Contaminant bioavailability in soils, sediments, and aquatic environments

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   Figure 1

   Projection of the hydroxylapatite structure down the c axis, as well as the two cation sites in hydroxylapatite. Structural data from ref. 52. Atom sizes are not to scale.

   
   
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   Figure 2

   Pyromorphite crystals formed from the reaction of dissolved Pb with hydroxylapatite. (A) An ex situ tapping mode AFM image of effluent from the AFM fluid cell. Scan size = 661 nm on a side. (B) SEM image of pyromorphite crystals deposited atop the AFM cantilever after reaction of dissolved Pb with hydroxylapatite in an AFM liquid cell. [Reproduced with permission from ref. 51 (Copyright 1998, Elsevier Science).]

   
   
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   Figure 3

   SEM images of the reaction products of hydroxylapatite and solid-phase forms of Pb (cerussite) at pH 5 (A) and pH 7 (B). [Reproduced with permission from ref. 21 (Copyright 1996, American Chemical Society).]

   
   
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   Figure 4

   SEM micrograph of sudax root grown in Pb-contaminated soil mixed with hydroxylapatite. Note the pyromorphite crystals on the root.