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題名 | 銫-137技術應用於土壤沖蝕研究之回顧與展望=Application of Caesium-137 Technique in Soil Erosion Studies: A Review and Perspective |
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作者 | 李建堂; | 書刊名 | 國立臺灣大學理學院地理學系地理學報 |
卷期 | 26 1999.11[民88.11] |
頁次 | 頁25-44 |
分類號 | 434.227 |
關鍵詞 | 銫-137; 土壤重新分布; 堆積速率; 沖蝕物來源; Caesium-137; 137Cs; Soil redistribution; Sedimentation rate; Sediment source; |
語文 | 中文(Chinese) |
中文摘要 | 自從 1950 年代世界各國競相於大氣中試爆核子武器後,銫 -137 為核分裂所產 生的人造放射性元素逐漸分布於全球, 其於地表之分布量主要與緯度和降雨量有關。 銫 -137 在土壤中的移動主要為物理性的沖蝕作用所控制,例如,水、風及農地翻耕等。 在已 知樣本的重量下,利用非破壞性的γ射線光譜儀計算在 662 千電子伏特( keV )的放射次 數,即可計算出銫 -137 在土壤及沖蝕物中的放射能量。自從美國於 1970 年代開始利用銫 -137 為追蹤劑來量測土壤沖蝕, 顯示銫 -137 技術有極大的潛力,不但可用於追蹤沖蝕物 的來源,並可預估一地區長期( ~40 年)土壤淨沖蝕與堆積速率。 研究者可利用此技術來 探討土地利用如何影響土壤沖蝕的各項問題,同時也可用來確定更有效率的水土資源保育方 式。雖然在過去二十多年來,利用銫 -137 技術於量測土壤沖蝕之研究與日俱增,但是其應 用幾乎完全侷限於溫帶地區, 也未曾用於臺灣從事土壤沖蝕方面之研究。 本文首先介紹銫 -137 的分布背景和特性、此技術之優點及限制, 然後回顧其在不同土壤沖蝕研究領域之應 用,包括:(1) 量化土壤沖蝕與堆積的重新分布情形;(2) 量化現代沉積層的堆積速率;及 (3) 量化及追蹤沖蝕物的來源。 |
英文摘要 | Caesium-137 (�� Cs) is an artificial radionuclide produced primarily as a result of atmospheric thermonuclear weapon tests since the 1950s. Caesium-137 has been globally distributed, with fallout rates generally related to latitude and precipitation depth. The movement of �� Cs in soils is primarily controlled by physical erosion processes, such as water, wind and tillage. Caesium-137 activity in soils and sediments can be determined by non-destructive direct gamma spectrometry by counting the gamma emissions (662 keV) of a known mass of soil. The utilization of �� Cs as a tracer for measuring soil erosion since the 1970s has shown significant potential for identifying sediment source areas and estimating long-term (~40 yr) net soil erosion and deposition rates within various environments. This approach allows the researcher to address the question of the influence of land use on soil erosion, and to identify more effective and efficient controls for soil and water conservation. Despite the increasing utilization of the �� Cs technique in soil erosion research, its application has been restricted almost exclusively to temperate soils. Until now, it has not yet been used in Taiwan for erosion studies. This paper introduces the distribution background and unique characteristics of �� Cs, the advantages and constraints of using the �� Cs technique first, then reviews its applications to quantify: (1) rates and patterns of soil redistribution; (2) modern sediment accumulation rates; and (3) to identify sediment source areas. |
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