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This paper presents the methods and techniques used in the recently developed JKMRC/FEI Mineral Liberation Analyser (MLA). The MLA system consists of a specially developed software package and a standard modern SEM fitted with an energy dispersive spectrum (EDS) analyser. The on-line program of the MLA software package controls the SEM, captures sample images, performs necessary image analysis and acquires EDS x-ray spectra unattended. Typically, 40 to 100 images (containing 4000 to 10,000 particles) are acquired for each sample block and a dozen blocks (of 30 mm in diameter) are measured overnight. The MLA off-line processing program transforms raw particle image with x-ray data into particle mineral maps and calculates bulk and liberation data from particle mineral maps

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The preharvest drainage of rice paddy fields during the grain filling stage can result in a substantial mobilization of Cd in soil and, consequently, elevated grain Cd concentration. However, the processes controlling the mobilization of Cd remains poorly understood. Using 12 field-contaminated paddy soils, we investigated the factors controlling the temporal changes in Cd solubility in paddy soils that were incubated anaerobically for 40 d followed by a 20 d oxidation period. Soluble and extractable Cd concentrations decreased rapidly upon flooding but increased during the oxidation phase, with Cd solubility (aqueous Cd/soil Cd) largely depending upon porewater pH. Furthermore, inhibiting sulfate reduction or inhibiting oxidation dissolution of Cd-sulfides had little or no effect on the mobilization of Cd in the subsequent oxidation phase. Both sequential extraction and X-ray absorption spectroscopy (XAS) analyses revealed that changes in Cd solubility were largely dependent upon the transformation of Cd between the Fe–Mn (oxyhydro)­oxide fraction and exchangeable fraction. Mobilization of Cd upon soil drainage was caused by a decrease in soil pH resulting in the release of Cd from Fe–Mn (oxyhydro)­oxides. Taken together, Fe–Mn (oxyhydro)­oxides play a critical (and prevalent) role in controlling the mobilization of Cd upon soil drainage in paddy systems.

Endosperm Bran Husk 51-68% Cd-thiolate 32-49% Cd-car boxyl 53-56% Cd-thiolate 17-47% Cd-phytate 80-92% Cd-thiolate 8-15% Cd-car boxyl XRF -Cd distribution in rice grain XAS -Cd chemical speciation Bran Cd (mg/kg) 0 2 4 6 8 10 12 14 (Brown rice Cd -polished rice Cd) during milling (mg/kg) -0.5