Leaching and Distribution of Cation in Multi-layered Reclaimed Soil Column with Intermediate Macroporous Layer

대공극층위 형성 간척지 다층토주의 양이온 용탈 및 분포

  • Received : 2010.09.29
  • Accepted : 2010.10.19
  • Published : 2010.10.30

Abstract

To investigate desalinization patterns of surface reclaimed saline-sodic soil (RSSS) with subsurface layer of macroporous medium, multi-layered soil columns were constructed. For the multi-layered soil columns, gypsum was treated at the rate of 5 cmolc $kg^{-1}$ in surface (top) while coal bottom ash (CBA) was placed into intermediate layer below the gypsum-treated surface soils followed by the reclaimed saline-sodic soil as bottom layer (BL). The lengths of top soil was 30 cm long while the lengths of the CBA were 20 and 30 cm long. The saturated hydraulic conductivities (Ksat) were $0.39{\times}10^{-4}$ and $0.31{\times}10^{-4}cm\;sec^{-1}$ for RSSS(30 cm)-CBA(20 cm)-BL(20 cm) and RSSS(30 cm)-CBA(20 cm)-RSSS(20 cm), respectively while the lowest $K_{sat}$. was $0.064{\times}10^{-4}cm\;sec^{-1}$ for RSSS(30 cm)-CBA(20 cm)+BL(20 cm). The time required to reach the lowest EC in eluent, 0.3 dS $m^{-1}$ from 33.9 dS $m^{-1}$ was shorter in multi-layered soil columns with GR-CBA than that of RS-SRS, representing that rate of desalinization was greater than 99%. Exchangeable Na decreased by 94.8~96.2 %, while exchangeable Ca increased by 98~129 %.

간척지 토양에서 대공극 중간층위의 형성이 가지는 제염 촉진 효과를 구명하기 위하여 석탄바닥재를 대공극층으로 가지는 다층토주 (multi-layered soil column)를 만들어 실내 실험을 수행하였다. 시험토양의 투수성을 조사한 결과, 표토층은 초기 $K_{sat}$ 0.25 cm $hr^{-1}$에서부터 240시간 후 투수가 정지하여 $K_{sat}$ 0 cm $hr^{-1}$을 나타내었고 심토층은 초기부터 투수가 되지 않아 $K_{sat}$ 0 cm $hr^{-1}$을 나타내었다. 표토에 5 $cmol_c\;kg^{-1}$의 석고를 혼합한 다층토주의 $K_{sat}$ 값은 표토 30cm+CBA 20 cm+심토 20 cm 토주에서 $0.39{\times}10^{-4}cm\;sec^{-1}$를 나타내었고, 표토 30cm+CBA 30 cm+심토 20 cm 토주에서 $0.31{\times}10^{-4}cm\;sec^{-1}$을 나타내었다. 반면 대공극층을 가지지 않은 표토 30cm+ 심토 20 cm 토주는 $K_{sat}$ $0.64{\times}10^{-4}cm\;sec^{-1}$로 매우 낮은 값을 나타내었다. 다층토주 용출액의 EC가 1 dS $m^{-1}$ 이하로 감소한 시간은 대공극 중간층을 가진 토주가 대공극층이 없는 토주 (표토 30 cm+심토 20 cm)에 비해 크게 짧았다. 다층토주 용출액의 양이온 농도는 심토층을 가진 다층토주는 $Na^+>Mg^{2+}>K^+>Ca^{2+}$ 순으로 높았고, 심토층이 없는 다층토주는 $Na^+>Mg^{2+}>Ca^{2+}>K^+$순으로 높았다. 다층토주의 이온용출 후 표토의 화학성은 모든 토주에서 EC가 0.31 dS $m^{-1}$ 이하로 감소하여 시험전의 33.9 dS $m^{-1}$에 비해 99% 이상 저하되었다. 토양의 치환성 Na는 0.1~0.2 $cmol_c\;kg^{-1}$ 범위로 시험전에 비해 95~96% 감소하였고, 반면 치환성 Ca는 2.56~2.96 $cmol_c\;kg^{-1}$ 범위로 시험 전 대비 98~129% 증가하였다.

Keywords

References

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