雲林縣口湖地區土壤鹽化現象的研究

由於下水超抽使得研究區地下水之水理水頭下降，更導致當地的地層下陷，使得區內農地可能因地層下陷及海水入侵而遭受污染。在2005年7月及2006年1月兩次調查共採樣了研究區33個點位及198個土壤樣本，進行土壤化性分析，分析的項目包括：土壤飽和抽取液之pH、電導度值，以及Na(上标 +)、K(上标 +)、Ca(上标 2+)、Mg(上标 2+)、Cl(上标 -)、SO4(上标 2-)、HCO3(上标 -)、CO3(上标 2-)、NO3(上标 -)等9組離子濃度，利用Piper水質結構圖、pH、電導度等指標，配合土壤圖、地下水水位、水文地質、氣候、微地形、歷史文獻等地理資訊進行空間分析。分析的結果顯示：區內土壤樣本的鹽度均已屬於不適於耕作狀況；土壤鹽度空間分佈大致以內陸向海岸遞增；不同土層間的鹽度大呈現向下遞減的趨勢，且沿海地區土層污染源主要來自海水，內陸地區其污染源主要為農業污染。研究顯示：本區的土壤鹽度與古潟湖堆積環境、土壤水作用力、養殖漁業放流水、距海遠近等因素關係密切；其次，在洪氾期間農地土壤鹽度有下降的現象，土壤電導度值與海水的電導度值差距頗大，與一般人視海水倒灌是造成土壤鹽化的原因之認知有所差距。

關鍵字

土壤；土壤鹽度；土壤鹽化作用；地下水；口湖

並列摘要

Due to the overpumping of groundwater, the hydraulic head of wells in study area was rapid decline. When the hydraulic head was lowered and sustained a long time, occur land subsidence, and maybe result the intrusion of salt water. The soil of farms could be contaminated because of land subsidence and intrusion of seawater. In study area we collected 99 soil samples from 33 sampling sites. And the items of measurement included: pH, electrical conductivity (EC) and ions' concentrations of Na(superscript +), K(superscript +) Ca(superscript 2+), Mg(superscript 2+), Cl(superscript -), SO4(superscript 2-), HCO3(superscript -) and CO3(superscript 2-) in soil solution samples. And then make use of these data to analyze the chemical compositions of these samples. The outcome of analyses revealed: the salinity of all soil samples far surpass normal condition. Furthermore, the more upper soil horizons have the higher salinity, and the more upper horizons have higher proportion contaminated by seawater. We come at a result in the study that soil salinity relates to ancient lagoon, stratum sinking, soil capillarity, cultivating fishery to put the water out of the pool improperly ,and distance from the sea. Moreover, during inundation, soil salinity is like brought low in the farmland.