| Emamectin Benzoate(EB)is one of the typical representatives of biological pesticides,which is widely used in agriculture and is one of the most used agricultural pesticides in Jiangxi Province.In the process of EB being used,it can accumulate in relevant organisms and produce strong toxic accumulation effect.However,most of the research on EB focuses on its insecticidal mechanism and effect on pests,while the toxicity effect and water quality benchmarking studies are rarely reported.At the same time,the mixed pollution of pesticides exists widely.Traditional research only studied the single toxicological effect of pesticides and ignored the combined toxicological effects.Therefore,this project carried out the following studies:(1)The aquatic organisms in China were selected as the test species,the acute and chronic toxic effects of EB were determined,and the water quality standards for aquatic organisms of EB were deduced by using methods such as SSD and SSR.The water ecological risk of the pollutant was evaluated.(2)Took native aquatic organisms as the object,the effects of single EB and the combined effects of EB and cadmium on the antioxidant enzymes and MDA of three species in water were studied.(3)The combined toxicity of EB was measured and evaluated.The results of acute toxicity experiment showed that the sensitivity of native species to EB were in order of Daphnia magna >Chironomus p Lumosus > Limnodri Lus hoffmeisteri >Macrobrachium nipponense > Misgurnus anguillicaudatus > Rhodeinae sinensis Gunther > Rana nigromaculata > Ctenopharyngodon Idella.The SSR method and the SSD method of two mathematical models(Log-normal,Log-logistic)were used to derive the acute and chronic baseline values of EB,acute baseline values was0.019 ug/L,0.029 ug/L and chronic baseline values was 0.0022 ug/L,0.0015 ug/L.Using the chronic benchmark value derived from SSR to evaluate the ecological risk of EB and HQ > 1 was obtained.Therefore,this paper speculates that EB has a greater ecological risk to the paddy field environment and may cause poisoning to invertebrates in the paddy field.So the use of pesticides should be more cautious in the future.Due to the lack of EB exposure data,its ecological risks to other aquatic environments need to be further studied.The experiment of the effect of single dose of EB on oxidase showed that under the same exposure concentration,exposure time had a significant effect on the activity of oxidase in body.Different species,with the increase of exposure time,the change trend of oxidase activity in the body was different;under the same exposure time,the exposure concentration can significantly affect the oxidase activity in body.Specifically,the activity of ACh E,CAT,GST,SOD of Ctenopharyngodon idella,Macrobrachium nipponense and Limnodri Lus hoffmeisteri first increased and then decreased at different concentrations of toxicants,and the change trend of MDA level was increased with the increase of the concentration.The activities of antioxidant enzyme and the PNEC of MDA of Ctenopharyngodon idella were ACh E = 46.2 ug/L,CAT = 46.2 ug/L,GST < 46.2 ug/L,SOD = 46.2 ug/L,MDA < 46.2 ug/L.The activities of antioxidant enzyme and the PNEC of MDA of Macrobrachium nipponense were ACh E = 1.18 ug/L,CAT = 1.18 ug/L,GST = 1.18 ug/L,SOD = 1.18 ug/L,MDA < 1.18ug/L.The activities of antioxidant enzyme and the PNEC of MDA of Limnodri Lus hoffmeisteri were ACh E < 0.1 ug/L,CAT < 0.1 ug/L,GST < 0.1 ug/L,SOD = 0.1 ug/L,MDA = 0.1 ug/L.Inaddition,according to the sensitivity of different species of oxidase to changes in EB concentration,the above four enzymes and MDA can be used as stress indicators of Ctenopharyngodon idella;ACh E,CAT,GST,SOD can be used as oxidative stress indicators of Macrobrachium nipponense;CAT and SOD can be used as a stress indicator of Macrobrachium nipponense.Acute toxicity experiment of binary mixture for EB and cadmium showed that after EB and cadmium were mixed according to the toxicity unit of 1:1,the toxicity of a single dose of Ctenopharyngodon idella,Macrobrachium nipponense and Limnodri Lus hoffmeisteri for 96 h were EB > cadmium.Therefore,the effects of EB and cadmium on the three aquatic organisms are all antagonism.Chronic toxicity experiment of binary mixture for EB and Cadmium showed that the activities of antioxidant enzyme and the PNEC of MDA of Ctenopharyngodon idella were ACh E < 43 + 156 ug/L,CAT < 43 + 156 ug/L,GST = 43 + 156 ug/L,SOD= 43 + 156 ug/L,MDA < 43 + 156 ug/L.The activities of antioxidant enzymes and the PNEC of MDA in Macrobrachium nipponense were ACh E < 0.95 + 1.02 ug/L,CAT <0.95 + 1.02 ug/L,GST =1.15 + 1.23 ug/L,SOD < 0.95 + 1.02 ug/L,MDA = 0.95 +1.02 ug/L.Compared with EB single-dose exposure,the effect of EB and cadmium binary mixed exposure was different,and the combined effect of the two would affect the toxicity.Therefore,when evaluating the EB risk of water body,it should comprehensively consider whether it is mixed with heavy metals or other pollutants. |
