以地理統計結合X射線螢光光譜分析推估土壤銅濃度的空間分佈

Estimation of the Spatial Distribution of Copper Concentrations in Soil Using Geostatistics Combined with X-ray Fluorescence Spectrometry (XRF) Analysis

楊晴晴(Ching-Ching Yang) ； 鄭景智(Ching-Chih Cheng) ； 劉曜文(Yao-Wen Liu) ； 李達源(Dar-Yuan Lee) ； 莊愷瑋(Kai-Wei Juang)

《作物、環境與生物資訊》 9卷2期 (2012/06) Pp. 108-122

https://doi.org/10.30061/CEB.201206.0005

摘要

土壤重金屬的空間分佈是界定危害範圍與擬定污染整治策略的重要依據，然而取得正確可靠的重金屬空間分佈資訊，常必須依賴密集採樣的土壤調查與大量的化學檢測分析。為有效提升土壤重金屬污染調查的正確性與效益，本研究提出以地理統計結合X射線螢光光譜（XRF）分析推估土壤中銅濃度的空間分佈。本研究以鄰近彰化縣鹿港鎮一處約0.3公頃的農地為研究區，並以規則網格點配置50個採樣位置，採樣位置點間的最小距離約7 m，每個位置皆採取表層（0-15 cm）、底層（15-30 cm）和深層（30-60 cm）土壤樣本，分別以手持式X 射線螢光光譜儀檢測銅濃度的XRF 讀值，並將所有樣本再以王水萃取－原子吸收光譜法（王水／AAS法）測定其銅濃度。結果顯示，XRF 讀值與王水／AAS 法測值間有顯著的高度相關，可經由建立兩者的直線迴歸模式，修正XRF分析來自基質效應干擾的偏差，故僅需少數王水／AA 法測值資料足以建構與XRF 讀值的關係模式，即可將XRF讀值修正換算成相對應於王水/AA法的估算值。再者，以地理統計的空間推估模式，將XRF讀值資料經關係模式換算成對應於王水／AA法的估算值，應用於推估土壤銅濃度的空間分佈，其推估的準確度高，可提供界定污染危害範圍的可靠依據。因此，本研究提出以地理統計結合XRF分析的應用策略，確實能有效減少王水／AA法的分析樣本數，並正確推估出重金屬濃度的空間分佈。

關鍵字

土壤污染 ； 重金屬 ； X射線螢光光譜 ； 空間變異 ； 克利金法

並列摘要

Spatial distribution of heavy metals in soil is essential for delineating hazardous areas and determining remediation strategies. However, intensive sampling for soil survey and large amounts of chemical analysis and measurements are required for obtaining the reliable information about the spatial distribution of heavy metals. In order to increase the accuracy and efficiency of soil pollution survey, in the present study, geostatistics combined with X-ray fluorescence spectrometry (XRF) analysis was applied to estimate the spatial distribution of heavy metals in soil. The study site was an agricultural land located at Lukang Township, Changhua County. There were 50 gridding nodes drawn for soil sampling. The least distance between two sampling nodes was about 7 m. Samples were collected from the depths of 0-15 cm (topsoil), 15-30 cm (subsoil) and 30-60 cm (deep soil) at each sampling location. The XRF readings for copper concentration were measured using a portable X-ray fluorescence spectrometer. Copper concentration of each soil sample was also determined using aqua regia extraction/atomic absorption spectroscopy (aqua regia/AAS). Results showed that XRF reading significantly correlated with aqua regia/AAS measurement. The linear regression models between XRF reading and aqua regia/AAS measurement were created for adjustments in XRF reading to correct the matrix effect. If one obtains enough data by aqua regia/AAS measurement to develop a relationship model between XRF reading and aqua regia/AAS measurement, XRF readings can then be transformed into the aqua regia/AAS measuring domain. In addition, the reliable estimation of spatial distribution of copper in soil was performed by using the spatial estimation model of geostatistics with the transformed data of aqua regia/AAS measurement from XRF readings. The results indicated that geostatisctics combined with XRF analysis could be used to estimate the spatial distribution of heavy metals corrected with a fewer dataset obtained by aqua regia/AAS.

並列關鍵字

Soil pollution ； Heavy metal ； X-ray fluorescence spectroscopy ； Spatial variation ； Kriging