Trace Elements in Thai Oxisols on Limestone in Relation to Rainfall

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• 作者：Worachart Wisawapipat^a ; ^b ; Irb Kheoruenromne^b ; ^{irbs@ku.ac.th} ; Anchalee Suddhiprakarn^b ; Robert J. Gilkes^c
• 关键词：Geochemistry ; Tropical soils ; Factor analysis ; Arsenic contamination
• 刊名：Procedia - Social and Behavioral Sciences
• 出版年：2012
• 出版时间：2012
• 年：2012
• 卷：40
• 期：Complete
• 页码：673-680
• 全文大小：317 K

文摘

Trace element concentrations of 7 profiles of Oxisols derived from calcareous sedimentary rocks under tropical monsoonal and the tropical savanna environments have been investigated using XRD, SXRD, XRF, and ICP-OES analytical techniques so as to provide baseline values for estimating environmental contamination of soils with heavy metals. Kaolinite was the dominant mineral of the clay fraction with moderate amounts of goethite and hematite. Gibbsite was only present in Ak1 profile under more humid conditions contributing to high anion exchange capacity (AEC). Trace element concentrations in these soils conform to those for worldwide normal soils. However, the extraordinary high arsenic (As) concentration in Ak1 soil represents a hazardous concentration (313 mg kg^-1), which may have been inherited from the parent rock. Arsenic in this soil is probably not toxic because it is immobile in an oxidized environment, and is sorbed onto soil constituents particularly sesquioxides. Factor analysis showed that for soils under various rainfalls were deficient. For the whole soil samples, three main groups of similar geochemical behavior existed. Different concentrations of elements of the Ca group (Ca, Ni, Cr, Mg, Ba, Be, Gd, Rb, K, Co, Mn, Zn, La, Cu, V, Ce, P, Cd, Sc, Pb, clay, SSA and CEC) and the Si group (Si and sand), resulted in soils developed under the tropical monsoonal and the tropical savanna climates being clearly different. The Fe group (Fe, Ti, Al, Mo, Ge, Se, Sr, Ga, Th, Hf, U, As and Sb) separated the soils developed of under a tropical monsoonal into two groups based on the very high concentrations of Fe, Al and As in Ak1 profile.