Sadataka Shiba

Ground Improvement. Modelling of Remediation of Polluted Soil by In-Situ Electrokinetic Treatment.

In order to investigate the efficiency of the in-situ electrokinetic method for the remediation of the soil contaminated with heavy metals, a mathematical model based on the physico-chemical transport phenomena has been constructed and the remediation process is simulated numerically with use of the model. The elecrokinetic remediation is realized by applying a fixed low voltage direct current between the anode and the cathode which are set into the contaminated zone and saturating the zone with purge water. The numerical simulations show that the electrokinetic method is effective for the remediation of the polluted soil especially with heavy metals. The electric current and the electric potential between the anode and the cathode are the important operational variables for the elecrokinetic remediation. It has been proved that the removal process can be divided into the two stages, i.e., the first stage and the second stage, according to the manner of the time variation of the electric current (i.e., the time variation of the spatial characteristics of the removal). The remediation process progresses from the anode to the cathode.

Effect Of Electric Field Induced Within Rain Drops OnAcid Rain Formation

In order to take account of the effect of the electric potential induced by charged chemical species in rain drops on acid rain formation, a new mathematical model, which contains the electro-migration term in addition to the conventional terms, has been constructed. The electric field in rain drops is brought about by the movement of ions which is produced by the absorption of acidic atmospheric pollutant. The ions undergo the electric force caused by the electic field in rain drops and they move toward the certain direction depending on their charge. The numerical simulations by the new model developed here discloses that: (1) the electro-migration of ions makes H+ concentration higher than that estimated neglecting the electro-migration; (2) the distibution of H+ concentration tends to uniform under the elecric potential field; and (3) the electric potential is higher at the drop center than at the drop surface.