Advances in air quality biomonitoring with the terrestrial moss pseudoscleropodium purum

Resumo

Terrestrial mosses are widely used to estimate the levels of contaminants in the atmosphere. The so-called "moss biomonitoring technique" was developed in the Nordic countries at the end of the 1960s as a means of studying the atmospheric deposition of heavy metals. Bryophytes are often considered as ideal organisms for use as biomonitors because of particular characteristics that confer them with a high cation exchange capacity, which enables them to capture and accumulate contaminants from atmospheric deposition. In addition, they can also retain particles (which become strongly bound to their tissues), they are widely distributed in various types of habitats, and they can be easily and inexpensively maintained in the laboratory. Use of the technique has spread to other European countries and rest of the world, and mosses have been used to estimate the levels of different types of contaminants. Despite all the research done during all of these years, further research on some aspects (methodological and ecophysiological) of the technique is still required to optimize the use of Pseudoscleropodium purum as a biomonitor. Thus, the principal objectives of this Thesis are listed below: i) Propose a method of determining the optimal size of sampling area for application of the biomonitoring technique with the moss P. purum by examining the spatial structure in the concentrations of some metals; ii) Verify the suitability of P. purum as a biomonitor of atmospheric contamination through: ii.a) analysis the spatial variation of N concentration in native moss; ii.b) Characterization of heavy metals emissions in industrial environments and compile emission inventories; e ii.c) researcher the relationship between the uptake of pollutants in P.purum and physicochemical characteristics of pollutants. iii) Assess physiological effects in P.purum causes by heavy metals presents in the atmosphere. With the results of the different studies it gets to the conclusion that: i) The size of the sampling site (SS) did not affect the results obtained when using the moss P. purum to monitor air pollutants; the dimensions of the SS were irrelevant for those elements that displayed spatial independence or linear spatial structure. However, other factors such as the number of subsamples collected and the weight of each can affect the results. ii) P. purum cannot be used to biomonitor atmospheric contaminants such as N and some heavy metals and metalloids. Nitrogen is an essential element that is metabolically regulated in moss; and on the other hand, mosses can only yield qualitative estimates of the concentrations of heavy metals and metalloids emitted by different industries. They do not integrate all of the contaminant load as most contaminants are retained on the moss surface as particulate material and interact with the moss and compete with other elements for cation exchange sites; iii) Different physiological parameters of the moss P. purum (i.e. moss growth, chlorophyll fluorescence and spectral reflectance) cannot be used to evaluate air quality, for the following reasons: the different processes related to atmospheric contaminants, such as atmospheric deposition, accumulation in moss, physiological parameters, and moss growth are not significantly related and moreover. As the present studies were only carried out with the moss P. purum, these conclusions must be verified using other species.