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Release of dissolved cadmium and sulfur nanoparticles from oxidizing sulfide minerals
De Livera, J., Mike J. McLaughlin, D. G. BEAK, G. M. Hettiarachchi, AND J. Kirby. Release of dissolved cadmium and sulfur nanoparticles from oxidizing sulfide minerals. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL. Soil Science Society of America, Madison, WI, 75(3):842-854, (2011).
Journal Article for the Soil Science Society of America Journal
Cadmium enrichment (relative to Fe and Zn) in paddy rice grain occurs during the pre-harvest drainage of flooded soil, which causes oxidative dissolution of sulfide minerals present in reduced soil. We investigated this process over a range of environmentally realistic Cdcontaining sulfide minerals/mixtures, comparing Cd and Fe-co-precipitated sphalerites (0.6 to 1.2 mol % Cd, 24 mol % Fe, 74.8 to 75.4 mol % Zn) with mixtures of the pure sulfides at concentration ratios equal to co-precipitated sphalerites, as well as comparing freeze- and oven-dried sulfide minerals. Solutions were analyzed for dissolved and nanoparticulate elements to determine potential phytoavailability. Cadmium and Fe release from co-precipitated (Cd, Fe, Zn) sphalerites and mixtures of pure sulfides was mostly congruent, however Zn was released in preference to Cd. The Zn:Cd ratio in solution of a mixture of pure sulfides was higher than that of a co-precipitated (Cd, Fe, Zn) sulfide (Zn:Cd ratio 126 in both starting solids), which may have been due to galvanic interactions. The greater crystallinity of the oven-dried (Cd, Fe, Zn) co-precipitated sphalerite resulted in lower Cd:Fe and Cd:Zn ratios in solution and preferential release of Cd. Nanoparticles comprised as much as 50 % of ‘dissolved S’, but did not contribute to ‘dissolved’ metals. Under the environmentally realistic scenario of co-precipitated sphalerite or pure sulfide mixtures, oxidation is unlikely to give rise to the increased availability of Cd relative to Fe and Zn to rice during pre-harvest drainage. The U.S. EPA has not subjected this manuscript to internal policy review. Therefore, the research results presented herein do not necessarily reflect Agency policy. Mention of trade names of commercial products and companies does not constitute endorsement or recommendation for use.
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