The Inhibiting Performance Of Microcystis Aeruginosa By Hydrogen Peroxide Photochemical Produced From Straw Decomposition Products

The problem of algae blooms caused by eutrophication has been increasingly serious in surface water bodies. Especially in recent decades, algae blooms were not only brought serious harm to human production and life, but also caused serious ecological disaster. Due to the increase of nutrient concentrations resulted from human activities and natural processes, these problems become more and more serious. Meanwhile the demands of water quality improvement in water environment also need to meet in globe scope. Therefore, people attempt to explore efficient and environmental friendly methods on algae pollution control.At present, the researchers have developed a variety of methods to control algae growth, but these methods have some disadvantages such as secondary pollution. Recently using straw to inhibit algae and cyanobacterical growth in water body is paid for more attention as an environmentally friendly and low-cost technology, so investigating the relevant techniques has practical significance for the algae and cyanobacteria control in water environment. However, at present the poor understanding of photochemical mechanisms involved in the process of algal inhibition using straw cannot provide exact theory support for this technology, and limits its practical application.In this project three common straws in China, rice, barley and wheat straw, were selected as research materials. A series of methods, such as spectrum analysis of straw breakdown products, determination of apparent quantum yield of reactive oxygen species, analysis of chlorophyll a, reactive oxygen species quenching, were employed to reaserch the process of straw decomposition, photochemical properties of its organic products, photochemical formation of reactive oxygen species from straw decomposition products, and performance of algae inhabitation by reactive oxygen species.Results of the straw decomposition products structure and absorption characteristics indicated that decomposition products were similar to IHSS humic acid and fulvic acid, and both of them contained chemical structures of quinones and phenolic groups. These kinds of soluble organic matters as important photosensitizers in natural water bodies were able to absorb photon energy to undergo photosensitive reactions which were thought related to algea inhibition. In addition, the content of oxygen-containing functional group species increased with the increase of dissolved oxygen concentrations in water, which contributed to the increase of reactive oxygen species photochemical predicted from straw decomposition products. Specific optical properties?higher phenolic hydroxyl group contents and lower E2/E3? were found in barley straw organic matter obtained through aerobic decomposition?A-BSOM?. The appearance of protein-like structures in barley straw organic matter?BSOM? indicated that bacteria or fungi probably transformed the structure of BSOM and brought other organic matter, which may account for its distinct optical properties, while in rice and wheat decomposition products only fulvic-like structures were observed.All straw decomposition products generated ROS vis photochemical processes under the simulated solar irradiation. The abilities of aerobic straw decomposition products to generate ROS were higher than those of non-aeration. Specific optical properties of BSOM reveal its outstanding ability to produce H₂O₂ and ·OH. The22OH?37??14.73?10-5? of A-BSOM was three times value of SRHA,whereas the22OH?37? value of non-aerobic decomposition of barley straw was still higher than that of SRHA.The22OH?37? value of rice straw orgnic matter was slightly lower than those of SRHA and SRFA, but much higher than that of wheat straw orgnic matter.The tendency of the ?·OH value of straw organic matters were similar to the 22OH?37? value.The ability of SRFA to generate 1O2 vis photochemical processes was higher than straw organic matter, but the 21O?37??2.75?10-3? of aerobic wheat straw organic matter was slightly lower than that of SRFA,higher than that of SRHA, which was 1.5 times value of A-BSOM.Results from photochemical algal inhibiting experiments, indicated that the photosensitization of straw decomposition organic matters have a significant inhibitory effect on Microcystis aeruginosa growth. Among three ROS produced from photosensitive reaction of straw decomposition organic matters, H₂O₂ contributed to 70%-80% of the total inhibition rates of Microcystis aeruginosa growth. Therefore, due to its high H₂O₂ generating ability, aerobic decomposition barley straw demonstrated high-efficient inhibiting ability for Microcystis aeruginosa growth.