Trace element geochemistry in Brazilian Cerrado soils
Trace element geochemistry in Brazilian Cerrado soils
复制标题
DOI：
10.1016/j.geoderma.2003.10.003
复制
发表时间：
2004-07
期刊：
影响因子：
6.1
通讯作者：
J. Marques;Darrell G Schulze;Nilton Curi;S. Mertzman
中科院分区：
文献类型：
--
作者：
J. Marques;Darrell G Schulze;Nilton Curi;S. Mertzman
巴西中部高原的塞拉多地区拥有地球上最古老的土壤，其中一些土壤自白垩纪晚期就开始风化。该地区目前正在经历快速的农业和工业化。本文的目的是：(1)清查原始塞拉多土壤的原生微量元素含量；(2)更好地了解在极长时间的成土风化过程中，排水良好的土壤中哪些微量元素积累，哪些微量元素消耗。我们在3个不同地貌表面的3个广泛分离的区域对45个土墩的0-20和80 - 100 cm层进行了采样，并通过x射线荧光分析测定了总元素含量。塞拉多土壤与世界土壤含量比较，Sc、V、Cr、Ga、Zr、Nb、Ce、Th含量均≥世界平均水平的1.2倍，Y、La、U含量基本相同，Mn、Co、Ni、Cu、Zn、Rb、Sr、Ba、Pb含量均<世界平均水平的0.4倍。在酸性pH下，风化过程中积累的微量元素为五价（Nb5+）、四价（Ti4+、Zr4+、U4+、Th4+）或三价（Sc3+、V3+、Cr3+、Ga3+、Y3+、La3+、Ce3+），而在酸性pH下消耗的微量元素为二价或一价（Rb+、Mn2+、Co2+、Ni2+、Cu2+、Zn2+、Sr2+、Ba2+、Pb2+）。在酸性环境下长期的成土风化过程中，微量元素地球化学特征反映了主元素地球化学特征，即一价和二价阳离子被浸出和耗尽，而三价、四价和五价元素则积累。
The Cerrado Region on the Central Plateau of Brazil contains some of the oldest soils on Earth, with some soils weathering in place since the late Cretaceous. The region is currently undergoing rapid agriculturalization and industrialization. The objectives of this paper are: (1) to inventory the native trace element contents of pristine Cerrado soils, and (2) to better understand which trace elements accumulate and which are depleted in well-drained soils over extremely long periods of pedogenic weathering. We sampled the 0–20- and 80–100-cm layers of 45 pedons located in three widely separated areas on three different geomorphic surfaces and determined total elemental contents by X-ray fluorescence analysis. In comparing the contents of Cerrado soils to soils worldwide, the contents of Sc, V, Cr, Ga, Zr, Nb, Ce, and Th are ≥1.2 times the world average, Y, La, and U are about the same, and Mn, Co, Ni, Cu, Zn, Rb, Sr, Ba, and Pb are <0.4 times the world average. Trace elements that accumulated during weathering are either pentavalent (Nb5+), tetravalent (Ti4+, Zr4+, U4+, Th4+), or trivalent (Sc3+, V3+, Cr3+, Ga3+, Y3+, La3+, Ce3+) at the acid pH of these soils, while trace elements that were depleted are either divalent or monovalent (Rb+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Sr2+, Ba2+, and Pb2+) at acid pH. Thus, trace element geochemistry over long periods of pedogenic weathering at acid pH mirrors major element geochemistry in that mono- and divalent cations are leached and depleted, while tri-, tetra-, and pentavalent elements accumulate.