Structure, Function And N₂O Release Research Of The Artificial Water Ecosystem With Red Mud Adding

In water ecosystem, the absorption of sedment、plants、animals, and according to release gases(such as N2O)by microbial process of nitrification/denitrification will decrease the concentration of nitrogen pollutions. The concentrations of nitrogen pollutants in aquatic ecosystems also significantly affect the structure and function of aquatic ecosystems. Through aquatic ecosystem simulation experiment, to study the effect of different red mud concentration on water quality, plants and microorganisms in the sediment, as well as the effect of N2O emissions during nitrogen removal process. The results showed that:(1) In the experimental stage, pH and conductivity have significant differences between adding red mud with the control group (P<0.05), and with increasing the concentration of red mud, the conductivity significantly increase. In the early stage of the experiment, the total phosphorus removal rate is significantly improved after adding red mud, and the removal efficiency under red mud concentration of lOg/L is significantly greater than the lower concentration (<7g/L). During interim experiment, the total nitrogen removal rate is significantly improved after adding red mud, and the removal efficiency under red mud concentration of10g/L is significantly greater than the lower concentration (<7g/L). After adding red mud, total nitrogen, total phosphorus content in sediment significantly decrease, it shows significant differences between larger and lower concentrations of red mud.(2) After adding red mud, the stem diameter, internode numbers show a trend that the first increase after decreasing with increasing concentrations of red mud; And during previous experiment, the growth of plant height and leaf numbers are restrained because the addition of red mud, In later days, under the concentration of red mud10g/L, the added value of height is more than the control group. The stems、leaves and total dry weight increase first and reduce after, the root dry weight increases with red mud concentration increases. Under the concentration of red mud10g/L, leaf dry weight significantly decreases than the control group; the total dry weight, root dry weight increase significantly than the control group.(3) Through cluster analysis, red mud impacts microbial community structure in sediment, with the increasing of concentration of red mud, the community similarity is larger and larger. When the concentration of red mud is between7g/L and10g/L, the community similarity is larger, with smaller community structure differences. Among lower concentrations (<5g/L) systems, the similarity is poor. With increasing concentration of red mud, diversity index (H) shows the trend that first increase and then decrease, when the concentration of red mud lie in the middle value (5g/L), the community is most species-rich; dominance index (D) first decrease and then increase; the evenness index (E) first increase and then decrease, the smallest appears in the concentration of red mud10g/L.(4) Under different gradient of red mud, N2O fluxes first increase then decrease along with time. The lowest release fluxes value appear during earlier days and later days, are10-30ug(m2h)-1, The maximum N2O fluxes appear during interim experiment, are35-140ug(m2h)-1, adding red mud was significantly greater than in the control group. It is find that changes of the pollutants concentration, plants, microbial community structure and sediment-related pollutant concentrations and enzyme activity influence each other, mutual influence N2O release water in aquatic ecosystems.Bases on the research of red mud artificial water ecosystem, this paper reveals the interaction relationships between red mud, plants, microorganisms, water quality and the release of N2O flux, provides the reference basic data for nitrogen removal and N2O release research in water ecosystem.