| Triadimefon is one of the most widely used triazole fungicides in China,and its use is increasing year by year.Due to the low utilization rate,triadimefon enters the aquatic environment and threatens the ecological safety.It has been reported that triadimefon affected the development and reproduction of fish and amphibians,and the long-term toxicity and risks of triadimefon to ecosystem cannot be ignored.However,most studies are focused on the toxic effects at individual-level of one generation and only for vertebrates,while the research on the long-term toxic effects and mechanisms of triadimefon on invertebrates and the assessment of higher-level ecological risks are lacking.Invertebrates also occupy important ecological niches.Meanwhile,the risk assessment of pollutant exposure at population-level may be more in line with the actual situation of protecting ecosystem than at individual-level.In this study,we took Daphnia magna as a model organism and conducted multi-generational toxic exposure experiments to explore toxic effects and mechanisms of triadimefon under long-term exposure condition.The investigation and prediction of exposure concentrations of triadimefon in China was carried out as well,and their risks in surface water were evaluated by risk quotient（RQ）,the joint probability curve（JPC）,and the population risk quantitative assessment method,which may provide support for the development of environmental criteria and standards for triadimefon.The main research work and conclusions are as follows:（1）Studies on the toxic effects of triadimefon to Daphnia magna showed that the development and the reproduction of Daphnia magna were significantly inhibited with the concentration of triadimefon at 0.1 mg·L-1.When it was higher than 0.1mg·L-1,both population number and intrinsic rate of increase showed a decreasing trend with the increase of exposure concentration.The proportion of Daphnia magna（14-21 d）was in the order of F2>F1>F0,and high concentration group>low concentration group.At the same concentration,the inhibitory effect of triadimefon on Daphnia magna was F2>F1>F0.These results indicated that triadimefon affected the development and reproduction of Daphnia magna at individual-level,and population number and intrinsic rate of increase at population-level.With the increase of concentration,age structure of the population tended to decline.After multi-generation exposure to triadimefon,the toxicity to Daphnia magna was higher than that of parent,and long-term exposure to triadimefon would reduce fitness of individuals and cause attenuation of Daphnia magna population.The Daphnia magna plays a linking role in the food chain of aquatic ecosystems,and the decline will seriously threaten the safety of ecosystems.（2）The results for exploring toxic mechanism of triadimefon through transcriptome analysis showed that the feasible pathways included protein absorption and digestion,pancreatic secretion,and neural body-receptor interaction in F0,protein digestion and adsorption,retinol metabolism,oxidative stress,and steroid hormone biosynthetic in F1,and antigen processing and presentation,steroid biosynthesis,and glutathione metabolism in F2,respectively.Triadimefon can produce endocrine disrupting effects by affecting biosynthesis of steroid hormones,thereby inhibiting their growth and development and reducing reproductive capacity.（3）Ecological risk of triadimefon was assessed at different levels in combination with exposure data.Results showed the risk value of the rice field ditches in Zhejiang Province was at high risk（9.23）,and three reservoirs in Guizhou Province（RQ values were 4.02,3.15,and 2.61 respectively）reached medium risk,indicating that the risks in these areas needed to be paid attention.Reproductive toxicity and developmental toxicity were all distributed in low-risk areas,but reproductive-based risk was higher than developmental risk.These results indicate that the current concentration of triadimefon in surface water of China will pose risks to the population. |
