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A new simple method is proposed for identifying sources of small scale pollution, by determining the tissue concentrations of pollutants in terrestrial mosses. The method is based on spatial characterization of the processes that generate accumulation of pollutants in these organisms. The steps involved in implementing and applying the method are: (i) obtaining data on pollutants in moss samples collected at least at 35 pairs of sampling sites (SS) separated by 1 km distance; (ii) study of the distribution of the differences in concentration between the pairs of SS, eliminating pairs affected by foci that generate small scale processes; (iii) characterization of the resulting normal distributions and calculation, for different levels of significance, of the probability of a value lying within these distributions, and (iv) application of the calculated quantiles to data corresponding to the differences in concentrations between pairs of SS in the vicinities of foci of small scale pollution, to determine which elements can be considered as pollutants. Given the small number of data required once the distribution of the differences has been established, the method is an inexpensive, efficient way of establishing the probability that a pollutant is being emitted from a particular source. The method is very useful for verifying the results of pollution inventories, evaluating new technologies and improving the design of regional networks for biomonitoring of air quality with terrestrial mosses.

Plants are used as target organisms in most biomonitoring studies of atmospheric deposition of dioxins and furans (PCDD/F) because the most common route of entry of these pollutants into ecosystems is through soils and plants. However, comparison of the results of such studies is difficult because different plant species are used. In the present study we propose the use of mosses as biomonitors of PCDD/F deposition because of their suitable characteristics (absorption of substances from the atmosphere only, large absorbing surface, wide distribution of some species, etc.). We measured the PCDD/F concentrations in tissues of Pseudoscleropodium purum collected in areas far from known sources of pollution and in the surroundings of potential sources of these pollutants (several types of industries, incinerators and burning rubbish dumps). Part of the samples were collected with the aim of monitoring changes in the pollution intensity around some selected sources over time, others were collected to study the spatial gradient of pollution around other sources. Our results indicate that the measurements of the concentration of PCDD/F in the moss tissue allow the detection of strong and weak pollution sources and that these measurements are sensible enough to monitorize changes in the pollution intensity along time, as well as to describe the spatial gradients of pollution created around point sources, and the differences in the relative abundance of isomers (homologue profiles) among different sources. We concluded that mosses are as good biomonitors for PCDD/F as they are for other types of pollutants.