Abstract
The effect of heavy-metal-pollution on soil, in terms of cellulose decomposition, was investigated, through the field survey of 3 areas (Toyama, Ohta, Tsushima) in Japan. The decomposition of cellulose was examined by measuring exo-cellulase activity, a component of the cellulase complexes. The results obtained are as follows. 1) The ratios (heavy-metal-content of each area/natural content) were on average : Toyama soils Cd 3.0, Zn 4.2 and Cu 1.2 ; Ohta soils Cd 6.5, Zn 6.6, Cu 28.0 ; Tsushima soils Cd 23.0, Zn 20.0, Cu 3.0. The degree of heavy-metal-pollution was in the following order : Tsushima> Ohta> Toyama soils. 2) A good co-relation between the heavy-metal-content and the exo-cellulase activity was observed only with Ohta soils, since the soils were sampled from a paddy field with small spacial variability. 3) The extraction way of heavy metals (exchangeable, total) made no difference on the relation to the exo-cellulase activity. 4) The exo-cellulase activity of air-dried soils were considerably lower than those of remoisted soils with Toyama and Tsushima soils, but no such consequences observed in Ohta soils. Therefore, the exo-cellulase activity data of remoisted soils is preferable to those of air-dried soils when observing the relation between the heavymetal-content and the exo-cellulase activity. Moreover, the relation was made clearer when dividing the exo-cellulase activity in terms of carbon content. 5) No relation was observed between heavy-metal-content and the exo-cellulase activity with Toyama soils, the least polluted of the 3 areas. On the other hand, negative relations were observed with Ohta soils and Tsushima soils, the most polluted of the 3 areas.
