Study On The Migration And Transformation Of BTEX Under The Influence Of Different Physical Factors Based On TMVOC Model

As a typical organic pollutant in petrochemical sites,volatile organic compounds are easy to transform between soil and groundwater,which makes it difficult to monitor and repair.Temperature,air pressure,water level and buried depth are important factors affecting phase transformation.Taking benzene series as the representative,this paper explored the migration and transformation rule of benzene series in soil and groundwater under the physical factors such as air pressure fluctuation,water level buried depth change and media difference through laboratory experiments and numerical simulation,identified the main controlling factors of migration and transformation,and provided theoretical support for the remediation technology of contaminated sites.The main research results are as follows:(1)Based on TMVOC software,one-dimensional migration simulation of benzene series was designed under atmospheric pressure,buried depth of water level and medium parameters,and factors affecting migration and transport of benzene series were studied.The results show that when the pressure fluctuation cycle is increased by 1 k Pa,the mass fraction of benzene at 10 cm below the surface increases by 0.1%～0.5% compared with that without the pressure fluctuation cycle.The mass fraction loss ratio of NAPL phase and gas phase at different water levels of 21 cm,31 cm and 41 cm is 1:2:1.34,1.33:1.19:1.The mass fraction of benzene and xylene at the interface of different dielectric layers increased linearly with the increase of time under the condition of heterogeneous dielectric parameters.The mass fraction of toluene and ethylbenzene decreased linearly with time.(2)Through automatic machine learning,the sensitivity of BTEX to different parameters in the process of migration and transmission under the influence of different physical factors was obtained.The results showed that under the condition of air pressure fluctuation,the sensitivity was ranked as porosity > pollutant leakage rate > atmospheric pressure > buried depth > permeability medium > density.Under the condition of different water level and buried depth,the sensitivity order is porosity medium > density > permeability > buried depth > pollutant leakage rate >atmospheric pressure;Under different medium parameter conditions,the sensitivity order is porosity > medium density > permeability > pollutant leakage rate >atmospheric pressure > buried depth.At the same time,grey relational degree was used to screen out the main controlling factors affecting migration and transformation.The ranking results were as follows: porosity > pollutant leakage rate > permeability >atmospheric pressure > medium density > buried depth.(3)A generalized two-dimensional numerical model for a study area was established to simulate the migration and transformation process of pollutants in soil and groundwater after continuous leakage under the condition of atmospheric pressure fluctuation.The results show that when the atmospheric pressure is increased by 3k Pa,the mass fraction distribution area in liquid phase increases by 23.30%.