Inhibitory Effects Of Macrophytes Pyrolysis Bio-oil On Skeletonema Costatum

Into this century the average number of red tides in China sea has raised to 79 times, and the total contaminate area is 10 000 30 000 km³ with an annual 16 300 km³,both of the 3.4 times to the 1990s. Red tide is one of the most important ocean environmental problems. The technologies of controlling red tide have some shortcomings such as some physical methods are not economic, and some chemicals used as red tide inhibitors are not safe for the ocean ecosystem, therefore, safe, effective and economic red tide control technologies are desired. Meanwhile, aquatic plants as one important part of wetland system have a tremendous biomass, and as the protection work in our country, wetland area expands gradually, so how to improve the economic value of wetland plant biomass, and protecting resident's enthusiasm became a new demand. If aquatic plants cannot promptly remove from wetland system, the absorbed nitrogen and phosphorus in plants may decay the water quality when released back into the water.Biomass pyrolysis is a promising biomass use and disposal technology,this method can turn the low energy density biomass into high energy density gas,liquid and solid products. The liquid product which collected as by-product during the preparation of coke process, were called bio-oil,it has complicated composition and also shows biological activity, can inhibit some plants and the growth of harmful microbes. In this research three kinds of common wetland macrophytes Arundo donax L., Ph.australis Trin. and Typha orientalis Presl were chosen as biomass materials for pyrolysis at 250, 300, 400, 500 and 600℃. Bio-oils produced at these temperatures were collected to study their inhibition effects on Skeletonema costatum growth. Results showed that all the Bio-oils exhibited inhibition effects on S. costatum, and higher inhibition rates followed by the increase of Bio-oil concentrations. For P. australis and T. orientalis, the most effective Bio-oils were produced at 400℃, with the 72 h EC₅₀ values of 0.82 and 0.85 mg·L^-1 respectively, while for A.donax, bio-oil at 300℃had the strongest inhibition rate (EC₅₀, 1.29 mg·L^-1) on S. costatum. The 300℃pyrolysis Bio-oil of A. donax was methylated and then analyzed by GC-MS. The GC-MS results showed that benzene and phenolic compounds were the main components, and the most abundant substance was 2-methoxyphenol. Effects of A donax. 300℃, P.australis. 400℃and T orientalis 400℃bio-oils on the malondialdehyde (MDA) change and antioxidant enzymes system (SOD,POD,CAT) active were evaluated to reveal the preliminary inhibition mechanism. Results showed that for all the three kinds of bio-oil, the higher the MDA contents followed by the increase of Bio-oil concentrations. SOD, POD and CAT activity raised with Bio-oil added concentration increased. The ROS alteration was also evaluated, hydrogen peroxide (H₂O₂), superoxide (O_2·^–) and hydroxyl radicals (?OH) content first increased and then decreased, or kept increase trend under the different bio-oil actions. Peroxidation damage as the result of ROS excessive accumulation could eventually cause algal death.