Speciation and localization of arsenic in white and brown rice grains

Andrew A. Meharg*, Enzo Lombi, Paul N. Williams, Kirk G. Scheckel, Joerg Feldmann, Andrea Raab, Yongguan Zhu, Rafiql Islam

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

263 Citations (Scopus)

Abstract

Synchrotron-based X-ray fluorescence (S-XRF) was utilized to locate arsenic (As) in polished (white) and unpolished (brown) rice grains from the United States, China, and Bangladesh. In white rice As was generally dispersed throughout the grain, the bulk of which constitutes the endosperm. In brown rice As was found to be preferentially localized at the surface, in the region corresponding to the pericarp and aleurone layer. Copper, iron, manganese, and zinc localization followed that of arsenic in brown rice, while the location for cadmium and nickel was distinctly different, showing relatively even distribution throughout the endosperm. The localization of As in the outer grain of brown rice was confirmed by laser ablation ICP-MS. Arsenic speciation of all grains using spatially resolved X-ray absorption near edge structure (micro-XANES) and bulk extraction followed by anion exchange HPLC-ICP-MS revealed the presence of mainly inorganic As and dimethylarsinic acid (DMA). However, the two techniques indicated different proportions of inorganic:organic As species. A wider survey of whole grain speciation of white (n=39) and brown (n=45) rice samples from numerous sources (field collected, supermarket survey, and pot trials) showed that brown rice had a higher proportion of inorganic arsenic present than white rice. Furthermore, the percentage of DMA present in the grain increased along with total grain arsenic.
Original languageEnglish
Pages (from-to)1051-1057
Number of pages7
JournalEnvironmental science & technology
Volume42
Issue number4
DOIs
Publication statusPublished - 15 Feb 2008

Keywords

  • DIETARY EXPOSURE
  • ACCUMULATION
  • EDGE COMPUTED MICROTOMOGRAPHY
  • X-RAY-ANALYSIS
  • COMPARTMENTALIZATION
  • PHYTOCHELATIN COMPLEXES
  • ELEMENTS
  • SOILS
  • BANGLADESH
  • CONTAMINATION

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Science(all)
  • Environmental Chemistry

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