Localized Intensification of Arsenic Release within the Emergent Rice Rhizosphere

Yin, D.-X. and Fang, W. and Guan, D.-X. and Williams, P.N. and Moreno-Jimenez, E. and Gao, Y. and Zhao, F.-J. and Ma, L.Q. and Zhang, H. and Luo, J. (2020) Localized Intensification of Arsenic Release within the Emergent Rice Rhizosphere. Environmental Science and Technology, 54 (6). pp. 3138-3147. ISSN 0013-936X

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Abstract

Behavior of trace elements in flooded/lowland rice soils is controlled by root-zone iron oxidation. Insoluble iron species bind/capture toxic elements, i.e., arsenic. However, it was recently observed that within this territory of arsenic immobilization lies a zone of prolific iron release, accompanied by a significant flux of arsenic in close proximity to rice root apices. Questions still remain on how common this phenomenon is and whether the chemical imaging approaches or soils/cultivars used influence this event. Here, three types of ultrathin/high-resolution diffusive gradient in thin films (DGT) substrates were integrated with oxygen planar optodes in a multilayer system, providing two-dimensional mapping of solute fluxes. The three DGT approaches revealed a consistent/overlapping spatial distribution with localized flux maxima for arsenic, which occurred in all experiments, concomitant with iron mobilization. Soil/porewater microsampling within the rhizosphere revealed no significant elevation in the solid phase's total iron and arsenic concentrations between aerobic and anaerobic zones. Contrary to arsenic, phosphorus bioavailability was shown to decrease in the arsenic/iron flux maxima. Rice roots, in addition to their role in nutrient acquisition, also perform a key sensory function. Flux maxima represent a significant departure from the chemical conditions of the bulk/field environment, but our observations of a complete rhizosphere reveal a mixed mode of root-soil interactions.

Item Type:
Journal Article
Journal or Publication Title:
Environmental Science and Technology
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/1600
Subjects:
ID Code:
150002
Deposited By:
Deposited On:
15 Dec 2020 16:30
Refereed?:
Yes
Published?:
Published
Last Modified:
26 Jan 2021 12:12