Study On The Time-dependent Toxicity Interaction Within Mixtures Of Antibiotics And Heavy Metals To Chlorella Pyrenoidosa

The massive production and application of various types of antibiotics has made it be the most common contaminant in the water environment.Antibiotics in the environment are more likely to change the environment of microbial species,destroy the ecological system balance,and cause human health hazards.Heavy metals are one of the typical pollutants in the environment which are enriched and non-degradable and can produce toxic effects.Heavy metals and antibiotics in water may coexist in various forms and concentrations to form a wide variety of mixed contaminants.The cumulative toxicity and interaction of mixture contaminants may pose a greater risk to the ecological enviroment and even biological health.Therefore,the study of the combined toxic effects of antibiotics and heavy metals has important environmental significance.Due the toxicity interaction in the mixture is a widespread phenomenon,Chlorella pyrenoidosa(CP)was taken as indicator and 96-well microplate was chosed as exposure experiment carrier,five kinds of aminoglycosides(Amikacin sulfate,Gentamicin sulfate,Kanamycin sulfate,Paromomycin sulfate and Tobramycin),and five kinds of heavy metals(chromium,copper,manganese,and zinc)were choosed as the research object.Uniform design(UD-ray)methods was employed to design the binary,ternary and nine-compnent mixture systems,respectively.In each binary and ternary mixture systems,five rays with different concentration ratios were arranged,and in the nine-component one,ten rays with different concentration ratios were designed.The toxicity of each mixture ray was detemined by the time-dependent microplate toxicity analysis(t-MTA)The obtained toxicity data in different exposure time was fitted by non-linear least squares method.Taking concentration addition(CA)as the reference model,the toxicity interaction within designed mixtures were evaluated.The main results obtained in this thesis are summarized in detail as follows:(1)The toxicity of aminoglycoside antibiotics and heavy metals to CP increased with the prolongation of exposure time.But the changes of CP toxicity with different substances were different.Among them,AMI,GEN,PAR,Cd,Cu 5 kinds of substances high inhibition rate,toxicity is strong,the highest inhibition rate of 80% to 98%.TOB was almost non-toxic at the first three time points(12,24 and 48 h).With the increase of exposure time,the toxicity only increased in high concentration area,and the maximum inhibition rate reached 70% at 96 h.The toxicities of these nine pollutants were different at the same exposure time,and the order of toxicity was changed with time.(2)In the mixture system of aminoglycoside antibiotics(simple mixture),CA prediction line fell within the 95% confidence intervals(CIs)of the concentration-response curve(CRC)of most of the mixture-ray showing additive effect and no time-dependent characteristics.The remaining binary mixtures have a time-dependent interaction.(3)In the mixture system of antibiotics and heavy metals(simple mixture),CA prediction line for most of the binary mixtures in the low concentration region fell within the CIs showing the additive effect,while in the high concentration region,CA prediction CRCs were below the Cis displaying synergism.The toxicity of the two systems showed time-dependency,and the toxicity to CP increased with the prolongation of exposure time,but increased slowly after 72 h.(4)In the ternary mixture(simple mixture system)of antibiotics and heavy metals,the remaining mixture systems exhibits time-dependent characteristics,except that the mixture exhibiting additive action(AMI-GEN-Cd R1,R3,R4,R5 and other 98 mixture of radiation)with no time-dependent characteristics.(5)It was of time-dependent toxicity for the nie-component mixture system of antibiotics and heavy metals(complex mixtures).During 48 ~ 96 h,R1 and R2 showed a synergistic effect,and the synergistic effect decreased with the time lengthening.R5,R6,and R7 in the first 48 h showed additive action,and the antagonistic effect appeared within 72 ~ 96 h.And the remaining rays diplay time-dependent synergism.