Spatial and temporal association of As and Fe species on aquatic plant roots
Spatial and temporal association of As and Fe species on aquatic plant roots
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DOI：
10.1021/es015647d
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发表时间：
2002-05-01
影响因子：
11.4
通讯作者：
Sutton, S
中科院分区：
文献类型：
--
作者：
Hansel, CM;La Force, MJ;Sutton, S
在水生植物根部表面形成的Fe（III）沉淀物（菌斑）可以提供一种衰减和外部排除金属的手段。目前，金属（类）螯合在根表面的机制尚未解决。因此，我们研究了两种常见的水生植物，Phalaris arundinacea（芦苇canarygrass）和香蒲（香蒲）的根铁和砷的衰减和协会的机制，使用X射线吸收光谱和X射线荧光显微断层扫描。两者的铁饰板P. arundinacea和T.宽叶香蒲（Typha latifolia）主要由水合氧化铁（ferrihydrite）组成，少量针铁矿和少量菱铁矿。具有来自纤铁矿以及更大比例的结晶矿物的显著贡献的斑茅属植物。针铁矿和纤铁矿的共存表明在牙根表面存在化学多样性的微环境。砷以两种吸附态砷的组合形式存在，主要由砷酸盐（约82%）和少量（约18%）的As（III）-铁（氢）氧化物复合物组成。此外，砷和铁在根表面的空间和时间的相关性进行了观察。虽然铁（氢）氧化物沉积物在根部周围形成连续的表层，但As存在于根部外部和内部的孤立区域。根表面相关的作为一般对应于区域的铁水平提高，因此可能会发生作为一个直接后果的铁相异质性和优先作为吸附反应。
The formation of an Fe(III) precipitate (plaque) on the surface of aquatic plant roots may provide a means of attenuation and external exclusion of metals. Presently, the mechanisms of metal(loid) sequestration at the root surface are unresolved. Accordingly, we investigated the mechanisms of Fe and As attenuation and association on the roots of two common aquatic plant species,Phalaris arundinacea(reed canarygrass) andTypha latifolia(cattail) using X-ray absorption spectroscopy and X-ray fluorescence microtomography. Iron plaque of bothP. arundinaceaandT. latifoliaconsist predominantly of hydrated iron oxides (ferrihydrite) with lesser amounts of goethite and minor levels of siderite.Typha latifolia, however, differs fromP. arundinaceaby having a significant contribution from lepidocrocite as well as a greater proportion of crystalline minerals. Coexistence of goethite and lepidocrocite suggests the presence of chemically diverse microenviron ments at the root surface. Arsenic exists as a combination of two sorbed As species, being comprised predominantly of arsenate- (∼82%) with lesser amounts (∼18%) of As(III)−iron (hydr)oxide complexes. Furthermore, both spatial and temporal correlations between As and Fe on the root surfaces were observed. While the iron (hydr)oxide deposits form a continuous surficial rind around the root, As exists in isolated regions on the exterior and interior of the root. Root surface-associated As generally corresponds to regions of enhanced Fe levels and may therefore occur as a direct consequence of Fe phase heterogeneity and preferential As sorption reactions.