[Influence of combined ecological floating bed on nitrogen and phosphorus between overlying water and sediment]

A new type of combined ecological floating bed was developed on Swan Lake. It was combined with aquatic and hydrophilous plants and ancillary equipments that included floating controllers, water-cycling aerator systems and wave-making systems. Combined ecological floating bed changed the physical and chemical environment of Swan Lake and had an effect on the transportation and transformation of TN, NH4(+) -N and TP between overlying water and sediment during the experiment. The concentration change of TN, NH4(+) -N and TP and the effect of DO, Eh and pH on the nutrient in the overlying water and sediment were investigated. The results indicated that: in overlying water, the removal efficiencies of TN, NH4(+) -N and TP were 61.92%, 63.09% and 80.0%, respectively; the removal efficiencies of TN and NH4(+) -N were 23.79% and 37.04%, respectively; the concentration of TP increased by 43.71% in sediment during the experiment. The combined ecological floating bed influenced environmental factors such as DO, Eh and pH in overlying water in some degree. DO concentration rose from 8.7-8.9 mg x L(-1) to 9.3-10.4 mg x L(-1), and Eh concentration was from 163-178 mV to 191-198 mV. Both of them were higher than those in the contrast area. Phosphorus release was inhibited, and phosphorus adsorption was promoted through improving DO and Eh of the overlying water. The pH volatility was less and maintained between 7.51 and 8.32, and did not promote phosphorus release in sediment. TN, TP and NH4(+) -N in overlying water and TN and NH4(+) -N in sediment were significantly positively correlated with each other and with TP in sediment. The pH had no significant correlation with TN, TP and NH4(+) -N in overlying water and sediment. DO was significantly positively corrected with Eh in overlying water and was significantly negatively corrected with TP in sediment.