M.T. Boquete

Spatial structure of trace elements in extensive biomonitoring surveys with terrestrial mosses

The size of the area affected by contamination processes mainly depends on the type of contaminant and the way it is emitted. In regular sampling, the size of the sampling grid will therefore interact with the scale at which the contamination processes are produced, for each contaminant, so that the grid will only enable characterization of those processes that occur at scales larger than the grid, i.e. large scale processes. The present study analysed the data corresponding to tissue concentrations of Cd, Cu, Fe, Hg, Mn, Pb, Se, V and Zn in the terrestrial moss Pseudoscleropodium purum obtained in regular sampling surveys with grids of different sizes (15x15, 7.5x7.5 km) plus a series of accessory points located at 1 km from the 15x15 km sampling grid; all sampling sites were located in Galicia and were sampled in March 2004. The objective of the study was to characterize the interaction between the scale of the sampling grid and the scale at which the contamination processes are produced, for each contaminant, to enable adjustment of the size of the grids to the scale at which the contamination processes are mainly produced. For this purpose, the spatial structure of the concentration of each element was analysed by use of semivariograms created with a robust estimator of the semivariance. The results of the study verified the existence of a real interaction between the scale of the sampling grid and the scale of the contamination processes. The results also demonstrated how in the study area, the contamination processes associated with Cd, Pb and V are generally small scale processes, whereas those associated with Cu, Hg and Se are generally large scale processes.

Do mosses exist outside of Europe? A biomonitoring reflection

The passive moss biomonitoring technique has been proved a useful environmental tool for the study of the air quality. However, after more than 40years of its discovery, it has not been used yet in decision making when dealing with atmospheric pollution. Scientific efforts and funding are wasted when these sort of findings do not have a meaningful impact on society. Thus, the aim of this review is to showcase the reasons preventing the worldwide application of the moss technique. The results showed that the possible reasons underlying this problem are the lack of standardization of the technique, transmission of a false idea of robustness, and the lack of a theoretical background. Knowing and accepting these problems is the first step to encourage scientists and funding bodies to invest their efforts in really improving the technique for its application in environmental policies and not only in scientific circles.

Trace element concentrations in the moss Hypnum cupressiforme growing in a presumably unpolluted area.

In this study we determined the concentrations of As, Cd, Hg, Ni and Pb in samples of the moss Hypnum cupressiforme collected during 5 different sampling surveys (2006-2014) in a presumably unpolluted area in northern Spain (25 sampling sites). We then applied factor analysis (FA) to the data to explore the factors underlying the spatial and temporal variability in the concentrations. The percentage of variance explained by the FA ranged between 34 and 98%, and was usually higher than 70%. The FA yielded 5 factors that explained the variance in the concentrations of Cd, As, Hg and Pb in all sampling surveys and also a single factor that explained the variance in Hg and Pb concentrations in 2006. Although the lack of obvious sources of pollution in the study region (at least for the elements considered) suggests that most elements (except perhaps Ni) probably originated from long-range atmospheric transport, this would not explain the results of the FA. We suggest that rather than being due to the origin of the pollutants (as frequently assumed), the spatio-temporal variability in the concentrations of these elements is probably determined by a series of other factors: the physicochemical characteristics of the pollutants and of the moss binding surfaces, physiological processes (e.g. moss growth), and the characteristics of the sampling sites (e.g. vegetation cover, elevation, slope, aspect). We therefore conclude that the assumption that variations in element concentrations in moss tissues are due to the origin of the pollutants is an oversimplification that leads to erroneous interpretation of the results of biomonitoring studies with terrestrial mosses.