Speciation pattern

The interpretation of previous attempts at measuring the impact of metals on microbially mediated processes has been hindered by the use of a wide range of experimental conditions and measurements. Already, a shift from studies based on total metal concentration to those based on bioavailable metal concentrations has occurred. The next step will entail accurately predicting and measuring metal speciation patterns in order to identify microbial responses to metal speciation. Only then will it be possible to develop more effective methods to quantify and mitigate deleterious effects of metals on the myriad processes that microbes mediate in the environment. 

Z. Slejkovec, Z. Bajc, D. Z. Doganoc, Arsenic speciation patterns in freshwater fish, Talanta, 62 (2004), 931-936. 

With regard to the number of factors it should be obvious that to obtain a separation of the four groups mentioned later, at least four factors must be used. If other species which have quite different patterns of behavior over the set of points are included in the calculation, sufficient additional factors must be included to account for each speciation pattern or the patterns will smear over the factors. 

Finally, after all of the above have been taken into account, it is possible to "rotate" a set of factors with different types of rotation yielding somewhat different species loading (9 ). If the speciation patterns for the points are not distinct however, rotation of the factors cannot achieve a separation. We have found Varimax rotation, which maximizes the squared loadings of variables in each factor while retaining the orthogonality of the factors to be most useful. 

Finally, it is interesting to note that the relation between the global mobility of trace elements in the aquatic system (Figure 2) and the speciation patterns summarized above is not direct. Although most of the fully hydrolyzed species appear as mobile elements (phosphorus, carbon, rhenium, boron, arsenic, molybdenum), some elements in this family are amongst the least mobile elements... 

Moreover, the use of the configuration of the different organolead species in the sample (referred to as speciation pattern) may be used to obtain valuable information of the sample. For example, the DEL/ TriEL and Pborg/Pbmorg ratios could help in assessing the age of the air masses transporting the species, the distance away from emission sources, and time spent over the ocean. 

In this context, to focus on critical metal species concentrations, i.e. their temporal and spatial variation, may help to predict in due time disturbances of typical element cycles, e.g. by changing speciation pattern, which may arise by a project (see Fig.3.3). 

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