摘要:隨著全球暖化現象與酸沉降的增加,森林生態系已受到明顯影響而干擾營養元素與毒性元素的生地化循環,但有關土壤中超高鉻、鎳背景濃度的森林土壤生態議題,目前仍欠缺系統性研究,因此本計畫擬以三年時間探討溫帶(奧地利)、亞熱帶(日本)、熱帶(台灣)等三種氣候帶之森林生態系中,蛇紋岩土壤在風化過程及遇酸化作用後之鉻、鎳及其相關元素的富集、釋出、溶解與流失等動態。分年主題、工作架構與目的如下:第一年(102年)主題為「不同氣候帶森林生態系中蛇紋岩土壤風化指標之建立與元素的富集及流失」,採自奧地利、日本、台灣至少9個土壤剖面,分析元素全量並測定理化及礦物鑑定,研究目的為:(1)由元素全量分析建立土壤風化指標,了解不同氣候帶蛇紋岩土壤相對風化速率,(2)以質量平衡模式比較不同氣候條件下各種關鍵元素在蛇紋岩土壤剖面中的富集及流失程度,(3)探討蛇紋岩土壤理化特性、礦物特徵與風化指標、元素之富集與流失間的關係。第二年(103年)主題為「不同氣候帶森林生態系中蛇紋岩土壤之鉻、鎳釋放動態」,分析各種化學型態的鉻、鎳,並進行萃取動力學試驗,以模擬不同風化強度下的鉻、鎳釋放過程,研究目的為:(1)探討不同離子強度下蛇紋岩土壤中鉻、鎳的溶解變化,(2)比較蛇紋岩土壤在不同森林生態系中受無機酸與有機酸影響下,鉻、鎳的釋出速率,(3) 了解不同氣候帶下各種化學型態的鉻、鎳與其溶解釋出的關連性。第三年(104年)主題為「不同氣候帶中蛇紋岩土壤鉻氧化能力之比較」,分析六價鉻與三價鉻、及各種型態的錳,並進行鉻氧化力試驗,研究目的為:(1) 探討不同氣候條件下蛇紋岩土壤剖面中六價鉻佔總鉻的比例,(2)比較各氣候帶蛇紋岩土壤鉻氧化潛勢及影響因子,(3)了解可還原性錳、六價鉻、及易變性(labile)鉻之間的關連性,(4)探討鉻氧化潛勢與土壤風化程度的關係。
Abstract: Serpentinitic soils in forest ecosystems are paid little attention to study the biogeochemical processes of nutrient and toxic elements such as high background Cr and Ni levels with respect to the increase of global warming and acid deposition. Therefore, this study for three years proposed to collect soil horizon samples from various serpentinitic pedons (at least 9 pedons) in the forests under temperate (Austria), subtropical (Japan), and tropical (Taiwan) pedo-climates, and further study the gain, loss, release and dissolution processes of Cr, Ni, and their related elements during weathering and acidification of the soils. The subtitle, framework, and purpose of the 3-yr study are as follows: the subtitle of the first year (2013) is “Establishment of weathering index and gain and loss of elements in serpentinitic soils of forest ecosystems under different climates” which total content of element, physio-chemical property, and mineral composition will be performed for the aims: (1) to understand the relative weathering rate of studied serpentinitic soils by the weathering indices based on total analysis of element, (2) to compare the gain and loss of target elements in the soil profiles by the mass balance model, and (3) to explore the relationships among soil property, weathering index, and the elemental mass balance. The subtitle of the second year (2014) is “Release dynamics of Cr and Ni in serpentinitic soils of forest ecosystems under different climates” which chemical fractions of Cr and Ni will be measured by the sequential extraction procedure, and the test of extraction kinetics for Cr and Ni with different extracting agents will be also performed to simulate the release processes of the metals under acid rainfall. The aims of 2nd year are: (1) to determine the dissolved Cr and Ni in the soils by various acids with different ion strengths, (2) to compare the dissolution rates of Cr and Ni in the soils by different inorganic and organic acids, and (3) to understand the relationship between chemical fraction and release ability of Cr and Ni. The subtitle of the third year (2015) is “Comparison of Cr oxidation capacity in serpentinitic soils under different climates” which Cr(VI), Cr(III), various forms of Mn, and Cr oxidation capacity will be measured for the soils. The aims of 3rd year are: (1) to explore the proportion of Cr(VI) in total Cr through the soil profiles, (2) to compare the Cr oxidation capacity and its controlling factors in the soils, (3) to understand the interaction of reducible Mn, Cr(VI), and labile Cr, and (4) to explain the oxidation potential of Cr related to weathering degree in the soils.