선상지(扇床地) 육성(陸成) 잠재특이산성토(潛在特異酸性土)의 특성과 개량

Characteristics and Improvement of Potential Acid Sulfate Soil Derived from Continental Materials on Alluvial Fan

1. 연세층(現世層)(Holocene deposits)의 선상지(扇狀地) 하부(下部)(Fanbase)에 분포된 육성잠재특이산성토(陸成潛在特異酸性土)는 용천(湧泉)이 산재(散在)되어 있는 배수(排水) 약간불량답(若干不良畓) 조건으로서 토층(土層)에는 7~30%의 석력(石礫)이 있는 식양질(埴壤質) 퇴적토(堆積土)이었다. 2. 잠재특이산성토층(潛在特異酸性土層)은 암회갈색(暗灰褐色)으로서 유기물함량(有機物含量)이 3.3~3.8%로 높았고 치화성(置換性)양이온 함량(含量)이 낮은 반면(反面) 황함량(黃含量)이 0.34~0.41%로 높기 때문에 산화후(酸化後) pH($H_2O$)가 3.4~3.8로 낮았다. 3. 잠재특이산성토층내(潛在特異酸性土層內)의 지하수(地下水)(용정(湧井))중(中)에는 약 80ppm의 $SO_4$와 Na, K, Ca, Mg 등의 ion이 다량함유(多量含有)되어 있었고 지표수(地表水)는 더욱 증발(蒸發), 농축(濃縮)되어 있어 인근(隣近) 하천수(河川水)와는 확연(確然)히 달랐으며 잠재특이산성토층(潛在特異酸性土層)은 용출(湧出)되고 있는 지하수(地下水)에 기인(基因)된 것으로 보였다. 4. 형태(形態) 및 이화학적(理化學的) 특성(特性)을 기준(基準)한 Taxonomy 분류(分類)에 의하면 Fine loamy, mixed, Acid, mesic, Sulfic Haplaquepts로 볼 수 있었고 해설적(解說的) 분류단위(分類單位)는 "Week Potential Acid Sulfate Soil" 이었다. 5. 암거배수(暗渠排水)와 석회시용(石灰施用) 및 용토(容土)처리는 표토의 황용탈(黃用脫)과 용수현상(湧水現狀) 억제로 개량 당년(當年)부터 정상적(正常的) 벼재배가 가능하였으나 개량(改良) 3년 후에는 pH가 다시 5.0이하로 되었다.

A Potential acid sulfate soil derived from continental Holocene deposits on the fan-base was found and it was characterized with improvement practices. Artesian wells were scattered in the area, and the imperfectly drained soils were featured by having fine loamy with 7~30% of gravels. The potential acid sulfate soil layers were typified by having darkness in color with around 3.3~3.8% of O.M. and 0.34~0.41% of total sulfur. Soil pH ranged from 3.4 to 3.8 but it was decreased to 1.9~2.5 after oxidation with $H_2O_2$. Ground water sprang out from an artesian well contained a high amount of minerals such as Na, Ca, Mg, K, etc. and about 80ppm of sulfate which seemed to be responsible for pyrite formation. The soil was classified to member of "Fine loamy, mixed, acid, mesic, sulfic Haplaquepts" in taxonomically, and "weak potential acid sulfate soils" in interpretatively. The installation of tile drains with adding fine earth and liming were effective. However, the pH goes down to 4.8 again after 3 years of improvement practices.