X-ray spectromicroscopic investigation of natural organochlorine distribution in weathering plant material
X-ray spectromicroscopic investigation of natural organochlorine distribution in weathering plant material
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DOI：
10.1016/j.gca.2007.09.001
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发表时间：
2007-12-01
影响因子：
5
通讯作者：
Myneni, Satish C. B.
中科院分区：
文献类型：
--
作者：
Leri, Alessandra C.;Marcus, Matthew A.;Myneni, Satish C. B.
天然有机氯（Cl-org）普遍存在于土壤腐殖质中，但对植物腐殖化过程中不同氯形态的分布和循环却知之甚少。X-射线能谱分析表明，在不同的风化阶段，栎叶中Cl-有机物和无机Cl-有机物的分布变化很大，其中以风化初期变化最大。在从树木收获的健康或衰老的叶子中，Cl-inorg出现在与毛状体相关的稀疏分布的高度局部化的“热点”中以及在整个叶组织中的扩散浓度中。与毛状体相关的Cl-inorg以氢键形式或固体盐基质形式存在，而在低Cl浓度的扩散区域中的Cl-inorg仅以氢键形式出现。大多数固相Cl-inorg在早期风化阶段从叶组织中浸出，而H-键合的Cl-inorg似乎随着降解的进行而缓慢地浸出，持续到高级风化阶段。在未风化的叶子，芳香族和脂肪族氯-有机被发现在罕见的，但集中的热点。相比之下，在风化的叶子，芳香氯-有机热点是普遍的，往往与铁或锰浓度升高的地区相一致。芳香Cl-org在早期风化阶段高度溶于叶中，在更高级阶段不溶。这些结果，结合光学显微镜，表明真菌在风化叶材料中的芳香族Cl-org的生产中发挥作用。脂肪族氯有机体发生在集中的热点风化的叶子，以及在低氯浓度的扩散区。通过光谱显微镜研究，揭示了风化橡树叶中Cl的分布和形态，为自然有机质衰变过程中Cl-有机质的形成和循环提供了新的认识。(C)2007爱思唯尔有限公司保留所有权利。
Natural organochlorine (Cl-org) is ubiquitous in soil humus, but the distribution and cycling of different Cl species during the humification of plant material is poorly understood. Our X-ray spectromicroscopic studies indicate that the distributions of Cl-org and inorganic Cl-Clinorg) in oak leaf material vary dramatically with decay stage, with the most striking changes occurring at the onset of weathering. In healthy or senescent leaves harvested from trees, Cl-inorg occurs in sparsely distributed, highly localized "hotspots" associated with trichomes as well as in diffuse concentration throughout the leaf tissue. The Cl-inorg associated with trichomes exists either in H-bonded form or in a solid salt matrix, while the Cl-inorg in diffuse areas of lower Cl concentration appears exclusively in H-bonded form. Most solid phase Cl-inorg leaches from the leaf tissue during early weathering stages, whereas the H-bonded Cl-inorg appears to leach away slowly as degradation progresses, persisting through advanced weathering stages. In unweathered leaves, aromatic and aliphatic Cl-org were found in rare but concentrated hotspots. In weathered leaves, by contrast, aromatic Cl-org hotspots are prevalent, often coinciding with areas of elevated Fe or Mn concentration. Aromatic Cl-org is highly soluble in leaves at early weathering stages and insoluble at more advanced stages. These results, combined with optical microscopy, suggest that fungi play a role in the production of aromatic Cl-org in weathering leaf material. Aliphatic Cl-org occurs in concentrated hotspots in weathered leaves as well as in diffuse areas of low Cl concentration. The distribution and speciation of Cl in weathering oak leaves depicted by this spectromicroscopic study provides new insight into the formation and cycling Of Cl-org during the decay of natural organic matter. (C) 2007 Elsevier Ltd. All rights reserved.