Oxidized microzone

Some chemicals, such as phosphate, are trapped in lake sediments by sorption in an "oxidized microzone" that contains iron (+III) oxides... 

Voiatiie compounds suoh as ethanoi or 1-butanoi provide experimentai COD vaiues from 52 to 62% of the theoretioai vaiues, which may be a resuit of the heat produoed by both the addition of suiphurio aoid to the sampie in the open oontainer and the high-temperature microzones oreated by cavitation, which wiii promote the ioss of these compounds before they are oxidized by dichromate. 

Inhibitor approaches similar to those described earher for water samples have been used in sediments (Henricksen et ah, 1981 MUler et ah, 1993). The methyl-fluoride and difluoromethane methods (Cafifey and MUler, 1995 MUler et al., 1993) seem particularly promising because the gases can diffuse thoroughly into the core with minimal disturbance of microzones and gradients. These NH4 oxidation inhibitors are added to cores and the accumulation of NH4+ over time is assumed to represent the net rate of nitrification. Other processes that consume NH4+ would lead to an underestimate of the rate. De Bie et al. (2002) found that both... 

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