Redistribution of iron oxides in aggregates induced by pe plus pH variation alters Cd availability in paddy soils

文献类型： 外文期刊

第一作者： Li, Shanshan

作者： Li, Shanshan;Chen, Shibao;Wang, Meng;Lei, Xiaoqin;Zheng, Han;Sun, Xiaoyi;Wang, Lifu;Han, Yun

作者机构：

关键词： pe plus pH; Cd availability; Fe oxides; Aggregate; Paddy soil

期刊名称：SCIENCE OF THE TOTAL ENVIRONMENT （ 影响因子：7.963； 五年影响因子：7.842 ）

ISSN： 0048-9697

年卷期： 2021 年 752 卷

页码：

收录情况： SCI

摘要： In this study, the effect of unstable pe+ pH levels on the transformation of Fe oxides in different-sized soil fractions and its impact on Cd speciation were explored. Paddy soil samples collected from two locations in China were cultivated for two months under one of four pe + pH conditions: flooding + N-2 (T1), flooding (T2), 70% water holding capacity (T3), and 70% water holding capacity + O-2 (T4). Chemical analysis and X-ray diffraction (XRD) were used to identify the mineralogical phases and species of Fe and Cd in paddy soils. The results show that the decrease of soil pe+ pH level favored the transformation ofwell-crystallized Fe oxides (Fec), such as hematite and goethite, into poorly-crystallized (Feo) and organically-complexed (Fe-p) forms. The transformation promoted the binding of Cd to Fe oxides and was primarily responsible for up to a 41.8% decrease of soil DTPA (diethylenetriaminepentaacetic acid)-extractable-Cd content. In addition, the decline in pe+ pH value reduced Fe concentrations in soil particle fractions of 0.2-2-mm(17.8%-30.6%) and<0.002-mm(20.7%-31.7%) of the two flooding treatments. The decreased Fe concentrations were closely associated with less Fec contents in these same fractions and more Fe-o and Fe-p in coarser aggregates (P < 0.01). Importantly, the increase in contents of Fe-o and Fe-p in the 0.002-2 mm fraction were significantly correlated with content of Fe-/Mn-oxide-bound Cd (OX-Cd) in larger particle-size fractions (P< 0.01). Furthermore, the increasing content of OX-Cd played a crucial role in reducing DTPA-Cd content. This study demonstrates that low pe+ pH values favor the transformation of crystalline Fe oxides into a poorly-crystallized and organically-complexed phase, which facilitates Cd accumulation in coarser aggregates and enhances Cd stability in paddy soils. (C) 2020 Elsevier B.V. All rights reserved.

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