Studies On Nitrogen And Phosphorus Pollution In Ophiocephalus Argus Pond And Decontamination Effects Of Ipomoea Aquatica Etc

This research based on the nutrition level and plankton survey of Ophiocephalus argus culture ponds, compared the effects of water purification depending on aquatic plant for example Ipomoea aquatica. It discussed the feasibility on the breed aquatics of Ophiocephalus Argus by replacing Alternanthera philoxeroide with Ipomoea aquatica, and confirmed the cultivation of Ipomoea aquatica for Ophiocephalus argus and water quality. The obtained results are as follows:1:To investigate nitrogen phosphorus levels and plankton population in the water of Ophiocephalus argus in the Dongting Lake, TN concentration was over high year-round; TP concentration was too high on September (1.34 mg/L); NH3-N concentration exceeded standard on September (0.025 mg/L) and October (0.034 mg/L); NO2--N exceeded standard on July (0.23 mg/L) and November (1.35 mg/L).The main problem is TN too high. The quantity of plankton revealed that water was in the a-contamination all year around.2:The results of the water purification experiment with three kinds of aquatic plants are as below. The growth rate of Ipomoea aquatica is 1.25 times higher than Alternanthera philoxeroide's, and Ipomoea aquatica grown well. The average value of TN, NH3-N, TP and DO in the water bred Ipomoea aquatica is 88.1%,90%,1.19 times and 1.09 times than which of Alternanthera philoxeroides. The ability for eliminating nitrite nitrogen of Alternanthera philoxeroide is better than Ipomoea aquatica and NO2-N consistence in the water bred Ipomoea aquatica is 1.01 times than Alternanthera philoxeroides'. So it's feasible to decontaminate Ophiocephalus argus ponds water in the Dongting Lake area with Ipomoea aquatica instead of Alternanthera philoxeroide.3:Put different quantity of Ipomoea aquatica in the Ophiocephalus argus breeding ponds, and detect Ipomoea aquatica growth, water physical and chemical properties and planktonic biomass. The results are as below:(1) The growth rate of Ophiocephalus argus is highest (31.7%), where the planting density is 30%; its livability is 23% meanwhile, the high removal rate of nitrite nitrogen (84.1%). The effects of removing TN and ammonia nitrogen is good where the planting density is 20%, the ratio is 38% and 8.8%. When the amount of cultivation is between 20%-30%, the water has a high level of dissolved oxygen.(2) Planktonic biomass increased after the Ipomoea aquatica breeding. The dominant species of phytoplankton before breeding is Cosmarium globosum, and the dominant species of which is Oocystis lacustris. The Chlorophyta proportion greatly increased after the breeding.(3) According to the main physical chemical and biological indicators in Ophiocephalus argus breeding water and the combined revenues of cultivating Ophiocephalus argus and Ipomoea aquatica, the amount of Ipomoea aquatica cultivation should between 20%-30%.