Carbendazim is a pesticide commonly used in Ethiopian flower farms and has harmful effects on aquatic, invertebrate, and mammalian life. Previous studies have explored ways to remedy carbendazim toxicity; however, the use of constructed wetland (CW) systems for carbendazim removal from farm water runoff has not been explored in depth. The primary aim of this study was to investigate the efficacy of a CW system for carbendazim removal from wastewater runoff. A two-stage pilot CW was built and tested for its efficacy of carbendazim removal under saturated conditions and varying hydraulic loading rates. The influent was pumped into the first vertical-flow mesocosm. The drained water was then pumped into the second mesocosm. The collected effluent was tested for carbendazim removal. Carbendazim removal efficiencies up to 91.80% (with a hydraulic loading rate of 100 Ld−1 and influent carbendazim concentration of 10 μg L−1) were observed. Statistical analysis indicated that the removal of carbendazim was not correlated with the initial carbendazim concentration but was negatively correlated with the hydraulic loading rate used. Two pesticide removal mechanisms were briefly probed to determine their participation in carbendazim removal. Substrate sorption accounted for 18% of total carbendazim removal; furthermore, plant uptake also played an active role.
Behavior of the mosquitofish (Gambusia affinis) toward the Japanese medaka (Oryzias latipes) was tested under exposure to environmental 17α-ethinylestradiol (EE2), a synthetic derivative of natural estrogen, estradiol. The mosquitofish were exposed to EE2 at different concentrations-0, 0.5, 5.0, and 50.0 ng/L-for 2 days, before their behavioral changes toward the medaka were observed. Results indicate that female mosquitofish became more aggressive at the high level of EE2 (50 ng/L), in terms of how persistently they attempted to approach the medaka. The males showed increased aggressive behavior toward the medaka, by significantly increasing the number and persistence of approach attempts at the low (0.5 and 5 ng/L) levels of EE2. At the highest EE2 concentration (50 ng/L), however, the number of attempts decreased, while the persistence increased in the males showing the same pattern as in the females. All behavioral changes were reversed once EE2 was removed from the environment.
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