Behavior Characteristic And Simulation Study On Nitrobenzene In Rivers-groundwater System

Rivers and groundwater are closely hydraulic connection. In the process of river rechargegroundwater. The river once contaminated, often in a relatively short time easily lead to thedownstream of large area pollution, resulting in groundwater contamination，However, theorganic contamination in groundwater is the most difficult to control and most harmful.Therefore, the impact of river organic pollution of groundwater has become a global hotissues of the water environment. The behavioral characteristics of organic pollutants in theriver-groundwater system have important theoretical and practical significance. In this study,the National Natural Science Foundation:" the project of river pollution impact ongroundwater and simulation studies （40,872,163）, and the major projects of the NationalWater Weihe Guan middle of groundwater to the river ecosystem base flow protection（2008ZX07012-002-003-003）" as the basis, and select representative organic compounds"three to" nitrobenzene as characterized pollutants, and the theory of environmentalchemistry as a guide, using a combination of indoor batch experiment and numericalsimulation methods, carried out the system study of nitrobenzene on migration convection,hydrodynamic dispersion, adsorption and block, biochemical conversion, analog forecastand repair in the Weihe River and its coastal groundwater, and reveal the behavioralcharacteristics, provides the reference for the deep research nitrobenzene’s pollutionmechanism and the repair technology in rivers-groundwater system. Makes the followingprogress:The hydrodynamic force dispersion coefficient （0.38cm2/min） and other basic hydrologygeology parameter were obtained by the tracing experiment in seepage trough. The migrationlaw show that By convective diffusion, adsorption and biodegradation, the role ofnitrobenzene concentration of the observation points over time and space became smaller andsmaller, until below the detection limit.Isothermal non-equilibrium adsorption results showed that sediments quickly reach themaximum adsorption capacity to nitrobenzene within2to3hours in Wei-he Guan middle ofthe upper, middle and lower reaches of the three represents section, and the maximumadsorption capacity and organic carbon contained in the sediments （f oc） positive correlation,and apparent equilibrium can be achieved within10to13hours. isothermal equilibriumadsorption test result indicated the double model type adsorption model which is composedof Linear and the Langmuir equation may describe the nitrobenzene isothermal equilibriumadsorption rule well, and may reflect the dominant and controlling role of adsorption,forsediments with low organic carbon content, the Langmuir adsorption is strong. the mainfactor is the role of hole filling or capillary condensation. For sediments with high organiccarbon content,linear adsorption is strong, the main factor is the absorption of the solid-phaseorganic matter. The combination of solute migration model in the aquifer, defines theexpression of the block coefficient（R） of the dual-mode adsorption isotherm model, andreveal a correlation between the solute liquid concentration and block coefficient.The nitrobenzene biodegradable process meet Monod equation. In Wei-he Guan middle ofthe upper, middle and lower reaches of the three represents section. when the nitrobenzene concentration near1.5mg/L, the microbial maximum specific growth rate reached themaximum after8days, this time the nitrobenzene biodegradation rate approximately is60%.When the nitrobenzene concentrations greater than1.5mg/L, microbial growth isinhibited, the degeneration effect increases not obviously, even also has the decliningtrend.Under river water-deposit coexistent condition，When nitrobenzene is0.5mg/L,maximum specific growth rate up to the maximum in three-section microorganisms （averageof about0.40/h）,and are greater than the river（average of about0.29/h）, thereforeexplained that river water-deposit coexistence system degeneration ability increases.Based on laboratory test results, and established a mathematical model of migration andconversion of nitrobenzene in underground water, and solute transport processes andadsorption, biodegradation can be mathematically simulated using the Matlab programmingto calculate a one-dimensional on the groundwater flow field in seepage trough, as a result,consistent with the experimental observations better,and the model was used to simulationand prediction of the nitrobenzene concentration in the groundwater of the study area, andalso achieved good results.In view of the nitrobenzene enters in the water-bearing stratum medium to be limited,the low concentration characteristic, the attempt use the three methods of KMnO₄-O₃,KMnO₄-H₂O₂, and KMnO₄-ultrasonic wave to conduct the repair research separatelygenerally, their repair efficiency can reach more than95%,90%,93.5%,and three reactionsystem are in line with the first-order reaction kinetics.