Transport Of Volatile Organic Chemicals Benzene In The Unstaturated Porous Media And Prevention And Control Of Pollution

Geological environment of organic pollution, especially organic contamination in the groundwater, what has become a hotspot of scientific research, and concerned by social and public. The vadose zone as the contaminants into the groundwater must pass through the channel of vadose zone, compared to inorganic pollution, organic contaminant with variety and big toxicity, difficult to completely degrade under natural conditions. Migration, transformation and existing forms by both their nature(solubility, volatility and adsorption constants, etc.) constraints pollutants and also influenced by the surrounding environmental factors, at the same time, repair work also faces enormous challenges.This paper summarizes the domestic and foreign vadose zone VOC transfer theory. Based on the State Key Laboratory of Geological Hazard Prevention and Geological Environment Protection autonomy project “Study on the migration and transformation of the unsaturated zone solute” as the basis for a homogeneous sand and sand with loam interlayer containing. Benzene as the main line of research, using soil column experiment, combined laboratory analysis research, through experiments of benzene migration in the unsaturated zone, provide the basis for the restoration technique. Based on soil column test two different cross-sectional configurations, through the experiment of bromide ions migrate as tracer, systematic and comprehensive analysis of the migration of benzene under constant flow conditions in the unsaturated zone was done. By analyzing the characteristics of water infiltration, matric potential variation with time, migration and distribution of benzene in different soil column benzene ion mobility research relations.There are following conclusions:1.Test for determination of saturated hydraulic conductivity, respectively, through fixed and variable head of water measured sand saturated hydraulic conductivity was 11.5m/d, silty loam saturated hydraulic conductivity was 7.96╳10-3m/d; Determination of the diaphragm by the pressure of two soil samples desorption curves used VGM model, fit the four parameters by MATLAB software.2. Temperature assay results bromine ions adsorbed fine sand and silty loam in different concentrations of bromine ions by Freundlich adsorption model fitting, fine sand obtained: K=1.7902, silty loam: K = 1.7754, exponent n <1, indicating that the Br- increasing the amount does not cause an increase in the amount of adsorption, description of the Br- will not increase the degree of adsorption with clay soil content increases.3. From the benzene adsorption kinetics curve: Sand the characteristic pollutant adsorption equilibrium time than silty loam in length, about 25 h to equilibrium; silty loam adsorption equilibrium time and adsorption capacity of about 8h silty loam compared. sand about 10mg/Kg.4. Benzene adsorption isotherm experiment: the use of the model Henry soil adsorption capacity for analysis, fine sand and silty loam Adsorption of benzene-based linear adsorption distribution coefficient Kdpowder> Kdsand, silty loam namely benzene the adsorption capacity is greater than the silt and clay content, the higher the more easily adsorbed, the higher sand content, the stronger the migration of contaminants.5. Br- concentration on the adsorption of benzene experiment: the high bromide ion concentration, adsorption point surface of the medium is affected, resulting in adsorption medium terephthalic gradually decreased, but overall, the Br-concentration of benzene the only effect of the adsorbed trace.6. Homogeneous wetting front advancing from the sand with a certain timetable exhibit nonlinear soil and sand folder structure, when the wetting front in the upper soil wetting front advancing the process and the same homogenous sand, into the layered interface after wetting front advancing speed decreased, there is a certain infiltration reduction effect of stratification interface.7. The addition of layered sand loam can significantly change the shape of the curve through the initial breakthrough time increases, the slope of the curve becomes smaller, increasing the clay content of such bromine ions and benzene through the process in the soil severely disrupted. Clay content, the more slowly the water and solute transport in the soil of speed, blocking effect on soil solute relatively stronger.8. For groundwater restoration projects volatile organic compounds can be effectively combined with laboratory assay, indigenous seepage experiments, as well as hydro-geological survey of the study area to effectively control the further pollution of groundwater contamination, and put forward recommendations to repair aging late pollutants.