Primary Study On The Quantitative Dynamics And Synergistic Pollutant Removal Action Of Microorganisms In The Rhizosphere Of Several Macrophytes

Due to rapid industrial development and growth of population, water resources are becoming scarce, and water contamination is appearing to be a serious problem, and eutrophication has been a serious phenomenon, become the most difficulty in environmental remediation for water pollution. With the increase of attention to the environmental ecology, using the phytoremediation methods to rehabilitate polluted groundwater (including river, lake and reservoirs) has become more and more popular. Our research focused on the use of plants such as macrophytes that can absorb nitrogen, to assess their ability to purify nitrogen polluted water, and quantitative dynamics and synergistic pollutant removal action of microorganisms in the rhizosphere macrophytes. The main purpose was to understand abilities of different macrophytes species rehabilitate eutrophicated water.The research assessed the function of rhizosphere microorganisms by experiment of nitrogen uptake kinetics of macrophytes. We studied the community structure and quantitative dynamics of two plants in Rihu Laker and Wocaijiang River in Ningbo in different seasons. By the field investigation, we accumulated the basic data community structure and synergistic pollutant removal action of microorganisms in the rhizosphere of several macrophytes. The research focused on E.crassipes and M.aquaticum to assess there ability to purify nitrogen, organic compounds polluted water, and quantitative dynamics and synergistic pollutant removal action of microorganisms in the rhizosphere of macrophytes under nutrient solution of antimicrobial treatment and normal treatment. Our main research work and conclusions follows:1. The nutrient uptake kinetics of M.aquaticum and E. crassipes were investigated using the modified depletion method under nutrient solution of antimicrobial treatment and normal treatment. The maximum uptake rate (Imax) and Michaelis–Menten constant (Km) were estimated by iterative curve fitting. The Imax and Km for the plants was significantly different between two plants. The Imax for NO₃^--N,NH₄⁺-N in E.crassipes is higher than that in M.aquaticum, illuminated that M.aquaticum was proper for treatment of the seriously polluted water. Imax for NO₃^--N,NH₄⁺-N in M.aquaticum increased by 15.34%,36.50% under antimicrobial treatment. Km for NO₃^--N decreased by 21.54%, and Km for NH₄⁺-N increased by 34.74%. Imax for NH₄⁺-N in E.crassipes increased 86.46%, and that for NO₃^--N decreased 47.37%. Km for NH₄⁺-N in two macrophytes both decreased, and that for NO₃^--N both increased. The results showed that rhizosphere microorganisms could effect the NO₃^--N,NH₄⁺-N in E.crassipes and M.aquaticum by change t rhizosphere factors.2. In this experiment, we measured the numbers of rhizosphere microorganisms in Myriophyllum aquaticum and Alternanthera philoxeroides in Rihu Laker and Wocaijiang River in Ningbo, and their correlation with environmental factors. The population diversity of microorganisms was studied by Sherlock Microbial Identification System (Sherlock MIS). The results indicate: Plants rhizosphere effects was significant. In Rihu laker, the microbial number in the rhizosphere of Myriophyllum aquaticum was significantly higher than that in the rhizosphere of Alternanthera philoxeroides. There was no significant difference between the numbers of bacteria in the rhizosphere of two plants. The numbers of rhizosphere actinomyces and fungi were significant different between plants. There correlation between the numbers of rhizosphere microorganisms and environmental factors. The correlation restricted by the environmental factors. There was a positive correlation between the numbers of rhizosphere microbes and TN in Rihu Laker. The numbers of rhizosphere microbes and TN had no correlation in c. The numbers of rhizosphere microbes had positive correlation with microorganisms in water, and had negative correlation with TP and COD, and had no correlation with water tempterature and Chla in both Rihu Laker and Wocaijiang River. Community Structure of rhizosphere microbes of macrophytes changed with season. Diversity of rhizosphere microorganisms restricted by eutrophication degree, climate and species of macrophyte and so on. In summer, the diversity index of rhizosphere microbes in M. aquaticum was 1.52 and 1.10 in Rihu Laker and Wocaijiang River. And the index changed to be 1.01 and 2.17 in autumn. The diversity index in A. philoxeroides was 1.43 and 1.48 in summer, and changed to be 1.06 and 1.66 in autumn. The predominant microbes in the rhizosphere of macrophytes Pseudomonas, Micrococcus, Chryseobacterium, Acinetobacter. There were some special microorganisms(e.g., Staphylococcus, Acidovora, Arthrobacter) were found because of the difference of environmental factors.3. The research focused on E.crassipes to assess it's ability to purify nitrogen, organic compounds polluted water, and quantitative dynamics and synergistic pollutant removal action of microorganisms in the rhizosphere of E.crassipes under nutrient solution of antimicrobial treatment and normal treatment. The results showed that, at the same condition, the removal efficiency of NH₄⁺-N is lower that of NO₃^--N. Antimicrobial treatment had no significant effect on the removal of NO₃^--N. A significant effect was found on the removal of NH₄⁺-N between antimicrobial treatment and normal treatment. It showed that rhizosphere microbes played an important role in removal of NH₄⁺-N. The removal efficiency of COD under normal treatment was significant higher than that under antimicrobial treatment, especially when the concentration of COD in the initial solution was 60mg/L, 120mg/L. At low concentration , there was a positive correlation between variation rate of rhizosphere microorganisms and removal efficiency of NH₄⁺-N, and a negative correlation was found between variation rate of rhizosphere microorganisms and removal efficiency of NO₃^--N. The results showed that rhizosphere microorganisms was important for the removal of NH₄⁺-N. It's also found that rhizosphere microorganisms played on important role in the removal of organic compounds. Differernt kinds of microorganisms played a role in the removal of organic compounds at different concentration of COD.4. The research focused on M.aquaticum o assess it's ability to purify nitrogen, organic compounds polluted water, and quantitative dynamics and synergistic pollutant removal action of microorganisms in the rhizosphere of M.aquaticum under nutrient solution of antimicrobial treatment and normal treatment. The results showed that, the removal efficiency of NO₃^--N had no significant different between antimicrobial treatment and normal treatment at low concentration of nitrogen. The same result was found in the removal efficiency of NH₄⁺-N. The removal efficiency of NO₃^--N under antimicrobial treatment and normal treatment was respectively 31.30%, 37.57% at high concentration of nitrogen. It was significant different between two treatment. There was no significant difference in the removal efficiency of NH₄⁺-N between two treatment at high concentration of nitrogen. When the concentration of COD in the initial solution was 120mg/L, 180mg/L, the removal efficiency of organic compounds under normal treatment was significant higher than that under antimicrobial treatment. No significant difference was found when the concentration of COD in the initial solution was 60mg/L. A negative correlation was found between variation rate of rhizosphere microorganisms and removal efficiency of NO₃^--N. There were significant correlation between variation rate of bacteria and removal efficiency of COD and NH₄⁺-N under antimicrobial treatment. It showed that the bacteria in the rhizosphere of M.aquaticum played a role in the removal of COD and NH₄⁺-N. There was no close connection between the removal of NO₃^--N and microbial activity in the rhizosphere M.aquaticum.