Temporal Variability of Metal Uptake in Different Cell Compartments in Mosses

The total concentrations and the extra-and intracellular concentrations of Ca, Cd, K and Zn were determined in samples of the moss Pseudoscleropodium purum, collected every 3-4 days at two sampling sites (one located in a contaminated zone, n=101, and another in an uncontaminated zone, n=62). The medians for the total concentrations and the concentrations in the different cell compartments varied widely over time in for the elements studied. In addition, the variability was always lower for the total concentrations, being usually the highest for the extracellular concentrations. For metabolically important elements (i.e. Ca and K), the temporal variability was due to variation in the concentrations of these elements in the extracellular fraction caused by environmental factors. For Zn, the variation was caused by the presence of metal bound to particles on the moss surface and its effect on the extracellular fraction, whereas for Cd, the intracellular concentration was independent of the total concentration. The results enabled us to conclude that neither of the cell compartments considered integrates the studied contaminants, showing a high temporal variation along time, especially for the extracellular location.