained in molecular simulations,respectively.The parameter prediction model incorporating both parameters K_Fand E_ahad a higher predictive power for the combined toxicity than the classical mixture model.