Experimental Study On The Mechanism Of Solute Transport In Porous Media

Nowadays, solute transport in porous media is an important issue in hydrogeology and engineering geology and tracer experiment is an important method in these researches. In order to study the mechanism of nonreactive and reactive solute transport in porous media, one-dimensional physical models of homogeneous porous media were set up based on the review and analysis of the related previous studies. Using inert tracer NaCl and Brilliant Blue to conduct nonreactive solute transport contrast experiment, then ADE and TPL are used to simulate the breakthrough curves. Processing and analyzing the fitting results, we get the mechanism and regularity of nonreactive solute transport in porous media. Finally, we use the reactive tracers NQS and AN simulated groundwater contaminants to carry out reactive solute transport experiments, and get the breakthrough curves of reactants and products. Summarized the experimental results in this paper, the following conclusions were drawn as:(1) Stronger sorption of NaCl to silica sand and glass beads, the mobility of NaCl with water movement is worse than Brilliant Blue, and the dispersivityis stronger. The tailing of NaCl is more obvious. In summary, Brilliant Blue is more suitable than NaCl as an inert tracer tracing solute transport experiments in porous media.(2) In homogeneous porous media, r2 and RMSE of ADE are very close to TPL’s, they are good fitting model, but in heterogeneous porous media, r2 of TPL is closer to 1 and RMSE is closer to 0 than ADE, so TPL is more precise.(3) Diffusion coefficient D of ADE with the migration distance increases, the flow rate increases and an increase in particle size is increasing, and the retardation coefficient of NaCl is bigger than Brilliant Blue, but the law of the change with velocity and particle size is not obvious.β2 of TPL is decreasing with the velocity increases and the transport distance increases in heterogeneous porous media, it indicate that the Non-Fickian phenomena is more obvious with the velocity increases and the transport distance increases. However, solute transport is accordding with Fick’s law in homogeneous porous media.(4) In reactive solute transport, ideally the peak concentration of product is 0.10mmol/L, but it only reached 0.05mmol/L in the experiment, proved that dielectric barrier have some impact on the chemical reaction. The prediction error of ADRE model decreases to 2%. Di is increasing with the velocity increases and the particle size increases, but m and β0 are only related to flow velocity and has little to do with medium porosity, the mechanism needs further research.