| Antifouling paint is a kind of special coatings which utilize active substances of antifouling to prevent the erosion of Marine microorganisms on underwater facilities. Diuron is an active substance which widely used in antifouling paint. It distributes in the basic components of the ecosystem after entering the aquatic ecosystem. What’s more, Diuron will produce serious ecotoxic effects when it is reaching a certain concentration. Chironomid (Diptera: Nematocera) is widely distribute in the world’s major bio geographic region. It is the main component of benthic fauna. Its migration is relatively weak in larval stage and it is sensitive to environmental factors, that making them an excellent indication of the water environment biological detection.In this research, Chironomus kiiensis as the test living thing. According to the OECD-233, Standard Laboratory Culture Techniques of Chironomus kiiensis was created. Spiked water method of Chironomids life cycle toxicity test and spiked sediment method of Chironomid life cycle toxicity test were carried out. Both substance detection of Diuron in water-sediment system and the allocation of Diuron in each phase are explored. The results showed that Diuron made Chironomus kiiensis produce obvious ecotoxicological effects, mainly includes the following four points.1. Holdback development and decrease emergence ratio of Chironomus kiiensis.According to the caculation method of development rate in OECD-233, namely Sediment-Water Chironomid Life-Cycle Toxicity Test Using Spiked Water or Spiked Sediment, the development rate of Chironomid in each group and every parallel were obtained. Wherein, the average developmental rate of various concentrations of the parental generation Chironomus kiiensis, the 50% effective concentration (EC50) was about 5mg/L. Two generations of Chironomid larvae exposed to the same concentration of the overlying water containing Diuron, the developmental rate of offspring generation Chironomus kiiensis was significantly lower than the parent generation, which indicated increased sensitivity of offspring. The EC50 was about 4.33mg/L. When the concentrations of Diuron were greater than 1.94mg/L, the developmental rates of two generation of Chironomus kiiensis had significant difference (p<0.05). From the emergence ratio of parent generation of Chironomus kiiensis, emergence rate decreased with the concentration of Diuron increased, the EC50 was 7.56 mg/L. Exposed to the same concentration of Diuron, emergence rate of offspring generation of Chironomus kiiensis, its emergence rate declined slightly compared with the parent generation and the EC50 was 5.24mg/L. Progeny of Diuron tolerance decreased. The effect of hindering development and decrease emergence ratio could be passed from parental generation to offspring generation.2. Increase the the sex ratio ((?):(?)).The sex ratio of two generation of Chironomus kiiensis effected by Diuron, its response curve was like a inverse U-shaped curve. There was no significant difference between different generations. The sex ratios of two generation of Chironomus kiiensis were increasing gradually as the increasing of the concentration of Diuron when the concentration of Diuron was less than 3.08mg/L. When exposured in concentrations of Diuron were greater than 3.08mg/L and the sex ratio of two generation of Chironomus kiiensis showed a downward trend. When the concentration of Diuron was 3.08mg/L, the sex ratio of parental generation of Chironomus kiiensis had significant difference (p<0.05) compared with the control group. As for Chironomus kiiensis, larve was in favor of becoming female individual when it was exposured to low concentrations of Diuron.3. Reduce the fertility of adult Chironomus kiiensis.Reference to OECD-233, the calculation method of fecundity of Chironomus kiiensis was by the number of spawning eggs devide the total number of females. Test results from the study of spiked water method showed the fertility of two generations have a downward trend when concentration of Diuron was above 1.22mg/L. Diuron effect fecundity of patental generation of Chironomus kiiensis, the EC50 was 1.99mg/L and the EC50 of offspring generation was 2.68mg/L after exposured to the same concentrations of Diuron. The fertility of parental generation of Chironomus kiiensis was slightly less than the fertility of offspring generation of Chironomus kiiensis (p>0.05).4. Equal spiked levels of Diuron, toxicity on Chironomus kiiensis by spiked overlying water method was stronger than spiked sediment.Based on two kinds of test results of the comparative analysis of standard addition method, the standard addition Diuron in water test of parental generation of Chironomus kiiensis, the EC50 was 7.56 mg/L and the offspring generation of Chironomid kiiensis was as low as 5.24 mg/L. However, the effective concentration of Diuron on two generations of Chironomus kiiensis was more than 48.18 mg/L by the standard addition method of spiked sediment experiment. What’s more, the distribution of Diuron in each phase in the study showed that the quantity of Diuron in overlying water was the most important factor of the toxicity effect on Chironomus kiiensisin special development stage.Above all, a certain concentration of Diuron can holdback the development of Chironomus kiiensis and reduce the emergence rate and fecundity of adult Chironomus kiiensis. What’s more, Diuron in overlying water would have more obvious toxicity on Chironomus kiiensis compare with sediment. |
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