| In order to prevent and control diseases and insect pests in agricultural production,a large number of pesticides are used,and the digestion cycle of pesticides is different,which makes a variety of pesticide mixtures remain in various environmental media,such as water bodies and soils.Therefore,the study on the toxicity of pesticide mixtures has more practical significance than the study on the toxicity of single pesticide.Hormesis effect refers to the phenomenon that poisons or pollutants produce stimulative effects in low-concentration areas and inhibitive effects in high-concentration areas.Its concentration-response curve(CRC)has a biphasic J-type characteristic.A large number of experimental facts show that pollutants exhibiting the phenomenon of the Hormesis effect are universal.Since there are substances with J-type concentration-effect spectrum characteristics and substances with S-type concentration-effect spectrum characteristics,it is necessary to study substances with S-type concentration-effect spectrum characteristics and substances with J-type concentration-effect spectrum characteristics The prediction and evaluation method of the composition of the mixture effect.Copper quinoline and imidacloprid are commonly used pesticides in agricultural production to deal with pests and diseases,and they also can be used in combination.8-Hydroxyquinoline is a metabolite intermediate of copper quinoline.Copper quinoline releases copper ions when it produces bactericidal effects.Therefore,copper quinoline,8-hydroxyquinoline,copper sulfate(copper ion)and imidacloprid may all coexist in the real environment.The photoluminescent bacteria were selected as the test organisms based on the microplate toxicity analysis method,and in view of the fact that mixed pollutants in the actual environment have a more common hormesis effect phenomenon.The hormesis effects of copper quinoline,8-hydroxyquinoline and copper sulfate were systematically investigated with imidacloprid which does not have the hormesis effect.Based on the microplate toxicity analysis method,the short-term(VF-S-MTA)and long-term microplate toxicity analysis methods(VF-L-MTA)of marine photobacterium Vibrio fischeri were constructed.The toxixcity experiments were performed for copper phenanthroline,copper sulfate,8-hydroxyquinoline,and imidacloprid.The results showed that the order of the toxicity of the five reagents to Aliivibrio fischeri in the long and short-term exposure time was: 8-hydroxyquinoline copper > 8-hydroxyquinoline >imidacloprid > copper sulfate pentahydrate > trifluoroacetic acid.At the same time,the pollutant concentration range,the exposure time,the concentration intervals and the choice of solvents are all important factors that affect the hormesis effect.In order to fully evaluate the toxic interactions of mixtures with J-type concentration-effect spectrum characteristics,copper quinoline,8-hydroxyquinoline,copper sulfate and imidacloprid were used as the target compounds in seven different molar ratios as 12:1、10:3、8:5、1:1、5:8、3:10 and 1:12.In general,the results showed that the mixture of imidacloprid and 8-hydroxyquinoline was antagonistic in the high concentration range,and synergistic in the low concentration range;the mixture of imidacloprid and copper sulfate was antagonistic in the high concentration range,and additive in the low concentration range.The mixture of copper sulfate and8-hydroxyquinoline had different interactions in different concentration,that were synergistic in the high concentration range,while antagonistic in the low concentration range;the mixture of 8-hydroxyquinoline and copper quinoline was synergistic in all the designed concentration ranges.The results showed that the CA and IA models,the isobologram,and the co-toxicity coefficient method can all be used to evaluate the toxicity of binary mixtures containing J-type concentration-effect spectrum characteristics.Among them,the CA and IA models have good consistency with the isobologram method. |
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