Soil and groundwater pollution from trichloroethylene has recently been noted. In the present work kinetics for decomposition of trichloroethylene using Fenton's reaction are discussed. This study found that the reaction was first-order for concentration of trichloroethylene, 0.8-order for concentration of iron ion and half-order for concentrations of hydrogen peroxide. The reaction rate constant was given as 0.205 (l · mol^-1) ^1.3 · s^-1. Additional experiments were carried out in the presence of humic acid (HA), the most abundant organic compound in soil. The reaction with HA was first-order for concentrations of trichloroethylene and Fe (II) iron, and 0.8-order for concentration of hydrogen peroxide, and the reaction rate constant was 0.865 (l · mol^-1) ^1.8 · s^-1. In spite of small difference in reaction order, these reaction rates are almost the same with and without humic acid under the present conditions.
At the initial stage of these reactions, concentrations of trichloroethylene were found to be reduced rapidly. The correlation to calculate the reduction amounts is proposed. Finally, equations to predict the variation of trichloroethylene concentration using Fenton's reaction are suggested.

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The amount of annual average dry deposition of SO₄^2-, NO₃^-, NH₄⁺, Cl^-, Ca²⁺, Mg²⁺, K⁺, Na⁺ at Toyama Prefecture were estimated to be 3.5∼8.1, 0.42∼4.7, 6.5∼12, 0.38∼1.4, 0.42∼0.85, 0.31∼0.94, 0.23∼0.69, 4.1∼8.4 mmol/m²/year, respectively.
The influence of the Miyake Island volcanic eruption on Toyama Prefecture was detected in the monthly variation of the amount of dry deposition. The amount of dry deposition of nssSO₄^2- in September 2000 reached a maximum value of 23mmol/m²/year.
The amount of dry deposition of Ca²⁺ showed the maximum in spring. This (is/might be) caused by the influence of yellow sand. In this season, the amount of dry deposition of other ions was also more than other seasons. In winter, the amount of dry deposition of nssSO₄^2- and NO₃^- were small. In summer, the amount of dry deposition of Ca²⁺, K⁺, Na⁺, and Mg²⁺ showed a tendency to be slightly low.

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