Đang chuẩn bị liên kết để tải về tài liệu:
Herbicides Environmental Impact Studies and Management Approaches Part 5

Tham khảo tài liệu 'herbicides environmental impact studies and management approaches part 5', khoa học tự nhiên, công nghệ sinh học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Investigation of Degradation of Pesticide Lontrel in Aqueous Solutions 69 No positive results were obtained in the first set of experiments in which DCPA solutions were treated with UV radiation alone Fig. 3 curve 1 . After 8 h of irradiation optical density did not change thus the herbicide was not degraded at all. To eliminate stagnation zones and to provide uniform illumination of the reaction-mixture layers distant from the UV lamp the solution was bubbled with the inert gas argon. Figure 3 curve 2 shows that the concentration of the starting substance decreased by 5 after 3 h of the reaction after that however the reaction completely stopped. To increase the oxidative effect of hard UV radiation the reaction mixture was bubbled with air instead of argon. The cooperative action of UV atmospheric oxygen and mixing almost completely degraded the herbicide after 24-25 h of the reaction Fig. 3 curve 3 . Simultaneous treatment with UV oxygen and hydrogen peroxide reduced the degradation time to 8 h Fig. 3 curve 6 . Irradiation under the conditions of ozone bubbling accelerated DCPA oxidation four- to fivefold as compared to air bubbling other factors being the same . The herbicide was oxidized almost completely after 6-6.5 h of the photochemical reaction Fig. 3 curve 4 . Thus bubbling of the reaction mixture with argon i.e. mechanical mixing with inert gas slightly accelerates DCPA degradation but the use of air is much more efficient. In our experiments agitation with air or oxygen flow 1 increased the reaction surface and 2 supplied the solution to the reaction zone. In addition ozone is one of the products of photochemical oxidation of oxygen when affected by UV irradiation the ozone molecule in turn dissociates to an electronexcited oxygen atom and an oxygen molecule in the singlet state. These chemical species having high oxidizing potentials attack herbicide molecules and degrade them either partially or completely Shinkarenko Aleskovskii 1982 . Experiments .