Studies On The Time-dependent Characteristics Of Joint Toxicity Interaction Within Some Typical Envrionmental Pollutants To Vibrio Qinghaiensis Sp.Q67

Contaminants coexist in various forms and concentrations in the environment,then form a variety of complex mixture pollutants.The joint toxiciy interactions（synergism or antagonism）within mixtures have potential environmental and health risks.Some studies have shown that some contaminants are of time-dependent toxicity.While studies on the dynamic changes of the toxic interactions within mixtures over time.Therefore,analysis on the ecological toxic effects of typical pollutants in water environment,especially the time-dependent toxicity,can not only explain the variation of toxicity over time,but also provide basic information for their risk assessment.Currently,Vibrio qinghaiensis sp.Q67（Q67）and 96 microtiter plates were used as experimental carriers.Five kind of antibiotics:Apramycin sulfate（APR）,dihydro streptomycin（DIH）,chloramphenicol（CHL）,tetracycline hydrochloride（TET）,kanamycin sulfate（PAR）,two kind of pesticides:metalaxyl（MET）,glyphosate（GLY）and a heavy metal:lead chloride（Pb Cl2）were chosen as the research objects.Using direct equipartiotion ray design（EquRay）and uniform design methods（UD-Ray）to design binary,ternary,pentabasic,six-component and eight-component mixture systems.The toxicity of contaminants and their mixtures at different exposure times to Q67 was determined by microplate toxicity analysis.And the toxicity interaction of the mixtures at different exposure times was analyzed by non-linear fitting concentration-toxicity data and CA（concentration addition）model.The main results are as followed:（1）Five kind of antibiotics:APR,DIH,CHL,TET,PAR and MET have time-independent toxicity to Q67,While glyphosate（GLY）and heavy metal（PbCl₂）show obviously acute toxicity but almost keep unchanged with exposure time lengthening.Taking the negative logarithm of mean effection concentration(pEC₅₀),The order the eight contaminants at different time points varies with time 2h:DIH>PAR>CHL>APR>GLY>TET>MET>PbCl₂.（2）All the binary mixture systems except PbCl₂-APR,PbCl2-TET,toxicity interactions within the remaining binary mixture systems in different exposure time points is additive.In the binary mixture system of PbCl₂-APR and PbCl₂-TET,R1 and R2 are additive in the whole exposure time.R3,R4 and R5 are additive at exposure times of 0.25 and 2 h,but synergistic at low concentration and additive at high concentration in the times of 4,8 and 12 h.All binary mixtures of MET and antibiotics are antagonistic in the exposure time of 0.25 and 2 h.Hereafter,with the exposure time lengthening,the interaction of MET-PAR gradually chang from antagonism to synergism;the toxicity interactions of MET-DIH,MET-CHL and MET-TET gradually change from antagonism to additive;and the toxic interactions of MET-APR gradually change from antagonism to additive at high concentration and synergistic at low concentration.Meanwhile in some one exposure time,the toxicity interaction of MET-PAR,MET-CHL enhance with concentration ratio of MET increase.The binary mixtures of GLY-PAR and GLY-APR showed significantly time-dependent toxicity interaction.（3）The toxicity of pentabasic antibiotic mixture systems showed time-depe ndent and concentration-dependent toxicity to Q67.Among them,U1,U3 and U5 show antagonism at high concentration.The ternary mixture of heavy metal s and pesticide（U1-U5）is antagonistic at different exposure time points.In th e hexahydroxy mixture systems,MET-APR-PAR-CHL-TET-DIH and PbCl₂-APR-PAR-CHL-TET-DIH systems show additive in different exposure times.The to xicity interaction in the mixture systems of GLY-APR-PAR-CHL-TET-DIH and GLY-PbCl₂-MET-APR-PAR-CHL-TET-DIH changes from antagonism to synergis m with prolongation of time,which illustrates that the mixture toxicity of som e chemicals is not a sum of individual toxicities at some exposure times and i t is necessary to consider the toxicological interactionin within mixtures.