Research On The Biocontrol Technology,Mechanism And Utilization Of Alligator Weed(Alternanthera Philoxeroides)

As an exotic invasive plants, alligator weed, Alternanthera philoxeroides (Martius) Grisebach, has become the world's evil nature grass. Its invasion has caused serious ecological damage, economic losses and social impact. It is urgent to find an eco-safe, cost-effective measures to control its invasion. This study relies on the National Eleventh Five-Year "water pollution control and governance of major science and technology topics---Nansi degradation of wetland ecosystem restoration and water quality improvement technology and demonstration of subject (one of the subjects of the Huaihe River Basin water pollution control technology research and integrated demonstration projects). The purpose of this study is to invent a comprehensive technology to control and utilization alligator weed. Based on the status research of alligator weed in Shandong Province Nansihu basin, the method and mechanism of reed alternative control and the preapared way of activated carbon were researched. This research will guide the control of alligator weed in Nansi Lake basin, Shandong Province, even northern China.The results of site survey and system research in Nansi Lake Basin, Shandong Province showed that:the section rate of of Alternanthera philoxeroides in Shandong Province Nansihu basin was up to71.1%. And the basin was in the transitional period by the invasion phase of stable phase or even to settle in stage. The distribution of Alternanthera philoxeroides in the region was effected by the economic development of the basin, river hydrology, water quality, ecological conditions and revetment. Alternanthera philoxeroides invasion in the region leaded to large potential risks on the aspect of fisheries, rivers and lakes of the Nansi Lake basin water quality, biodiversity and flood control.The reed alternative control of Alternanthera philoxeroides with a pilot in the Xiaosha river downstream showed that:reed alternative control technology effectively inhibited the growth of Alternanthera philoxeroides. Before and after the implementation of the demonstration project, Alternanthera philoxeroides by the blanket-like shaped into a single plant. And plant length, biomass, coverage had a higher degree of reduction. In August, the coverage dropped from30percent in2009to5.9percent in2011, with a24.1percent reduction. Before and after the implementation of the demonstration project, xerophilous alligator weed plant length by2m in August (2009) reduced to0.6-1.0m in August (2011). The demonstration project of test river water also enhanced the water quality. From May2010to November2011, the average of the effluent of COD, NH3-N, TN, PO43--P, TP were as follows:26.00mg/L and1.43mg/L,5.40mg/L, and0.21mg/L,0.47mg/L, and average removal rates were:33.9%,35.1%,9.7%,20.1%,16.3%.The pilot river biodiversity had been effectively improved which meant the number of planktonic algae from the point of view was decreasing, before the implementation of the94kinds to101kinds of cell density, and biodiversity was increased significantly, and the estuary at the Shannon-Weaver biodiversity index increased from1.17to3.00, indicating that the river water quality was from pollution in the transition to light pollution. Reed bionic plant and Alternanthera philoxeroides mixed experimental showed that there were strong phenotypic plasticity of Alternanthera philoxeroides roots, stems, and leaves in respense to shade. Aquatic alligator weed by allelopathic inhibition was significantly higher than xerophilous alligator weed; Under the concentration of50%, the extract of reed had significant impact on germination of alligator weed. In hydroponics habitat conditions, the RI(allelopathic effect index. If positive, it means the performance role in promoting and the greater its value, the stronger allelopathic to promote. If negative, it means the inhibitory effect and the higher absolute value, the stronger the suppression effect was-0.87. In xerophilous habitat conditions, RI was-0.4. comparing to control group, the first germination days were all postponed under the allelopathic effect. During stress time, carotenoid content of Alligator weed in hydroponics habitat and xerophilous habitat decreased on the average of43.1%and38.3%respectively. The extract of reed had a strong inhibitory effect on the root activity of Alligator weed under the hydroponics habitat,while has little impact on that growing under native habitat. In hydroponics habitat conditions, the average allelopathy index was-0.81on root activity and the inhibition increased with the increasing of concentration of extract of reed. The extract of reed had inhibition effect on the activity of catalase (CAT), which indicated that the inhibition effect had a trend of strengthen with the increasing of concentration of reed extract and stress time. It meant the growing of concentration and sress time increased the inhibition of CAT activity, which accelerated the inactivation of enzyme. The extract of reeds had some differences effect on the contents of nitrogen and phosphorus of alligator weed in the different habitats. In xerophilous habitat conditions, the content of P decreased rapidly with the increasing of concention.In summary, the reeds and water extracts of Allelopathy Mechanism were that when the extract of reed acted on Alternanthera plant drought, it causes the imbalance of reactive oxygen species metabolic system in alligator weed, damaged or reduced the reactive oxygen species scavenger, increased production of reactive oxygen species and destroyed the mambrane strunture. Besides, it also reduced the chlorophyll and carotenoid content of alligator weed, thus affecting photosynthesis and root activity, and affected the root absorption of N and P, as well as other substances, thus inhibiting the germination and seedling growth and development of alligator weed.In order to improve resource utilization of Alligator weed, this paper explores the preparing process of activated carbon by Alligator weed under different activatior and conditions and studies the feasibility of optimal conditions. With phosphoric acid as an activator, the optimum preparation conditions were activation temperature600℃, activation time1h, impregnation1:4, soaking time12h. Under this condition, the yield of activated carbon was37.44%and adsorbtion of I2was752.36mg/L. According to the analysis of FTIR, the activated carbon samples containing such functional groups:carboxyl (-COOH), phenol, alkenyl (-C=C), alcoholic hydroxyl group (R-OH), amine, ether (-C-O-C), and so on. The XRD diffraction analysis showes that some carbon atoms in the activated carbon were in the formation of more stable crystal structure of the lamellar graphite, but some was still amorphous, making the lamellar gap increases, which increased the surface area of activated carbon. Determining by N2adsorption-desorption isotherms, the adsorption type of activated carbon sample was the type IV isotherm with a hysteresis loop of type H4. That indicates that pore size was mainly concentrated in the mesoporous range and the channel is a narrow wedge-shaped hole. Calculated by the BET equation and BJH methods, specific surface area of activated carbon samples was1100.720m2/g and its total pore volume was0.610cm3/g with average pore size of2.216nm, which also showed that the activated carbon mainly in the mesoporous range. The pore size distribution was mainly concentrated in the2-5nm and the rate of mesoporous range was72.0%.The analysis of SEM showed that the surface of activated carbon had developed aperture and aperture had various sizes, showing a variety of shapes of oval, crack-shaped or irregular in shape, in which the pore size was mesoporous range. The surface morphology of activated carbon is rough, showing the concave and convexuneven, honeycomb-like structure.The results of activated carbon adsorption of Fe (Ⅲ) showed that average adsorption efficiency was above60%and adsorption of Cu (Ⅱ) showed that average adsorption efficiency was above40%.