Toxicological Effects Of Bentazone And Mefenacet To Aquatic Organisms And The Study Of Water Quality Criteria

Bentazone and Mefenacet are two important herbicides,which have been widely used in agricultural production.They have been detected in many countries around the world,and they have been listed in the list of environmental pollutants.Studies of Bentazone and Mefenacet were mainly focused on the herbicidal effect,but there are few reports on their toxic effects and aquatic biological standards.So far,there is no proposed relevant reports on the China aquatic biological benchmark values of Bentazone and Mefenacet.Therefore,this study selected China aquatic species as the test species to study the toxic effects of Bentazone and Mefenacet.SSR and SSD methods were used to derive the water quality of my country’s Bentazone and Mefenacet.And the benchmark value is used as a reference to evaluate the ecological risk of the water body.In addition,this study chose the enzyme activity of antioxidant enzyme as the observation indicators to explore the effects of Bentazone and Mefenacet in the antioxidant enzyme system.In this study,the toxicity test results showed that the sensitivity of native species to Bentazone were in order of Daphnia magna>Rana nigromaculata>Oryzias Latipes sinensis>Limnodri Lus hoffmeisteri>Rhodeinae sinensis Gunther>Misgurnus anguillicaudatus>Macrobrachium nipponense>Chironomus p Lumosus.The order of sensitivity to Mefenacet were in order of Rhodeinae sinensis Gunther>Oryzias Latipes sinensis>Daphnia magna>Rana nigromaculata>Misgurnus anguillicaudatus>Limnodri Lus hoffmeisteri>Chironomus p Lumosus>Macrobrachium nipponense.Toxicity experiments were carried out in accordance with the derivation requirements of 3 phyla and 8 families.SSR method and SSD method with three mathematical models（log-normal,log-logistic and Burr TypeⅢ）were used to derive the acute and chronic baseline values for Bentazone and Mefenacet.Among them,the acute baseline values of Bentazone are 46.14 mg/l,5.47 mg/L,37.33 mg/L,and 39.36 mg/L,and the chronic baseline values of Bentazone are 4.76 mg/L,1.92 mg/L,2.34 mg/L and 2.02mg/L;The acute baseline values of Mefenacet are 3.82 mg/L,2.21 mg/L,3.36 mg/L,and 2.22 mg/L,and the chronic baseline values of Mefenacet are 1.51 mg/L,0.43 mg/L,0.66 mg/L and 0.43 mg/L.The chronic reference value was derived by reference to SSR method to evaluate the ecological risks of Bentazone and Mefenacet.The evaluation results showed that both HQ were less than 0.1,hence the two herbicides had no ecological risks.Furthermore,The SSD between native and non-native species and between freshwater and marine species were compared based on the toxicity data of Bentazone in China and abroad.The result showed that the sensitivity of non-native species was higher than that of native species at HC₅;the sensitivity of native species were higher than non-native species at HC₅₀;and The sensitivity of freshwater species is higher than that of seawater species.Chronic SSD of Bentazone and benthioate were compared based on our chronic toxicity data.The result showed that benthioate is more dangerous to aquatic organisms than Bentazone.Using Rhodeinae sinensis Gunther、Macrobrachium nipponense and Daphnia magna as objects,chronic experiment was carried out to find the the effects of Bentazone and benthioate on antioxidant enzyme system.The results show that the antioxidant enzymes activities in organism were changed with the prolongation of exposure time.Among them,the trend of Rhodeinae sinensis Gunther and Macrobrachium nipponense were the same:ACh E was inhibited;CAT and MDA were induced;GST and SOD were induced and then they were inhibited.ACh E in Macrobrachium nipponense was inhibited,and other antioxidant enzymes were induced.Different concentrations of the toxic substances showed that enzymes activities trend of Rhodeinae sinensis Gunther,Macrobrachium nipponense and Daphnia magna were induced and then they were inhibited,and all activities of MDA were up-regulated.All measured enzymes activities PNECs of Rhodeinae sinensis Gunther were 15.55 mg/L（MDA）、18.66 mg/L（SOD）、<12.96 mg/L（ACh E）、<12.96mg/L（GST）和<12.96 mg/L（CAT）;Enzymes activities PNECs of Macrobrachium nipponense were 23.46 mg/L（MDA）、<16.29 mg/L（SOD）、<16.96 mg/L（ACh E）、19.55 mg/L（GST）和16.96 mg/L（CAT）;Enzymes activities PNECs of Daphnia magna were<1.15 mg/L（MDA）、1.4 mg/L（SOD）、<1.15 mg/L（ACh E）、<1.15 mg/L（GST）和1.27 mg/L（CAT）.