Keywords: 
• carbamate pesticides /
• Vibrio qinghaiensis sp.-Q67 /
• toxicity characterstic /
• antagonism /
• linear model

Abstract: Taking five carbamate pesticidies, aldicarb (ALD), baygon (BAY), carbofuron (CAR), methomyl (MET) and pirimicarb (PIR) as mixture components and uniform design ray procedure as design method, the toxicity of the five carbamate pesticides and six rays (U1, U2, …, U6) in the pentabasic mixture system to Vibrio qinghaiensis sp.-Q67 were determined by the microplate toxicity analysis method. Concentration addition (CA) model was applied to analyze the toxicity interaction (synergism or antagonism) within mixture system. The results showed that the two functions, Logit and Weibull, could well describe the concentration-effect data of the five pesticides and six mixture rays with R² > 0.99 and RMSE < 0.032. According to the negative logrithm of the value of median effective concentration (pEC₅₀), the toxicity order of the five carbamate pesticides is as follows: BAY (pEC₅₀ =2.87) > CAR (pEC₅₀ =2.67) > ALD (pEC₅₀ =2.00) > MET (pEC₅₀ =1.99) > PIR (pEC₅₀ =1.79). Based on the results predicted by CA, two of the six carbarmate pesticide mixture rays (U1 and U5) exhibit additvie action and four rays (U2, U3, U4 and U5) show antagonism. In addtion, U2 and U4 show clear antagonism on the whole concentration-response curve, while U3 and U6 diplay weak antagonism at the medium-high and medium-low concentration regins, respectively. Toxicity of the five pentabasic mixture rays well negatively correlate with the p_i of the component MET (r= -0.9238) and the fitted linear model can well predict the toxicities of the six mixture rays.