抄録
Nitrate movement under simultaneous influence of hydraulic, electric and chemical gradients was investigated. A one-dimensional ion migration model was developed and compared with laboratory column experiments. Operation of subsurface drainage with an electrode was dis-cussed as an application. The ion transport equation was developed utilizing non-equilibrium thermodynamics. Onsagefs reciprocal relations were applied to reduce the number of linear phenomenological coefficients that relate flux to driving forces. Then phenomenological coefficients were ex-pressed using known or measurable physical, chemical and electrical properties of solute and porous media. Without water flow, nitrate concentration increased at the anode by 2.5 times after 100 hrs of 30 V application. Two flux rates (0.112 and 0.225 cm min * *), and three inflow concentrations (100, 500 and 1,000 ppm NO3-N) were used to evaluate nitrate transport in the column. Nitrate concentra-tion at the anode increased by 10 to 20% at the end of all experiments. However, the concentra-tion in the column was same as inflow concentration. The application of electrokinetic nitrate removal by installed subsurface drainage with on-off (no flow then flush out) operation is recommended over a continuous flow approach. The numerical model results showed very low flux rates (i.e. 2.68X 10_3cm minィ)are required for nitrate accumulation in a sand column, and the experimental results confirmed no accumulation at a flux rate of 0.112 cm min-1.
