Arsenic adsorption on iron plaque and uptake in duckweed (Spirodela polyrhiza L.) affected by chemical species

American Science Press
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Environmental Science and Technology, 2007, 1, pp. 319 - 325
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The effect of iron plaque formation on plant surfaces and chemical species on arsenic uptake in Spirodela polyrhiza L. were investigated. Arsenate [As(V)] or arsenite [As(III)] concentration in S. polyrhiza L. was significantly (p < 0.05) higher than that of methyl arsenic species (MMAA or DMAA). In particular, the concentrations of As(V) and As(III) in CBE-extracts of plants with Fe-plaque were about 43% and 58% respectively higher then plants without Fe-plaque,. On the other hand, the As(V) and As(III) concentrations in tissues of plants with or without Fe-plaque remained almost unchanged. The results suggest that a significant amount of arsenate and arsenite were adsorbed on the Fe-plaque of S. polyrhiza L. surfaces. The concentrations of MMAA and DMAA in tissues and on CBEextracts of S. polyrhiza L. were not significantly affected (p > 0.05) by the Fe-plaque on plant surfaces. These results indicate that methyl arsenic species might not be adsorbed on Fe-plaques. However, the significantly higher concentration of MMAA into the plant tissues than that of DMAA suggests that MMAA is more bioavailable to this plant. The ratios of As/P and As/Fe were significantly higher in tissues and CBE-extracts of plants exposed to inorganic arsenic species than plants exposed to methyl arsenic species. The results indicate enhanced uptake and adsorption of As(V) and As(III) than MMAA and DMAA in relation to phosphate and iron.
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