土壤微量元素空間分佈之分析：以花蓮吉安地區為例

Abstract

The information of spatial distribution of soil properties is important for us on managing and utilizing soil resources. The objective of this study was to evaluate the spatial distribution of a data set of concentrations of soil trace elements by conventional statistical and geostatistical in a five-meter interval grid sampling field located at Chian of Hualien. The average, data distribution, coefficient of variance, and spatial structure of soil trace element concentration were investigated. The results showed that the ranges of the concentrations of Fe, Mn, Cu, Zn, Cd, Cr, Ni, and Pb were N.D. -893.1，0.8-272.5, 0.04-20.9, N.D.-32.8, 0.11-0.85, 0.17-2.22, 0.23-3.90, and 0.7-23.2 mg/kg, respectively. The averages of those elements were 218.7, 124.6， 7.37, 6.1, 0.49, 0.67, 1.87, and 8.1 mg/kg, respectively. Elements studied except Mn, Cd, and Ni, the coefficients of variation of concentrations of the elements studied were all greater than 40%. It suggests that the variabilities of trace element concentrations in the studied field are quite large. The spatial distribution for those elements (except Mn) had the same spatial structures and geographic distribution. The ranges of spatial dependence of those elements were between 65.8 to 86.6 m and nugget/sill ratios were 0.08 to 0.50, indicating strong to moderate spatial dependence. The contour maps of soil indicated that the spatial distribution of those trace elements might be related to the farming operations. The results obtained from this study also suggested that using geostatistis could provide the spatial structure of soil trace elements and avoid the spatial distribution being masked by using average in conventional statistics. 土壊資源之管理與利用首先需掌握土壤性質的空間分佈，本研究以傳統統計(conventional statistics)及地理統計(geostatistics)分析花蓮縣吉安鄕5公尺之細密網格採樣的土壤資料，除探討土壤微量元素含量之平均値、資料分佈及變異係數 外並以地理統計技術分析其空間結構。 在本研究區內土壤中鐵、錳、銅、鋅、鎘、鉻、鎳、鉛元素之濃度範圍分別爲N.D.-893.1、0.8-272.5、0.04-20.90、N.D.-32.8、0.11-0.85、0.17-2.22、0.23-3.90及0.7-23.2 mg/kg，而其平均濃度則分別爲 218.7、124.6、7.37、6.1、0.49、0.67、1.87 及8.1 mg/kg，但其變異係數除錳、鎘及鎳外均大於40%，顯示資料的變異頗大。在空間分佈上，除錳元素外，其他鐵、銅、鋅、鎘、鉻、鎳、鉛等元素均具有地理同位性及相似的空間結構，其空間相依距離均介於65.8公尺至86.6公尺之間，而空間相依性指標（碎塊變異數/門檻値，nugget/sill）的比値則介於0.08〜0.50之間，爲強到中等程度之空間相依性。透過濃度分佈等値線圖與作物種植位置圖的比較，可以發現各 元素之濃度空間分佈圖形與田區規劃有關連性，表示本研究區的微量元素之空間分 佈可能已受到耕作制度的影響，造成其空間特性的改變。 由本研究之結果發現，利用地理統計可以提供傳統統計方法所無法提供的空間結構資料，避免平均値被少數極端値資料稀釋，而掩蓋濃度分佈的眞實狀況。