Acute Toxicity And Oxidative Stress Effects Of Imidazolium Nitrate Ionic Liquids With Different Carbon Chain Lengths On Earthworms

Ionic liquids?ILs?,a substance consisting of cations and anions that is liquid at room temperature.ILs have many advantages such as simple preparation,high thermal stability,non-volatilization,strong solvency and high conductivity,and they are widely used in electrochemical,organic synthesis,catalytic reaction,extraction and separation reactions.Due to the good water solubility of ILs,a large amount of usage will inevitably lead to a large amount of ILs entering the water and soil environment medium.ILs hardly degrades in the soil and exists in the environment for a long time to affect organisms,so it is of great significance to study the negative environmental effects of ILs on the environment and organisms.Due to the diverse structure of ILs,different carbon chain lengths,different cationic groups and different anionic species all lead to different toxic effects of ILs on organisms.It is also of great significance to study the toxicological regulation of ILs.In order to study the effect of different carbon chain lengths of ILs,in this study,five ILs[C_nmin]NO₃?n=2,4,6,10,12?were selected to study their toxicity on earthworms?Eisenia fetius?,the acute toxicity of ILs was determined by artificial soil test and filter paper test and the LC₅₀0 was calculated to determine the regulation between acute toxicity and carbon chain length.After that,the the subchronic toxicity tests were conducted?28 d?.The earthworms were placed in artificial soil with ILs concentrations of 5,10,20,and 40 mg·kg^-1.The contents of reactive oxygen species?ROS?,the activities of antioxidative enzymes?superoxide dismutase SOD,catalase CAT and peroxidase POD?,detoxification enzyme,and the degree of lipid peroxidation?malondialdehyde MDA?and DNA damage?tail value OTM obtained from comet assay?were measured on days 14 and 28 after exposure respectively.Simultaneously evaluate the toxicity effects of the five ILs on earthworms,compare the toxicity damage of ILs with different carbon chain lengths,provide theoretical basis and data support for future applications,and help to establish a friendly-IL structure database.Through this study,we can get the following results:?1?The toxicity order of these five ILs was:[C₁₀mim]NO₃<[C₁₂mim]NO₃<[C₄mim]NO₃<[C₆mim]NO₃<[C₈mim]NO₃.At the beginning of the experiment,with the increase of carbon chain length?C_n<C₈?,the toxicity performed accorded with"alkyl-chain effect",when the length of carbon chain was 10,the toxicity of ILs decreased,showing"cut-off effect".?2?The content of ROS in earthworms increased with the increasing ILs toxicity?increased concentration,prolonged exposure time or increased toxicity of ILs itself?,and the maximum increase of ROS content in earthworms occured at[C₈mim]NO₃ in the present study.?3?When excessive ROS accumulated,the activity of antioxidative enzymes?SOD,CAT and POD?and detoxification enzyme GST in earthworms changed with the increasing ILs toxicity?increased concentration,prolonged exposure time or increased toxicity of ILs itself?,and the maximum change in earthworms occured at[C₈mim]NO₃ in the present study.?4?With the accumulation of ROS,excess ROS can combine with macromolecules such as lipid,protein and DNA,which also led to the change of redox state and oxidative damage in the body.Earthworms in almost all treatment groups have varying degrees of oxidative damage.Earthworms got the most serious oxidative damage after exposure to[C₈mim]NO₃.?5?In artificial soil,the five ILs used in the present study can maintain stable throughout the experimental period,the content of ILs in the 10 mg·kg^-11 of[C₈mim]NO₃ changed the most during the whole period and the changing rate was 7.39%.The changing rates of ILs in other treatment groups within 28 days were all less than this.