CONICET | Buscador de Institutos y Recursos Humanos

Open-pit mining activity impacts air quality, mainly through the emission ofparticulate matter. At present, the lichen Punctelia hypoleucites (Nyl.) Krog isbeing evaluated as bioindicator of air pollution in Bajo de la Alumbrera, animportant open pit mine in Catamarca, Argentina. To interpret the bioindicatorresponse it is important to know how the elements are distributed in differentlichen structures. Knowing the origin of the accumulated elements is alsoimportant for associating this response to a specific source of pollution. Therefore,the aim of this work is to analyze the elemental distribution of Ca, K, S, Fe withinthe vegetative and reproductive lichen structures, in order to estimate elementaccumulation in P. hypoleucites exposed in sites with different degree of mineinfluence. Lichens were transplanted in bags to three monitoring sites: one siteinside the mine, an off-mine site 15 km away, and a site far away of the minewhere the lichens were collected (control). After three months, the samples wereanalyzed by particle induced x-ray emission (PIXE). 2D maps of elementalconcentration were obtained by micro-PIXE by scanning a 50-MeV 16O5+ beamover cryosectioned tissue samples at Buenos Aires Tandar accelerator. In alltransplant sites, the K/Ca ratio in P. hypoleucites was higher in apothecia (0.9 -1.7) than in thalli (0.3 - 0.5), while Fe was preferably distributed in the upper andlower cortex of both structures. At the site inside the mine, Fe content for bothstructures was the highest. Sulphur was distributed homogeneously in all the layers of lichen thalli and apothecia at the off-mine and control sites. At the siteinside the mine it was observed an overlap of S and Fe maximun content in theapothecium cortex, suggesting a mineralogical association of these elements.Consequently, Mössbauer spectroscopy was applied in order to determine ironspecies. It was identified pyrite particles together with others minerals of iron indifferent degrees of oxidation. These results allow inferring the mining origin ofthe atmospheric particulate material trapped by the lichen in the mining area. Onthe contrary, the distribution of Ca and K would indicate a different origin forthese elements. With the analytical techniques applied in this study the traceabilityof the accumulated Fe in P. hypoleucites was achieved. This information isvaluable for air biomonitoring in the Bajo la Alumbrera mine area.