Kalani Baer Henshaw, Ganga Hettiarachchi, Jonathan D. Judy
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引用次数: 0
Abstract
Phosphorus (P) dynamics in the soil subsurface are relatively unstudied, especially in forest soils, and may be important in areas with groundwater-fed surface water bodies. Here, we use X-ray absorption near-edge P spectroscopy (P-XANES) and X-ray fluorescence microprobe mapping (µ-XRF) to examine P speciation and co-localization with Fe and Al as a function of depth in soils from coniferous and deciduous forests. P-XANES revealed similar trends in P speciation with depth for both forest types, with Al-P and Fe-P being dominant, whereas Ca-P and organic P were minor constituents. Correlation plots derived from µ-XRF mapping revealed a strong correlation between P and both Fe and Al at all depths. At depths of up to 378 cm, a range that includes A, E, and B horizons, the relationships between P and Al/Fe were remarkably consistent, consisting of a population of P diffusely associated with Al/Fe, consistent with Fe- or Al-adsorbed P, as well as P linearly correlated with Al/Fe in several discreet groupings, indicative of the presence of specific P compounds. At depths below 378 cm, the relationships between P and Al/Fe changed dramatically, with correlation plotting indicating the disappearance of any diffuse P:Al/Fe relationships. This change occurred concurrently with a decrease in oxalate extractable P, suggesting that the P present in this deep soil horizon may be present in a more stable form that is less available for transport, as well as potentially indicating that P adsorbed to Fe/Al did not readily pass through the overlaying Bw soil horizon.
对土壤表层下磷(P)的动态研究相对较少,尤其是在森林土壤中,而且在有地下水注入地表水体的地区可能非常重要。在这里,我们使用 X 射线吸收近缘磷光谱(P-XANES)和 X 射线荧光微探针绘图(µ-XRF)来研究针叶林和落叶林土壤中磷的种类以及与铁和铝的共定位关系。P-XANES 显示,两种森林类型的土壤中,钾的种类随深度变化的趋势相似,铝-钾和铁-钾占主导地位,而钙-钾和有机钾则是次要成分。根据 µ-XRF 图谱绘制的相关图显示,在所有深度,P 与铁和铝都有很强的相关性。在深度达 378 厘米(包括 A、E 和 B 层)时,P 与 Al/Fe 之间的关系非常一致,包括与 Al/Fe 扩散相关的 P 群(与铁或铝吸附的 P 一致),以及与 Al/Fe 呈线性相关的 P 群(在几个分散的组中),表明存在特定的 P 化合物。在 378 厘米以下的深度,钾和铝/铁之间的关系发生了巨大变化,相关图显示任何弥散的钾:铝/铁关系都消失了。这一变化与草酸盐可提取钾的减少同时发生,表明存在于这一深层土壤层中的钾可能以更稳定的形式存在,不易迁移,也可能表明吸附在铁/铝上的钾不易通过上覆的 Bw 土壤层。