Abstract
The effect of a horizontal permeable reactive barrier (HPRB) installed under cultivating topsoil with high amount of fertilizers was examined by a series of laboratory and field experiments. The HPRB contains a sustained-release organic compound such as an industrial stearic acid which can supply electron donor in pore water for biological denitrification. The pilot-scale experiment has been conducted at a tea plant field in Makinohara tableland over six months, and the HPRB with 2 % (w/w) beaded type stearic acid was compacted by load of 15 kN/m2 with 20 % of water content under surface of the field between G.L. -0.9 m and G.L. -1.1 m. Average nitrate concentration in pore water upper part (G.L. -0.65 m) of the HPRB was about 40 mg/L, and the removal rate of nitrate concentration in pore water by the HPRB was 98 % during experimental period. While the water content of the HPRB increased approximately 5 % compared with the high-permeability layer, the saturated hydraulic conductivity of the HPRB was almost same as cultivating topsoil layer. These results showed that the cultivating topsoil was not flooded even the time of strong rain. Total organic carbon in pore water through the HPRB were less than 10 mg/L during experimental period. These results showed that the HPRB was effective in situ remediation technique for decreasing non-point nitrate contamination in cultivating fields without maintenance and secondary environmental pollution.
