Abstract
We found the phenomenon that insolubilized matter of polymer accumulates as an impermeable membrane in soil when an aqueous solution of a polymer with carboxyl groups such as polyacrylic acid is percolated in to the soil. In order to make this phenomenon clearer, we conducted experiments of layer formations in a soil column. The results obtained are as follows. 1. When an aqueous solution of polymers containing 2.0 g kg^<-1> of polyacrylic acid and 0.3 g kg^<-1> of polyacrylamide was percolated into a soil column for 20 to 100 h, the percolation rate of the solution gradually decreased and became 1×10^<-5> cm s^<-1>. 2. An impermeable layer in the soil column was formed by insolubilized polymer gel and soil particles. 3. Calcium was dominantly concentrated in the impermeable layer. The amounts of calcium and carboxyl groups of the polymer constituting the impermeable layer were nearly equivalent. Therefore, calcium is considered to play an important role in the layer formation. 4. Out of the comparison between the pore space in the soil and the gel volume in the impermeable layer, it may be inferred that the thickness of the impermeable layer is about 2 mm. The formative phenomenon of the impermeable layer found by the authors includes migration, immobilization and accumulation of organic substances in the soil. Thus, this phenomenon might become a model for studying the dynamics of organic matters in soils.
