Study On The Transport Process Of Ammonium Nitrogen In The Three Phases Of Gas Liquid And Solid In Bioretention

Bioretention as one of the best management measures for urban non-point source pollution control,and it has been widely used to treat pollutants in rainwater runoff.However,there are relatively few studies on the transport process of ammonium nitrogen in the gas-liquid-solid three-phase bioretention.In this paper,we planted ryegrass by adding different proportions(volume ratios of 0%,2%,4%,6%,8%,10%)of soil fillers(newspaper,wood chips and humic leaves)to the sandy soil,build a laboratory bioretention,simulating artificial rainwater,discussing the distribution characteristics of ammonium nitrogen in the three phases of gas,liquid and solid.The focus is on the study of the transport and change of ammonium nitrogen in bioretention in the gas-liquid-solid three-phase under the condition of adding different proportions of soil fillers to the sand.Provide basic data for the later bioretention research.The main research conclusions are as follows:1、Through the analysis of the gas phase distribution characteristics of ammonium nitrogen in bioretention by simulating artificial rainwater,the results show that:(1)When different proportions of newspaper,wood chips and humic leaves are added to sand,each group of media is simulated artificially The ammonia volatilization peak is reached on the second day,the first day and the second day after the rain;when different proportions of newspaper and wood chips are added to the sand,the ammonia volatilization rate starts from the fifth to the sixth day after the artificial rain is simulated It tends to the volatilization rate of the blank experimental group.(2)When adding 2%newspaper,4%newspaper,2%wood chips and 4%humic leaves to sandy soil,it will help the volatilization of ammonia.(3)When a certain proportion of newspaper,wood chips and humic leaves are added to sandy soil,the volatilization of ammonia is mainly controlled by air film.(4)The logistic nonlinear regression model was used to dynamically fit the cumulative amount of ammonia volatilization when adding humic leaves,and the fitting effect was better,R~2 was 0.8905.2、Through the analysis of the liquid phase distribution characteristics of ammonium nitrogen in bioretention by simulating artificial rainwater,the results show:(1)Compared with no plants,plant ryegrass and add different proportions of newspaper and humic leaves to sand,The removal rate of water quality ammonia nitrogen has been improved to varying degrees.When ryegrass was planted,the order of the removal rate of ammonia nitrogen in each group of media was newspaper>humus leaves>sand>wood chips.(2)The isotherm adsorption process of ammonia nitrogen by the four media is in good agreement with the Freundlich isotherm adsorption process,indicating that the adsorption isotherm process of ammonia nitrogen by the four media are all multi-layer adsorption processes.According to the Freundlich adsorption isotherm,the adsorption capacity of the four media in descending order is newspaper>humus leaves>sand>wood chips.3、Through the analysis of the solid phase distribution characteristics of ammonium nitrogen in bioretention by simulating artificial rainwater,the results show that:(1)Adding 6%newspaper,6%wood chips,and 2%humic leaves to the sandy soil will affect the soil ammonia nitrogen.The cumulative contribution is small;when the simulated artificial rain passes through each group of media,the soil ammonia nitrogen content is the highest in the first day;as the drying time increases,the soil ammonia nitrogen content shows a decreasing trend.(2)After adding different proportions of newspapers to the sandy soil,after the first and second simulated rainwater,with the increase of time,the change of soil nitrate nitrogen content shows a gradual increase trend.4、The analysis of the gas-liquid-solid three-phase distribution characteristics of ammonium nitrogen in bioretention through artificial simulation rainwater,the results shows that:(1)the cumulative amount of ammonia volatilized in the sandy soil group accounts for 4.6731%of the input of ammonia nitrogen.When 4%newspaper,2%wood chips,and 4%humic leaves were added to sandy soil,ammonia volatilization accumulated the largest amount,accounting for 26.2504%,16.9151%,and 10.9091%of ammonia nitrogen input,respectively.(2)The ammonia nitrogen content of the sandy soil group flowing out of the system with rainwater accounts for 0.2372%of the ammonia nitrogen input.When adding different proportions of newspaper,wood chips and humic leaves to sand,the proportion of ammonia nitrogen flowing out of the system with the rainwater to the input of ammonia nitrogen ranges from 0.0028%to0.0047%,1.7209%to 3.3994%,and 0.0068%to 0.0101%,respectively.(3)The cumulative amount of soil ammonia nitrogen in the blank group accounts for 51.8376%of the input of ammonia nitrogen.When different proportions of newspaper,wood chips and humic leaves are added to the sandy soil,the range of the cumulative amount of soil ammonia nitrogen to the input of ammonia nitrogen is as follows 26.9370%～69.4557%,28.6355%～50.9289%,38.8353%～53.1038%.