| Organochlorine pesticides (OCPs) are one of the most serious environment pollutants throughout the world. Endosulfan was one kind of water-insoluble organochlorine-based pesticide that is widely used as a broad spectrum insecticide worldwide. Constructed wetlands were gaining recognition as one of the most potential management practices for the reduction of pesticide concentrations in agricultural runoff. So, it is significant for the research of removal of pesticides in wetland system.This paper first analyzed the response of the artificial wetland plants and microorganisms on the organochlorine pesticide endosulfan pollutants, the results showed that under the stress of endosulfan in different levels, plants can produce different kinds of antioxidase enzyme and protein to resist such stress. The activity of antioxidase enzyme rise and the growth of plants was restrained when the concentration of endosulfan reached0.2～2μg/L, while the plants withered and even died under the stress of10μg/L endosulfan. Besides, under the stress of endosulfan in different levels, the cellular proteins of the plants expressed differently. These cellular proteins with different functions, including resisting related stress protein, participating in photosynthesis, transcription of RNA and translating related proteins, played a key role in resisting the stress of endosulfan. Similarly, the microbial response resulted differently. As the level of endosulfan elevated, the amount of phospholipid fatty acid (PLFA) increased first, reached its peak when the concentration of endosulfan elevated to2μg/L, and then began to decline when the concentration of endosulfan continued to increase. And under the endosulfan in different levels, the micropopulations in the soil were different to some extent—with different diversity index, homogeneous degree as well as richness. When the concentration of endosulfan reached10μg/L, the microbial diversity notably declined due to the serious stress. As the nitrogen removal in constructed wetlands is very important evaluation indexes.The article also studied the impact of endosulfan on the ecosystem nitrogen cycle, reveal the mechanism of constructed wetland containing endosulfan sewage and its response of biological. When added in some domestic sewage, the mean removal efficiency of COD and ammonia nitrogen (AN) was steadily over70%while the mean removal efficiency of TN, nitrate and nitrite was steadily in40%-70%. By studying the nitrogen content in plant leaves and soil and the emission of N2O by wetland system, endosulfan was found to have very little influence to the nitrogen content in the soil (it is close to the blank sample), but have a significant effect on the nitrogen content in the plant—the nitrogen content decreased evidently when the endosulfan level elevated. Under low level of endosulfan, the activity of microbes rised as the level elevated and the N2O emission slightly increased; but when the concentration of endosulfan reached10μg/L, the activity of microbes decreased, as a result, the N2O emission was declined.The result of a kinetic equation fitting for the degradation of pollution indicators in the wetland system was good. The degradation of COD, TN and AN was fast when the concentration of endosulfan was0.5μg/L and the speed of degradation was lowest when endosulfan was10μg/L. The gap of nitrite degradation trend was smaller under varying degrees of stress. The speed of nitrate and nitrite degradation was fastest when the concentration of endosulfan was2μg/L. The N material balance research showed that substrate adsorption and degradation of drainage system were the main ways for the denitrification of wetlands. Nitrification-denitrification of plants and microorganisms were also the ways for the denitrification of wetlands.In sum, after adding endosulfan, plants change the rate of photosynthesis, trigger the antioxidant enzyme defense system and accumulate the functional protein to resist the stress of endosulfan. Microorganism and nitrogen cycle in artificial wetland ecosystem were affected to a certain extent. |
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