The nature of an iron oxide—organic iron association in a peaty environment

Fe oxides deposited in ditches draining a bog in the Harz Mountains, Northern Germany, consist essentially of a two-XRD line ferrihydrite that has a magnetic hyperfine field of only 46·5 T at 4·2 K. Pyrophosphate extraction led to an incomplete separation of this from organically-bound Fe, which was depleted in the residue and particularly enriched in the dialysate of the extract. Decomposition of humics with H 2 O 2 led to a further depletion of organic Fe, but also increased the number of XRD lines of the ferrihydrite to six, and raised the hyperfine field by ∼1 T. These modifications are probably the result of an improved interparticle coherence.