Trace metal availability

Parker, D. R. and Pedler, J. F. (1997). Reevaluating the free-ion activity model of trace metal availability to higher plants, Plant and Soil, 196, 223-228. 

The simple definition of biological availability as the fraction of the total trace metal available for uptake by the biota implicitly assumes that all relevant organisms will have similar uptake characteristics. In addition the use of biological availability as a chemical parameter involves the assumption that it can be identified with particular chemical species or groups of species. Perhaps surprisingly many of the studies carried out to date have lent support to these assumptions, though the detailed mechanisms of the uptake processes remain unclear. Some of the inorganic chemical species identified as... 

Trace Metal Availability for the Model Cell - Calculation and Discussion. 

For a particular diffusion layer thickness S the thermodynamic availability, as measured with an ISE or calculated from a speciation model, and the electrochemical availability, as measured by ASV, represent limiting cases of a continuum of trace metal availability. The nature of this continuum is most simply defined by considering the flux of the free metal ion across the diffusion layer to a surface which senses the metal availability. The ratio of the observed flux (J) to the limiting flux (J] ) is unity for ASV measurements under current limiting conditions and zero for ISE measurements. 

These effects, and the nature of chemical measurements of trace metal availability should be borne in mind when planning or interpreting experiments on the uptake of trace metals by phytoplankton cells. 

It is interesting to consider the variations in trace-metal availability in the oceans throughout... 

To obtain citric acid as the metabolic product again requires interference with the normal Krebs tricarboxylic acid cycle in such a way that citric acid metabolism is blocked. Usually this is achieved by careful regulation of concentrations of trace metals available as coenzymes to the various enzyme pathways used by A. niger, so that some of these are rendered ineffective (are blocked). 

From a practical standpoint, stream fulvic acids which comprise over 90% of the stream humic substances are not an important food source for aquatic organisms, but all stream humic and fulvic acids are positive influences on biological growth in respect to phosphorus and nitrogen nutrient cycling, trace metal availability, and limiting potential metal toxicity. 

Table 5-2 Some Examples from In Situ Studies for Prediction of Trace Metal Availability to Eenthic Organisms from Sediment Characteristics (after Tessier Campbell, 1987)...

How may SOM alter micronutrient and trace metal availability in soils ... 

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