Aluminum iron, crystalline-bound

Metal oxide coatings are most important for manganese, iron, and cadmium transport at Sites 3 and 4, but represent less than 25% of the total metal transport in all cases. Crystalline-bound aluminum (> 80% ) and iron (> 50% ) represented the dominant transport mode, which was unimportant for copper, cadmium, and manganese, and crystalline lead contributed about 20 and 6% at Sites 3 and 4, respectively, to total lead transport. The decrease in crystalline lead at Site 4 may result from dilution of lattice-bound lead by solid organic lead emanating from the sewage effluent. 

Delhi soils by studying its speciation in the soil profile and to assess if there was any spatial variability. Soils representing the Aravali Ridge and the alluvial floodplains of river Yamuna were collected as a single, undisturbed core up to a depth of lm and the profile differentiated into four layers- 0-17 cm, 17-37 cm, 37-57 cm, and 57-86 cm. Pseudo total Aluminum and Iron in the soils were speciated into the operationally defined species (weakly exchangeable, organic matter complexes, amorphous oxides and hydroxides, and crystalline or free oxides) by widely recommended selective extraction procedures. Both A1 and Fe in these soils are bound predominantly as Fe oxides and silicates and have only very low percentages in the easily mobilizable pools. 

In discussing nickel exposure, it is important to consider what form of nickel a person is exposed to and its bioavailability. Such information is not often available. Although high concentrations of nickel may be found in contaminated soil and sediment, it may be embedded in a crystalline matrix or bound to hydrated iron, aluminum, and manganese oxides and, therefore, not bioavailable. 

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