Impacts Of Environmental Factors On Ecotoxicological Effects Of Combined Contamination With TiO₂-NPs And Cd In Sediments

Nanoparticles?NPs?will be inevitably released into aquatic environment due to its widespread application.The unique physicochemical properties of NPs potentially alter the ecotoxicity of other persistent toxic substances?PTS?coexisting with NPs.The behaviour and physicochemical property of NPs will change under the influence of environmental factors,thus alter the interaction between NPs and PTS.However,investigations concerned about environmental factors influencing ecotoxicity of combined contamination with NPs and PTS is scarce at present.In the present study,the degree of DNA damage,Na⁺,K⁺-ATPase activities,protein carbonyl and malondialdehyde?MDA?content in the hepatopancreas of Bellamya aeruginosa following 21-d chronic bioassay were investigated to get insight into the ecotoxicological effects of conbined contamination with non-toxic concentration of titania nanoparticles?TiO₂-NPs?and Cd in the presence of four kinds of environmental factors:humic acid?HA?,pH,electrolytes:Ca?NO₃?₂ and Na₂SO₄ and surfactant:Sodium dodecyl benzene sulfonate?SDS?.The results indicated that,at the treatment group of TiO₂-NPs joint high concentration of Cd(25?g·g^-1),the degree of DNA damage and protein carbonyl content raised significantly with increase of HA content,conversely,the Na⁺,K⁺-ATPase activities and MDA content declined significantly.It means the ecotoxicity was enhanced.Because of the humic acid strengthen dispersity of TiO₂-NPs in sediments allowed more Cd adsorbed on the TiO₂-NPs,and make more Cd which used TiO₂-NPs as the carrier enter in vivo of Bellamya aeruginosa.This generated higher ecotoxicity.When the pH value of sediments was 9,the degree of DNA damage of every treatment group?including the control group?raised significantly.At the treatment group of TiO₂-NPs joint high concentration of Cd,the protein carbonyl content raised significantly,the Na⁺,K⁺-ATPase activities and MDA content declined significantly with increase of pH value and indicated increase of ecotoxicity.The degree of DNA damage and protein carbonyl content declined significantly,Na⁺,K⁺-ATPase activities raised significantly in presence of electrolytes.At the treatment group of TiO₂-NPs joint low concentration of Cd(5?g·g^-1),the degree of DNA damage,MDA and protein carbonyl content at the treatment group of Na₂SO₄ both lower significant than at the treatment group of Ca?NO₃?₂,and the Na⁺,K⁺-ATPase activities showed opposite.It means the ecotoxicity of TiO₂-NPs joint Cd is declined in presence of electrolytes and the effect of decline in presence of Na₂SO₄ is stronger than Ca?NO₃?₂.At the treatment group of TiO₂-NPs joint low concentration of Cd,the degree of DNA damage raised significantly with the increase of SDS.At the treatment group of TiO₂-NPs joint low concentration of Cd,the MDA content declined significantly with increase of SDS content.Compare with lower content of SDS,the high content(0.1 mg·g^-1)SDS enhanced significantly protein carbonyl content.It means the ecotoxicity of TiO₂-NPs joint Cd was enhanced in presence of SDS.This research indicated that influenced by environmental factors,the ecotoxicity of NPs joint PTS will change.Therefore,in order to assessment the ecological risk of NPs accurate,the environmental factors should be considered.