초록
석탄회가 토양의 투수성을 개선하는데 이용될 수 있을까 알아보기 인하여 토성이 서로 다른 4가지 토양, 식토, 식양토, 사질식양토, 사토에 무연탄회와 유연탄회를 각각 0, 10, 20, 40, 60, 80, 100%(w, $w^{-1}$)를 처리하고, 직경 5.4 cm 길이 11 cm의 스테인레스스틸 관에 토양컬럼을 만들어 항압법에 의하여 포화수리전도도 (Ks)를 측정하였다. 무연탄회와 유연탄회의 입자는 다같이 구형이었고, 입자의 크기 분포는 미사질이었다. 무연탄회 입자 표면은 매끄러웠고 반면에 유연탄회의 표면은 약간 거친편이었지만, 그들의 포화수리전도도값은 거의 비슷하였고, 토양에 처리하였을 때 포화수리전도도에 미치는 효과도 거의 같았다. 투수성이 불량한 식토에 석탄회 20%를 처리하여 Ks값이 $10^{-8}m\;s^{-1}$ 수준에서 $10^{-7}m\;s^{-1}$ 수준으로 10배정도 증가되는 효과가 있었으나, 40% 이상 처리에서는 그 이상의 효과는 나타나지 않았다. 식양토에 대한 석탄회 처리는 $10^{-7}m\;s^{-1}$ 수준의 Ks값이 그대로 유지되었으며, 영향을 주지 못하였다. 한편 투수성이 비교적 높은 사질식양토에 석탄회를 10%처리함으로써 Ks값이 $10^{-5}m\;s^{-1}$에서 $10^{-6}m\;s^{-1}$수준으로 10배정도 감소되었고 20%이상 처리하였을 경우 $5.0{\times}10^{-7}m\;s^{-1}$ 경우 수준으로 거의 50배 감소되었다. 투수성이 너무 높아 보수력이 거의 없는 사토에서는 석탄회 10% 처리하였을 경우 Ks값이 $10^{-4}m\;s^{-1}$에서 $10^{-5}m\;s^{-1}$수준으로 10배정도 감소되었고 20% 처리하였을 경우에는 $10^{-6}m\;s^{-1}$ 수준으로 100배정도 감소되었으며 40% 정도 처리하였을 때 $5.0{\times}10^{-7}m\;s^{-1}$ 수준으로 약 500배 감소되어 보수력이 증가할 것으로 판단된다.
Fly ash is the fine ash particles that are flying out of chimney of the thermoelectric power plant where coals are used as fuel. There are two kinds of fly ashes from anthracite and bituminous coal. By scanning electron microscope(SEM) morphological feature of fly ash was confirmed to the exact spherical particles with the diameter variation from the fine to the largest about $50{\mu}m$(mainly silty particle). Surface of anthracite ash particle was very smooth but that of bituminous was somewhat coarse. To find the utilization of fly ash for improving soil permeability, soils of 4 kinds of different texture, clay, clay loam, sandy clay loam and sand mere applied with 7 levels of fly ash: 0, 10, 20, 40, 60, 80, 100%(w/w) and their saturated hydraulic conductivity(Ks) were determined at each application by constant head method. In clay soil with low water permeability, Ks value was increased about 10 times from $10^{-8}$ to $10^{-7}m\;s^{-1}$ level with application of 10% fly ash and it was slightly increased with increasing fly ash application from 40 to 80%. In clay loam Ks value was about $10^{-7}m\;s^{-1}$ level and its value was not influenced by the fly ash application. In sandy clay loam with relatively high permeability, Ks value was decreased about 10 times from $10^{-5}$ to $10^{-6}m\;s^{-1}$ level with application of 10% fly ash and also decreased about 50 times from $10^{-5}$ to $5.0{\times}10^{-7}m\;s^{-1}$ with application of more than 20% fly ash. In sand with very high permeability, Ks value was decreased about 10 times from $10^{-4}$ to $10^{-5}m\;s^{-1}$ level with application of 10% fly ash and also decreased about 100 times from $10^{-4}$ to $10^{-6}m\;s^{-1}$ level with application of 20% fly ash and continuously decreased about 500 times from $10^{-4}$ to $5.0{\times}10^{-7}m\;s^{-1}$ level with application of more than 40% fly ash. In conclusion by fly ash application saturated hydraulic conductivity was increased in clay soil, on the contrary it was decreased in sandy soils. Fly ash may be used as a material for amelioration of soil permeability.
(Dept. of Agricultural Chemistry, Chungbuk National University)